Abstract:[Objective] The distribution of Fe, Al oxides, and microbial community diversity in red soil microaggregates, and their relationships were studied in order to provide a theoretical basis for the improvement of subtropical red soil structure. [Methods] This study was conducted on a chinese fir plantation, which is the typical plant stand in the subtropical red soil region. The contents of Fe, Al oxides, bonded organic matter, and microbial communities of different soil microaggregate grain sizes in different soil layers (topsoil, 0—10 cm; middle soil, 10—20 cm; subsoil, 20—30 cm) were measured. Their relationships were analyzed by the redundancy analysis method (RDA). [Results] Different forms of Fe, Al oxide contents in soil micro-aggregates were present in the following order: dithionite-citrate-bicarbonate-extractable oxides (Fe_d, Al_d) >> acid ammonium oxalate-extractable oxides (Fe_o, Al_o) > sodium pyrophosphate-extractable oxides (Fe_p, Al_p). In general, Fe and Al oxide contents increased slowly with decreasing soil micro-aggregate grain sizes. The Fe_p and Al_d contents decreased slowly with increasing soil depth, and Al_p content in the subsoil was far greater than in the topsoil. The main microorganisms in the chinese fir plantation soil were bacteria, and gram-positive and negative bacteria. The effect of micro-aggregate grain size on microorganisms was greater in topsoil than in middle soil and subsoil. The phospholipid fatty acids (PLFAs) of microorganisms in soil micro-aggregates of 50—200 μm diameter were greater than in micro-aggregates of other diameters. The richness, Shannon index, and Simpson index of microorganisms were greatest in topsoil, and the richness and Shannon index of microorganisms were greatest in soil micro-aggregates with the lowest diameter. RDA revealed that antino bacteria PLFAs, gram-positive bacteria PLFAs, and microbial Shannon and Simpson indexes were highly significantly and negatively correlated with Fe_d. Bacteria PLFAs showed highly significant positive relationships with Al_d and Al_o contents. Fungus, bacteria, gram-negative bacteria, arbuscular mycorrhizal fungus PLFAs showed negative relationships with Fe-Al bonded organic carbon 〔Fe(Al)-SOC〕 content. [Conclusion] The distributions of Fe, Al oxides, and microbial community diversity in subtropical red soil micro-aggregates were affected by soil layers and micro-aggregate size. Different types of microorganisms were affected by different forms of Fe and Al oxides, and bonded organic carbon.

Abstract:[Objective] Differences of plant species composition, community structure, and diversity in different soil erosion control years in the granite erosion area were compared and analyzed in order to provide a scientific basis for soil erosion control and ecological reconstruction in the granite erosion area. [Methods] The method of replacing time with space was adopted. In the Pingjiang River basin of Xingguo County, Jiangxi Province, four artificial forests with different treatment years of 4, 14, 24, and 34 years were selected as the research objects, and the untreated forest and secondary forest were taken as the control. The species composition, community structure, and plant diversity of plant communities in different areas were investigated and analyzed by the quadrat survey method. [Results] ① 43 species of plants were investigated, belonging to 31 families and 41 genera, including 17 species in the arbor layer, eight species in the shrub layer, and 18 species in the herb layer. ② The “bamboo ditch + arbor, shrub and grass” measures could effectively increase plant diversity and promote vegetation restoration and succession. The Simpson index and Shannon-Wiener index of forest lands with different management years were greater than those of forest lands without artificial management. ③ With the increase of water and soil loss control years, the Simpson, Shannon-Wiener, and evenness indexes of the plant community showed upward-decreasing-increasing trends, and they were all smaller than secondary forests. ④ There were fewer common species in the woodland of different treatment years, secondary forest, and untreated forest, which showed dissimilarity on the whole. [Conclusion] It is difficult to effectively restore plant diversity in granite erosion areas only by natural closure. The “bamboo ditch + arbor, shrub and grass” measures could effectively promote vegetation restoration and increase plant diversity.

Abstract:[Objective] Changes in the ecological stoichiometry of nitrogen and phosphorus in a natural riparian zone and a strongly artificial disturbed riparian zone were explored in order to provide a scientific basis for the restoration of riparian zones and environmental protection in the Linfen section of the Fenhe River. [Methods] The spatiotemporal distribution characteristics and influencing factors of nitrogen and phosphorus in the soil-plant system between a natural riparian zone and a strongly artificial disturbed riparian zone were studied by correlation analysis and partial redundancy analysis methods. [Results] The contents of plant total nitrogen (TN) and total phosphorus (TP) in riparian zones decreased first and then increased during the period of dry season, normal season, wet season. The contents of plant TN and TP in the near-bank area were higher than in the far-bank area. The internal stability of plant TN and TP in riparian zones was higher in the natural riparian zone than in the strongly artificial disturbed riparian zone. Plant TP values in the two riparian zones were weakly sensitive to state index, and N/P values were absolutely stable. The interaction of soil pH value, TN, and TP, with plant TN and TP contents were obvious in riparian zones. [Conclusion] The spatiotemporal distribution characteristics of nitrogen and phosphorus in the soil-plant system were similar to those in soil in typical riparian zones of the Linfen section of the Fenhe River. The ecological stochiometric characteristics of nitrogen and phosphorus of the soil-plant system were significantly affected by human activities.

Abstract:[Objective] The influence of concentrated infiltration from rainfall runoff on soil of rain gardens in Xi’an City, Shaanxi Province was studied in order to provide a scientific reference for the reasonable configuration and application of concentrated infiltration technology of urban rainfall runoff. [Methods] Runoff data from two rain garden treatments (RD₁: accepting roof rainfall runoff; RD₂: accepting roof and road rainfall runoff) was acquired from 8—9 years on the campus of Xi’an University of Technology. From 2016 to 2018, 16—18 rainfall events were monitored to determine the pollutant load of chemical oxygen demand (COD), total suspended solids (TSS), N, P, and the event mean concentration (EMC) of heavy metals in the rainfall runoff of the two rain gardens. From April 2017 to February 2019, a total of seven soil samples at different soil depths in the two gardens were collected to determine NH₄-N, NO₃-N, TN, TP, total organic carbon (TOC), and heavy metals (Cu, Zn, and Cd) to assess the vertical distribution of N, P, TOC, and heavy metal contents in the rain garden soils. [Results] The EMC concentrations of COD, TSS, NH₄-N, TN, and TP in RD₁ were all greater than those in RD₂, but opposite results were obtained with regard to heavy metals. The contents of NH₄-N and TN showed a gradually decreasing trend with soil depth. However, the contents of NO₃-N and TP in the soil gradually increased with soil depth, and they were all greater below 50 cm than the contents in the upper layer (0—50 cm). The TOC content in the rain garden soil showed a gradually decreasing trend with soil depth. Heavy metal contents were large in the 0—30 cm soil layer. Cu and Zn mainly existed in the form of iron-manganese oxide bound state and residue state, while Cd mainly existed in the form of exchangeable and carbonate-bound forms. The contents of Cu, Zn, and Cd in rain garden soil had good relationships with TOC (R²>0.8). [Conclusion] Concentrated infiltration in rain gardens had a clear influence on soil N, P, and heavy metals. NO₃-N and TP leaching occurred in rain garden soil. The contents of NH₄-N and TN in rain garden soil were mainly concentrated in the 0—50 cm soil layer, while heavy metals were mainly concentrated in the 0—30 cm layer.

Abstract:[Objective] The degree of damage to small leaf poplar (Populus simonii) by coal mining subsidence was studied in order to provide a theoretical basis for the later restoration of artificial forests. [Methods] Damages in the Lijiata mining area to P. simonii root systems at different cracks in different slope positions were observed and recorded. The relationships between root damage rate and damage types and slope position, crack types, dislocation differences, crack widths, and the horizontal distances from roots to cracks were analyzed by using mathematical statistical software in order to characterize damage characteristics of P. simonii root systems. [Results] ① The horizontal P. simonii root system was mainly distributed in 0—60 cm soil layer. The number of roots in 0—10 cm soil layer was the largest, accounting for 40.1%—43.2% of the root system, and the roots in 50—60 cm soil layer accounted for 0.63%—3.71% of the root system. The fraction of the root system gradually declined with increasing soil depth. ② Root damage was most serious on slopes. All types of root damage existed in the subsidence cracks and sliding cracks, with damage following the order of pull apart>skin crack>twist>pull out. There was no pull out damage in the sliding cracks, and damage followed the order of skin crack>twist>pull apart. Root damage in the subsidence cracks was most serious. ③ The number of damaged root systems decreased gradually as root diameter increased. Roots with diameters less than 2 mm were almost pulled apart, and roots with diameters less than 5 mm were mainly pulled apart. Roots with diameters bigger than 5 mm were dominated by skin cracks, and then were pulled apart. The thicker the root was, the less the pull apart occurred, and the more skin cracks were observed. When roots were bigger than 11 mm in diameter, the number of skin cracks increased rapidly. ④ The main factors causing root damage can be ranked from large to small as crack width, dislocating difference, and distance from root to crack. The wider the crack, the greater the dislocation difference was, and the more serious was the P. simonii root system damage. Smaller root crack distance resulted in greater amounts of root damage. When the root crack distance was less than 1 m, the root damage was most serious. [Conclusion] The degree of root damage under different types of soil cracks differed. Different treatment measures should be formulated for vegetation restoration suitable to different fracture types in coal mining subsidence areas.

Abstract:[Objective] The soil stability, soil and water conservation functions, and anti-scourability of different vegetation types were assessed in order to provide a scientific basis for species selection and function improvement of the Hongze Lake embankment shelterbelt. [Methods] Root biomass, soil organic matter, soil bulk density, porosity, water-stable aggregates, anti-scouribility, and soil erosion resistance of Populus simonii var. przewalskii, Celtis sinensis, P. simonii var. przewalskii×Metasequoia glyptostroboides, Cynodon dactylon, and M. glyptostroboides were analyzed using the weight method, the potassium dichromate heating oxidation method, the ring-knife method, the wet sieving method, the Sobolev anti-rush experiment, and the hydrostatic disintegrating method, respectively. [Results] Among all of the vegetation types, P. simonii var. przewalskii was greatest in diameter at breast height, height, crown width, and canopy density. Root biomass of the five vegetation types decreased with the increasing soil depth from 0 to 45 cm, and C. sinensis had the highest values in each soil layer among the tested plants, followed by P. simonii var. przewalskii and C. dactylon (except for the third soil layer). In most cases, Populus simonii var. przewalskii and C. sinensis significantly increased soil organic matter, soil bulk density, and total porosity. Additionally, the amounts of microaggregates (＜0.25 mm) under P. simonii var. przewalskii and the amounts of macroaggregates (>0.25 mm) under C. sinensis were much greater than those under other vegetation types in the 0—15 and 15—30 cm layers. The protecting effects on the embankment varied with the vegetation type. The soil under P. simonii var. przewalskii and C. dactylon was highest in soil anti-scouribility and erosion resistance, followed by those under Populus spp. and P. simonii var. przewalskii×M. glyptostroboides. The protecting effects under M. glyptostroboides were the lowest. Significantly positive relationships were observed for the effects on protecting the embankment from erosion indicated by soil anti-scouribility and erosion resistance with root biomass, soil organic matter, soil bulk density, and total porosity. [Conclusion] Therefore, soils under P. simonii var. przewalskii, C. sinensis, and C. dactylon had high stability, and thus, these vegetation types have great potential for protecting embankments from erosion. For the present shelterbelt mainly planted to P. simonii var. przewalskii, reasonable forest improvement and plant community configuration could be used as effective measures to improve the function of the Hongze Lake embankment shelterbelt.

Abstract:[Objective] The effects of freezing and thawing on soil erosion resistance of three land use types (sloping farmland, grassland, and shrub land) were studied in order to provide a theoretical basis for vegetation restoration and construction in the seasonal freezing and thawing area of the Loess Plateau. [Methods] Based on a series of natural freezing and thawing cycles, field monitoring, and undisturbed soil scouring tests, the effects of freezing and thawing on soil erosion resistance of the three aforementioned land use types were determined. [Results] ① Compared with sloping farmland, the degree of freezing for grassland and shrub land was lower, and with shrub land having the lowest freezing degree and the best frost resistance. ② Freezing and thawing aggravates soil loss in varying degrees and reduces soil erosion resistance. The anti-scourability coefficient of grassland and shrub land was significantly higher than that of sloping farmland, indicating that vegetation coverage can effectively improve frost resistance and anti-scourability of soil under freeze-thaw conditions. ③ The total sediment loss before and after freezing and thawing for grassland and shrub land increased by 31% and 16.5%, respectively, and the anti-scourability coefficient decreased by 23% and 14%. The increase of sediment loss in grassland during freezing and thawing was higher, and the anti-scourability coefficient decreased the most. [Conclusion] Due to seasonal freezing and thawing of grassland and shrub land, the degree of grassland freezing is more severe, and the erosion resistance of grassland soil is worse than that of shrub land soil. Grassland may have a higher risk of soil erosion due to the seasonal freezing and thawing process.

Abstract:[Objective] The effects of different fertilization treatments on soil hydraulic properties and their changes with depth were analyzed in order to provide a theoretical basis for formulating scientific fertilization programs, and to promote the sustainable development of agriculture. [Methods] Based on a 36-year long-term fertilization experiment in the Loess Plateau, four fertilization treatments were selected, including no fertilization (CK), fertilization with nitrogen and phosphorus (NP), fertilization with manure (M), and fertilization with nitrogen, phosphorus, and manure (NPM). Changes in soil properties were evaluated by measuring soil organic matter content, bulk density, porosity, and moisture parameters. [Results] ① NPM and M significantly increased organic matter content in the 0—20 cm soil layer compared with CK and NP, but there were no significant differences in the 30—40 cm soil layer; ② NP significantly reduced soil porosity of the 0—20 cm soil layer compared with CK, M, and NPM; ③ All fertilization treatments significantly increased field capacity and available water holding in the 0—20 cm soil layer compared with CK, and NPM had the greatest effect; ④ NPM significantly increased the saturated hydraulic conductivity of the 0—10, 10—20, and 20—30 cm soil layers. [Conclusion] The combined application of organic and chemical fertilizers can improve physical properties and increase available water holding capacity of the surface soil, while the application of chemical fertilizers will cause the surface soil to compact, resulting in unfavorable conditions for crop growth.

Abstract:[Objective] The characteristics of the hardness and thickness of a sandy soil crust in Yellow River floodplain and their influencing factors were studied in order to provide scientific references for the protection of soil resources. [Methods] Four different underlying surface treatments, i.e., cultivated land with two crops in a year (T₁), cultivated land with one crop in a year (T₂), bare land (T₃), and spontaneous recovery land (T₄), were designed to conduct the experiment. The hardness and thickness of the soil crust, meteorological factors, and vegetation factors were observed and recorded, and the relationships among the hardness and thickness of soil crust and influencing factors were explored by statistical tests and correlation analysis. [Results] The average value of soil crust hardness of T₃ was the highest among the four treatments, followed by T₄, T₁, and T₂. Significant correlations between soil crust hardness and soil temperature, vegetation height, vegetation coverage, and near-ground surface wind speed were observed under T₁ and T₂ (p＜0.05). The soil crust thickness of T₁ was the highest, followed by T₃, T₂, T₄. There was a significant positive correlation between soil crust thickness and near-surface wind speed for T₁ and T₂ (p＜0.05), and soil crust thickness was significantly correlated with cumulative water replenishment and soil temperature (p＜0.05) under T₃ and T₄. For the treatments located in cultivated land, the contribution of vegetation to crust hardness and thickness was the highest, reaching 37%. For the treatments located in uncultivated land, the contribution of near-ground surface wind speed and cumulative water replenishment to crust thickness and hardness was above 51% and 45%, respectively. [Conclusion] Artificial cultivation was not conducive to the formation of aeolian sandy soil crust and the maintenance of hardness in the Yellow River floodplain. Crust thickness and hardness were significantly affected by vegetation, temperature, and wind speed near the ground surface. Aeolian sandy soil crust thickness, hardness change trend, and surface water content showed the characteristics of synchronous change, while the response of soil crust hardness exhibited some hysteresis. The main driving factors of soil crust hardness and thickness of aeolian sandy soil with cultivation measures were different from those without cultivation measures.

Abstract:[Objective] Vegetation interception and soil water-holding capacity were analyzed in order to provied a scientific basis for systematically evaluating the soil and water conservation functions of semi-arid shrub-encroached grasslands. [Methods] Characteristics of vegetation interception (including canopy and litter layer), soil water-holding capacity of the primary grassland and shrub-encroached grassland (including grass patch, sub-shrub patch, and shrub patch) were measured on the Loess Plateau. [Results] ① The capacity of canopy interception in shrub patches was increased by 0.3 mm with the increasing of aboveground biomass, while the capacity of litter interception was decreased by 0.5 mm through reduction in the litter biomass. ② During shrub encroachment, only shrub patches significantly improved soil water-holding capacity. Moreover, there were significant differences in soil water-holding capacity between sub-shrub and shrub patches. Compared with sub-shrub patches, the capacity of shrub patches was enhanced by 12.8 mm, and the increase mainly occurred in the surface soil (0—20 cm). [Conclusion] Shrub encroachment did not reduce the potential soil water-holding capacity. However, if shrubs continue to expand in area coverage, the interception ability of grassland ecosystem by canopy and litter layer might be weaken.

Abstract:[Objective] The temporal and spatial distribution characteristics of deep soil water leakage and infiltration under saturated conditions in Otindag sandy land were analyzed in order to provide a theoretical basis for the evaluation of the sandy land water cycle, water balance, and water resources. [Methods] Deep soil leakage in Otindag sandy land semi-fixed caragana microphylla (vegetation coverage 20%~30%) and fixed deep seep of Caragana microphylla (vegetation coverage 40%~50%) below 200 cm was continuously monitored by a recording apparatus. [Results] In the semi-arid, low-rainfall area of Otindag sandy land, the characteristics of deep soil water leakage in different types of sandy land were consistent with the characteristics of rainfall, but the spatiotemporal distribution of leakage was different. The leakage was largest and the infiltration rate was fastest under saturated conditions, while the duration was longest in the mobile sandy land. There was a significant correlation between deep leakage and monthly rainfall in the mobile sandy land (p＜0.05), and the fixed sand had no correlation in time and there was no obvious concentrated recharge period of seepage. [Conclusion] The vegetation in the semi-fixed and fixed sandy land affected deep leakage, and the higher the vegetation coverage, the greater the impact. The mobile sandy land can store more water and replenish underground water.

Abstract:[Objective] The migration characteristics of heavy metals in the surface soil of sloping farmland during water erosion process were analyzed in order to provide guidance for soil quality protection and for defense strategies against heavy metal migration and diffusion in karst soil erosion areas in China. [Methods] A simulated rain experiment was used to study loss characteristics of heavy metals (Cu, Ni, Cd, and Cr) from runoff and erosion in farmland under different slope conditions (10°, 15°, 20°, and 25°) and rainfall intensities (50, 70, 90, and 120 mm/h). [Results] ① Initial runoff and sediment yield increased with increasing of rainfall intensity and slope, then tended to gradually become stable. The critical slope for sediment yield was 20° under different rainfall intensities and slopes; ② Heavy metals mainly existed in granular form in the erosion process of topsoil, and migration amount was proportional to rainfall intensity. Heavy metal loss in granular form first reached a peak value under a rainfall intensity of 120 mm/h and a slope of 20°. Dissolved heavy metals varied with rainfall intensity, except for dissolved Ni that reached a maximum variation range of 0.0044 mg/L at 50 mm/h. Cu, Cd, and Cr all reached a maximum variation range of loss at 70 mm/h, and the maximum variation range of Cr was 0.0098 mg/L. The loss of dissolved heavy metals had no obvious relationship with slope change. ③ The heavy metal particle loss was related to sediment yield, and the high coefficient of determination for Cr (R²=0.99) indicated that sediment yield could well predict Cr particle loss. [Conclusion] 20° is the critical slope for sediment yield, and that migration of heavy metals is mainly in granular form. The fitting effect between sediment yield and heavy metal elements (Cu, Ni, CD, and Cr) is good, indicating that there is a strong correlation between heavy metal elements (Cu, Ni, CD, and Cr) and sediment yield.

Abstract:[Objective] The influence of culture conditions (carbon source, nitrogen source, and pH value) on the growth of wood-rot fungi was analyzed in order to provide a theoretical basis for prolonging the service period of Salix psammophila sand barriers. [Methods] Trichoderma citrinovicide, Xylogone sphaerospora, Trichoderma harzianum, Trichoderma koningiopsis, and Aspergillus niger in sand-buried sections of S. psammophila were the five fungi species used as research objects. The growth rate and biomass of mycelium under different culture conditions (solid and liquid) were investigated to determine the optimal growth conditions for each fungi species. [Results] ① Under solid culture conditions, T. citrinoviride, X. sphaerospora, T. harzianum, and A. niger grew fastest when glucose was used as the carbon source, and their growth rates were 12.97, 8.56, 13.25, and 5.22 mm/d, respectively; The best nitrogen source for T. citrinoviride was ammonium sulfate, and the growth rate was 13.06 mm/d. The best nitrogen source for X. sphaerospora, T. harzianum, and T. koningiopsis was peptone, and their growth rates were 9.44, 13.17, and 8.78 mm/d, respectively; The optimum pH value for the five species of wood-rot fungi was between 5 and 7. ② Under liquid culture conditions, glucose was the best carbon source for the five species of wood-rot fungi, and the biomass values per 100 ml of culture medium reached 446.67, 454.67, 728.67, 687.67, and 713.00 mg, respectively. The most suitable nitrogen source for T. citrinoviride, X. sphaerospora, T. harzianum, and T. koningiopsis was peptone. The biomass of A. niger was 610.00 mg when ammonium chloride was used as the nitrogen source. The biomass of the five species of wood-rot fungi was large in the pH value range from 5 to 7. [Conclusion] Under solid and liquid conditions, the most suitable carbon source for T. citrinoviride, X. sphaerospora, and T. harzianum is glucose, the most suitable nitrogen source is peptone, and the pH value is between 5 and 6. Under the liquid culture condition, the most suitable carbon source for T. koningiopsis is glucose, the most suitable nitrogen source is peptone, and the pH value is between 5 and 6. Under the liquid culture condition, the most suitable carbon source for A. niger is glucose, the most suitable nitrogen source is ammonium chloride, and the pH value is between 5 and 6.

Abstract:[Objective] The irrigation system suitable for the cultivation of Lycium barbarum in Northern Xinjiang Uygur Autonomous Region was studied to provide a scientific basis for the future irrigation of L. barbarum in this area. [Methods] The plant height, stem thickness, crown width, water consumption, and yield of L. barbarum were monitored, and the effects of different irrigation amounts and irrigation frequencies on the growth and yield of drip-irrigated L. barbarum were analyzed. [Results] ① Plant height of drip-irrigated L. barbarum increased with increasing irrigation amount annually. ② Annual net growth of drip-irrigated L. barbarum stem thickness increased with increasing irrigation amount. When the irrigation amount increased to a certain value, the increase in stem thickness decreased. ③ The water consumption intensity of drip-irrigated L. barbarum in each growth period followed the order of fruiting stage>bloom stage>spring shoot growth stage>autumn shoot growth stage> leaf opening stage. The relationship between water consumption and yield and between water consumption and water use efficiency (WUE) of drip-irrigated L. barbarum followed a quadratic parabolic relationship. ④ When water consumption increased from 583 mm to 676 mm, yield of drip-irrigated L. barbarum increased from 12 703.5 kg/hm² to 14 200.5 kg/hm². At the same time, WUE of drip-irrigated L. barbarum dereased from 1.45 kg/mm to 1.46 kg/mm, it did not decrease significantly. [Conclusion] In order to save water and produce high yields, we recommend drip-irrigated L. barbarum grown in the study area be provided with 5 700 m³/hm² of irrigation water over the entire growing season, applied as 10 irrigations of 570 mm during each application. The 10 irrigations should be applied as one irrigation during the leaf opening stage, two irrigations during the spring shoot growth stage, one irrigation during the bloom stage, four irrigations during the fruiting stage, and two irrigations during the autumn shoot growth stage.

Abstract:[Objective] The long-term changes of plant community structure (Carex muliensis, Carex meyeriana, Calthascaposa, Kobresia tibetica) and soil microbial community diversity in the Zogue Plateau wetland, and their evolutionary relationships were investigated in order to provide reference for vegetation restoration and ecological environment protection in this area. [Methods] The dynamic characteristics of aboveground and underground indexes of different plant communities were observed in four consecutive years (2016—2019). [Results] ① For plant α diversity, the Shannon-Wiener diversity index, Margalef richness index, and Pielou evenness index showed a consistent change trend that followed the order of Carex meyeriana>Carex muliensis>Kobresia tibetica>Caltha scaposa. However, the Simpson dominance index showed the opposite change trend. For plant β diversity, the Cody index also showed a consistent change trend that followed the order of C. meyeriana>C. muliensis>K. tibetica>C. scaposa, while the Sorenson index changed in the opposite trend. ② The contents of soil organic carbon, total nitrogen, total phosphorus, and total potassium showed a consistent change trend that followed the order of C. meyeriana>C. muliensis>K. tibetica>C. scaposa, and gradually increased with the increasing of years. Soil microorganisms were dominated by bacteria in the Zogue Plateau wetland, accounting for about 70% of the total microbial population, followed by Actinomycetes and fungi. The numbers of bacteria, fungi, and Actinomycetes followed the order of Carex meyeriana>C. muliensis>K. tibetica>C. scaposa, and numbers gradually increased with the increasing of years. ③ Soil microbial biomass carbon, nitrogen, and phosphorus followed the order of C. meyeriana>C. muliensis>K. tibetica>C. scaposa, and values gradually increased with the increasing of years. However, no significant differences were found in microbial biomass phosphorus among different years (p>0.05). ④ Soil microbial evenness index (E), species richness index (H), and carbon source using basic richness index (S) followed the order of C. meyeriana>C. muliensis>K. tibetica>C. scaposa, and values gradually increased with the increasing of years, while the dominance index (D_s) showed the opposite change tend, with no significant difference among different years (p> 0.05). ⑤ Soil microbial community diversity and plant diversity were significantly correlated with each other (p＜0.05). [Conclusion] There is a strong coupling between aboveground vegetation diversity and microbial community diversity in the Zogue Plateau wetland, and this coupling do not change with year, thereby indicating a unified response to changing environments.

Abstract:[Objective] The hydrological effects of the litter layer under the main artificial forests in Qingshuihe County, Inner Mongolia Autonomous Region were studied in order to provide a reference for the construction of water conservation forests and for the prevention and control of soil erosion in the loess hilly area in the future. [Methods] The study location consisted of five main artificial forests at the public welfare forest area of Qingshuihe County, Inner Mongolia. The experimental methods were mainly field survey sampling and the indoor immersion method, with SPSS 22.0 software used to correlate the obtained data, test the data for significant differences due to forest type, and conduct linear regression analysis. [Results] ① The total volume of the litter layer of the five forest types ranged from 8.49 t/ha to 25.52 t/ha, and the overall trend was basically consistent with the thickness performance. The specific performance followed the order of coniferous and broad-leaved mixed forest>Pinus tabuliformis forest>Larix gmelinii forest>Armeniaca sibirica forest>arbor-shrub mixed forest; ② The total maximum water holding capacity of the five forest types ranged from 10.10 t/ha to 38.82 t/ha, and the specific performance followed the order of coniferous and broad-leaved mixed forest>A. sibirica forest>P. tabuliformis forest>L. gmelinii forest>arbor-shrub mixed forest; ③ The total effective storage capacity of the five forest types varied from 8.58 t/ha to 36.97 t/ha. The overall trend was consistent with the maximum storage capacity. The specific performance followed the order of mixed coniferous and broadleaf trees forest>A. sibirica forest>P. tabuliformis forest>L. gmelinii forest>arbor and shrub mixed forest; ④ The dynamic water holding process of the five forest types of litter layer could be roughly divided into three stages: the rapid water absorption stage (0.5—2 h); the slow water absorption stage (2—6 h); and the stable (saturated) water absorption stage (6—24 h). [Conclusion] The water-holding capacity of the litter layer of broad-leaved tree species is stronger than that of coniferous forest species. Among the five forest types, the litter layer water conservation capacity is the best in the coniferous and broad-leaved mixed forest.

Abstract:[Objetcive] An evaluation model for the soil and water conservation function of vegetation at community scale was explored in order to provide a reference for soil and water conservation and ecological construction of vegetation in the Dabie Mountains. [Methods] Based on existing research, through the bibliometric method and expert experience method, the primary selection index for soil and water conservation function of vegetation was established, including 30 items characterizing vegetation type, vegetation structure, terrain, and so on. The measured values of the indicators were obtained through field investigation, and the indicators were analyzed and measured by the random forest method and the decision tree method. A multiple stepwise regression relationship between the measured values of the indicators and soil erosion was established to construct an evaluation model for soil and water conservation function of vegetation at community scale. [Results] A global regression model based on a random forest (R²=0.71) was better than the local regression model based on a decision tree (R²=0.69). Based on the global regression model of random forest, an evaluation model which included slope, forest age, shrub coverage, grass coverage, and litter thickness was constructed. The soil conservation functions of vegetation in the study area followed the order of protection forest (0.705)> timber forest> (0.529) economic forest (0.513)> shrub-grass (0.457). [Conclusion] In the evaluation of vegetation soil and water conservation function at community scale, the model constructed by random forest method has strong applicability, operability and is easy to grasp.

Abstract:[Objective] The suitable measures for controlling serious soil erosion in sloping mango (Mangifera indica) orchards in Panzhihua City, Sichuan Province were determined. [Methods] The effects of two engineering practices (D₁ and D₂ treatment) and one biological practice (A) were measured on surface runoff, sediment, nutrient content in runoff, and soil properties. [Results] Total runoff volume for the Medicago sativa planting treatment (A) in the two-year trial period was 22 515 ml. Total runoff volume in the A and D₂ treatments decreased by 45% and 16%, respectively, compared with the check treatment (CK). In addition, eight of the 17 runoff volumes measured in the A treatment were significantly lower than in CK. The total sediment of the A treatment in the two-year trial period was 1.65 kg, 28.3% lower than that of CK. There were no significant differences in nutrient contents in runoff or in soil properties due to the treatments. [Conclusion] In this arid valley area, the biological treatment of planting M. sativa between rows in sloping mango orchards can reduce surface runoff and sediment yield more effectively than the two engineering measures tested in this study, and achieve better soil erosion control.

Abstract:[Objective] The ecological security of oasis land in Yili River valley was studied from the perspective of ecological civilization, and the main factors influencing the ecological security of land in this area were analyzed, in order to promote the construction of ecological civilization. [Methods] The PSR-entropy weight TOPSIS model was used to evaluate the ecological safety of oasis land in the Yili River valley from 2000 to 2018. The study results were used to establish a barrier factor diagnosis model to determine the ecological safety of oasis land in Yili River valley. [Results] ① Overall, the ecological safety of oasis land in the Yili River valley showed a slow upward trend with a slight increase. The ecological security level of land was grade Ⅲ, and the ecological security of land was in a general state, during which there have been fluctuations and changes, with a small decline in some years. ② The land ecological security situation in the standard layer changed significantly. In general, the situation concerning the ecological safety of soil in the pressure layer decreased, and the land ecological security at state and response levels showed an overall upward trend. ③ The barrier degree of land ecological pressure level showed an increasing trend, and resistance to the improvement of land ecological security level gradually increased. The main barrier factors included per capita forest and grass area, population density, per capita cultivated land area, application amounts of agricultural chemical fertilizer, and other indicators. [Conclusion] Overall, ecological security of oasis land in the Yili River valley showed a good trend, but the main obstacle factors have had a bad impact on improvement speed. Corresponding countermeasures should be taken to promote sustainable utilization of oasis land in the Yili River basin.

Abstract:[Objective] Urban land carrying capacity in Liaoning Province was quantitatively analyzed and evaluated, and its obstacle factors were diagnosed in order to provide suggestions for the rational development of land use in Liaoning Province, and to produce new ideas for regional land carrying capacity evaluation. [Methods] Land use classification was carried out based on 2018 Landsat 8 OLI remote sensing images from 14 prefecture-level cities in Liaoning Province to obtain the land use area of various types. These data were combined with social and economic data to construct a land carrying evaluation index system. The AHP (analytic hierarchy process)-entropy weight TOPSIS (technique for order preference by similarity to an ideal solution) model was used to evaluate the carrying capacity of land resources. The obstacle degree model was used to evaluate the obstacle factors. [Results] The cities in Liaoning Province showed different bearing capacity states. The land carrying capacities of Panjin, Dalian, and Shenyang City were relatively high, but the social subsystem was the main obstacle factor restricting land carrying capacity. The carrying capacities of Anshan and Yingkou City were relatively low. The economic subsystem of Anshan City was the main factor limiting increases in carrying capacity. [Conclusion] The urban land carrying capacity of Liaoning Province is still far below its ideal state, and the coordinated development of the three subsystems of society, economy, and resources should be promoted to improve the land carrying capacity.

Abstract:[Objective] The matching coordination level and regional differences of agricultural water and land resources at the city scale in Heilongjiang Province was analyzed in order to provide scientific guidance for the optimal allocation of regional agricultural water and land resources and the improvement of agricultural production pattern. [Methods] Using agricultural water and land resource data from 13 cities of Heilongjiang Province from 2009 to 2019, the Gini coefficient and the matching coefficient method were used to analyze the spatial distribution characteristics of agricultural water and land resources and their matching temporal and spatial evolution patterns. According to the average value of agricultural water and land resources matching coefficient for many years, three control areas were determined: water conservation and storage, water and land optimization control, and water-saving irrigation. [Results] ① From 2009 to 2019, the Gini coefficient of agricultural water and land resources matching in Heilongjiang decreased from 0.488 6 to 0.375 1, showing a good trend with small fluctuations. ② The matching coefficient of agricultural water and soil resources showed a pattern of decrease-increase-decrease-increase, and a fluctuation range of 0.22—0.69. ③ The distribution of agricultural water and land resources in each city was not balanced, showing the characteristics of “more water and less land” in the northwest and central regions and “more land and less water” in the eastern and western regions. ④ The overall coordination level of agricultural water and land resources was improved, and regional differences were significant. The matching coordination level between the eastern and western regions was lower, the central region was relatively reasonable, and the northwest region was higher. [Conclusion] Because of climate change and artificial regulation, the coordination level of agricultural water and land resources in the province is still in a relatively unbalanced state, but there is still an opportunity for adjustment by designating different types of regulation areas, and by formulating targeted regulation measures.

Abstract:[Objective] The age, occurrence, and development of alpine meadow soil in the Three River headwater region were analyzed to provide guidance for maintaining soil and ecological security in the region. [Methods] The formation and development time of the soil profiles from Xiaqiong, Xiewu, Tongledong, and Doudicun in the Three River headwater region were determined using the optically stimulated luminescence (OSL) dating method of coarse-grained quartz and potassium feldspar (K-feldspar). [Results] The development time of alpine meadow soil in this area was Early Holocene (13—8 ka) and Late Holocene (3—0 ka). The four soil profiles were developed on slope and eolian parent material, respectively. The elemental geochemical characteristics of different soil layers were consistent with the typical aeolian loess in this area. [Conclusion] The development of alpine meadow soil was concentrated in the Holocene period. The parent material of soil was mainly the mixed parent material of slope deposits and aeolian deposits. The input of aeolian dust is of great significance to soil formation in the Three River headwater region, and is also the original material source of slope deposits in this area. The release of aeolian dust during the relatively arid period of Holocene is of great significance to the formation of meadow soil.

Abstract:[Objective] The safety level of sudden water pollution in the Yellow River basin was scientifically evaluated in order to provide a reference for improving the emergency response capacity to a sudden water pollution incident in the Yellow River. [Methods] Based on the principles of science, integrity, and data availability, 16 indicators related to the Lanzhou section of the Yellow River were selected through the PSR model to construct an evaluation index system. Based on the data of the Lanzhou section of the Yellow River from 2014 to 2019, the index weight was determined by GRA-PCA combination, and the matter-element extension model was used to obtain the safety evaluation level of sudden water pollution. [Results] The safety level of sudden water pollution in the Lanzhou section of the Yellow River was level Ⅱ (major hazard) in 2014; level Ⅰ (particularly major hazard) in 2016; level Ⅲ (greater hazard) in 2015, 2017—2019. The overall trend of decreasing from level Ⅱ (major hazard) to level Ⅲ (larger hazard) was basically consistent with the effect observed by the government of Gansu Province on the Yellow River in recent years. [Conclusion] The GRA-PCA matter-element extension evaluation model method was reasonable and operable. It can accurately evaluate the safety level of sudden water pollution in the Lanzhou section of the Yellow River, and also provide a reference for the evaluation of sudden water pollution safety levels in other river basins.

Abstract:[Objective] The water quality and health hazards regarding heavy metals in drinking water sources in rich ore karst areas were studied in order to improve environmental control measures of water sources, thereby providing a theoretical basis for local drinking water health risk management and a reference for controlling and preventing accumulations of heavy metals in water. [Methods] Drinking water sources in Bijiang District, Tongren City, Guizhou Province were taken as an example. Conventional water quality indicators and the content of heavy metals (Fe, Mn, Cu, Zn, As, and Pb) were monitored from January 2018 to June 2020. In addition, a water quality fuzzy evaluation was carried out by using the relative membership degree and grade eigenvalue, and the single entropy weight method with the clustering weight method. The content characteristics of heavy metals and health risks in wet and dry seasons were evaluated by using the health risk assessment model recommended by the U.S. EPA. [Results] Water quality of drinking water source areas had reached class Ⅲ of improved fuzzy synthetic evaluation. The main excess factors were total nitrogen and total coliforms. The maximum values of Fe and Pb in the surface water sources had exceeded the class Ⅲ water standards. Fe, Zn, and Pb mainly came from mining and industry, Mn and As mainly came from agriculture, and Cu mainly came from agriculture and traffic pollution. [Conclusion] The water quality evaluation results based on the combined weight and optimization of fuzzy synthetic evaluation were more credible and reasonable than the conventional model with a single weight. The carcinogenic heavy metal As was the main element causing health risks. Children are more susceptible to heavy metal hazards than adults. It is necessary to strengthen control and governance of health risks from heavy metals.

Abstract:[Objective] The rainfall intensity-duration threshold of rainfall-induced landslides in Huangshan City, Anhui Province was studied in order to provide technical support for detailed landslide early warning in all districts and counties of Huangshan City. [Methods] Rainfall duration of induced landslides was determined by comparing the effective rainfall before landslides at historical landslide points, and by using corresponding rainfall data in Huangshan City from 2004 to 2019. The rainfall intensity-duration (I-D) threshold curve for each district and county was established based on the empirical threshold Caine model. Considering the applicability of I-D curve in disaster early warning, and taking the landslide point in Shexian County as an example, the rainfall events that induced landslides in Shexian County were divided into the small and moderate rain group, the heavy rain group, and the heavy rain or above group according to the rain intensity standard of the meteorological forecast. The I-D threshold of combined rainfall in Shexian County was established according to the grouping classification of rain intensity. [Results] Most of the rainfall-induced landslides in Huangshan City were induced by long and medium duration rainfall. The complex I-D threshold could better reflect the inducing effect of various rainfall conditions on landslides, and this threshold could be directly used for early warning of landslides using precipitation forecasts. [Conclusion] I-D threshold has strong regional applicability, and the landslide rainfall threshold grouped by rainfall intensity according to precipitation forecasts is suitable for the construction of a landslide early warning system in this region.

Abstract:[Objective] Differences in plant community structure and diversity under different control models were compared in order to provide a scientific basis for soil erosion control and vegetation restoration measures. [Methods] The Tangbei small watershed in Xingguo County, Jiangxi Province was selected as the research area, and orchard development (model A) and ecological restoration (model B) were selected as the main soil and water loss control models. Selected secondary forests and no artificial governance forest land (control, CK) were used as control plots, and the community sampling method was used to investigate and analyze species composition, community structure, and plant diversity of the plant communities at each woodland location. [Results] ① The dominant species in model A, model B, secondary forest, and CK arbor-irrigation were Citrus sinensis, Pinus massoniana, Cyclobalanopsis glauca, and P. massoniana, respectively. The dominant species in the herbaceous layer were Digitaria sanguinalis in model A, and in the other three groups the dominant species were Dicranopteris pedata. Compared with the CK, the community structure of model A had changed, and the community structure of model B had not changed, still being dominated by positive pioneer plants such as P. massoniana and D. pedata. ② Species richness, Simpson diversity index, Shannon-Wiener index, and Evenness index of the secondary forest were the highest. Compared with the CK, models A and B had improved species richness and plant diversity, but both of these factors were lower than those of the secondary forest. The level of diversity was similar. ③ The overall performance of the plant communities in the four woodlands was very different, and there was only one plant species in common. Compared with model A, the community composition of model B, secondary forest, and CK were more similar. [Conclusion] Controlling soil erosion is beneficial to the restoration of vegetation. The orchard development model not only meets the requirements of soil erosion control and vegetation recovery, but also has certain economic benefits. It is a model worthy popularizing for soil and water loss control.

Abstract:[Objective] The response of surface microtopography characteristic index, and hydrological connectivity (IC) index to different resolutions of digital elevation model (DEM) was studied, and the best DEM resolution of IC was determined in a small watershed of an intensive sugarcane production area in order to provide a theoretical basis and reference for subsequent research on hydrological connectivity, agricultural non-point source pollution, and soil erosion. [Methods] The effects of different resolutions of DEM (0.05, 0.1, 0.2, 0.5, 1, 2, and 5 m) on surface microtopography characteristics 〔slope (S), slope length (L), surface roughness (S_R), standard deviation of elevation (SDE), and IC〕 were studied in an intensive sugarcane planting area in Southern China using ArcGIS and high-resolution images from an unmanned aerial vehicle (UAV). [Results] ① A decrease in pixel size (5—0.05 m) increased mean S and S_R by 29.13% and 1.62%, respectively, but decreased mean SDE and L by 98.72% and 72.09%, respectively. The decreased resolution increased the mean S of newly planted sugarcane, perennial sugarcane, newly planted sugarcane+watermelon, and Eucalyptus, but decreased their L. In contrast, their S_R first decreased at 5—1 m and then increased at 1—0.05 m, while SDE decreased generally. However, the S and S_R of the road decreased first at 5—1 m and then increased at 1—0.05 m, while L of the river increased first at 5—2 m, and thereafter decreased at 2—0.05 m. ② Mean IC increased first at 5—0.2 m, and then decreased at 0.2—0.05 m. The difference in mean IC of different land use types reached its maximum value (34.72%) at 0.5 m. At 0.1 m resolution, IC followed the order of river>newly planted sugarcane>newly planted sugarcane+watermelon>perennial sugarcane>road>Eucalyptus. The best DEM resolution for Eucalyptus, roads, and rivers was 0.5 m, while 0.1 m resolution was best suited for newly planted sugarcane, perennial sugarcane, and newly planted sugarcane+watermelon. ③ The best DEM resolution for a small watershed in an intensive sugarcane area was 0.1 m. [Conclusion] DEM resolution had a significant effect on IC and index of surface microtopography characteristics, with varied effects for different land use types. The optimal DEM resolution of 0.1 m was best suitable for the characterization of a small watershed in an intensive sugarcane area.

Abstract:[Objective] An ecological security pattern with urban characteristics was constructed in order to provide ideas for regional coordinated development of ecological environment protection and restoration of Ji’nan City, Shandong Province, and to provide references for constructing an urban characteristic ecological security pattern for a mountain-water-forest-farmland-lake-grass-spring system. [Methods] Habitat quality was evaluated for Ji’nan City based on the InVEST model, and the ecological sources were identified from the three perspectives of blue-green-spring. A resistance surface was subsequently constructed based on the natural geographical conditions and human disturbance. Finally, the ecological corridors were identified and the ecological security pattern was constructed using the minimum cumulative resistance model (MCR). [Results] The area of the ecological sources in Ji’nan City was 1 249.32 km², accounting for 12.20% of the total area. The ecological resistance surface presented the characteristics of “high in the middle, low in the north and south, and many clusters”. 119 ecological corridors with a total length of 1 395.37 km were identified, and formed a mountain-river corridor connecting Mount Taishan in the south and the Yellow River in the north. The area of the high, medium, and low ecological security buffer zones in Ji’nan City accounted for 40.41% of the total area, and an ecological security pattern of “one belt, three zones, two wings, nine points, and multiple corridors” was constructed. [Conclusion] The ecological source areas of Ji’nan City are mainly scattered in the southern mountainous areas. The crisscrossing rivers serve as natural corridors for communicating material and energy information.

Abstract:[Objective] An ecological safety network at Ningbo City, Zhejiang Province was constructed by identifying important ecological sources and potential ecological corridors in order to provide a reference for rationally guiding urban development and establishing key ecological protection areas. [Methods] The ecological source patches at Ningbo City were extracted by ecosystem service value clustering and the outlier analysis method. The multi-source ecological resistance surface was calculated by the minimum cumulative resistance (MCR). The gravity model was used to identify the importance of potential ecological corridors to establish ecological areas at Ningbo City, which formed an ecological safety network. [Results] ① In 2020, the ecosystem service value for Ningbo City was between 0 and 14 929.95 yuan/m², and the high-value clustering area accounted for 23.28% of the total area of Ningbo City. ② The ecological resistance values were between 1 and 3.775. The areas with higher resistance values were located in downtown Ningbo and Cixi City, and the lower values were located at Fenghua District, Ninghai County, and Xiangshan County. ③ Thirty-six common corridors, five generally important corridors, and four important corridors were identified through the gravity model, and 40 potential ecological nodes were generated. Seven ecological areas at Ningbo City were constructed to form an L-shaped ecological safety network pattern. [Conclusion] Ecological security is an important guarantee for guiding the rational development of cities. It promotes the harmonious coexistence of human and nature by protecting the integrity of regional ecological land, and by developing and maintaining potential ecological corridors.

Abstract:[Objective] The temporal and spatial evolution characteristics of net primary productivity (NPP) of the terrestrial vegetation ecosystem in the Yangtze River basin were studied to provide a reference for government departments to establish and adjust ecological function restoration projects. [Methods] The Zhou Guangsheng-Zhang Xinshi model (ZGS) and the Thornthwaite Memorial model were used to estimate NPP in the Yangtze River basin based on precipitation and temperature data from 2000 to 2019. Furthermore, Pearson correlation coefficient, linear regression analysis, and the Mann-Kendall trend test were applied to analyze the spatiotemporal variation of vegetation NPP of terrestrial ecosystems in the Yangtze River basin. [Results] ① The spatial and temporal variation of NPP derived from the above two models were basically homogeneous in the Yangtze River basin. Actual NPP and potential NPP were positively correlated (0.982). ② Both actual NPP and potential NPP in the Yangtze River basin increased over time at a rate of 6.85 g/(m²·yr) and 2.74 g/(m²·yr), respectively, from 2000 to 2019. ③ Actual NPP and potential NPP were higher in the southeast and lower in the northwest portions of the Yangtze River basin. The low values were mainly distributed in grassland ecosystems, and the high values were mostly distributed in forest ecosystems and farmland ecosystems. ④ The areas with increasing trends for actual NPP accounted for 80.64% of the total area, and 84.79% of the total area for potential NPP in the Yangtze River basin, mainly distributed in Yunnan, Qinghai, Tibet, the north of Sichuan, and most regions of Zhejiang and Shanghai. The areas with decreasing trends actual NPP accounted for 19.36% of the total area and 15.19% of the total area for potential NPP in the Yangtze River basin, mainly distributed in He’nan and Hubei Province. [Conclusion] The NPP of vegetation ecosystems in the Yangtze River basin has increased in the past 20 years, indicating that natural resource management and environmental protection policy implementation in the Yangtze River basin has produced remarkable positive effects on regional ecosystem protection and development.

Abstract:[Objective] The ecological environmental quality of a feldspathic sandstone area was investigated in order to provide a scientific basis for local ecological environmental management. [Methods] The spatial-temporal evolution of ecological environmental quality in a feldspathic sandstone area was analyzed using GIS and remote sensing technology, and a remote sensing ecological index (RSEI) model. [Results] ① RSEI extracted from the four-stage imaged data of a feldspathic sandstone area showed a trend of initially decreasing and then increasing, indicating that the ecological environmental quality was slowly improving. ② Greenness ecological index and humidity ecological index were positively related to ecological environmental quality in a feldspathic sandstone area, while dryness ecological index and heat ecological index were negatively related. Greenness ecological index had a higher contribution rate to ecological environmental quality improvement. ③ From 2001 to 2020, 36.79% of the total study area improved in ecological environmental quality. Over that same period, 15.68% of the total area deteriorated in ecological environmental quality, and the ecological degradation area was mostly classified as mild degradation. [Conclusion] The ecological environmental quality of a feldspathic sandstone area increased from 2001 to 2020. Ecological environmental quality was highly sensitive to human activities. The concept of ecological protection should be integrated into management practices to improve the ecological environment in order to achieve harmonious coexistence between man and nature.

Abstract:[Objective] The natural restoration of vegetation in the water level fluctuating zone (WLFZ) of the Xiaowan Reservoir on Lantsang River during a drought year were investigated to provide background information and a reference for studies related to the restoration and maintenance of vegetation in the area. [Methods] Based on a fixed sample site survey in a typical area of WLFZ in 2019, a drought year reset survey was conducted in July 2020 using a combination of unmaned aerial vehicle (UAV) remote sensing, GNSS positioning, and GIS spatial analysis to map the distribution of vegetation in WLFZ in the study area; quantitatively portray the species composition, area, cover, and distribution characteristics along a topographic gradient of vegetation in WLFZ in the drought year; and conduct a comparative analysis with the non-drought year of 2019. [Results] A total of 14 species of plants were counted, all of which were annual or perennial herbs. Cynodon dactylon, Polygonum plebeium, Epilobium hirsutum, and Ageratum conyzoides were the dominant species, accounting for 85.62%, 4.22%, 3.72%, and 3.12% of the total vegetation area, respectively. The proportions of C. dactylon in WLFZ were 50.21%, 9.94%, and 39.85% in sections H, M, and L (high, medium, and low), respectively; 95.53% of E. hirsutum was distributed in section H; 54.48% of A. conyzoides was distributed in section M; and 87.22% of P. plebeium was distributed in sections M and L. Most plants preferred to grow on gentle slopes below 25° in WLFZ, while E. hirsutum covered well on slopes less than 60°. Vegetation in WLFZ was influenced by topographic factors: distance to the nearest neighboring water body > elevation > slope > aspect. Drought resulted in an annual degradation of 59.75% of the vegetation, concentrated in the middle and lower parts of WLFZ, where a large amount of P. plebeium withered. [Conclusion] Vegetation recovery was more stable in the upper half of the zone than in the lower half, and the dominant species were significantly more stable than the non-dominant species, with C. dactylon and P. plebeium being more tolerant of flooding, while C. dactylon showed greater drought tolerance and recovery stability than P. plebeium. Drought stress and inundation stress had significant effects on the spatial distribution of vegetation in WLFZ. In drought years, drought stress had a slightly greater effect than inundation stress.

Abstract:[Objective] The decoupling mechanism between landuse carbon emission and economic growth was analyzed, and an empirical study was conducted in order to provide a reference for developing a green low-carbon circular economy in Guangdong Province during the 14th five-year plan period. [Methods] Using the carbon emission coefficient method, the landuse carbon emissions of Guangdong Province from 2003 to 2018 were calculated. With the organization for economic co-operation and development (OECD) decoupling model, the decoupling between landuse carbon emissions and economic growth was evaluated. The main factors affecting the decoupling were analyzed by the grey correlation model. [Results] ① The carbon emissions from land use in Guangdong Province increased from 239.256 9 tons in 2003 to 671.973 9 million tons in 2018, and the total carbon emissions increased by 432.716 9 million tons in 15 years, with an average annual growth rate of 7.2%. ② The decoupling index decreased from 0.948 3 in 2003 to 0.296 9 in 2008; increased from 0.941 8 to 1.123 6 and then decreased to 0.257 2 in 2009—2015; and decreased from 0.471 9 in 2016 to 0.416 8 in 2018. The decoupling relationship between landuse carbon emissions and economic growth in Guangdong Province had generally undergone the development process of “relative decoupling Ⅳ, relative decoupling Ⅱ, absolute linkage, relative decoupling Ⅰ, relative decoupling Ⅳ and relative decoupling Ⅱ ”, A stable decoupling state had not yet been formed. ③ From the perspective of carbon emissions, industrial structure and proportion of coal consumption were the main infuencing factors, with correlation values of 0.748 and 0.741. From the perspective of economic development, social fixed assets investment and scientific research funds were the main driving factors, with correlation values of 0.782 and 0.772. [Conclusion] The essence of decoupling development between landuse carbon emission and economic growth is the coordinated development of the regional economy, and resources and environment centered on carbon emission reduction. Landuse carbon emissions and economic development in Guangdong Province currently showed an increasing trend, although the growth rate of landuse carbon emissions is positive and lower than the growth rate of economic development. However, the growth rate of landuse carbon emissions is gradually slowing, and this development will be conducive to the absolute decoupling between land use carbon emissions and economic growth.

Abstract:[Objective] The resilience and main obstacle factors of the social-ecological system in Zhangjiajie City, a typical tourist city, in Hu’nan Province were analyzed to provide a theoretical basis for the sustainable development of Zhangjiajie City. [Methods] An evaluation system of the social-ecological system resilience of Zhangjiajie City was constructed based on three subsystems (social, economic, and ecological) and two aspects (vulnerability and response capacity). The characteristics of resilience changes and the main obstacle factors from 2010 to 2019 were analyzed using the set-pair analysis method and an obstacle degree model. [Results] ① The social-ecological system vulnerability index of Zhangjiajie City increased from 0.457 0 to 0.553 5, response capacity index increased from 0.229 5 to 0.769 4, and resilience index increased from 0.378 8 to 0.627 6. ② There were eight main obstacle factors affecting the resilience of the entire system, such as the proportion of employment in the tertiary industry. The average obstacle degree of the subsystems was greatest for the social subsystem, followed by the economic subsystem and then the ecological subsystem. [Conclusion] ① Although the resilience index of the social-ecological system of Zhangjiajie City was increasing, it currently remains in the middle resilience stage and needs further improvement. ② The obstacle degree of single factor and subsystems changes constantly, so it is necessary to monitor the trends of changes in order to adjust the countermeasures in a timely manner.

Abstract:[Objective] The spatial distribution of ecosystem services for Dongting Lake was studied to improve the ecosystem services in the study area and in the Yangtze River Basin, and provide a reference for soil conservation, land use, and ecological protection. [Methods] The tradeoff relationship between the quality of four ecosystem services and the four ecosystem service functions of water conservation, soil conservation, carbon storage, and habitat quality in 2005 and 2018 was evaluated for the Dongting Lake Ecological Economic Zone using the InVEST model. [Results] ① Land use conversion was mainly based on conversion between forest land and cultivated land, water area and cultivated land, and conversion of forest land and cultivated land into construction land. ② The water source conservation and soil conservation functions were significantly improved, and the carbon storage and habitat quality functions were slightly reduced. ③ The low-value areas of water conservation, carbon storage, habitat quality, and functional substance quality were located near the central lake area of the study area, while the high-value areas of soil conservation functional material quality were mainly located in the east, southwest, and northwest. [Conclusion] Land use and the quality of ecosystem services in the Dongting Lake ecological economic zone changed greatly during the study period as the area was affected by the objective needs of economic development and relevant ecological protection policies (such as returning farmland to lakes and returning farmland to forests). There is a tradeoff relationship between water conservation and habitat quality in the study area, a compatible relationship between water conservation and soil conservation, and a synergistic relationship among other ecosystem services. The InVEST model provides a more comprehensive assessment of ecosystem service functions.

Abstract:[Objective] The relationship between land use transformation and ecological security in Baotou City, Inner Mongolia Autonomous Region was analyzed from the perspectives of land use quantity transformation and social and economic comprehensive evaluation in order to provide a basis for building an ecological barrier area in Northern Xinjiang Uygur Autonomous Region. [Methods] Land use transfer of Baotou City during 2001—2020 was analyzed by using the information Atlas method of ArcGIS. The land ecological security, the dominant transfer index, and the invisible transfer index were calculated by using the comprehensive evaluation method. The coordinated development relationship was explored using the coupling coordination analysis model. The causal relationship was analyzed by using the econometric statistical method. [Results] ① The expansion of construction land was mainly based on the consumption of cultivated land during the study period, with a total of 489.91 km² of new construction land, 503.84 km² of new reduced cultivated land, and 84.43 km² of new grassland; ② The land ecological security in Baotou City had improved during the research period, and it was in the running stage and high-level coupling stage with land use transformation. The coupling degree between dominant transformation and ecological security was greater than the coupling degree between recessive transformation and ecological security; ③ The dominant transfer of land use had a negative impact on land ecological security, while the recessive transfer of land use had a positive impact on land ecological security. [Conclusion] The planners should not only pay attention to the quantity of land use transformation in Baotou City, but also pay more attention to the efficient use of the transformed land, improving the efficiency of land use, and ensuring the optimization of stock and the flow of land efficiency.

Abstract:[Objective] The spatio-temporal variation of ecological factors along the Yellow River in the Qingdao Water Diversion Project during 30 years of water diversion was quantified in order to provide a basis for the protection and management of the ecological environment. [Methods] Using remote sensing technology, the temporal and spatial variation of ecological factors (land use/cover, vegetation index and coverage, land surface temperature, soil moisture, and other factors) in the study area during 1990—2020 was analyzed to determine changes in the coastal ecological environment after the project operation. [Results] The areas classified as water, green land, and building land increased over time, while the area classified as unused land decreased significantly. Surface temperature fluctuated over the 30-year study period, while the temperature vegetation dryness index decreased from 0.758 to 0.433 and soil moisture increased significantly. These changes directly promoted high cover growth of vegetation. The mean value of the vegetation index increased by nearly 0.2. In addition, ecological factors were not independent of each other, and there was a certain degree of correlation. [Conclusion] The ecological environmental quality along the Water Diversion Project improved remarkably over 30 years, and urban and rural construction has rapidly developed during the project operation.

Abstract:[Objective] The temporal and spatial variation characteristics and influencing factors of water conservation in Liaoning Province were explored in order to provide a visual evaluation basis for the rational development and utilization of water resources and the restoration of water conservation function. [Methods] The spatial and temporal dynamics of water conservation in Liaoning Province from 2001 to 2020 were evaluated based on the water production module of the InVEST model. The main influencing factors were explored by using correlation analysis and Geodetector. [Results] During 2001—2020, the average annual water conservation in Liaoning Province fluctuated and increased, with an annual average value of 95.28 mm and a growth rate of 13.35 mm/(10 yr). The spatial distribution of water conservation decreased from east to west. Water conservation in Dandong, Fushun, and Benxi City was higher, while water conservation in Panjin, Jinzhou, Fuxin, and Huludao City was lower. [Conclusion] Water conservation was positively correlated with precipitation, surface water resources, mountain infiltration, and forest proportion, and negatively correlated with evapotranspiration, temperature, fragmentation degree, and construction land proportion. Climate factors and land use factors were the dominant factors affecting the spatial differentiation of water conservation in Liaoning Province. The explanatory power of a single factor was above 0.6, and the interaction of multiple factors was stronger than that of a single factor, among which the explanatory power of the interaction between precipitation, evapotranspiration, and each factor was 0.92.

Abstract:[Objective] The flood information recorded in floodplain sediments during the historical period was analyzed in order to reveal the extreme flood events and the regularity of flood occurrence, and to provide guidance for flood control and disaster reduction. [Methods] Particle size characteristics and flood events for the floodplain profile of Hengyang Reach of the Xiangjiang River in Hu’nan Province were studied based on particle size analysis of 91 samples from the flood plain combined with AMS ¹⁴C dating. [Results] ① The composition of floodplain sediments mainly included coarse silt, coarse sand, and fine sand. The grain size parameters showed that the profile flood sedimentary power was strong, the sorting coefficient was excellent, and the wide peak was in majority; ② The flood scale of the five flood stages of the Jixiang profile followed the order of stage B>stage D>stage A>stage C>stage E. In addition, between 34—40, 44—46 cm in stage B, and between 130 and 134 cm in stage D, the content of coarse sand increased abnormally, the content of coarse silt and fine silt was very small, and the median partilce size value was in the lowest range. Flood sedimentary power was extremely strong. The flood events were all in periods when Hengyang catastrophic flood events occurred; ③ The median particle size values were positively correlated with the average particle size values and the content of coarse silt + fine silt. There was a significant negative correlation between the content of coarse sand and average particle size values, the median particle size values, and the content of coarse silt + fine silt. [Conclusion] The flood scale of the Hengyang reach has, on the whole, shown an increasing trend since 6 390 B P Both sedimentary stage A and stage B are flood prone periods. The four indicators (content of coarse sand, average particle size values, median particle size values, and content of coarse silt + fine silt) could well identify flood events.

Abstract:[Objective] The changing trend of water-holding function in a subalpine area of Western Sichuan Province was analyzed in order to provide a scientific basis for defining the dynamic characteristics of water conservation in this area. [Methods] Taking the Zagunao River basin in the upper reaches of the Minjiang River as an example, the variation characteristics of water conservation capacity of the Zagunao River basin were studied based on precipitation, temperature, water, and sediment data collected at the outlet of the Zagunao River basin and by using the principle of water balance. [Results] ① Runoff was significantly reduced over time, with an average annual decrease of 2.83 mm (i.e., water-holding capacity increased by 28.3 t/ha annually), especially around year 2000 (when the ecological protection and ecological restoration project started) to 2020 when the average annual decrease was 3.12 mm (i.e., water-holding capacity increased by 31.2 t/ha annually); ② Sand content in the runoff also showed a significant decreasing trend, indicating that runoff in the area was decreasing while soil conservation capacity was increasing; ③ There was no significant fluctuation trend in precipitation over the study period, indicating that the observed runoff decrease was not caused by precipitation changes. [Conclusion] Ecological engineering, such as ecological protection and restoration, plays an obvious role in promoting water conservation.

Abstract:[Objective] The coupling and coordination relationship between urban resilience and land use efficiency in He’nan Province was studied to provide scientific support for increasing the regional security coefficient and realizing sustainable development. [Methods] A comprehensive evaluation index system based on urban resilience and land use efficiency was established, using the entropy method, the natural fracture point method, data envelopment analysis (CCR, BCC, super efficiency DEA model), and the coupling coordination degree model to measure urban resilience, land use efficiency, and the coupling coordination degree of these two quantities in 2019 in He’nan Province. The division of spatial types was also determined. [Results] ① The comprehensive resilience of 18 cities in Hen’an Province showed significant differences in both absolute values and spatial distribution. There was a negative correlation between economic resilience and ecological resilience; ② The overall level of urban land use in He’nan Province was at a good level, but there was a big gap between cities; ③ The coupling degree between urban resilience and urban land use efficiency in He’nan Province was relatively high on the whole, but the coupling coordination degree was lower than the coupling degree. Among them, 17 cities were in the stage of high-level coupling between urban resilience and urban land use efficiency, and only one city was in the low level coupling stage. Spatially, the coordinated cities were distributed in a “t” shape; ④ According to the coupling coordination degree and relative development degree, the 18 cities in He’nan Province could be divided into seven types: high coordination, basic imbalance, basic coordination—urban resilience lag, basic imbalance—land use efficiency lag, basic coordination—land use efficiency lag, basic imbanlance—urban resilience lag, serious imbalance—land use efficiency lag. [Conclusion] The urban resilience system is closely related to the land system. In the future, the construction of urban resilience and the improvement of land use efficiency should be taken as two starting points. Measures should be taken according to local conditions to promote the coordinated development of these two systems so as to achieve the goal of safe and sustainable urban development.

Abstract:[Objective] The temporal and spatial evolution of landscape ecological risk, driving forces, and their correlation with the spatial distribution of the COVID-19 epidemic were studied, in order to provide a theoretical reference for regional ecological environment protection, sustainable development, and epidemic control. [Methods] Landsat remote sensing images of Ruili City in Yunnan Province were used to extract landscape type distribution data in 2000, 2010, 2015, and 2021 by using methods such as landscape artificial disturbance intensity, an ecological risk assessment model, and the GWR model. The temporal and spatial changes of the landscape types and ecological risks in Ruili City from 2000 to 2021 were quantitatively studied. The relationships between landscape artificial disturbance intensity and landscape ecological risks, and the spatial distribution of the COVID-19 epidemic were determined. [Results] ① From 2000 to 2021, landscape types of Ruili City were mainly woodland and garden land. Forest and garden areas were relatively stable, while the area of arable land fluctuated, and the construction land area continued to expand; ② From 2000 to 2021, the intensity of landscape artificial disturbance in Ruili City was mainly low, slowly increasing outwards in a dotted pattern. The overall trend was expansion from the northwest to the southeast direction. The area of medium and high intensity areas continued to increase, and the intensity of the southern area along the Ruili River gradually deepened; ③ Landscape ecological risk level of Ruili City was classified as lower-risk and low-risk areas, and shifted from low-level to high-level over time. The low-risk areas were mainly located in the middle of the study area, and the medium-risk and high-risk areas were mainly located in the northwest and southeast areas. Landscape ecological risks in different periods were spatially clustered in high-high and low-low level, with strong autocorrelation; ④ The spatial distribution of the COVID-19 epidemic in Ruili City in 2021 presented the clustering characteristics of one main center and two secondary centers. The spatial distribution of the epidemic was correlated with the landscape ecological risk index and the intensity of landscape artificial disturbance. [Conclusion] During the study period, the landscape types of Ruili City changed significantly, the ecological risk increased, and the ecological environment showed a trend of deterioration. The change of landscape type in Ruili City was obvious, the ecological risk increased, and the ecological environment deteriorated. The spatial distribution of the COVID-19 epidemic was correlated with the landscape pattern. Urban construction land and ecological land had spatial aggregation and obstruction effects on the spread of the virus.

Abstract:[Objective] The law and causes of land use dynamic changes in Hehuang Valley of Qinghai Province from 1980 to 2020 were studied in order to provide a scientific basis for land resource management. [Methods] Land use data (1980, 1990, 2000, 2010, and 2020), land use transfer matrix, change analysis, comprehensive dynamic attitude, and cold and hot spot analysis were used to analyze the quantity and spatial changes of land use in Hehuang Valley during 1980—2020. [Results] ① The main land use changes were the increase of grassland from 1980 to 1990 and from 2000 to 2010, and the increase in cropland and unused land from 1990 to 2000. However, there were no significant changes in the number of different land use regions from 2010 to 2020. ② The conversion of unused land to grassland occurred mainly in the southwest and north from 1980 to 1990. From 2000 to 2010, the conversion of cultivated land to grassland mainly occurred in the central region. ③ Hot spots of land use change in Hehuang Valley were mainly located in Guide, Jianzha, Xunhua, Minhe, Hualong, Menyuan counties, Tongren City, and Pingan District. The cold spots were mainly located in Datong, Menyuan County, Ledu District, and Tongren City. [Conclusion] National and local policies and other factors have led to spatial and temporal differences in land use changes. Only by selecting research methods according to local conditions and focusing on different areas, can we optimize land use structure and realize the revitalization of urban and rural areas.

Abstract:[目的] 探究子午岭区气候变化和人类活动与植被动态变化关系，为子午岭区生态保护、植被恢复监测与评价、生态保护及人类活动管理提供科学依据。[方法] 基于MODIS EVI数据和气象数据等，利用像元二分法、相关分析、残差分析等探究了子午岭区2000—2018年生长季(4—10月)植被覆盖时空变化及其与气候变化和人类活动的关系，并定量分析了两者的贡献率。[结果] 2000—2018年子午岭区生长季植被覆盖指数(EVI)均值范围为0.003～0.549，19 a来研究区EVI变化速率为-0.19～0.25/10 a，且以0.055/10 a的增速增加；子午岭区植被覆盖度约为46%，植被覆盖以极显著改善为主。子午岭区植被覆盖的变化主要是因为人类活动和气候变化共同影响。2000—2018年子午岭区生长季均温和降水对EVI变化的影响不显著，人类活动对子午岭区EVI变化产生了正向影响。整体上气候变化对植被覆盖变化的贡献度为28.19%，人类活动贡献度为71.81%。[结论] 子午岭区植被恢复建设的生态效益逐渐增强，植被覆盖变化主要受人类活动的影响，气候变化的贡献相对较小。

Abstract:[Objective] The spatial distribution characteristics and impacts of land use transition in Haikou City were quantitatively identified in order to provide a scientific reference for land and space planning of Haikou City. [Methods] Based on a land use type transfer matrix, land function center of gravity migration, a wavelet coherence model, and other methods, the temporal and spatial characteristics of the land use transition in Haikou City from 2009 to 2018 and their influencing factors were studied. [Results] ① The area of urban living land in Haikou City increased over the past 10 years, while the area of agricultural production land decreased. Agricultural production land, woodland ecological land, and urban living land were the most widely distributed, and were distributed in the south, east, and north of Haikou City, respectively. The area of agricultural production land has primarily changed to areas devoted to industrial and mining production, urban living land, and rural living land. ② The center of gravity of production land in Haikou City has migrated to the northwest, with little spatial displacement. The center of gravity of ecological land has migrated to the southeast, and the center of gravity has shifted from Longtang Town to Yunlong Town. The center of gravity of residential land has migrated to the northweast, with the center of gravity now located in Longqiao Town. [Conclusion] Land use transition in Haikou City is most significantly affected by social factors, and economic factors have had the greatest impact on living land. Policy factors, such as land use planning and land remediation, can play a key role in promoting advantageous changes in land use.

Abstract:[Objective] The spatiotemporal variation characteristics of vegetation coverage in Fenhe River basin and their relationship with topographic factors were studied in order to provide a scientific basis for the green development of the basin. [Methods] Based on MODIS NDVI remote sensing images data, five years (2005, 2009, 2013, 2017 and 2020) of data for the Fenhe River basin from 2005 to 2020 were selected. A pixel dichotomy model was used to estimate the vegetation coverage of Fenhe River basin over the past 15 years. The spatio-temporal variation characteristics of vegetation coverage in Fenhe River basin were studied combined with linear trend analysis. Associated with DEM data, the relationship between vegetation coverage and topographic factors was discussed. [Results] The vegetation coverage of Fenhe River basin demonstrated an increasing trend from 2005 to 2020, with an average of more than 60%, mainly medium, medium-high, and high vegetation coverage. The vegetation coverage along the Lüliang Mountains and Taihang Mountains was in good condition. The impact of topographic factors on vegetation coverage could be summarized as: ① Vegetation coverage in Fenhe River basin increased continuously with increasing vegetation, and was greatest in areas higher than 2 000 m in elevation. ② Vegetation coverage in Fenhe River basin increased with increasing slope, and the coverage reached maximum values in areas with slopes greater than 12°. ③ There was little correlation between slope aspect and vegetation coverage in Fenhe River basin. Changes in vegetation coverage showed a gentle trend, but coverage was higher on shady slopes. [Conclusion] Vegetation coverage in Fenhe River basin is good, and vegetation growth is getting better year by year. Topography is an important factor affecting vegetation growth.

Abstract:[Objective] Land use change and its impacts on the ecological environment of the urban agglomeration of Chengdu Plain under the influence of rapid urbanization were analyzed and measured in order to provide a theoretical basis for optimizing land use structure and ecological environment management in the region. [Methods] Based on land use data from 2000 to 2019, the characteristics of land use changes in space and time for the urban agglomeration of Chengdu Plain were analyzed. The ecological effects of land use changes were then analyzed quantitatively in the region. [Results] ① The area of land use change in the urban agglomeration of Chengdu Plain from 2000 to 2019 showed typical characteristics of “four increases and two decreases”, of which the largest increase and decrease were construction land (an increase of 1 704.59 km²) and cultivated land (decrease 911.04 km²), respectively. In addition, the construction land and waters changed significantly over time. ② During 2000—2019, forest land had been the most important ecological land in the urban agglomeration, and its importance was as high as 53.81%, while the importance of the ecological value of construction land, water area, and unused land did not exceed 2%. In the state of urban expansion under the following conditions, changes in the four types of land use of cultivated land, forest land, construction land, and grassland had a greater impact on the ecology of the region, and the total ecological value contribution rate of changes in land use was 94.76%. ③ The ecological environment index of the urban agglomeration during the study period showed a pattern of decreasing first and then increasing. In general, the quality of the ecological environment in the region remained dynamic and stable, showing a relatively upward trend after 2015. [Conclusion] The government should control land use patterns, make intensive use of construction land, protect the quality and quantity of cultivated land, focus on implementing policies to protect forests and grasslands, and restore and improve the ecological environment of the urban agglomeration of Chengdu Plain, so as to enhance the sustainability of urban agglomeration development effectively.