Abstract:Based on the meteorological and natural disaster data in the Yangtze river basin during the last 60 years, we studied the influence of El Niño- Southern Oscillation( ENSO) events on the climate in the nine subbasins or regions of the Yangtze river basin including Jinshajing/Yalongjiang river, Mintuojiang river, upstream of Yangtze river.Statistical analysis of the relationships between climate factors (precipitation,temperature, natural disaster events etc.) and the ENSO event clearly showed that they had significant impacts on the precipitation and temperature in Yangtze river basin. Most El Niño events or years were warmer and drier with an increased probability of drought. Most La Nina events or years were cooler and wetter with an increased probability of flooding. T he whole basin flood disasters happened twice during the past 60 years, both of which occurred in the years transiting from El Nino events to LaNina events. El Niño had more significant and stronger influences on the climate than did La Nina. The meteorological conditions of the ENSO event during 2009 - 2010 was similar to those of 1998 during which a huge flood occurred.During 2010-2011 and the ensuing transition from the El Nino event to the LaNina event, it is more likely for the whole basin flooding to occur. For better preparedness, weather monitoring and prevention measures must be strengthened.

Abstract:A one-dimensional unsteady state governing equation was developed to simulate moisture transport on the basis of unsaturated seepage flow in capillary landfill covers in response to precipitation and evapotranspiration(ET).The numerical method was used to solve the governing equation with precipitation and ET data of Dalian in 1976(which has the most amount of precipitation in flood season in 48 years). Parametric analysis was conducted to simulate variations in plants, precipitation rate and event duration. The results show that the proposed ET cover of shallow capillary barrier effectively stored rainfall during strong rainfalls and released pore water of soil between rainfalls. Compared with the condition of no plants, ET cover stored and releases water more effectively with plants. Precipitation rate and event duration had significant influences on water content variations of the covers. T he variation ranges of water contents became greater as precipitation rate and event duration increased, and the covers become saturated gradually from up to down,which shows that ET covers of this kind are not suitable for areas with strong rainfall.

Abstract:In order to explore the water permeability of sand layer and its controlling factors in the Tengger Desert,an infiltration experiment was carried out in the region.The results show that during the first stage before a steady infiltration rate was reached,the moving sand dunes have the highest starting infiltration rate,followed by the half-fixed sand dunes and low-lying-lands in order. After about 6.3~ 8.8 min, the infiltration rate of sand layers became stable.The saturated infiltration rate of half-fixed sand dune was slightly larger than that of the moving sand dune, while the rate of the low-lying-land remained the smallest.The moving sand dune and the half-fixed sand dune had almost same high infiltration capacities and the low-lying-land has the smallest infiltration capacity.As typical characteristics,the sand layers had high and steady infiltration rates and need only a short period from start to approch steady infiltration rates,owing to the coarse but uniform texture and good pore connectivity.The high infiltration rates provided very good conditions for the transformation from rainfalls to groundwater.For the three infiltration models,the Koctakob formula was the best in describing the water permeability of sand layers,the H orton formula the second,and the general formula the most unfavourable.

Abstract:Based on the technology of remote sensing and geographic information systems,a karst sinkholebased semidistributed hydrological model was applied to study the impacts of various land use scenarios on runoff and hydrological processes within different years in the Houzhai River Basin located in Puding County,Guizhou Province. The results show that compared with the original land use type, forest and paddy field reduce substantially the runoff and the bare rock scenario increases the runoff slightly but not significantly.The runoff discharge followed the order as bare rock>forest land>paddy field under the extreme scenarios.An optimal land use scenario was designed according to the characters of land use with differential terrains.The simulated runoff discharges under the optimal scenario decreased, comparing to the original land use scheme. It seemed that the optimal scenario improves the efficiency of water resource utilization. Under the scenarios of the extreme land use and the optimal land use, runoff discharges were affected by land use to a greater degree in summer and autumn and to a less degree in winter and spring. The karst hydrological processes response to land use strongly in dry years, moderately in normal years, and weakly in wet years.

Abstract:Temporal changes of the total iron, free iron, chelated iron,amorphous iron,free degree,complex(chelating) degree and activation degree of soil iron oxides in the topsoil of the paddies after reclamation in the Sanjiang Plain were studied.The results showed that total iron in the topsoil of the paddies increased exponentially with time since reclamation. Free iron showed a fluctuating upward trend with the wave troughs appeared in the 3rd year and the 11th year, and the wave peaks in the 5th year and the 14th year. Chelated iron increased during the first eight years after reclamation, reached 1562.41 mg/ kg at the 8th year, and then decreased. Amorphous iron decreased exponentially with time. Free degree of soil iron oxides first increased then decreased, and reached a maximum value of 0.46 at the 8th year.Complex degree increased continuously to a maximum value of 0. 18 during the first 8 years, with a slower increasing rate from the 5th to 8th year;and decreased gradually after the eighth year. Activation degree decreased exponentially with time.Different variation trends of free degree,complex degree and activation degree of soil iron oxides between paddies and soybean fields were caused by water flooding in paddies and differences in farming methods between the two systems. Compared with the natural wetland, rice cultivation increased contents of free iron,chelated iron and amorphous iron as well as free degree of soil iron oxides, but decreased contents of complex degree and activation degree of soil iron oxides. However, complex degree and activation degree of soil iron oxides in paddies were greater than those in soybean cultivation stage.

Abstract:An experiment was conducted on plots of 10 degree slope at the teaching and experiment farm in Yunnan Agricultural University in 2005-2006. The effect of maize intercropped with vegetables and pasture on runoff and sediment was investigated. The result show that the soil and water conservation function of maize intercropping was better than monoculture of maize. Compared with monoculture maize, the runoff and sediment of intercropped maize have been reduced by 24. 4%~ 34. 1% and 13. 0% ~ 50. 9% in 2005, 8. 5%~ 55. 3% and 32. 5%~ 85. 3% in 2006, respectively. Maize intercropped with pasture had the best soil and water conservation effect, followed by maize intercropping with potatoes and cabbages. A significantly positive correlation had been identified between runoff and sediment with rainfall intensity and erodibility.

Abstract:Muddy water infiltration is a common phenomenon in the Loess Plateau.The difference between infiltration processes of muddy water at different initial soil water contents is significant.Taking clear water as the control,we investigated the infiltration characteristics and infiltration decline rates of muddy water at different initial soil water contents.The results showed that the initial(at the end of first minute) and final stable infiltration rates as well as the cumulative infiltration volumes decreased exponentially as the turbidity increased.Those relationships appeared less variable with an increase in turbidity.For the same time duration,the cumulative infiltration volumes were always the greatest with clear water,and increasingly smaller as suspended solid concentration increased.The results of this study may be helpful to study soil erosion mechanism.

Abstract:This paper studied Sophoramoorcro f tiana population by establishing two plots(20 m × 30 m)on semi-fixed and fixed sandy lands in the middle reaches of the Yarlung Zangbo river.The height and diameter at basic height(DBH)of each individual tree in each community were measured,and life history was charac- terized using DBH class structure,static life table,survival curves.The results showed that the DBH class structures of Sophora moorcrof tiana on the semi-fixed sandy land and fixed sandy land were similar,being broad at the base and narrow at the top with the individual numbers reduced as the DBH classincreases.Sophora moorcrof tiana population structure belonged to the growing type on the semi-fixed sandy land and approached mature type on the fixed sandy land.The seedlings of Sophora moorcro f tiana had high mortality rate,while the adult trees had lower mortality rate,with the survivorship curve following the Deevey TypeⅡ.

Abstract:Wind is one of the main driving forces of soil wind erosion,effecting surface heat balance and water circulation. Based on wind speed data collected at 12 stations in wind erosion area of Loess Plateau during 1957-2009,accumulation deviation from average and Mann) Kendall test were used to analyze the characteristics of average wind velocity,maximum wind speed and days of air-suspended sands(DTS,wind velocity>6 m/s). T he results show that Guyuan and Yanchi Counties had the highest averages wind speed and Hequ County has the lowest. Counties of Guyuan,Henshan,and Suide had the most days of air-suspended sand. The annual average speeds at three stations,i.e.,Jingyuan County of Gansu Province,Yinchuan City of Ningxia Hui Autonoumous Region and Suide County of Shaanxi Province exhibited a linear increasing trend during the period,but showed decreasing trend at other stations. The annual maximum wind speeds of the study area decreased in the whole period. The annual maximum wind speeds were mostly found in April or May,when soil wind erosion occurred easily because of the tillage and low vegetation coverage at the early spring. T he most DT Ss were found in May and more DT Ss were recorded at Guyuan,Hengshan and Suide Counties are more than at the other areas.

Abstract:The shortage of soil water is a limited factor affecting restoration and the growth of vegetation in arid and semi-arid areas. Investigations of soil water content variations within depth of 0-60 cm in various microhabitats is therefore of great practical significance for guiding vegetation restoration. Soil samples were collected on sampling grids and soil water content were then measured via oven drying method. The results show that average soil water contents at depth of 0-60 cm was in order from high to low as semi-shade,semi-sunny,and sunny slopes. The average soil water content in 0-60 cm layer varied significantly among hilly slope,shallow gully,small gully,large gully bottom,large gully sunny or semi-sunny slope,large gully shade or semi-shade slope and valley slope on the same aspect of different types. The distribution of soil water content depended mainly on topography and vegetation growth status: the topography affected redistri-bution of precipitation and sunshine,and the vegetation determined rainfall interception and transpiration.Based on soil water content variations,the 21 microhabitat of three aspects were divided into 3 groups,with average soil water contents of 11.68%,8.68% and 5.77%,respectively.

Abstract:The dynamic changes of saline soil evaporation,water content and salinity in response to straw mulching were investigated. T he results showed that,(1) soil evaporation decreased with the increase of straw mulching,however,the reduction efficiency of the straw mulching remained steady when straw mulching quantity was over 7500 kg/hm²;( 2) evaporation inhibition rate were 80.54%,79.01%,62.45 %,and 37.93%, with straw mulching of 10500 kg/hm², 7500kg/ hm², 4500 kg/hm², and 1500 kg/hm²,respectively;(3)the watercontents of soil layers increased with the amounts of straw mulching. When straw mulching was 7500 kg/hm², the water content reached its maximum and the salinity approached its lowest level in the soil layer of 0-10 cm, with an increase of 9. 28% and a reduction of 3. 21% comparing to the control, respectively. Therefore, straw mulching on saline soils can potentially reduce water loss through evaporation, enhance water use efficiency, inhibit surface salt accumulation, and then significantly improve soil quality of saline soils.

Abstract:The characteristics of Pedicularis verticillata communities under different soil water conditions in Bayanbulak alPine grassland were studied using transect and Point samPling methods.The results indicated that the comPosition of the community structure changed with soil water contents.The richness of Plant sPecies was the greatest at 1 meter away from the water source, where P.verticilata was Predominant absolutely with a dominance value of 42.50%; away from the water source, its dominance values and above-ground biomass decreased gradually as the soil water contents decreased.The sPecies richness, diversity and evenness indices of P.verticilata community differed significantly under different soil water conditions.The PoPulation density and above ground-biomass of P.verticilata were the greatest at the Places closest to the water source,but at the Places further away from the water source where soil water content was around 25.5%,the Plant achieved the highest seed yield and the second Peak above-ground biomass, indicating that P.verticilata is not a“water-loving”Plant.Gramineae and other grasses dominated increasingly with the decrease of soil water contents.Soil water content was clearly the most imPortant factor to regulate P.verticilata community structure in Bayanbulak alPine grassland.Controlling the seed sPread near the water source may be the effective aPProach to limit the ramPant exPansion of P.verticilata.

Abstract:Using the method of empirical orthogonal function(EOF) and the data of 23 years at 96 meteorological stations in Shaanxi Province,we calculated the feature vector distribution of precipitation fields and the time-coefficient series.The results showed that the EOF method was capable of revealing the spatial and temporal distributions of precipitation field for Shaanxi Province,with the first three EOFs reflecting the three typical vector distribution fields and explaining 81.10% of total variation. The spatial distribution of precipitation in Shaanxi Province had three typical modes:the whole region, north-south, and eas- t west patterns. In general, the values of the three feature vector distribution fields increased from north to south,with the largest value centered on the southern tip of the province,indicating a wetter south with a larger inter-annual precipitation variation and a drier north with a smaller inter-annual precipitation variation. Analysis of the eigenvectors of the corresponding time factor coefficients showed that the precipitation fields in Shaanxi Province mainly exhibited six types. Compared to the statistical results of 23 years, these results were consistent with the typical precipitation fields.

Abstract:Soil bulk density,soil porosity,soil moisture capacity and water storage characteristics for six main forest types in Wuyishan Scenery District were studied.Results are as follows.(1)The soil bulk density in the top 60 cm followed the order of: chinese fir forests> masson pine forests> shrubs> mixed forest>moso bamboo forests> broadleaf forest.(2)The total porosity and maximum water-holding capacity were:broadleaf forest> moso bamboo forests>mixed forests> shrubs> masson pine forests> chinese fir forests;and the capillary porosity and field moisture capacity were: Moso bamboo forests> broadleaf forests> mixed forests > shrubs> masson pine forests> chinese fir forests; the soil noncapillary porosity was broadleaf forests> mixed forests > shrubs > masson pine forests> chinese fir forests> moso bamboo forests; the soil capillary waterholding was moso bamboo forests> broadleaf forests> shrubs> mixed forests > masson pine forests> chinese fir forests.(3)In the layer of 0-60cm,the order of soil total storage capacity was broadleaf forests> moso bamboo forests> mixed forests> shrubs> masson pine forests> chinese fir forests.The storage volumetric capacity of moso bamboo forests was the largest,but its transmission volumetric capacity was the smallest.Given the same site condition,the soil physical characteristics of the broadleaf forest were superior to those of the others and therefore provided the best function of soil and water conservation.

Abstract:The rocky desertification is a result of both nature processes and societal activities.Studying the driving mechanism of the rocky desertification is a prerequisite of restoring and rebuilding the karst fragile ecosystem.In order to quantify the effect of the climatic factor on the rocky desertification,all potential driving forces were selected including elements of physical geography,climate,population,community economy and the man) land relationships.These elements were correlated to a rocky desertification index,and the significant factors were then used in the patrtial least square(PLS) regression analysis.The significance of all kinds of driving factors for the rocky desertification were judged quantitatively by utilizing a variable importance projection(VIP)index.T he analysis shows that the physical geography element is the primary factor causing the rocky desertification,but the climatic element,especially precipitation amounts,is one of the direct driving forces,which increases as precipitation levels increase.

Abstract:The effect of initial water content on saturated hydraulic conductivity( KS10) and salt leaching of alkaline soil was researched using column leaching experiments in laboratory.Saturated hydraulic conductivity was measured at six different initial water contents.The results indicated that saturated hydraulic conductivity decreased with an increase in initial water content,showing a significant negative linear correlation. With an increase in initial water contents,the pH value decreased while electrical conductivity(EC)increased.The pH value in leachate increased but the EC decreased as the KS10 increased,both following logarithmic functions.In addition,the saturated hydraulic conductivity of alkaline soil and salt leaching efficiency decreased slowly in the condition of prolonged immersion.

Abstract:Based on determinations of soil moisture content and particle size,the features of soil moisture content,dried soil layer,the suitability of grassland development,soil reservoir and so on were studied in the south of the Qinghai Lake in the Eastern Tibetan Plateau.The results indicate that the soil moisture content increased with depth.Permanently dried soil layer developed at the depth of about 1m.Soil layers were increasingly dry with depth; weakly dried soil layer shifted to moderately dried soil layer from upper to lower parts of soil profiles,which could be related to the warming and drying climate and low precipitation.Although during rainy year the moisture contents of the upper soil profile were significantly higher,the dried soil layers could not receive enough water to restore in this area.The soil texture of the South Qinghai Lake was similar to silty soils found in the Loess Plateau.However,the soil was shallow,resulting in soil reservoir of poor adjustment ability.T he dried soil layer and poor soil reservoir suggested that grassland vegetation consuming less moisture are more preferable than forests in this area.

Abstract:Repeated freeze-thaw cycles cause changes in soil cohesion and internal friction angle,increasing the erodibility of the soil.This study discussed the variations of soil bulk cohesion and internal friction angle in the freeze-thaw cycles and analyzed the freeze-thaw effects on soil anti erodibility. The black soil was selected as the study object.The changing trend of cohesion and internal friction angle of the soil were invest-igated through indoor freeze-thaw experiments with consideration of different freezing cycles and various soil moisture contents. The results show that freeze-thaw cycles affected greatly the soil cohesion and slightly the internal friction angle. With increasing numbers of freeze-thaw cycles, soil cohesion decreased and then achieved a stable state after three freeze-thaw cycles.With the increase of soil moisture,soil cohesion reduced and then increased in individual freeze-thaw cycles. At same freeze-thaw temperature, soil cohesion was affected greatly in the first freeze-thaw cycle, and very little in the following cycles. In contrast to soil cohesion, internal friction angle did not change significantly in the whole process of freeze-thaw cycles.

Abstract:Soil moisture properties under the pure and mixed plantations of Pinus koraiensis and Frax inus mandshurica were measured and analyzed. The result showed that for each soil layer or the whole soil profile, the soil bulk density under the mixed plantation was lower than that of the pure plantation of Pinus koraiensis. But the total porosity, capillary porosity, non-capillary porosity, soil maximum moisture capacity, capillary capacity, field capacity, wilting point, available water capacity, water storage capacity, permeating coefficient under the mixed plantation were all significantly greater than those of the pure plantation of Pinus koraiensis, with the relative increases averaged over the entire profiles being 19.17%,21.50%,12.17% ,32.68%,24.29%,42.22%,19.72%,27.71%,12.17% and 39.44%, respectively.The results showed that the soil pore condition in the mixed plantation,compared with the pure plantation, was improved, resulting in better functionality of water and soil conservation.

Abstract:In order to study the relationship between spatial heterogeneities and distribution of plant community, the soil moisture,salt,organic carbon, total nitrogen and total phosphorus were investigated in the Changyi Marine Ecological Special Protection Area in September,2009.The results show that,the water content closely related with dissolved salt content and organic carbon with high coefficiencies(p<0.01).Meanwhile, the organic carbon significantly corelated with total nitrogen(p<0.05), but not with the total phosphorus.The soil water content and salt content increased from the land to the sea, while the organic carbon, vegetation composition and coverage decreased at the same time. Moving seaward, the species abundance and diversity of plant decreased, evolving from diversified shrubs and herbs dominated by Setaria viridis to predominantly salt-tolerant community of Tamarix chinensis Lour.,Suaeda glauca, and then to mono-species of Suaeda salsa(L.)Pall.

Abstract:The soil organic carbon(SOC) contents, distribution of organic carbon in soil aggregates, and organic carbon contribution rates of variously sized soil aggregates were studied during vegetation restoration in Ziwuling Mountain. The results show that the weighted mean of SOC was 3. 54 g/kg for the 0-100cm soil profile of sloped cropland,while the weighted means of SOC of 0-100cm soil profiles of abandoned land, grassland, shrub and arbor phases were 6.8%,36.6%,41.5% and 73.6%, respectively, higher than that of slop cropland. T he increasing magnitudes of SOC contents of 0-20 cm soil layer were higher than those of soil layers below following vegetation restoration.The SOC contents of aggregates of all sizes in the 0-5 and 5-10cm soil layers increased gradually and the SOC enriched in the macroaggregates(>2mm) over time along with vegetation restoration. No clear change of SOC contents in the 10-20 cm soil layer for aggregates of all sizes. The SOC contribution rates of>5, 5~ 2 and 2~ 1mm aggregates in 0-20 cm soil layer of abandoned land, grassland, shrub and arbor were higher than that of sloped cropland, indicating that the increased part of SOC in 0-20 cm soil layer were stored mainly in>1mm aggregates during vegetation restoration.

Abstract:An aquatic eco-security monitoring system is the basic and primary work providing fundamental data in order to protect and restore aquatic eco-environment.Aquatic eco-security monitoring is to assess the relevant factors about aquatic environment and habitat,including atmosphere,soil,biology,and aspects of human influences.It emphasizes water quality and biology.The paper discussed the current situation about aquatic eco-security monitoring in Poyang Lake and try to analysis its characters and deficiencies.In order to make the monitoring work better,the paper gives five suggestions to form a data sharing mechanism,which are to improve the aquatic eco-security monitoring system,to divide the monitoring system into subareas,to expand the number of monitoring spots(especially the remote sensing and wireless monitoring spots),to enlarge the scope of monitoring aspects(develop from water quality to water ecology),and to construct the data platform of aquatic eco-monitoring in Poyang Lake.

Abstract:Erosion is an exogenic agent of landscape evolution.Quantitatively calculation of erosion rates and the reveal of the climate-erosion-tectonics feedback system are important research subjects in Geosciences.The average rates of exhumation can be obtained from thermochronology on time scale of millions of years,and erosion rates from hydrological measurement on time scale of tens of years.As a supplement,erosion rates on time scale of ten thousands of years can be calculated by measuring cosmogenic nuclide(¹⁰Be and ²⁶Al)from river terrace deposits or basin sediments.Cosmogenic nuclides were primarily generated by reaction of quartz grains exposed near earth surface by galactic cosmic radiation,which were then suddenly and deeply buried to shield off cosmicrays after exposure of short time on the ground surface.Generally,the quartz grains have a short time exposure and low cosmogenic nuclide concentration.In addition,the cosmogenic nuclide decreases over time after burial.Quantitatively calculation of erosion rates from ¹⁰Be and ²⁶Al is a concept based on dating river terrace deposits or basin sediments by determination of ¹⁰ Be concentration.Combining ¹⁰Be and ²⁶Al measurements,surface exposure ages or erosion rates can then be calculated.The method is precise,easily accessible and widely applicable.It can be used for longer time scales and broader spatial scales,and it is a new method important to landscape evolution research from Quaternary to Holocene.

Abstract:To improve the uniformity of irrigation system and the design precision level of emitters,this study using a 3D camge measurement system(MCS-60)measured the structural parameters of channels in twenty-five combinations(from seven cylinder emitters and four pipe thickness).The hydraulic performances of the combinations were also tested by an automatic testing platform.The curves of the flow and pressure,flow rate coefficient and flow index were obtained.The results show that the flow rates of the same emitters can varied up to 20% with polypropylene (PE)pipes of different wall thickness.The PE pipe thickness affected the flow rate coefficients greatly,and the flow index to a less degree.The width of the emitter flow path was another factor for the influence of the PE pipe wall thickness.The more the width of the flow path,the bigger the change caused by pipe wall thickness.

Abstract:Because of the particular geological environmental setting,the geo-hazards frequently occurred in Daduhe River between Jiajun County and Detuo County,undercutting the safety of engineering activities in this area.The traditional field survey is limited in its short vision fields and inaccessible remote areas,while the interpretation based on remote sensing images could be used to obtain the distribution and scale of the hazards and then to solve the dilemma.Furthermore,the interpretation can be used in boundary delineation,categorization and characterization,identification of disaster genesis,scale and harmful degree,and development trend.Based on the Worldview(resolution:0.5m) remote sensing image of Daduhe River between Jiajun County and Detuo County,this paper processed the image systematically to rebuild orthophoto map and three-dimensional remote sensing image.Combined with field survey and geologic engineering comprehensive evaluation,the features and forming mechanism of large-scale landslide were studied.

Abstract:With the development and utilization of Qingdao's coastal shoals and marshes,it becomes increasingly necessary to develop appropriate and effective techniques of afforestation to ameliorate the saline-alkali land.Based on the measures and experiences of ameliorating coastal saline-alkali land of other regions such as Dongying of Shandong Province and Tianjin City,considering the local conditions in Qingdao City,we have put together a suit of measures to removing salts including tile drain,salt impeding layers and soil replacement.In conjunction with the engineering measures,plant management techniques such as selection of salt-tolerable species,use of improved fertilizers and proper planting.Taken together,these comprehensive measurements could effectively reduce evaporation from soil surface,lower groundwater levels,impede salt accumulation in the surfaces,and therefore form a healthy eco-cycle.

Abstract:Geostatistics method was used to analyze the spatial distribution patterns of heavy metal elements,and Nemerow integrated index method was used to assess environmental qualities regarding heavy metals in tea-planting areas of Rizhao City.The results of assessment were then displayed with Kriging interpolation in ArcMap.T he results show that the distributions of all the heavy metals except Cd and Pb were comparatively uniform.The single factor pollution index indicate that the majority of the research areas was clean except that Cd and Ni pollution existed in some parts of the area.The spatial distribution of Nemerow integrated pollution index show that 88.41% of the research areas soil was classified as levelⅠ,and 6.44% as level Ⅱ,and 5.14% as level Ⅲ,while no area as Ⅳ and levelⅤ.

Abstract:Based on high-precision GPS(Trimble 5700) measurement data on hillslopes of Ziwuling area,this paper validated the existing models for predicting ephemeral gully erosion thresholds.The results show that the existing models were 10% ~ 40% over-predicting or 20%~ 35% under-predicting of the distribution area of ephemeral gully erosion on hillslopes.A new critical model for predicting ephemeral gully erosion on hills-lopes was then established through the high-solution DEM generated by GPS,GIS and statistical analysis.The GPS measurement data on hillslopes of the Ziwuling area were then used to validate the newly established critical model.The results show that the new model well predicted the distribution area of ephemeral gully erosion on hillslopes with a low relative error of 5% .

Abstract:DPM model,built on the principles that the dust emission flux is proportional to the dust saltation flux and the kinetic energy flux of saltating particles,is composed of two components:the saltation flux of soil microaggregates and dust particle emission.To validate the applicability of DPM to sem-iarid areas,we selected fourtypical types of farmlands( soils) in the sem-iarid north-central Shaanxi Province,measured and calculated thesurface aerodynamic roughness,microaggregate distribution of surface soils,friction velocity,and threshold friction velocity on each study area,and comparatively analyzed the DPM model simulation accuracy betweenthe different soil types and between different seasons.The results showed that DPM model can be used to simulate dust emission flux of the different soil types in the sem-iarid farmlands,and can better simulate dust emission flux for the summer and winter seasons in the sem-iarid farmlands.

Abstract:The principle of relative stability of a dam system is the theoretical basis for planning silt-retention dams,therefore,it is of significance to study the relative stability of a dam system in planning silt-retention dams.T his paper uses Matlab 7.0-based improved BP algorithm and chaos optimization and back-propagation (COBP) model to assess the stabilities of thirteen dams in Majiagou watershed according to seven major factors affecting the stability of a dam system,i.e.dam control area,dam number,total reservoir storage,silting-allowable volume,water depth,ant-iflood capacity and silted area.Results show that seven dams out of the thirteen dams are unstable,which is confirmed by the stability coefficient analysis of each dam.The out-put of the COBP model is thus reliable.This paper further analyzes the reasons for the instabilities of seven dams and makes them stable by increasing dam height and number.All of the thirteen smal-lwatershed dams in Majiagou watershed become stable after they are replanned.This demonstrates that the COBP method has practical values in assessing the stability of a dam system.

Abstract:Taking the Chaohe River Basin above the Miyun Reservoir as a study area,the influence of soil and water conservation measures on annual runoff was assessed quantitatively by the rainfall-soil and water conservation-runoff statistical model established on the basis of multiple regression analysis using historical annual runoff,annual precipitation and areas of soil and water conservation measures in the drainage basin during 1961-2005.The results showed that during 1961-1970,1971-1980,1981-1990,1991-2000 and 2001-2005,the average annual runoff-reduction effects were 2.54%,3.52%,28.71%,6.87% and 48.02%,respectively,with an average of 22.96% during 1981-2005.The average annual runof-freduction effect was the greatest during 2001-2005,intermediate during 1981-1990,and the smallest during 1991-2000.The runoff reduction effects of soil and water conservation measures were more profound in the drier period.

Abstract:Based on the qualitative description of the driving factors for grassland degradation in the mixed cropland-grassland region in Northern Shaanxi Province,we chose the dominant factors that were closely correlated to the grassland degeneration and also relatively easy to acquire,and obtained the most dominant factors affecting the grassland degradation using a principal component analysis and multiple linear regression analysis.Furthermore,for those selected factors,we proposed the prevention measures to control the degeneration of grassland in Northern Shaanxi Province.In addition,we suggested some concrete counter measures based on the moisture conditions and the severity of grassland degradation.Finally,we proposed a model of reconstructing the degradated ecosystem in Northern Shaanxi Province.

Abstract:Stand density is referred to as the number of trees standing in the process of tree growth on a unit area,which closely related to forest growing conditions,stability,forest yield,quality and other factors.Based on a survey on Larix principis plantations with various densities in State-owned Forest Bureau of Mulan in Hebei Province,the study proposed a competition index of crown width by adopting the Hegyi model, which uses a single wood competition index model to calculate the competition index.By fitting crown width,stem diameter at chest height and relative crown width competition index,the management density was found varying in response accordingly to the diameter,given a competition level.T he management densities of Larix principis plantation were calculated for the competition indices of 0.2,0.4,0.6,and 0.8,respectively.

Abstract:Firewood collection,which reduces vegetation cover,is one of the primary reasons causing soil erosion.We studied farmers'fuel selection behavior based on field surveys as well as theoretical analyses,and found that the proportion of farmers'commercial fuel consumption has increased significantly both in terms of fuel materials and total thermal values in Changting County from 1960s to 2000s,with the latter increased faster than the former.Fuel substitution is not only a low-cost soil erosion controlling measure for government,but also a source of net income for rural households due to increases in labor opportunity cost(e.g.,farmers can make more money working in a manufactory than collecting firewood).The profit margins of using three surveyed fuel substitution schemes over the firewood decreased from"biogas & electricity" to "honeycomb briquette & electricity" to "liquefied petroleum gas( LPG) & electricity".Further theoretical analysis of comprehensive cost of firewood collection,farmers'fuel choice,and typical fuel substitution process shows that government intervention is an important factor in moving forward the fuel substitution and controlling soil erosion.

Abstract:Indices of structure density,measured sediment blocking capacity,and single-dam control area were surveyed,compiled and analyzed for the large and medium sized check-dams in Northern Shaanxi Province in the special action of check-dam safety inspection.The results show that the total control area of large and medium sized check-dams was 28703.84 km² and the total sediment discharge reduction was 4.11@10¹⁵kg,highlighting the critical role of check-dams on sediment blocking and silting.Positive pair-wise correlations were found significantly among building density of check-dams,capacity of sediment blocking and control areas of the single-dam.The silted check-dams of Yulin City were utilized mainly for crops limited to a few species only,while in Yan.an City,the silted check-dams were confined to sediment holding only.The management and protection of check-dams were conducted collectively through governments.The most serious potential safety hazard of the check-dams could be the hidden danger in the dam body.

Abstract:As one of the most serious ecological problem in China, soil erosion has attracted extensive attention.Currently,the RUSLE model and GIS technology are commonly used to estimate rainfall and runoff erosion.This study introduced the theory of security patterns(SPs)into the estimation of soil erosion based on RULSE and GIS,and then constructed a risk pattern of soil erosion for Diebu County in Gansu Province.The risk pattern proposed a series of specific solutions targeting the soil erosion, such as transforming slopes into terraces,enhancing the protection of slopes,increasing the vegetation coverage in the key point or zone in the risk pattern and so on.These methods would help enhance fragmentation of erosion patches,decrease erosive power of surface runoff, and weaken the scale-effect of erosion, and eventually decrease or solve the soil erosion problem. Besides,the risk pattern could also be used to guide the reform and change of land use patterns.

Abstract:Mung bean is one of the most important economic crops and traditional crops in Northern Shaanxi Province.Developing drought-resistant mung bean cultivation techniques suitable for regional characteristics is the essential part for optimizing the cultivation models for minor grain crops and improving the regional agriculture.Five treatments were set up,including plastic film mulching on ridge,plastic film mulching on" W"shape ridge,plastic film mulching on whole plot,straw mulching on whole plot and no mulching as control.Comparing soil temperature,water consumption,water use efficiency,plant characters and yield of mung bean in different treatments,the results show that plastic film mulching significantly increased the yield of mung bean and the straw mulching did not.In the three plastic film mulching treatments,plastic film mulching on ridge was the most effective treatment in improving both water use efficiency and yield of mung bean.Owing to its additional simplicity of its installation,the plastic film mulching on ridge should be considered as the first option as the drought resistant cultivation technique of mung bean in Northern Shaanxi Province.

Abstract:Guizhou Province is a typical karst mountainous area,accounting for 61.96% of the total exposed karst area in China.The rocky desertification in the region is serious,the ecological environment is fragile,and the biological diversity is especially vulnerable.Based on biological diversity,this paper established a comprehensive assessment index system of biological diversity using five indices of species richness,diversity of ecosystem types,completeness of the vertical stratification,species endemism,and number of invasive species.Using the established system,we evaluated the biological diversity of each county( districts,cities)for the entire Guizhou Province.The overall results were reported in four grades: excellent,good,average,and poor.There were 10 counties rated as excellent,accounting for 11.36% ; 29 counties as good,accounting for 32.96%; 39 counties as average,accounting for 44.32%;and 10 counties as poor,accounting for 11.36%.The regions with better grades are in remote mountain areas in northeast and southeast of the province,while the areas with lower grades mainly lies in flat terrain in central province.

Abstract:Based on the energy theory and its analysis methods,the changing trends of the 8 energy indices[energy yield ratio(EYR),energy investment ratio(EIR),energy used per person(EUPP),energy dollar ratio(EDR),energy density(ED),environment loading ratio(ELR),energy-based sustainability index(ESI)and population carrying capacity(PCC)]in Shanxi Province from 1980 to 2008 were analyzed,and the numerical values of the eight indices were also predicted for the year 2012.The results were summarized as follows.(1)The EIR,EUPP,ED increased continuously,while the EDR decreased during the past 29 years,indicating that the economic system of Shanxi Province have been highly developed.(2)The EYR and the ESI decreased continuously,while the ELR continued rising during the past 29 years,indicating that the quick development of the economic system in Shanxi were at the expense of substantial resources consumption and environmental damage.(3)The energy indices predicted for Shanxi in 2012 according to the changing trends showed that if Shanxi continues with the same development model,the competitiveness of production will decline and the pressures to the environment will increase,leading to the irreversible degradation or loss of function in the eco-economic system.

Abstract:Changes of land use have great impacts on terrestrial ecosystems.The trends of land use changes were analyzed based on the land,social,economic,and environmental data.Using the methods of the composite index and analytic hierarchy process(AHP),we established the ecological risk assessment systems considering natural,societal,and economic pressure,and evaluated ecological risk index and composite risks of land use structure including cultivated lands,forestlands,grazinglands,and water body.The results showed that the ecological risks were the greatest in cultivated lands,and smallest in water bodies.T he order of the risks is:cultivated land>woodland>land for inhabitation,mining and manufacturing > grazing and pasture land>unutilized land>land for transport facilities>land for water conservancy facilities.The ecological risks caused by economic pressure,nature pressure,and society pressure were greatest,intermediate,and smallest,respectively,while composite risk increased.The ecological risks are related to an unreasonable structure of land-use,increase in population,decrease in water resources and increase of natural disaster.

Abstract:The ecological system of the western mountains in Shanxi Province is vulnerable,and soil and water loss has been widely recognized for long time.T he application of converting farm land to forest has efficiently improved ecological environment of the region,profoundly influencing the sustainable development of regional economy of the society.T he comprehensive assessment of converting farm land to forest can provide information regarding the effects of engineering implementation on the society,economy and ecology.Taking Jixian County of Shanxi Province as an example,this study evaluated and analyzed the comprehensive ecological,social,and economic effects of the conversion application between 2000 - 2008.T he results indicate that the comprehensive effect of the conversion in Jixian County was started as negative in 2000,but then increased substantially since the start of 2001.

Abstract:Studies regarding plant phosphorus accumulation and utilization efficiency can provide scientific basis for reasonable application of phosphate.Dynamics of phosphorus content of winter wheat and utilization efficiency of winter wheat was conducted based on the long-term positional fertilization experiment on dry highland of the Loess Plateau.The results show that the phosphorus contents of winter wheat plants with application of phosphate fertilizer presented a V shape curve.Phosphorus contents of winter wheat were high during the early growth period,and decreased with the crop growth,and reached the minimum in the filling stage,and then rebounded in the last stage.Phosphorus of winter wheat accumulated mainly in two stages,i.e.,stage of jointing ) flowering and stage of filling ) mature.Sufficient supply of phosphorus in these two stages could ensure better growth of winter wheat.In terms of phosphorus utilization efficiency,yield and other indicators,phosphate application should be controlled in a reasonable range between 45~ 90 kg/ hm² in the scenario of nitrogen application 90 kg/ hm².

Abstract:On the base of field suvey in standard plots,the overall diversity,plant community diversity and species diversity index were analyzed for Robinia p seudoacacia L.plantations in Chunhua County of Shaanxi Province on the Loess Plateau.The relationship between path rank,average tree height and density were also explored.Results show that after several years of natural recovery in Robinia p seudoacacia L.plantations,12 shrub species belonging to 10 genera of 7 families,and 46 species in 37 genera of 17 families in herbaceous layers were found.The plant species richness and the diversity index increased significantly.The stratification between shrub and herbaceous layers under trees was more obvious.In contrast,the plant diversity and the important values in the herbaceous layer were higher than those of the shrub layer.Understory plants grew significantly better on the sunny and downhill slopes with angles less than 35 degree and medium density of 1 000~ 1 500 tree/ hm².The tree diameters decreased accordingly with the increase of forest density.When density was less than 1 500 tree/ hm²,the average height was significantly increased with the average density.

Abstract:Based on the statistical data of land resources and grain yields during 1989-2008,we analyzed the cultivated land use intensity,food security,and their correlation for the regions along the Yangtze River in Anhui Province using the methods of principal component analysis and regression prediction.The results were as follows.(1)Temporal changes of the land cultivation intensity were evident,with two increasing periods and two decreasing periods; the spatial differences were also apparent with a decreasing trend from north to south.(2)Food security index was generally at a safe state,with the index following a fluctuating upward trend and unbalanced regional development.(3)The correlation between cultivation intensity and food security index was strong.The above results might provide a theoretical basis for the regional intensive use of cultivated land resources and food security assurance for the study region.

Abstract:Experiments were conducted to study the water conservation functions of litter and surface soil under six forest types in mountainous area of Northern Hebei Province.The results show that in terms of effective interception capacity,the rank of litter layers was poplar forest( 3².3² t/hm²)>birch forest(²8.59t/hm²)>Mongolian oak forest(²0.²6t/hm²)>chinese pine-Mongolian oak mixed forest(19.49t/hm²)>Larix principis-rup prechtii forest( 13.53 t/ hm²)>chinese pine forest(13.²3t/hm²);in terms of soil maximum water-holding capacity,the order was poplar forest> chinese pine-Mongolian oak mixed forest>birch forest>chinese pine forest>Larix princip is:rupprechtii forest> Mongolian oak forest; regarding soil infiltration characteristics,the rank was chinese pine-Mongolian oak mixed forest> poplar forest> birch forest> chinese pine forest> Mongolian oak forest> Larix principis - rupp rechtii forest.The values of evaluation indices were calculated based on weights that were determined using the method of hierarchy analysis.The evaluation results show that chinese pine-Mongolianoak mixed forest had the best water conservation function,followed in order by poplar forest,birch forest,Mongolian oak forest,chinese pine forest,and Larix principis-rup prechtii forest had the worst.

Abstract:The drought resistance of Nitraria tangutorum from four geographical populations,i.e.,Jiuzhoutai District of Lanzhou City( LZJ),Minqin County of Wuwei City(WWM),Linze County of Zhangye City(ZYL) and Jinta County of Jiuquan City(JQJ),are investigated regarding physiological and biochemical indices,including net photosynthetic rate,chlorophyll,soluble sugar,proline,malondialdehyde,superoxide dismutase and peroxidase.Using the methods of subordination function,grey correlation analysis and principal component analysis,the relationship of drought resistance with the indexes were evaluated systematically.The results show that the drought resistance of Nitraria tangutorum from four geographical populations was in order as JQJ> WWM> ZYL> LZJ,indicating a increasing trend of drought resistance with increasingly adverse circumstances.T his implies that the plant adapted to environmental conditions through adjusting its physiological features.T he seventeen drought resistant indices were restricted by and relied on each other in comprehensively conditioning drought resistance of Nitraria tangutorum.However,the main two mechanisms,i.e.,the xanthophyll cycle-dependent thermal energy dissipation and the photoprotective mechanism of photoinhibition,played the leading roles in the drought resistant mechanisms of Nitraria tangutorum.

Abstract:The construction of expressway results in the changes of the ecosystem service value via changing the land use types.Based on the classification and evaluation method of global land ecosystem service value first used by Costanza et al.(1997) as well as ecosystem service values of unit area of each land use type estimated by Chinese scholars,the changes in ecosystem service value of different land use types were evaluated after the construction of the Huxian-Mianxian section of Xi'an-Hanzhong expressway.During the construction,1116.4 hm² farmland,6.8 hm² orchard,1²5.² hm² woodland and 1²5.8 hm² grassland were used.However,after the construction,areas of the woodland and grassland were increased by 155.3 hm² and ²1.4hm²,respectively,due to vegetation restoration and landscaping.The ecological service values of climate adjustment,habitats,and recreation increased due to increases in woodland and grassland areas.The construction nullified the ecosystem service value of farmland and orchard,which reduced ecological service functions of biological control,food supply,and pollination by 90%,73%,and 6²%,respectively.In general,the overall ecosystem service value tended to decrease,about 1400 yuan per year per kilomemter after the construction of the expressway.However,the loss of ecosystem service value is expected to be far less than the economic and social benefits that the expressway can bring to the area.

Abstract:In order to prevent loss of soil and water,to avoid further damage of the ecological environment,and to expedite the restoration of the ecological system in Baiyekou reservoir project construction area,this study analyzed and predicted the risk and quantity of soil and water loss during construction for the submerged area,hydraulic stucture area and storage area during construction.Resuults show that disturbance from construction was the main reason for soil and water loss,leading to the increase of soil erosion mode.Based on the characteristics of soil and water loss in different function areas,soil and water conservation measures combining engineering and ecological restoration were recommended to stimulate self-repair capability for ecological system and enhance vegetation restoration.Plantation of tree species such as Pinus tabulaeformis,larch,and robinia with alfalfa in between are appropriate approaches for the area.

Abstract:Food security is a strategic concern of long-term regional development.Given the rapid population growth and continuing reduction in arable lands,increasing food production efficiency becomes the key to increase food production.Using the ESDA techniques and DEA Malmquist model,in conjunction with the spatial pattern of geographical research methods,we estimated grain production efficiency of 138 counties in Hebei Province from 1990 to 2005,and discussed the evolution characteristics and patterns of spatial clustering of the grain production efficiency on the county-level in Hebei Province.Results showed that grain production efficiency of 138 counties were aggregated spatially in the provincial region; however,the inter-regional differences were reduced.The local spatial aggregation pattern of grain production efficiency indices were significant,and the evolution of spatial aggregation pattern were evident on county-level in Hebei Province from 1990-2005.This study provides methodology for estimating spatial patterns of production efficiency,scientific basis for properly regionalizing production,and regional strategy for food security.

Abstract:Taking the buffer zone with the width of 10 km along the main stem of Nenjiang River as astudy area,based on the theories of landscape ecology,the influences on the stream restoration of landscape pattern changes of each individual type and the whole landscape were studied using Landsat images of 1976,1989,2000,2005,and 2008.The results showed that over the past 30 years,area of the water body of Nenjiang River decreased,extent of fragmentation of the landscape decreased,and the degree of meandering of the river decreased,all of which are not in favor of the restoration of biodiversity.The changes in farmland patterns exacerbated the deterioration of the water quality of Nenjiang River,and the changes in the whole landscape configuration did not favor the natural restoration of waters as well.However,since 2000,the changes in the forestland and wetland patterns to some degree favored the biodiversity restoration and water quality improvement of the river,as a result of the implementation of a series of ecological reconstruction policies and projects including returning farmland to forestland and grassland,planting tree and afforestation,protecting wetland.

Abstract:Aiming at the frequently occurred geological hazards.a assessment was done in Pengyang County,Ningxia Hui Autonomous Region.China.The locations of geological hazards were identified in the county based on both remote sensing interpretation and field surveys.Using five assessment indices including slope gradient.elevation.slope aspect.rainfall intensity and the proximity to main roads.a map of geological hazard level was produced based on geographical information system(GIS) and the model of information value(IVM).The results show that the model of information value and GIS improved the automation level.efficiency.and accuracy of the assessment.and then facilitate the realization of dynamic and scientific assessment of geological hazards.The map of geological hazard assessment provides scientific references for urban and rural planning and identifying appropriate construction sites for local governments.

Abstract:We assessed the vulnerability of the groundwater system of Shimengou,in order to provide scientific support for rational utilization and managements of the groundwater resources of the area.The study area was divided and then scored for each evaluation factor using indexes of depth of water,net recharge,aquifer media,soil media,topography,impact of the vadose zone,and hydraulic conductivity of the aquifer (DRASTIC).The vulnerability index was calculated through building matrix.Results showed that the groundwater vulnerability index was between 100 to 128 in the study region,which was between the low and medium range.The study region was divided into six sub-regions in two groups,and the vulnerability showed a decreasing trend from northeast to southwest.In general,groundwater vulnerability in the karst area is less severe than that of other lithologic areas.Groundwater vulnerability is determined by intrinsic attributes of aquifer,but it can be affected by external factors exerted by the human activities.