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米仓山不同退耕年限土壤理化性质变化特征
纪月1, 杜琳青2, 田鹏2, 赵广举1,3, 崔玉美2, 马亮乾2
1.西北农林科技大学 水土保持研究所, 陕西 杨凌 712100;2.西北农林科技大学 资源环境学院, 陕西 杨凌 712100;3.中国科学院 水利部 水土保持研究所, 陕西 杨凌 712100
摘要:
[目的] 研究不同退耕年限下的土壤理化性质特征,为区域生态系统服务功能的提升与生态文明建设提供科学依据。[方法] 以中国南北过渡带的米仓山退耕20,25,35,50 a的样地为研究对象,以未施肥耕地和天然林地为对照,采用“时空替代法”,分析米仓山地区不同退耕年限土壤理化性质特征。[结果] ①土壤机械组成在退耕前期无明显变化,在退耕50 a时与天然林地相似。退耕20,25,35,50 a样地的土壤大粒径团聚体百分含量较耕地均有不同程度的升高,其增幅分别为17.70%,53.23%,52.50%和70.30%;②随着退耕年限增加,土壤容重呈下降趋势,退耕50 a样地土壤容重接近天然林地。不同退耕年限下土壤水分特征曲线均可用Gardner模型拟合,土壤持水性由高到低排序为:天然植被 > 退耕25 a > 退耕35 a > 退耕20 a > 耕地 > 退耕50 a。③土壤有机质及全氮含量随退耕年限增加呈显著增加趋势(p<0.05),且上层土壤含量高于下层土壤,呈现明显的表聚现象。上层土壤中退耕20,25,35,50 a的样地中土壤有机质及全氮含量较耕地分别提高了27%,134%,71%和343%和20%,76%,64%和246%,下层土壤中分别提高了7%,88%,53%和422%和12%,59%,35%和201%。全磷含量在0.55~0.36 g/kg之间波动,受退耕年限影响较小。[结论] 退耕还林措施能有效增加土壤容重,提升土壤大粒径团聚体、有机质和全氮含量,进而改善土壤理化性质,退耕50 a样地土壤的理化性质接近于天然林地。
关键词:  米仓山  退耕年限  土壤结构  水分特征曲线  土壤养分
DOI:10.13961/j.cnki.stbctb.2020.05.008
分类号:S157;S152.7
基金项目:国家科技基础资源调查项目“中国南北过渡带综合科学考查”(2017FY100904)
Soil Physical and Chemical Property Changes in Different Periods of Abandoned Lands in Micang Mountain
Ji Yue1, Du Linqing2, Tian Peng2, Zhao Guangju1,3, Cui Yumei2, Ma Liangqian2
1.Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China;2.College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China;3.Institute of Soil and Water Conservation, Chinese Academy of Sciences&Ministry of Water Resources, Yangling, Shaanxi 712100, China
Abstract:
[Objective] The soil physical and chemical properties under different types of cultivation for a fixed number of years were studied to provide a scientific basis for the improvement of regional ecosystem services and ecological civilization construction.[Methods] Soil samples of forest land with different vegetation restoration periods (20, 25, 35, and 50 years) were collected by a spatiotemporal method. Unfertilized farmland and natural forest were taken as the control area.[Results] ① The soil particle composition did not change significantly in the early stage of returning farmland and was similar to that of the natural forestland at 50 years, while the content of large aggregates in 20, 25, 35, and 50-year abandoned plots increased by different degrees compared with the cultivated land (17.70%, 53.23%, 52.50%, and 70.30%, respectively). ② With the increase in the number of years of vegetation restoration, the soil bulk density showed a downward trend and finally tended to natural vegetation. The soil bulk density of the 50-year plot was close to that of natural woodland. All the soil moisture characteristic curve fitted well with the Gardner model. The order of the soil water-holding capacity was as follows: natural vegetation > 25 years > 35 years > 20 years > farmland > 50 years. ③ With the increasing number of years of vegetation restoration, both soil organic matter and total nitrogen content obviously increased (p<0.05). The content in the upper layer of soil was higher than that in the subsoil, and there was a significant phenomenon of surface layer accumulation. The contents of organic matter and total nitrogen in the upper layer of soil increased by 27%, 134%, 71%, and 343%, and by 20%, 76%, 64%, and 246%, respectively, while those in subsoil increased by 7%, 88%, 53%, and 422%, and by 12%, 59%, 35%, and 201%, respectively. However, the content of total phosphorus was between 0.55 and 0.36 g/kg; thus, it was less affected by the fixed number of years of the returning farmland.[Conclusion] The grain for green project can obviously improve the soil bulk density, increase soil particle size aggregates, improve the content of organic matter and total nitrogen, and further improve soil physical and chemical properties. The physical and chemical properties of the soil abandoned in 50 years were close to that of natural forestland.
Key words:  Micang Mountain  grain for green years  soil structure  soil moisture characteristic curve  soil nutrient