拉萨河谷设施农地土壤质量变化及空间分异特征

Soil Quality Change and Spatial Differentiation Characteristics of Greenhouses Land Soil in Lhasa River Valley

青藏高原设施农地存在土壤质量变化的迹象,而拉萨河谷作为青藏高原地区设施农地的主要分布区,其土壤质量的整体变化及区域分异规律尚不明确。以大田耕地为参照,采集设施农地土壤样品240个和大田耕地土壤样品112个,测定了土壤理化指标21项,采用土壤综合质量指数和因子探测器方法,研究了设施农地土壤质量变化及空间分异特征,并辨识设施农地土壤质量变化的主要因子。结果表明:(1)拉萨河谷设施农地和本底土壤质量指数分别为0.36、0.43,两者80%的样地土壤质量等级均分布在Ⅴ~Ⅲ级;且设施农地土壤质量较高的样地主要分布在海拔3700~3750 m,距河流930 m内的阳坡地带。(2)较大田耕地,设施农地土壤质量指数平均下降了16.28%,且存在明显空间差异。其中堆龙德庆区土壤质量下降最明显,平均降低了74.46%。不同深度上,0~10cm范围内土壤质量下降最明显,平均下降了6.5%。(3)受海拔和坡向影响,设施农地土壤质量整体变化存在空间分异。即随着海拔增加和阳坡到阴坡的变化,设施农地土壤质量变化幅度均表现为明显增大趋势。(4)全区设施农地土壤质量变化普遍受到含盐量、速效钾和镉含量变化的影响,三者解释力均可达到20%以上。综上,本研究明晰了高原设施农地土壤质量整体变化及其空间分异,为该地区设施农业布局和发展提供了理论依据。

【Objective】Soil quality problems often arise in the process of greenhouse agriculture pursuing economic benefits.There are also signs of soil quality changes in the Tibet Plateau greenhouse land,and the regional differentiation pattern of soil quality changes in the Lhasa Valley.The Lhasa Valley is the main distribution area of greenhouse plots on the Tibet Plateau.Nevertheless,there is limited research that integrates the physical and chemical properties of its soil to reflect overall soil quality changes in the facility farmland with a comprehensive index,and the overall soil quality changes and their regional differentiation patterns are not yet clear.【Method】Taking the arable land soil samples as the references,this study collected 240 soil samples of greenhouse land and 112 soil samples of arable land.The texture,pH value,water-soluble total salt content,organic matter,total nitrogen,alkali-hydro nitrogen,total phosphorus,available phosphorus,total potassium,available potassium,and soil heavy metals elements(Cr,Ni,Cu,Zn,Pb,Cd,As,Hg)were determined.The comprehensive soil quality index and factor detector methods were used to study the soil quality changes and spatial differentiation characteristics of the greenhouse land soil in Lhasa Valley,and the main factors of soil quality changes in the greenhouse land soil were identified.【Result】The comprehensive soil quality indices of the Lhasa valley greenhouse land and the arable land soil were 0.36,and 0.43,respectively.The soil quality grades of 80%of both samples were distributed in V–III.The soil quality of the greenhouse land was relatively high on the sunny slopes within 930 m from the river at an altitude of 3,700–3,750 m in the area.Secondly,there were spatial differences in the degree of soil quality variation in the study area.The SQI of the greenhouse land decreased by 16.28%on average compared to that of the larger field farmland.Among them,soil quality in the Doilungdeqen County decreased most significantly,with an average decrease of 74.46%.At different depths,soil quality decreased most significantly in the range of 0–10 cm,in which the average decline was 6.5%,and the highest percentage of declining sample plots,at 66.67.Thirdly,there was spatial heterogeneity in soil quality changes in the greenhouse land affected by altitude and slope direction.With the increase of elevation and the change of soil quality from sunny slope to shady slope,the change of soil quality in the agricultural land facilities showed a significant trend of increase.Finally,analysis of the soil quality change factors in greenhouse land found that the soil quality change in the whole region was generally affected by changes in salt content,available potassium and cadmium content,and the explanatory power of all three could reach 20%.【Conclusion】Under the changing influence of salt accumulation,available potassium and cadmium content changes,the overall soil quality of the study area's greenhouse land showing a decreasing trend and varied significantly in different regions.This could provide a theoretical basis for the layout and development of greenhouse agriculture in the region.