1990—2022年天山北坡地区不同开垦年限耕层土壤盐分变化

Changes in the salt content of the plow layer soil during cultivation from 1990 to 2022 on the northern slope of the Tianshan Mountains

近年来,随着频繁的土地利用变化和大量耕地的开垦,土壤盐渍化已成为导致天山北坡耕地质量退化、阻碍绿洲农业发展的环境因素。本研究基于翔实的调查数据资料、土壤实测数据和中国土地覆盖数据集(CLCD),比较传统插值模型和随机森林插值模型对耕层土壤(0~30 cm)含盐量插值的优缺点;选取精度最高的定量预测模型对天山北坡地区耕层土壤含盐量定量预测,得到耕层土壤含盐量分布变化特征;以空间换时间,将近30 a新开垦耕地耕层土壤含盐量进行比较,分析开垦年限对土壤含盐量的影响。结果表明:(1)与传统的插值方法相比,随机森林算法能够更准确地预测盐渍化土地的土壤盐分分布情况。(2)天山北坡地区,耕层土壤含盐量存在较大空间异质性,即高海拔地区土体中的盐分会随着径流的淋溶,在低海拔的河流下游尾闾或低洼区靠近沙漠一侧积聚。(3)随着开垦年限的延长,天山北坡地区耕层土壤含盐量总体呈现下降的趋势,且土壤盐渍化程度倾向于聚集在一个中等的水平上,趋向于平衡或“中心化”。本研究增进了对当前耕地盐渍化状况及从原始荒地开垦到耕地后耕层土壤盐分变化历程的理解。这为干旱区备用土地资源的开发、管理和有效利用提供了理论支撑,并为农业的持续发展提供了科学依据。

In recent years,with frequent changes in land use and extensive reclamation of farmlands,soil saliniza-tion has become an environmental factor leading to the degradation of cultivated land quality and hindering the development of oasis-based agriculture on the northern slopes of the Tianshan Mountains.However,an objective understanding of the current status of soil salinization in cultivated lands and its evolution is lacking.This study,based on detailed survey data,actual soil measurements,and the China Land Cover Dataset,compares the advan-tages and disadvantages of traditional interpolation models and random forest interpolation models for estimating the salt content in the topsoil layer(0-30 cm).The most accurate quantitative prediction model was selected to quantitatively predict as well as obtain the distribution and change characteristics of the salt content in the plow layer soil of the northern slope of the Tianshan Mountains.By using space for time,the salt content in the plow layer soil of newly reclaimed farmland over 30 years was compared to understand the impact of cultivation dura-tion.The results showed that:(1)Compared to traditional interpolation methods,the random forest algorithm could more accurately predict the soil salt distribution of salinized land.(2)In the northern Tianshan region,there was significant spatial heterogeneity in the salt content of the topsoil,with salt concentrations in the higher alti-tude areas leaching with runoff and accumulating in the lower altitude areas near rivers or in depressions close to the deserts.(3)With the extension of cultivation years,the overall salt content in the plow layer soil of the north-ern slope of the Tianshan Mountains decreased,and the degree of soil salinization converged at a moderate level,trending toward equilibrium or“centralization.”This study has enhanced the understanding of the current salini-zation status of cultivated land and the alterations in soil salinity from the reclamation of virgin wastelands to cul-tivated lands.It provides theoretical support for the development,management,and effective use of reserve land resources in arid areas,and offers a scientific basis for the sustainable development of agriculture.