东北黑土区耕地侵蚀退化空间分异特征

Spatial Differentiation Characteristics of Soil Erosion and Degradation in Black Soil Cropland of Northeast China

摘要:

土壤侵蚀是引发黑土地退化的重要原因，目前仍缺乏有关东北黑土区耕地侵蚀退化的综合评价。厘清黑土区侵蚀退化空间分异特征及侵蚀退化类型，将有利于因地制宜实施黑土地保护与修复技术模式。本文基于东北地区土种调查和土系调查土壤样点理化性质，构建了土壤质量综合指数，并使用环境协变量和随机森林模型反演得到1980年和2010年90 m分辨率的耕地质量空间分布图。同时考虑不同侵蚀营力及强度和土壤质量退化程度划分出15种黑土地侵蚀退化类型。结果表明：东北黑土区约1/3耕地发生侵蚀退化，其中水蚀退化面积广且程度严重，最典型的是水蚀轻度-退化严重类型，分布在大兴安岭东侧、小兴安岭北部、松嫩平原南部及长白山北部；风蚀退化以风蚀重度-退化轻微类型为主，分布在松辽平原中部及科尔沁沙地；融蚀退化所占耕地面积较少且程度轻微，集中分布于大兴安岭西部山麓。整体而言，黑土地土壤质量越高，土壤退化程度越严重，受到重度侵蚀的影响较大，水蚀导致的耕地退化最为严重。针对空间分布各异的侵蚀退化类型应推广差异化的黑土地保护与可持续利用技术。

Abstract:

【Objective】Soil erosion is a significant cause of degradation in black soil. To make matters worse, there is little or no comprehensive evaluation of soil erosion-degradation in black soil cropland in Northeast China. Thus, clarifying the spatial differentiation characteristics of soil erosion and degradation, as well as the different soil erosion-degradation types will be conducive to the implementation of soil protection and restoration technologies tailored to local conditions.【Method】Based on the physical and chemical properties of soil samples collected during two periods of soil survey, the soil species survey in the 1980s and the soil series survey in the 2010s, a comprehensive soil quality index was constructed in this paper via principal component analysis, considering soil thickness, soil organic matter content, total nitrogen content, total phosphorus content, total potassium content, pH value, and bulk density. The spatial distribution maps of soil properties in the 1980s and 2010s were created with a 90 m resolution using environmental covariates and the random forest model. Fuzzy membership functions were built to evaluate soil quality, and soil degradation was the difference between the quality from these two periods. A total of 15 erosion-degradation types of black soil were classified based on two aspects: the intensity of soil erosion types and the degree of soil quality degradation.【Result】The results showed that about one-third of the cropland in Northeast China experienced erosion-degradation. Among them, water erosion is extensive and causes serious degradation. The most typical type was mild water erosion-serious degradation (occupying 23.7% of erosion croplands), which was distributed in the east of the Great Khingan Mountains, the north of the Lesser Khingan Mountains, the south of the Songnen Plain, and the north of the Changbai Mountains. Other types include mild water erosion-slight degradation (16.4%), severe water erosion-serious degradation (14.1%), mild water erosion-no obvious degradation (7.4%), severe water erosion-slight degradation (6.8%), and severe water erosion-no obvious degradation (3.1%). Additionally, the main type of wind erosion was severe wind erosion-slight degradation type (10.1%), which was distributed in the middle of the Songliao Plain and Horqin Sandy Land. This was followed by mild wind erosion-slight degradation (8.3%), severe wind erosion-serious degradation (3.2%), mild wind erosion-serious degradation (2.3%), mild wind erosion-no obvious degradation (1.9%), and severe wind erosion-serious degradation (1.3%). The land area of freeze-thaw erosion-degradation types was small (1.4%),having mild intensity and concentrated in the western foothills of the Great Khingan Mountains.【Conclusion】Overall, our study reveals that the higher the quality of black soil, the more likely it is to suffer serious degradation, which is greatly influenced by severe erosion. Also, the degradation caused by water erosion was the most serious. According to the different spatial distribution of erosion-degradation types, distinct black soil protection and sustainable utilization technologies should be promoted.