基于土壤侵蚀定位土芯元素示踪法和GIS技术红壤小流域坡地土壤肥力的综合评价

Soil Erosion Monitor Based on Fixed Soil Core Eu Tracer and Comprehensive Evaluation for Soil Fertility in Micro-Watershed on Red Soil Areas

利用定位土芯稀土元素(Eu)示踪法及中子活化技术,对蒋家塘小流域坡地土壤侵蚀空间分布规律进行了研究,并利用模糊数学的方法,建立了影响蒋家塘小流域侵蚀土壤肥力因素单因子评价模型,利用层次分析法确定各评价因子的权重,并用加权法得到每个评价单元的土壤肥力综合指数,根据其数值的大小,将土壤肥力分为高(>0.45)、中(0.25～0.45)和低(<0.25)3级。借助地理信息系统软件ARCVIEW3.1对蒋家塘小流域坡地土壤侵蚀状况和土壤肥力状况进行了分析,结果表明:地形部位较高,坡度较大,植被较少或裸露的坡顶及上坡部位,土壤侵蚀量较大,侵蚀程度严重;而在地形部位较缓,植被覆盖度较大的坡段土壤侵蚀量较小,侵蚀较轻。植被覆盖度较小,顺坡种植的坡段,土壤侵蚀量较大,土壤侵蚀严重;而植被覆盖度较大,等高梯田种植的坡段土壤侵蚀量较小,土壤侵蚀较轻;下坡部位土壤往往发生沉积。在整个小流域中,侵蚀程度严重(>100t/hm2·a)的坡地面积比例为15.67%,侵蚀程度中等(10～100t/hm2·a)的坡地比例为22.13%,侵蚀程度较轻(1～10t/hm2·a)坡地比例为5.60%,无侵蚀(<1t/hm2·a)的坡地比例为34.23%。土壤肥力较高的坡地面积比例为22.00%,中等的为34.75%,低下的为20.85%。蒋家塘小流域坡地土壤肥力水平多数处于中下等水平,占总流域面积?

The spatial distribution of soil erosion of Jiangjiatang watershed on red soil areas in Lanxi city, Zhejiang province, southern China, was studied using fixed soil core Eu tracer and meanwhile an appraisal on the soil integrated fertility index was also conducted using mathematical methodology. Two types of functions for calculating the values of soil fertility indices were developed according to principal of fuzzy mathematics, and these indices weight value were calculated applying the analysis hierarchy program, then soil integrated fertility indices in different units were also calculated. According to the results of the calculation, soil fertility was divided into high (>0.45), middle(0.25～0.45), low(<0.25)grades. The spatial distribution of soil erosion and the characteristics of soil fertility in this watershed were analyzed by ARCVIEW3.1, a GIS based software. The results were as follows: Soil erosion was serious in the upper parts of slopes with less plant coverage, but in the lower sections of the slopes with more plant coverage soil erosion was light. Soil erosion on slope land with traditional cultivation and less plant coverage was serious, but was less on slope land with terraces or more plant cover, in both these cases soil was deposit on the lower sections of the slopes. The areas of soil with serious erosion (erosion modulus: >100 t/hm2·a), modest erosion (10～100 t/hm2·a), light erosion (1～10 t/hm2·a), less erosion (<1 t/hm2·a) accounted for 15.67%, 22.13%, 5.60%, 34.23% of total watershed area respectively. Most of the soil in Jiangjiatang watershed was of middle and lower fertility, which accounted for 55.60% of area of this watershed or 71.62% of slopes in this watershed. The spatial distribution of soil integrated fertility index was in concordance with the spatial distribution of soil erosion. The soil fertility index in slope land, where the soil erosion was serious, was lower, and conversely, the soil fertility index was higher in areas where soil erosion was less serious. The coefficient of correlation between modulus of soil erosion and soil integrated fertility index was 0.801(n=33), which was positively significant.