皇甫川流域不同尺度景观分异下的土壤性状

The soil properties along landscape heterogeneity on different scales in Huangfuchuan Watershed

皇甫川流域地处我国北方农牧交错带中段,是该地区正在进行的国家重点基础规划(“973”)项目设置的范式点之一。按照区域-小流域-中小地形这样的景观分类的等级体系,通过代表小流域的样带设置、实地调查和取样分析等,对该地区区域尺度、流域尺度和中小地形尺度景观分异下的土壤性状进行了分析。在此基础上,对研究区优化生态-生产范式的空间配置问题进行了探讨。结果表明:(1)总体上该研究区土壤养分含量低、发育程度差。(2)不同地质地貌类型区的土壤特性存在差异,黄土丘陵沟壑区的小流域比沙化黄土丘陵区和砒砂岩裸露丘陵沟壑区的小流域的土壤养分和质地好,相对更适于发展耕地。(3)中小地形尺度下,坡向、坡度和坡位及土地利用与土壤性状的关系为:1阴坡和阳坡的土壤有机质含量存在差异显著,且土壤养分还随着坡的向阳程度的减弱而增加。川地的土壤养分也较高,但土壤偏砂性。2坡度与土壤粒径存在显著相关,坡度不同侵蚀强度也不同。15°是侵蚀加剧的临界值,把它作为当地的退耕坡度标准是合理的。3土壤表层养分总体表现为随坡位的下降而减少的趋势。4综合考虑中小地形条件,景观立地类型可以划分为川台地养分富集区,坡中下部养分严重流失区(坡度>15°)和坡梁缓坡地养分涵养区(坡度<15°)。5中小地形尺度下,样带剖面上土地利用变化对土壤性状的影响较大:乔木林土壤养分积累高、团粒结构好,灌木林由于放牧和沙化的影响,土壤养分最低,砂粒含量最高而粘粒含量最低。撂荒地的土壤养分少而农田和果园的土壤养分较高。荒草地的土壤养分条件较差。但就耕地与非耕地而言,土壤养分和质地并无显著差异。说明耕地熟化作用很弱,广种薄收、靠天吃饭现象十分普遍;(4)不同尺度景观分异下的土壤性状研究是优化生态-生产范式的构建的重要理论基础。

Huangfuchuan Watershed, one of the five important paradigm sites of the project of State Key Basic Research and Development Plan of China,as the transitional area of Loess Plateau and Erdos Plateau,located in the middle part of North Farming-pastoral Zone in China. On region scale,according to material types from underlying rock＇s erosion（Pisha sandy rock,loess soil and wind sandy soil） ,physiognomy conditions and soil erosion intensity,the whole watershed were divided into three regions ：hilly gullied loess region,wind sandy hilly gullied loess region and Pisha sandy rock hilly gullied region. Five transects of several typical small watersheds were investigated in three different regions. Topography, soil and vegetation data on transects were collected and sample analyzed. Though the statistical methods of average comparison,OneWay ANOVA and test of LSD, Duncan,soil properties in Huangfuchuan Watershed were analyzed on region,small watershed and small topography scale. Landscape ecology system of Huangfuchuan Watershed is constructed,which consists of regionsmall watershed- small topography The results of research show： （1）As a whole,soil nutrient content in this study area is low,soil texture is rough,and soil is alkalescent. （2）There are great differences in soil properties among the watersheds of three different geologic-landform regions. Soil nutrients and texture of small watersheds in hilly gullied loess region are better than those in wind sandy hilly gullied loess region and Pisha sandy rock hilly gullied region,which are suitable for farming. （3）On small topography scale ,soil properties are correlated with hill aspect ,slope ,position and land use： ①With the decrease of the degree exposing to sun,soil nutrient content increases. There is significant difference between soil organic matter of shady slopes and sunny slopes. Soil nutrient content and clay content of shady slope all are the highest, while pH is low. Most of soil texture type of shady slope are loam soil. Soil nutrients of valley lands are higher,but soil textures are sandy. ② Soil particle composition is related with hill slope and the intensity of soil erosion. When the hill slope degree is less than 15°,the small size particle of soil are loss and clay and silt content of soil are low. When hill slope degree is more than 25°, sand content sharply decreases while silt content is high comparatively. 15° is a critical value for erosion changing, it is reasonable for 15° as a slope degree standard of Returning Farmland to Forest and Pasture in this area. ③Slope degree increases with the fall of hill position in this area,and middle slope, where soil erosion is severe,is the dividing line for slope and ravine. Soil nutrients content approximately decrease with the fall of hill position. In middle slope, as its serious erosion ,soil nutrient content and clay content is the lowest. Because of erosion and deposit ,Soil nutrient content and pH of lower slope is higher and sand content of valley flatland is the highest. ④ Comprehensively considering small topography condition, landscape ecotope type can be classified to soil nutrient enrichment area in valley flatland,soil nutrient losses area in middle and foot slope （slope degree〉15°）, upper gentle sloping land conservation area. According to slope aspect ,slope can be classified into shady and semi-shady aspect sub-area ,sunny and semi-sunny aspect sub-area. ⑤ On the small topography scale ,land use type is the important factor affecting soil properties. Soil nutrient accumulation in woodland is high and soil structure is good. Because of being overgrazed and sand accumulating,soil nutrient content and clay content of shrub land is the lowest ,sand content is the highest. Soil nutrient of grassland is poor. Because of fertilizing and improving soils ,soil nutrient content of cropland and orchard land is higher than fallow land. The difference of soil properties between cultivated land and non-cultivated land is not significant which shows soil nutrient of cultivated land is low and production is poor in research area. （4） Based on the research of soil properties along landscape heterogeneity on different scales, the construction of the Optimized Eco-productive Paradigms in this kind of areas was discussed. There are different landscape spatial patterns in different geologic-landform regions. Landscape spatial patterns of small watershed in hilly gullied loess region were got.