沂蒙山区小流域坡耕地土壤颗粒结构与养分退化特征

Grain structure and nutrient degradation characteristics of soil from small watershed's sloping lands in Yimeng mountainous areas

为探讨坡耕地土壤退化程度及其与坡度的关系,在沂蒙山区选择典型小流域,通过测定流域内不同坡度坡耕地、弃耕地与生态林地的土壤颗粒组成、分形维数、土壤养分质量分数的变化及其相关性,研究坡耕地土壤颗粒结构与养分退化特征。结果表明:1)所有土地利用类型,土壤砂粒体积分数最高,黏粒体积分数最低,平均值分别为70.81%、0.75%;2)土壤颗粒分形维数、有机质质量分数为生态林地>弃耕地>坡耕地;3)坡耕地土壤颗粒分形维数随坡度增加而减小,其大小与土壤粉粒和黏粒体积分数分别呈极显著、显著正相关;4)所有土地利用类型,土壤有机质质量分数与砂粒体积分数显著负相关,与粉粒和黏粒体积分数显著正相关,土壤氮、磷、钾养分质量分数与土壤颗粒体积分数相关性不显著;5)研究区土壤具有粗骨性砂土的物理特性,坡耕地耕作或坡度加大会增强土壤粉粒和黏粒的流失,导致土壤颗粒分布的均匀性及其分维数下降,水肥保蓄性能和养分质量分数降低。

In order to explore the relationship between soil degradation and slope gradient of arable sloping lands, the correlation among soil particle composition, fractal dimension and nutrient content were measured for three land types, i. e. , arable sloping lands with different gradients, abandoned arable lands and ecological woodlands, at a typical small watershed in the Yimeng mountainous areas. The results indicated that, I ） for all the three land types, the content of sand was the highest while that of clay was the lowest, with an average ofT0.81% and 0.75% respectively; 2） both the fractal dimension of soil particles and organic matter content ranked in a descending order as ecological woodlands 〉 abandoned arable lands 〉 arable sloping lands; 3） the fractal dimension of soil particles declined as the slope gradient increased, showing a highly significantly positive correlation with the silt content and a significantly positive correlation with the clay content; 4） the soil organic matter content was significantly negatively correlated with sand content but significantly positively correlated with the silt and clay contents, while nitrogen, phosphorus and potassium contents had no significant correlations with soil particles content; 5） the soils in the study area were found to have the physical characteristics of coarse texture sand, and the intensified cultivation activity and increased slope gradient of arable sloping lands would aggravate the loss of silt and clay contents, which will further result in the decline of distribution uniformity, fractal dimension, water and fertilizer maintenance capacity as well as nutrient content of soil particles.