黄土台塬土地利用方式对土壤水稳性团聚体稳定性影响

论文以黄土台塬不同土地利用方式为对象,采用几何平均直径(GMD)、平均重量直径(MWD)、分形维数(D)、破坏率(PAD)、峰凸系数(CE)和偏倚系数(CS)对其土壤0.25 mm团聚体进行分析,探讨土地利用方式转变对土壤团聚体水稳性的影响及其最佳评价指标的选择。结果表明:不同利用方式土壤团聚体含量、GMD及MWD均表现为耕地乔灌混交林地乔木林地天然草地灌木林地;林和草的种植有利于促进土壤较大粒径团聚体的形成,其土壤1~5mm粒级团聚体占0.25 mm团聚体总量比重显著(53.90%~80.20%),结构非均匀性明显(灌木林地和天然草地土壤尤为突出);而耕地土壤0.25~1 mm粒级团聚体占0.25 mm团聚体总量比重较大(约81%),结构呈均匀性;林地和草地土壤剖面由上而下团聚体优势粒径逐渐变小,结构差异逐渐减弱,该趋势灌木林地和天然草地较为缓慢,而耕地在整个剖面上均呈优势粒径较小,结构均一;GMD和CS可较好地衡量整个剖面土壤团聚体水稳性,而PAD可更好地描述0~20 cm深度。

Stability Characteristics of Soil Water-stable Aggregates under Different Land-use Patterns on the Loess Plateau

The stabilities of soil aggregates of different land-use patterns in the Loess Plateau were studied, and the distributions of water-stable aggregates were obtained by fractionating the aggregates with a wet-sieving procedure. Geometric mean diameter (GMD), mean weight diameter (MWD), fractal dimension (D), destruction rate (PAD), peak convex coefficient (C_E) and bias coefficient (C_S) were used to analyze and compare soil aggregates stability (>0.25 mm). The study aimed to explore the stability of soil aggregates under different land use patterns, obtain the best indexes to represent soil aggregates stability and reveal the influences of land use transformation on soil structure. The content of soil water-stable aggregates, GMD and MWD under different land use patterns were all in the same order as farmland < arbor-shrub mixed forestland < arbor forestland < natural grassland < shrub forestland. Forest and grass were conducive to form larger-particle aggregates, in which the weight of soil aggregates with 1-5 mm particles accounted for 53.90%-80.20% of the weight of soil aggregates with particles greater than 0.25 mm and this structure was obviously inhomogeneous in forestland (especially shrub forestland) and grassland. For farmland, the weight of soil aggregates with 0.25-1 mm particles accounted for 81% of the weight of soil aggregates with particles greater than 0.25 mm and the structure was homogeneous. The size of dominant particles in the aggregation gradually became smaller from top layer to deep layer in soil profiles of forestland and grassland so that the differences of structure became less. This trend was sharp in arbor forestland, but it was slow in shrub forestland and natural grassland. There were significant positive correlation among GMD, MWD, C_E and C_S, while these indexes had negative correlation with D and PAD. The aggregate stability features in the whole profile could be described felicitously by GMD and C_S, while the soil at 0-20 cm depth could be described by PAD properly.