子午岭次生林植被演替过程的土壤抗冲性

在水土流失极为严重的黄土高原地区,土壤抗冲性决定着土壤的可蚀性.于2004年5月在黄土高原惟一的次生林区——子午岭林区,通过原状土冲刷实验对不同植被演替阶段下的土壤抗冲性进行了研究.结果表明： （1）随植被的正向演替,表层土壤（0～15cm）的抗冲性明显增大,但亚表层（15～30cm）和底层（30～50cm）土壤抗冲性则没有太大的变化;（2）植物根系能显著的增强土壤抗冲性,土壤抗冲系数与单位土体根系表面积具有极显著的（p＜0.001）线性相关关系;（3）土壤抗冲系数随土壤中水稳性团聚体含量和微生物量的增加而增大,且其相关关系极显著（p＜0.001）.综合根系（x1）、水稳性团聚体（x2）以及微生物（x3）对土壤抗冲性的影响,建立黄土高原地区土壤抗冲性方程： y=-4.89＋1.27x1＋0.079x2＋1.94E-3x3 （R^2=0.914 p＜0.001）.

Soil anti-scouribility during vegetation succession of Ziwuling secondary forest

In China, the Loess Plateau is well known for its high erosion rate and vulnerable ecosystem. The soil erosion by water has been considered the cause of the losses of plant nutrients and productivity, and off-site environmental problems have also become a concern in recent years.Vegetation is the main factor to improve the environment in which soil erosion and water loss occur. High soil erosion rate by water mainly relates to low soil anti-scouribility in the Loess Plateau. A great number of researches about soil anti-scouribility have been conducted in some regions whose vegetations are severely impaired. However, little attention has been paid to the changes of soil anti-scouribility in the succession process of vegetation communities. In the spring of 2004, five plant communities at different succession stages were investigated in Ziwuling secondary forest of Shaanxi Province. The soil anti-scouribilitys of the communities were measured with their undisturbed soil samples that had been exposed to a flow at a rate of 4 L/min on a washing flume slope of 15° for 15 min, and the root surface areas, water stable soil aggregates and soil microbes of the communities were also measured in the soil sampling plots. The objective of the study was to examine the change of soil anti-scouribility and its relation with the roots, water stable soil aggregates and soil microbes in the process of vegetation succession. The results indicated that: (1) The upper soil layers had a higher soil anti-scouribility than the lower soil layers, and the soil anti-scouribilitys in the upper soil layers increased with the vegetation successions; nevertheless, the soil anti-scouribilitys did not varied much among different stages of the vegetation successions in the lower soil layers. (2) The soil anti-scouribilitys presented a positive and linear relationship with the root surface areas per unit soil volume, and the root surface areas alone explained more than 78% of the variations in soil anti-scouribility. (3) The water stable soil aggregates and soil microbes also positively affected the soil anti-scouribilitys, and the relationships among them could be expressed in linear equations; and the water stable soil aggregates and soil microbes could explain 93.5% and 77.8% of the variations in soil anti-scouribility, respectively. A linear equation to express the effects of the roots, water stable soil aggregates and soil microbes on the soil anti-scouribilitys was obtained by multivariate regression. This study may provide a new perspective for the research on vegetation control of soil erosion by water, and the equation for the soil anti-scouribilitys probably contributes to the development of soil erosion models in the Loess Plateau.