应用Le Bissonnais法研究黄土丘陵区土壤团聚体稳定性

Application of Le Bissonnais method to study soil aggregate stability in the Hilly-gully region

以黄土丘陵区森林草原过渡带燕沟流域植被自然恢复过程中6种植被类型为研究对象,应用Le Bissonnais(LB)法测定了不同植被类型下土壤水稳性团聚体,对比分析了LB法3种处理的测定结果与传统湿筛法(Yoder)的差异性。结果表明:在LB法3种湿润处理下,快速湿润处理(FW)对土壤团聚体结构的破坏程度最大,处理后土壤水稳性团聚体以0.05～0.5 mm为主;慢速湿润处理(SW)对团聚体的破坏程度最小,处理后土壤水稳性团聚体主要以>2 mm团聚体为主;而预湿后扰动处理(WS)对团聚体的破坏程度介于FW和SW之间,处理后土壤团聚体粒径分布比较均匀。说明该区土壤团聚体破坏的主要机制是土壤孔隙中的气泡爆破产生的消散作用。退耕100a期间,植被群落由1年生草本(4 a)—多年生灌草(16 a)—半灌木(29 a)—灌木(55 a)—乔木(100 a)方向演替过程中,土壤水稳性团聚体由小粒径向大粒径方向转变,土壤结构趋于稳定。LB法3种处理中,FW处理与SW处理所测得>0.5 mm团聚体含量和平均重量直径与土壤有机质和物理性黏粒之间存在显著的相关性,而WS处理未达到显著水平(P>0.05)。说明土壤有机质和物理性黏粒主要影响消散和黏粒膨胀引起的崩解作用,而对机械干扰引起的团聚体破坏无明显影响。LB法3种处理中,慢速湿润方法所获得土壤团聚体稳定性特征更接近湿筛法,适宜于黄土丘陵区植被恢复过程中土壤水稳性团聚体的测定。

Soil aggregate stability is a key indicator for soil quality evaluation. The transition area from forest to grassland zone of the Hilly-gully region, located in Yangou Catchments in Yan＇an City, was taken as a research site. Soil samples from six vegetation types during vegetation natural restoration were used to measure soil water-stable aggregate using Le Bissonnais （LB） method, and compared the results of LB 3-treatments with the Yoder method. The results showed that, in the 3-treatments （fast wetting, slow wetting, and wetting stirring） of LB method, fast wetting （FW） was the most destructive degree to the soil aggregate stability, the distribution of soil water-stable aggregate mainly concentrated in 0. 05 -0.5 mm ; slow wetting （SW） was the least destructive degree to soil aggregate stability, soil water-stable aggregate content was mainly 〉 2 mm; the destructive degree of soil aggregate structure by wetting stirring （WS） was between FW and SW treatments, the soil water-stable aggregates size was well-distributed. It was explained that the primary destructive mechanism of soil aggregate structure was dissipation. During the period of 100a of abandoning cropland, the succession process of vegetation experience is annual herbaceous （4 a）-perennial herbaceous （16 a）-semi shrub （29 a）-shrub （55 a）-arbor （100 a）. With the succession process of vegetation, soil water-stability aggregate size shifted from small size to large size, soil structure was improved. The correlation between 〉 0. 5 mm soil aggregate content or mean weight diameter （MWD） measured by FW or SW and soil organic carbon or physical clay content was significantly different; but for WS treatment, there was no significant different between soil aggregate content or MWD and soil organic carbon or physical clay content. This result showed that soil organic matter and physical clay content mainly influenced dissipation and disintegration by clay swelling and mechanical stirring had no significant impacts on soil aggregate stability. Comparing with the Yoder method, SW and Yoder method have highly comparability, and SW treatment of LB method was suitable to measure soil water-stable aggregate during vegetation restoration in the Hilly-gully region.