退化红壤马尾松恢复林地土壤微生物生物量变化及其控制因素研究

CHANGE IN MICROBIAL BIOMASS AND ITS CONTROLLING FACTORS IN DEGRADED SOIL AFTER REFORESTRATION OF PINUS MASSONIANA

退化土壤植被恢复后土壤质量在凋落物参与下提高,但恢复土壤理化性质与土壤微生物生物量间的相互作用尚不清楚。本研究目标是调查退化红壤马尾松恢复林地凋落物清除对土壤理化性质和微生物生物量的影响,分析影响土壤微生物生物量的控制因素。研究结果表明,与侵蚀裸地相比,无论凋落物清除与否,马尾松恢复林地的土壤孔隙度、水稳性团聚体比例、土壤有机碳、全氮、土壤微生物生物量均有较大提高;其提高幅度受土层深度和坡位影响,主要表现为表层土壤大于亚表层土壤,坡顶和坡底土壤大于坡中土壤。与凋落物保留林地相比,凋落物清除林地土壤各项指标提高幅度降低。通径分析的结果表明,影响微生物生物量最重要的因素是土壤有机碳含量,其次为土壤孔隙度;凋落物则是通过孔隙度和有机碳来间接影响土壤微生物生物量。本研究说明土壤物理结构恢复对土壤生物学性质的恢复有重要意义。

Reforestation of degraded soil can improve soil quality through litter fall, but little is known about interactions between soil microbial biomass and soil physical and chemical properties. The objectives of this study are to determine effects of litter fall on physical and chemical properties and microbial biomass of a degraded soil 18 years after reforestation of Pinus massoniana and to analyze controlling factors on change in soil microbial biomass. Compared with the plot of eroded bare land, the reforested plot showed significant improvement in its measured soil properties, including soil porosity, proportion of water stable aggregate （ 〉 0.25 mm）, soil organic carbon and total nitrogen and soil microbial biomass irrespective of whether litter was removed or not. Magnitude of the increases varied with soil depth, slope position and litter management, being larger in the surface than subsurface soils, on the hilltop and foot-slope than on the middle slope. Compared with the treatment of litter preservation, the treatment of litter removal resulted in lower magnitude of the increases, Path analyses showed soil organic carbon content, was the most important factors affecting soil microbial biomass, followed by soil porosity, and then litter, which had some indirect effect through its contribution to soil porosity and soil organic carbon content. The findings of the study suggest that improving soil structural properties is important to recovery of soil microbial biomass.