<正>土壤微生物生物量是表征退化喀斯特植被恢复过程中土壤质量的重要特征之一。笔者以贵州花江喀斯特高原生态综合治理示范区内土壤为研究对象，分析了退化喀斯特植被恢复过程中不同生境、不同层次、根际和非根际土壤微生物生物量碳的变化特征。结果表明：退化喀斯特植被恢复过程中土壤中的微生物生物量碳存在较大差异。随着退化喀斯特植被的恢复，土壤微生物生物量碳明显上升，从大到小表现为乔木群落阶段、灌木群落阶段、草本群落阶段、裸地阶段，反映出土壤质量在逐渐恢复；土壤微生物生物量碳的变化特征在不同生境间从大到，J、主要表现为裸地和草本群落阶段为石沟、土面、石槽，灌木群落阶段和乔林阶段为石槽、土面、石沟；土壤剖面上均呈明显的垂直分布特征，即随土层深度的增加，呈递减趋势，根际和根外变化明显，表现为根际高于非根际。

In order to understand the plasticity of submerged macrophytes to environmental variations, an experiment on the g～owth response of Hydrilla verticillata to two sediment types (sand, clay+sand) and three densities was made. The results showed that compared with to sand sediment, (clay+sand) sediment greatly increased the plant height and stem diameter and decreased the root biomass allocation (P<0. 05). Lower density significantly increased the stem biomass allocation while decreased the leaf biomass ratio (P<0.05).’ For sand, plants at high density grew better, e. g., a great increase in relative growth rate and biomass (P<0.05). However, for clay+sand, density had an opposite influencing pattern, i. e., plants at high density had a slower growth (P<0.05). At high density, sand increased plant growth (P<0.05). At lower density, plants at (clay+sand) sediment grew faster (P