南京城郊不同植被类型土壤含水量变异规律

选择南京市城郊毛竹Phyllostachys edulis林和千金子Leptochloa chinensis草地, 分别在地下土壤5, 15, 30 cm深度埋设土壤水分探头, 在2.0 m高度处测定空气温度和湿度, 所有数据按照15 min间隔连续记录。研究了降雨间隔期不同植被土壤水分变异规律。结果表明:①不同土地利用类型受植物根系和凋落物影响, 相应层次间土壤体积含水量差异很大。草地相应层次土壤年平均体积含水量显著(P=0.05)低于毛竹林相应层次, 有凋落物覆盖的毛竹林0~40 cm土壤年平均含水量比草地多9.12%, 提高43.41%。②土壤含水量年平均变异系数在各土地利用类型内均和年平均土壤含水量呈显著(毛竹林:R2=0.77;草地:R2=0.986 4)负相关, 草地土壤年平均含水量变异系数变动为8.70%~16.80%, 毛竹林土壤年平均含水量变异系数变动为13.9%~16.4%, 下限显著高于草地, 波动幅度小, 表明毛竹林地土壤具有显著高于草地的水分涵养能力, 适合作为水源涵养林建设林种。③不同层次土壤含水量降雨间隔期呈指数显著(R2>0.9)相关关系消退。利用不同季节不同层次间土壤含水率指数模型, 可以预测森林抗旱能力并依次作出经营管理预案。

Surface volume soil water content in grasslands versus bamboo stands in a Nanjing suburb

In order to evaluate the water conservation function under forest soil, a Phyllostachys edulis bamboo stand and a Leptochloa chinensis grassland in the Tongshan Forestry Farm of Nanjing were selected with four sets (2 replications) of Decagon Em50 Data Loggers used to measure daily average soil Volumetric Water Content (VWC) at depths of 5, 15, and 30 cm with air humidity measured at a 2.0 m height for a year. All data were recorded continuously every 15 minutes. Results in the bamboo stand and grass land showed that (1) daily average soil VWC at 5 cm was 33.02%, at 15 cm was 26.16%, and at 30 cm was 30.60% with the lowest (at 15 cm) having the greatest root weight, root length, and soil compaction. In the grassland daily average soil VWC at corresponding depths was lower than the bamboo stand. For the 0-40 cm soil layer, the average annual VWC in the bamboo stand with thick litter on the ground was 9.12% higher than the grassland, improving by 43.41%. (2) For each land use type the average annual CV for daily average soil VWC was negatively and significantly correlated (R2>0.9, P < 0.001) to average annual soil VWC, varying between 8.70%-16.80% in the grassland and 13.9%-16.4% in the bamboo stand. Thus, due to plant roots and litter, daily average soil VWC in corresponding soil layers of the bamboo stand had better water conservation capabilities than the grassland. It is believed to be useful in water conservation forest construction with bamboo. (3) Simulated with exponential function model, seasonal daily average soil VWC correlated significantly (R2>0.9, P < 0.001) with rain day interval for different soil layers, which could be used to help predict drought and to assist in drought control management.