太湖地区竹林生态系统土壤硝态氮的分布特征——以浙江省安吉县为例

Soil Nitrate Distribution of Bamboo Forest Ecosystems in the Taihu Lake Region:A Case Study of Anji County in Zhejiang Province

为充分认识竹林生态系统在太湖流域水污染防治中的作用,于2009年7月-8月在浙江省安吉县对竹林土壤的硝态氮(NO-3-N)含量进行采样分析,并探讨了植被类型、地形条件等因素对土壤NO-3-N的影响。结果表明:①各采样点内,随土壤深度的增加,竹林土壤NO-3-N含量降低;②毛竹林0～30cm土壤层NO-3-N含量高于红笋竹林,而30～50cm土壤层则相反,但差异不显著;③林下植被为草灌结构的样点土壤NO-3-N含量高于林下植被为草丛结构的样点,这种差异在30～50cm上显著;④不同植被高度的土壤NO-3-N含量差异在0～10cm深度上达到显著水平;⑤土壤NO-3-N含量随海拔升高呈"先下降后上升"趋势,高海拔地区0～10cm土壤层的NO-3-N含量高于低海拔地区,10～30cm与低海拔地区相近,而30～50cm则小于低海拔地区;⑥位于陡坡的0～30cm土壤层NO-3-N含量均高于缓坡,而30～50cm土壤层则相反。综上分析,笔者认为竹林不同深度土壤NO-3-N的含量与植被状况、地形特点有密切关系。由于植被类型、覆盖度、枯落物以及地形条件的差异,影响了土壤水分获取及水分再分配进程,进而影响了土壤中NO-3-N的迁移和累积过程。

To examine the role of the bamboo forest in non-point source pollution control in the Taihu lake region,the soil profile nitrate concentration of 5 Phyllostachys pubescens plots and 5 Phyllostachys iridescins plots along the Xitiaoxi River from the upstream to the downstream were measured through July to August in 2009.The relationship between vegetation type and topographic factors and nitrate was analyzed.Results show that 1） soil nitrate concentration decreased with increasing soil depth.2） In Phyllostachys pubescens plots,the nitrate concentration at a 0-30 cm depth was higher than Phyllostachys iridescins plots;however,the soil nitrate at a 30-50 cm soil depth was higher on Phyllostachys iridescins plots than Phyllostachys pubescens plots.There was no significant differences between these two vegetation plots.3） Plots having understory vegetation types of grass and shrub had a higher nitrate concentration than understory vegetation type of grass.The differences were marked at a 30-50 cm soil depth.4） The soil nitrate concentration at a 0-10 cm soil depth in plots whose vegetation height was higher than 5 m was significantly higher than plots whose vegetation height was lower than 5 m.5） The nitrate concentration of bamboo forest soil decreased first and then increased with increasing elevation.The nitrate concentration at a 0-10cm soil depth above 200 m altitude was higher than those below 200 m altitude.The nitrate concentration at a 10-30 cm soil depth had a similar content between different elevations;however,the nitrate concentration at a 30-50 cm soil depth was higher at lower altitudes and lower at higher altitudes.6） The soil nitrate concentration at a 0-30 cm depth was higher for steep slopes and lower for gentle slopes.The soil nitrate concentration at a 30-50 cm depth for gentle slopes was higher than steep slopes.In summary,the soil nitrate of different soil depths was found to be closely related to vegetation type and topographic features.Soil water content and hydraulic redistribution which are significantly affected by vegetation,coverage,litter,and topographic factors play an important role in migration and accumulation processes of soil nitrate.