三种典型山地河岸林土壤氮含量时空格局对高地氮输入的响应

河岸林土壤和植被对高地养分的滤除功能是河岸带生态保护与恢复的基础。揭示特定河岸林土壤氮含量的时空格局对高地氮输入的响应,有助于加深对河岸林氮滤除过程和机制的认识。目前对高地氮输入下山地河岸林土壤对氮的削减作用及林型差异、距离梯度格局及其变化的规律尚不确切。本文以文峪河上游云杉、华北落叶松和杨桦三种典型山地河岸林土壤为研究对象,采用原位土壤实验槽并模拟高地氮输入的方法,分析土壤全氮、硝态氮和铵态氮含量在土层深度、距离上的梯度格局及其随时间的变化,分析不同林型和输入量之间的差异。结果表明:(1)三种山地河岸林土壤在不同氮输入下,土壤全氮和铵态氮含量随时间升高而硝态氮降低,华北落叶松林土壤对氮的转化最明显;(2)河岸林土壤中全氮含量变化率阈值在5 m附近,而铵态氮和硝态氮含量变化率阈值分别在9 m和10 m附近;(3)土层深度对土壤全氮和硝态氮含量起决定作用,而氮输入量大小显著影响了土壤铵态氮含量。研究结果可为流域污染防控中的山地河岸林类型选择和河岸带宽度设计提供依据。

Effects of Temperature and Nitrogen Input on Nitrogen Mineralization in Alpine Soils on Tibetan Plateau

[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.