沼泽湿地土壤氮矿化对温度变化及冻融的响应

通过室内控制培养试验方法,研究了不同温度和冻融循环过程对沼泽湿地土壤有机氮矿化影响。结果表明,湿地土壤中无机氮以铵态氮为主,温度和培养时间显著影响土壤有机氮的矿化,在温度-25~30℃之间,N的矿化速率、硝化速率随温度增加而增加,30℃时矿化速率（1.17mg.kg-1.d-1）和硝化速率（0.79mg.kg-.1d-1）最大。沼泽湿地土壤有机氮矿化培养时间以4~5周较为适宜。冻结温度和冻融次数显著影响土壤有机氮矿化过程,且-25~5℃冻融循环比-5~5℃冻融循环矿化累积量高。冻融循环促进了土壤有机氮的矿化,有利于土壤中有效氮的累积,为春季植物生长提供足够的氮素,对维持生态系统稳定有重要意义。

Effects of Temperature and Freeze-thaw on Soil Nitrogen Mineralization in Typical Calamagrostis Angustifolia Wetlands in Sanjiang Plain

As a mainly limiting factor for plant growth and net primary productivity,the availability of soil nitrogen is critical for the carbon budgets of terrestrial ecosystem.The climate warming in the Sanjiang Plain is obviously in recent years.In order to get a better understanding of the effect of temperature on the soil nitrogen mineralization to predict soil nitrogen cycling.The effects of temperature and freeze-thaw on soil nitrogen mineralization in typical Calamagrostis angustifolia wetland were evaluated by laboratory incubation method.Based on the analysis of inorganic nitrogen in soil extracts before and after incubation,the results showed that the NH＋4-N was the main characteristic in the soil inorganic nitrogen.The net mineralization of soil nitrogen was affected by temperature and incubation time.The net mineralization rate and nitration rate increased with temperature from-25 ℃ to 30 ℃.The mineralization rate（1.17 mg·kg-1·d-1） and nitration rate（0.79 mg·kg-1·d-1）had the highest value at 30 ℃ which could be the suitable temperature for nitrogen mineralization,and the appropriate incubation time was 4 weeks to 5 weeks.The marsh soil nitrogen mineralization was significantly affected by freeze temperature and numbers of freeze-thaw cycling.The lower freeze temperature generally promoted the nitrogen mineralization in the soils.The results implied that freezing-thawing of the wetland ecosystem accelerated the soil nitrogen mineralization,and increased the soil available nitrogen to favor the growth of plants and also increased the possibility of runoff loss of soil nutrients.