模拟增温和氮素添加对荒漠草原生态系统碳交换的影响

Effects of warming and N addition on ecosystem carbon exchange in a desert steppe

气候变暖和大气氮沉降是全球变化的重要驱动因子。在草地生态系统中,气温升高和大气氮沉降都会改变草地固碳(C)状况,然而温度增加和大气氮沉降是如何影响生态系统碳交换目前还不明确。本研究旨在研究增温和氮素添加对荒漠草原碳交换的影响。在短花针茅荒漠草原上采用2×2因素完全随机区组的裂区设计,使用红外辐射器来模拟气候变暖并且使用添加氮肥的方法来模拟大气氮沉降,在不同处理条件下测定生态系统净碳交换(NEE)、生态系统呼吸(ER)和总生态系统生产力(GEP),分析了2013和2014年影响短花针茅荒漠草原生态系统C交换的因素,结果如下:(1)增温使土壤温度显著增加了0.70℃(P<0.001),土壤湿度显著增加了7.58%(P<0.001)。(2)增温、氮素添加及其交互作用显著增加了GEP和ER(P<0.05),而对于NEE没有显著影响(P>0.05)。(3)2013年GEP在8月初达到峰值,ER在8月末9月初达到峰值,NEE随着GEP和ER的变化而波动;2014年GEP、ER和NEE均在8月末9月初达到峰值。(4)ER和GEP随着大气温度升高和降水增加而增大,土壤温度和土壤湿度也是影响生态系统C交换的重要因素。

Global warming and atmospheric nitrogen（ N） deposition are two of the most important global change drivers. In grassland ecosystem,increasing atmospheric temperature and nitrogen deposition are expected to modify the carbon sequestration; however,how warming and nitrogen addition affect ecosystem carbon exchange in the given conditions is unclear. The objective of this study was to assess the effects of global warming and N addition on C exchange of the desert steppe. A random split plot experiment（ 2×2 factors） in a desert steppe with dominant species of Stipa breviflora was conducted to mimic the climate warming using the infrared heaters and enrichment of nitrogen deposition by fertilizer addition. The gross ecosystem productivity（ GEP）,ecosystem respiration（ ER） and net ecosystem exchange（ NEE） were measured in different conditions. The integrated impact factors on ecosystem carbon exchange were analyzed during 2013 and 2014. The results showed that：（ 1） Warming significantly increased soil temperature and soil moisture about 0.70 ℃（ P〈0.001） and 7.58%（ P〈0.001）,respectively.（ 2） Warming,N addition and their interaction significantly increased the GEP and ER（ P〈0.05）,but they had no significant effect on NEE（ P 〉0. 05）.（ 3） In 2013,GEP peaked in early August,but ER reached peak during late August and early September,so NEE changed with GEP and ER. GEP,ER and NEE all peaked during late August and early September in 2014.（ 4） ER and GEP increased with the increasing air temperature and precipitation. Furthermore,soil temperature and soil moisture were also two of the most important factors affecting ecosystem carbon exchange.