不同载畜率对短花针茅荒漠草原土壤呼吸的影响

草地是我国最大的陆地生态系统,土壤呼吸是草地碳循环研究的重要内容,是土壤碳库输出的主要方式,影响大气中CO2浓度变化。放牧是草地主要利用方式之一,通过动物采食和践踏,改变植被冠层结构,对土壤理化性质、土壤有机质和土壤微生物产生影响,进而改变土壤呼吸速率。为探究不同载畜率对短花针茅（Stipa breviflora）荒漠草原土壤呼吸速率的影响,2011—2012年用Li-8100开路式碳通量测定系统,对生长季内（6—10月）4个不同载畜率处理下的土壤呼吸进行测定,测定周期为2周1次。辅助测定地下10 cm的土壤温度及土壤湿度,并分析土壤呼吸与土壤温、湿度的关系。结果表明：1）2011年不同载畜率对土壤呼吸速率无显著影响,表现为对照〉中度放牧〉轻度放牧〉重度放牧的变化趋势。2012年与对照（1.6μmol·m-2·s-1）相比,重度放牧（1.07μmol·m-2·s-1）显著降低土壤呼吸速率。总体而言,2011年土壤呼吸速率低于2012年,但差异不显著。2011年土壤温度（20.73℃）显著高于2012年（14.38℃）,不同处理间无显著差异,重度放牧区偏高。2012年土壤湿度（7.24%）显著高于2011年（4.11%）,对2年数据整体分析发现,轻度放牧区土壤湿度显著低于对照和中度放牧。2011年土壤湿度变化趋势为中度放牧〉对照〉重度放牧〉轻度放牧。2012年,轻度放牧土壤湿度最小,各处理间差异不显著。2）2011年,土壤呼吸与土壤温度月动态无明显规律,与土壤湿度呈现相反的变化趋势。2012年土壤呼吸的月动态与土壤温、湿度变化趋势相似。3）2011年,土壤呼吸速率随温度升高出现波动,与土壤湿度呈负相关。2012年,土壤呼吸速率随土壤温、湿度升高而增大。在干旱年份,降水减少会掩盖放牧对土壤呼吸的影响;在降雨较多的年份,重度放牧显著降低土壤呼吸速率。

Effect of different stocking rate on soil respiration in Stipa breviflora desert steppe

Grassland is the largest continental ecosystem in China, soil perspiration is the major research topic of grassland carbon cycle, and is the important carbon output, which is of impact on atmosphere CO2. Grazing is one of the major grassland uses, livestock grazing and trampling change vegetation canopy structure, soil physical and chemical properties, soil organic matter and microorganism, and then change soil respiration. To reveal the effect of stocking rate on soil respiration rate inStipa breviflora desert steppe, we used Li-8100 open circuit soil C Flux measuring system to measure the soil respiration of four stocking rates during growing season（June-October） in 2011 and 2012 once of two weeks. Meanwhile, we measured the soil temperature and soil moisture in 10 cm depth of soil, and analyzed the relationship between soil respiration and temperature, moisture. We found that stocking rates had no significant effect on soil respiration rate in 2011, the tendency was control〉moderately grazing〉lightly grazing〉heavily grazing. Soil respiration in heavily grazing （1.07μmol·m-2·s-1） was significantly lower than that in control （1.6μmol·m-2·s-1） in 2012. Soil temperature in 2011 （20.73℃） was significantly higher than that in 2012 （14.38℃）, there was no significant difference among all of treatments, but the highest temperature was observed in the heavily grazing. Soil moisture in 2011 （4.11%） was significantly lower than that in 2012 （7.24%）. We found that soil moisture in lightly grazing was significantly lower than that in control and moderately grazing. The tendency is moderately grazing〉control〉heavily grazing〉lightly grazing in 2011, and lightly grazing was of the lowest soil moisture in 2012, but there were not significant difference among the treatments. The monthly dynamic of soil respiration rate was of no regular correlation with soil temperature, negative to soil moisture in 2011,but was of similar trend to temperature and moisture in 2012. Soil respirati