黄土丘陵区3种典型天然草地群落土壤呼吸对模拟降雨的响应

土壤呼吸是影响陆地生态系统碳循环的关键生态学过程之一,降雨是土壤呼吸变化的重要驱动因子.为探明黄土丘陵区退耕草地群落土壤呼吸对降雨的短期响应规律,选择白羊草(Bothriochloa ischaemum)、达乌里胡枝子(Lespedeza davurica)、铁杆蒿(Artemisia gmelinii)为优势种的3种草地群落为研究对象,于2014年6月和7月,以未降雨群落为对照,对比测定了2种模拟降雨量(15 mm和50 mm)下连续8 d的土壤呼吸速率及土壤水分和土壤温度等.结果表明:2种模拟降雨量对3种草地群落土壤温度和土壤含水量均具有显著影响(p0.05).50 mm降雨下群落土壤呼吸速率增加量高于15 mm降雨.3种群落土壤呼吸对降雨的响应程度存在明显差异,其中,土壤呼吸速率峰值高低顺序为:白羊草(1.75 g·m~(-2)·h~(-1))铁杆蒿(1.69 g·m~(-2)·h~(-1))达乌里胡枝子(1.12 g·m~(-2)·h~(-1)).0~10 cm土壤含水量与土壤呼吸速率呈显著对数函数关系.3种群落土壤呼吸温度敏感性系数Q_(10)值变化范围是1.31~2.01,且月份和降雨量处理间均存在差异.研究表明,准确评估降雨格局改变背景下退耕草地生态系统碳收支需考虑群落类型的差异.

Soil respiration response to simulated rainfall pulses in natural grassland communities in loess hilly-gully region

Soil respiration is one of the key ecological processes of carbon cycle in terrestrial ecosystem, and rainfall is one important factor driving soil respiration change. In order to clarify the short-term response of soil respiration dynamics to rainfall pulses in grassland communities in loess hilly-gully region, soil respiration rate, soil water content and soil temperature in top soil layer were monitored in Bothriochloa ischaemum,Lespedeza davurica, and Artemisia gmelinii dominated grassland communities. Three simulated rainfall treatments (0 mm, 15 mm and 50 mm) were carried on in June and July, 2014, and the measurements were taken one day before and seven days after the simulated rainfall. Results showed that soil temperature and soil water content varied significantly with simulated rainfall sizes (p<0.05). Soil respiration rate under 50 mm rainfall was bigger than under 15 mm in each community or month. Significant differences of pulse effect existed among the three communities, and the peak values order was B. ischaemum (1.75 g·m^-2·h^-1) >A. gmelinii (1.69 g·m^-2·h^-1) > L. davurica (1.12 g·m^-2·h^-1). The relationships between soil respiration and soil water content in 0~10 cm soil profile were logarithmic function. The Q₁₀ values were 1.31~2.01 and varied with growth months and rainfall sizes. Our results imply that it is necessary to consider the community types for accurately evaluating the carbon budget of rehabilitated grassland communities in the region under rainfall pattern change phenomenon.