短期增温和增加降水对内蒙古荒漠草原土壤呼吸的影响

 利用红外辐射增温装置模拟短期持续增温和降水增加交互作用对内蒙古荒漠草原土壤呼吸作用的影响, 结果表明: 土壤含水量对月土壤呼吸的影响显著大于土壤温度增加的影响, 生长旺季的月土壤呼吸显著大于生长末季; 土壤温度和水分增加都显著影响日土壤呼吸, 但二者的交互作用对土壤呼吸无显著影响。荒漠草原7?8月平均土壤呼吸速率为1.35 μmol CO₂·m^–2·s^–1, 7月份为2.08 μmol CO₂·m^–2·s^–1, 8月份为0.63 μmol CO₂·m^–2·s^–1。土壤呼吸与地下各层根系生物量呈幂函数关系, 0?10 cm土层的根系生物量对土壤呼吸的解释率(79.2%)明显高于10?20 cm土层的解释率(31.6%)。0–10 cm土层的根系生物量是根系生物量的主体, 根系生物量对土壤呼吸的影响具有层次性。在未来全球变暖和降水格局变化的情景下, 荒漠草原土壤水分含量是影响生物量的主导环境因子, 而根系生物量的差异是造成土壤呼吸异质性的主要生物因素, 土壤含水量可通过影响根系生物量控制土壤呼吸的异质性。

Effects of short-term warming and increasing precipitation on soil respiration of desert steppe of Inner Mongolia

Aims Our objective was to examine the effects of global warming inducing environmental and biological changes on soil respiration of desert steppe.
Methods We used infrared heaters to carry out the interactive simulation of warming and increasing precipitation in a desert steppe of Inner Mongolia from June to September 2011. Our experimental design was set up with two temperature levels (control and warming) and three precipitation treatments (control, 15% and 30% increase of the average precipitation during 1987–2007), using a complete randomized block arrangement. Soil respiration rate was measured by a LI-8100 carbon flux system in these six different treatments. We analyzed the relationships between soil respiration and environmental factors, aboveground biomass, and belowground biomass at different soil layers (0–10, 10–20 and 0–20 cm).
Important findings Soil respiration in the desert steppe reached its peak value in the middle of the growing season. The average soil respiration rate of the desert steppe from July to August was 1.35 μmol CO₂·m^–2·s^–1. The soil respiration rate was 2.08 and 0.63 μmol CO₂·m^–2·s^–1 in July and August, respectively. Increasing soil moisture and temperature significantly influenced daily soil respiration, but their interaction had no significant effect on soil respiration. Soil moisture had greater impact on monthly soil respiration than soil temperature. Soil respiration rate showed a power function relationship with belowground biomass at different soil depths. The belowground biomass at 0–10 cm soil was the major part of the belowground biomass and could explain more variation of soil respiration rate (79.2%) than that at 10–20 cm (31.6%). Under the future climatic changes scenarios, soil moisture was a principal environmental factor affecting plant biomass, while belowground biomass was a major biological factor controlling soil respiration in the desert steppe. Soil moisture might control the heterogeneity of soil respiration by influencing the distribution of belowground biomass at different soil depths.