CO2浓度升高对森林土壤微生物呼吸与根（际）呼吸的影响

 根呼吸与微生物呼吸的作用底物不同,二者对高浓度CO₂的响应机理及敏感程度亦不同。在大气CO₂浓度升高的背景下,精确区分根呼吸与微生物呼吸是构建森林生态系统碳循环模型和预测森林生态系统碳源/汇关系所必需的。根（际）呼吸与微生物呼吸对高浓度CO₂的响应呈增加、降低或无明显变化等不同趋势,根（际）呼吸变化主要与根生物量明显相关,细根的作用大于粗根;土壤微生物呼吸变化存在较大的不确定性,微生物量和微生物活性与土壤微生物呼吸相关或不相关。根系统对高浓度CO₂的响应会潜在地影响微生物的代谢底物,进而影响微生物呼吸强度。凡影响土壤总呼吸的生物与非生物因子都会直接或间接地影响根呼吸与土壤微生物呼吸。

EFFECTS OF ELEVATED CO2 CONCENTRATIONS ON SOIL MICROBIAL RESPIRATION AND ROOT/RHIZOSPHERE RESPIRATION IN FOREST SOIL

Two main components of soil respiration, i.e., root/rhizosphere and microbial respirations, respond differently to elevated atmospheric CO2 concentrations both in mechanism and sensitivity because they have different substrates, derived from plant and soil organic matter, respectively. To model the carbon cycle and predict carbon source/sink of forest ecosystems, we must first understand the relative contributions of root/rhizosphere and microbial respirations to total soil respiration under elevated CO2 concentrations. Root/rhizosphere and soil microbial respirations have been shown to increase, decrease and remain unchanged under elevated CO2 concentrations. A significantly positive relationship between root biomass and root/rhizosphere respiration has been found. Fine roots respond more strongly to elevated CO2 concentrations than coarse roots. Evidence suggests that soil microbial respiration is highly variable and uncertain under elevated CO2 concentrations. Microbial biomass and activity are related or unrelated to rates of microbial respiration. Because substrate availability drives microbial metabolism in soil, it is likely that much of the variability in microbial respiration resulted from differences in the response of root growth to elevated CO2 and subsequent change in substrate production. Biotic and abiotic factors influencing soil respiration were found to affect both root/rhizosphere and microbial respirations.