武夷山不同海拔土壤呼吸对变暖和变冷的响应

Responses of soil respiration to warming and cooling at different elevations of Wuyi Mountain

由于人类活动,我国亚热带地区正面临剧烈的气候变化,这可能对土壤呼吸有潜在影响。本研究选择武夷山国家公园内针叶林(1442 m)和常绿阔叶林(645 m)为对象,通过土柱置换试验模拟变暖(针叶林置换到常绿阔叶林)和变冷(常绿阔叶林置换到针叶林),探讨模拟变暖和变冷对土壤碳过程的影响,测定两个海拔样地的原位和置换处理的微气候环境、土壤呼吸、土壤碳氮及活性碳。结果表明:模拟变暖经历了升高的土壤温度和减少的土壤湿度;相反,模拟变冷经历了减少的土壤温度和增加的土壤湿度;与针叶林原位培养土柱相比,模拟变暖显著增加土壤呼吸99.6%,且显著减少温度敏感性(Q_(10));与常绿阔叶林原位培养土柱相比,模拟变冷显著减少土壤呼吸43.3%,显著增加温度敏感性(Q_(10));土壤温度是解释土壤呼吸动态变化的控制因素,土壤湿度与土壤呼吸的关系未达到显著水平(P>0.05);置换试验结束后,常绿阔叶林和针叶林土壤有机碳含量分别增加12%和10%,这可能与死根及凋落物的分解有关;变暖和变冷处理土壤有机碳均略有减少,这可能由土壤呼吸强度差异来解释;置换试验结束后,变暖使土壤微生物量碳减少,但可溶性有机碳增加;变冷使土壤微生物量碳增加,而可溶性有机碳减少,表明活性有机碳对变暖和变冷不一致的响应。因此,在涉及变暖和变冷的气候场景下,在构建气候变化响应模型时应该考虑土壤呼吸对变暖和变冷的响应。

Subtropical areas are subjected to rapid climatic change owing to anthropogenic activities,which could potentially affect soil respiration.In this study,a coniferous forest(CF)at 1442 m and an evergreen broad-leaved forest(EBF)at 645 m were selected as research objects in the Wuyishan National Park,Fujian Province,China.The effects of simulated warming(soil monoliths transferred from CF to EBF)and cooling(soil monoliths transferred from EBF to CF)on soil carbon processes were explored using a reciprocal soil monoliths translocation experiment.The microclimate,soil respiration,soil organic carbon,soil total nitrogen and soil labile organic carbon were measured for in situ and transferred treatments at both elevations.The results showed that soils experienced warming had higher temperature and lower moisture.In contrast,soils experienced cooling had lower temperature and higher moisture.Simulated warming substantially increased soil respiration by 99.6%and significantly decreased temperature sensitivity(Q_(10)) compared with the CF incubated in situ.Simulated cooling substantially reduced soil respiration by 43.3%and increased Q_(10) compared with the EBF incubated in situ.Soil temperature was the factor driving changes in soil respiration,whereas soil moisture had no relationship with soil respiration(P>0.05).At the end of the experiment,soil organic carbon contents of the EBF and CF were increased by 12%and 10%,respectively,which might be related to the decomposition of dead roots and leaf litter.The soil organic carbon content decreased slightly under both the warming and cooling treatments,which could be explained by the differences in intensity of soil respiration.At the end of the experiment,warming reduced soil microbial biomass carbon,but increased dissolved organic carbon.In contrast,cooling increased soil microbial biomass carbon and decreased dissolved organic carbon,indicating that soil labile organic C may not respond equally to warming and cooling.Therefore,the responses of soil respiration to warming and cooling should be considered for the construction of climate change response models when both warming and cooling are involved in the climate change.