首页|Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations
Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations
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Interest in the dynamics of soil respiration(Rs)in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on Rs and its heterotrophic and autotrophic respiration components(Rh and Ra,respec-tively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO2 efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rh and Ra.Seventeen years after thinning,mean annual Rs,Rh and Ra increased,while the contribu-tion of Rh to Rs decreased with thinning intensity.Thinning significantly decreased winter Rs because of the reduction in Rh but had no significant effect on Ra.The temperature sensitivity(Q10)of Rh and Ra also increased with thinning intensity,with lower Q10 values for Rh(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory vari-ables and pathways related to Rh and Ra dynamics.Thin-ning increased soil moisture and nitrate nitrogen(NO3--N),and the enhanced nitrogen and water availability promoted Rh and Ra by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO3--N in stimulating Rs components following long-term thin-ning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO2 emissions.The increased Q10 values of Rs components indicate that a large increase in soil CO2 emissions would be expected following thinning because of more pronounced climate warming in alpine regions.
Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,People's Republic of China
State Forestry Administration Key Laboratory of Forest Resources and Environmental Management,Beijing Forestry University,Beijing 100083,People's Republic of China
Academy of Agriculture and Forestry Sciences,Qinghai University,Xining 810000,People's Republic of China
College of Landscape Architecture,Zhejiang A&F University,Hangzhou 310000,People's Republic of China
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National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNatural Science Foundation of Gansu ProvinceYouth Science and Technology Fund Program of Gansu Province
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