Abstract
Partitioning the components of soil respiration is crucial to understand and model carbon cycling in forest ecosystems. In this study, total soil respiration (RS), autotrophic respiration (RA), heterotrophic respiration (RH), litter respiration (RL), litterfall input and environmental factors were synchronously monitored for 2 years in a subtropical Michelia wilsonii forest of southwestern China. RH rates were often higher than RA rates during the two years except for the middle growing season (from July to September). The mean rate of Rs, RA, RH and RL was 1.94 μmol m-1 s-1, 0.85 μmol m-1 s-1, 1.09 μmol m-1 s-1 and 0.65 μmol m-1 s-1, respectively, during the 2-year experiment. Annual CO2 emission derived from RA, RH and RL was 3.26 Mg C ha-1 a-1, 4.67 Mg C ha-1 a-1 and 2.61 Mg C ha-1 a-1, respectively, which accounted for 41.4%, 58.6% and 32.9% of RS. Over the experimental period, the ratio of RA/RS increased with soil temperature but the opposite was true for RH/RS and RL/RS. The Q10 value was 2.01, 4.01, 1.34 and 1.30, respectively, for RS, RA, RH and RL. Path analysis indicated that environmental variables and litterfall production together explained 82.0%, 86.8%, 42.9% and 34.7% variations of monthly fluxes of RS, RA, RH and RL, respectively. Taken together, our results highlight the differential responses of the components of RS to environmental variables.
Highlights
Soil respiration (RS) is the second largest flux of carbon dioxide (CO2) between terrestrial ecosystems and the atmosphere [1, 2]
We investigate the components of RS for two years using root trenching and litter exclusion techniques in a subtropical Michelia wilsonii forest of southwestern China
Rainfall was 872.8 mm and 944.8 mm, respectively, in 2016 and 2017. It was higher in summers but lower in winters (Fig 1B)
Summary
Soil respiration (RS) is the second largest flux of carbon dioxide (CO2) between terrestrial ecosystems and the atmosphere [1, 2]. RS accounts for roughly 80% of ecosystem respiration across global forests [3]. RS is complicated by tree growth and the subsequent input of plant litter to soil [5, 6]. RS is overwhelmingly the product of respiration by plant roots (autotrophic respiration, RA) and soil organisms (heterotrophic respiration, RH) [7, 8]. CO2 flux derived from decaying litter accounts for a considerable part of RS, which is strongly controlled by the quantity and quality of litter and climate variables [5, 8, 9].
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