Abstract
To better understand the soil carbon dynamics and cycling in terrestrial ecosystems in response to environmental changes, we studied soil respiration, litter decomposition, and their relations to soil temperature and soil water content for 18-months (Aug. 2010–Jan. 2012) in three different-aged Pinus massoniana forests in the Three Gorges Reservoir Area, China. Across the experimental period, the mean total soil respiration and litter respiration were 1.94 and 0.81, 2.00 and 0.60, 2.19 and 0.71 µmol CO2 m−2 s−1, and the litter dry mass remaining was 57.6%, 56.2% and 61.3% in the 20-, 30-, and 46-year-old forests, respectively. We found that the temporal variations of soil respiration and litter decomposition rates can be well explained by soil temperature at 5 cm depth. Both the total soil respiration and litter respiration were significantly positively correlated with the litter decomposition rates. The mean contribution of the litter respiration to the total soil respiration was 31.0%–45.9% for the three different-aged forests. The present study found that the total soil respiration was not significantly affected by forest age when P. masonniana stands exceed a certain age (e.g. >20 years old), but it increased significantly with increased soil temperature. Hence, forest management strategies need to protect the understory vegetation to limit soil warming, in order to reduce the CO2 emission under the currently rapid global warming. The contribution of litter decomposition to the total soil respiration varies across spatial and temporal scales. This indicates the need for separate consideration of soil and litter respiration when assessing the climate impacts on forest carbon cycling.
Highlights
Soil respiration is a major process controlling carbon (C) loss from terrestrial ecosystems [1]
Dynamics of soil and litter respiration The litter respiration, litter-free soil respiration, and the total soil respiration rates did not vary with forest age across the experimental period (Table 3)
Effects of forest age on soil and litter respiration Ewel et al [31] suggested that soil respiration decreased with forest age in temperate forests, while it increased with forest age in tropical and subtropical forests
Summary
Soil respiration is a major process controlling carbon (C) loss from terrestrial ecosystems [1]. Given the predicted increase in atmospheric CO2 concentrations, litter as a main C source for the total soil CO2 efflux will increase [4]. Litterfall represents a major flux of the vegetative C to soil, and changes in litter inputs are likely to have wide-reaching consequences for soil C dynamics [5]. The total respiration together with litter inputs data could be used to evaluate C dynamics in soils [10,11]. To better understand and predict the soil C dynamics and cycling in terrestrial ecosystems in a changing world, studies of the relationships between soil respiration and litter decomposition in response to environmental changes are still required
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