Abstract
This study aims to evaluate the impacts of changes in litter quantity under simulated N deposition on litter decomposition, CO2 release, and soil C loss potential in a larch plantation in Northeast China. We conducted a laboratory incubation experiment using soil and litter collected from control and N addition (100 kg ha−1 year−1 for 10 years) plots. Different quantities of litter (0, 1, 2 and 4 g) were placed on 150 g soils collected from the same plots and incubated in microcosms for 270 days. We found that increased litter input strongly stimulated litter decomposition rate and CO2 release in both control and N fertilization microcosms, though reduced soil microbial biomass C (MBC) and dissolved inorganic N (DIN) concentration. Carbon input (C loss from litter decomposition) and carbon output (the cumulative C loss due to respiration) elevated with increasing litter input in both control and N fertilization microcosms. However, soil C loss potentials (C output–C input) reduced by 62% in control microcosms and 111% in N fertilization microcosms when litter addition increased from 1 g to 4 g, respectively. Our results indicated that increased litter input had a potential to suppress soil organic C loss especially for N addition plots.
Highlights
The reactive nitrogen (N) deposition has increased from 32 Mt N year-1 to approximately 116 Mt N year-1 since 1860 at global scale and it is expected a further enhancement in future [1, 2], due to human activities such as fertilizer application, fossil fuel combustion and legume cultivation [3]
Litter total N concentration increased by 8.8% in the N addition plots as compared with the control plots (P = 0.002), but no differences were found for litter total C, total P, cellulose, lignin and polyphenol concentrations (Table 1)
Our results clearly demonstrated that increased litter input had a potential to suppress soil organic C loss both litter decomposition and CO2 release rate increased with increasing input of fresh leaf litter
Summary
The reactive nitrogen (N) deposition has increased from 32 Mt N year-1 to approximately 116 Mt N year-1 since 1860 at global scale and it is expected a further enhancement in future [1, 2], due to human activities such as fertilizer application, fossil fuel combustion and legume cultivation [3]. Increased N deposition can dramatically alter soil N availability and N cycling [4, 5], litter quantity and quality and soil physicochemical environment [6], and affect litter decomposition processes in terrestrial ecosystems [7, 8]. It is important to understand impacts of N deposition on carbon (C) flux of ecosystems [6, 9], since soil organic C (SOC) dynamics is strongly linked to soil N dynamics. Effects of N deposition on soil C cycling have been widely studied, but the results are still highly inconsistent [10]. Plant litter decomposition and soil respiration are two major.
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