Abstract
Increases in bioavailable nitrogen (N) level can impact the soil carbon (C) sequestration in many forest ecosystems through its influences on litter decomposition and soil respiration (Rs). This study aims to detect whether the litter management can affect the influence of N addition on Rs. We conducted a one-year field experiment in a camphor forest of central-south China to investigate the responses of available N status and soil Rs to N addition and litter manipulation. Four N addition plots (NH4NO3; 0, 5, 15, 30 g N m−2 year−1 as N0, N1, N2, N3, respectively) were established with three nested litter treatments: natural litter input (CK), double litter input (LA), and non-litter input (LR). We found a short-lived enhancement effect of N addition on soil (NO3-N) and net nitrification (RN), but not on (NH4-N), net ammonification (RA), or mineralization (RM). N addition also decreased Rs in CK spots, but not in LA or LR spots, in which the negative effects of N additions on Rs were alleviated by either litter addition or reduction. A priming effect was also observed in LA treatments. A structural equation modeling analysis showed that litter treatments had direct positive effects on soil available N contents and Rs, which suggested that litter decomposition may benefit from litter management when N is not a limiting factor in subtropical forests.
Highlights
The anthropogenic input of reactive nitrogen (N) has increased 3- to 5-fold on a global scale [1], mainly through fossil-fuel burning and artificial nitrogen fertilizer applications [2]
The Q10 values were affected by litter changes, which was 2.08 for CK, 2.16 for LA, and 2.28 for litter input (LR) treatment, respectively (Table S1)
We found that annual Rs (Figure 1a) were significantly decreased (37.7%~40.4%) but were not amplified by incremental N addition levels, which ranged from 21% to 57% of the meta-analysis [12]
Summary
The anthropogenic input of reactive nitrogen (N) has increased 3- to 5-fold on a global scale [1], mainly through fossil-fuel burning and artificial nitrogen fertilizer applications [2]. N input has led to many ecological effects in terrestrial ecosystems [3], such as soil acidification [4], nutrient imbalance [5], biodiversity loss [6,7], greenhouse gas emission [8], and global climate change [9]. Whether the altered soil N status that resulted from the increased N level can influence soil carbon (C) dynamics in forest ecosystems is not well understood. As the increasing concern about the effects of globally
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