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- Title
Variations in the nitrogen saturation threshold of soil respiration in grassland ecosystems.
- Authors
Wang, Chao; Ren, Fei; Zhou, Xuhui; Ma, Wenhong; Liang, Cunzhu; Wang, Jinzhou; Cheng, Jianwei; Zhou, Huakun; He, Jin-Sheng
- Abstract
Over the last century, anthropogenic activities have increased nitrogen (N) deposition considerably, which significantly affects ecosystem processes and has the potential to induce N saturation in the future. The continuous increase in N deposition may cause a non-linear response in soil respiration (Rs), an important component of carbon (C) cycling. However, little is known about N saturation threshold of soil respiration. In this study, we conducted coordinated experiments in four grassland types across northern China with four N addition levels to explore patterns in the Rs saturation threshold. Our results showed that an Rs saturation threshold generally exists in grassland ecosystems in response to N addition gradients. The N saturation threshold of Rs occurred at an average rate of 50 kg N ha−1 yr−1, but varied widely with grassland type; the N saturation threshold occurred at rates of 100, 50, 50, and 25 kg N ha−1 yr−1 in the alpine meadow, meadow steppe, typical steppe, and desert steppe, respectively. Autotrophic respiration (Ra) and heterotrophic respiration (Rh) responded to N addition gradients differently. Ra increased initially and became saturated at a rate of 50 kg N ha−1 yr−1 and declined thereafter. In contrast, Rh decreased monotonically after N addition. Structural equation models further confirmed that the effects of N addition gradients on Rs were primarily determined by the non-linear response of belowground biomass. Interestingly, the compiled global dataset showed that the N saturation threshold of Rs increased with precipitation and soil moisture. These findings indicate that the stimulating effect of N deposition on Rs and Ra might diminish with increasing N deposition in the future, especially in dry grassland ecosystems.
- Subjects
CHINA; SOIL respiration; GRASSLAND soils; HETEROTROPHIC respiration; STRUCTURAL equation modeling; MOUNTAIN meadows; ECOSYSTEMS; STEPPES
- Publication
Biogeochemistry, 2020, Vol 148, Issue 3, p311
- ISSN
0168-2563
- Publication type
Article
- DOI
10.1007/s10533-020-00661-y