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Unimodal Response of Soil Methane Consumption to Increasing Nitrogen Additions

Peng, Yunfeng, Wang, Guanqin, Li, Fei, Yang, Guibiao, Fang, Kai, Liu, Li, Qin, Shuqi, Zhang, Dianye, Zhou, Guoying, Fang, Huajun, Liu, Xuejun, Liu, Chunyan, Yang, Yuanhe
Environmental science & technology 2019 v.53 no.8 pp. 4150-4160
biogeochemistry, ecosystems, field experimentation, highlands, meta-analysis, methane, models, nitrogen, prediction, soil, steppes, China
Nitrogen (N) status has a great impact on methane (CH₄) consumption by soils. Modeling studies predicting soil CH₄ consumption assume a linear relationship between CH₄ uptake and N addition rate. Here, we present evidence that a nonlinear relationship may better characterize changes in soil CH₄ uptake with increasing N additions. By conducting a field experiment with eight N-input levels in a Tibetan alpine steppe, we observed a unimodal relationship; CH₄ uptake increased at low to medium N levels but declined at high N levels. Environmental and microbial properties jointly determined this response pattern. The generality of the unimodal trend was further validated by two independent analyses: (i) we examined soil CH₄ uptake across at least five N-input levels in upland ecosystems across China. A unimodal CH₄ uptake-N addition rate relationship was observed in 3 out of 4 cases; and (ii) we performed a meta-analysis to explore the N-induced changes in soil CH₄ uptake with increasing N additions across global upland ecosystems. Results showed that the changes in CH₄ uptake exhibited a quadratic correlation with N addition rate. Overall, we suggest that the unimodal relationship should be considered in biogeochemistry models for accurately predicting soil CH₄ consumption under global N enrichment.