Data and code for: Suppression of nitrogen deposition on global forest soil CH4 uptake depends on nitrogen status

<p>Methane (CH4) is the second most important atmospheric greenhouse gas (GHG) and forest soils are a significant sink for atmospheric CH4. Uptake of CH4 by global forest soils is affected by nitrogen (N) deposition; clarifying the effect of N deposition helps to reduce uncertainties of the global CH4 budget. However, it remains an unsolved puzzle why N input stimulates soil CH4 flux (RCH4) in some forests while suppressing it in others. Combining previous findings and data from N addition experiments conducted in global forests, we proposed and tested a &ldquo;stimulating-suppressing-weakened effect&rdquo; (&ldquo;three stages&rdquo;) hypothesis on the changing responses of RCH4 to N input. Specifically, we calculated the response factors (f) of RCH4 to N input for N-limited and N-saturated forests across biomes; the phased changes in f values supported our hypothesis. We also estimated the global forest soil CH4 uptake budget to be approximately 11.2 Tg yr&ndash;1. CH4 uptake hotspots were located predominantly in temperate forests. Furthermore, we quantified that current level of N deposition reduced global forest soil CH4 uptake by ~3%. This suppression effect was more pronounced in temperate forests than in tropical or boreal forests, likely due to differences in N status. The proposed &ldquo;three stages&rdquo; hypothesis in this study generalizes the diverse effects of N input on RCH4, which could help improve experimental design. Additionally, our findings imply that by regulating N pollution and reducing N deposition, soil CH4 uptake can be significantly increased in the N-saturated forests in tropical and temperate biomes.</p> <p>Specifically, Data Set S1 (CH4_exp dataset in main text) was used to derive the response factors of soil CH4 flux to N input in global forests; Data Set S2 (CH4_obs dataset in main text) was used to estimate the soil CH4 fluxes in global forests; Data Sets S3&ndash;S7 were used to classify the N-limited and N-saturated forests on global level; Data Set S8 contains environmental factors (MAT, MAP, soil texture, etc.) for global estimations on grid level; Data Set S9 contains global forest soil CH4 budgets reported in previous studies. The data analysis process and produced figures can be replicated with the uploaded R script (Code S1).</p>