Fig. 5: Effect of natural N deposition on observed soil respiration (SR) in forests.
From: A general framework for nitrogen deposition effects on soil respiration in global forests
To remove the influence of basal SR differences across biomes and N status, N deposition-induced SR change (∆SRN) was estimated as the difference in SR between forests with N deposition rates below 1 kgN ha–1 yr–1 and forests with N deposition rates above the level. Panels (a–f) are the partial dependence plots showing the change in soil respiration (∆SRN) along the natural gradient of N deposition in different forest biome-N status combinations. These plots were derived from random forest regression models fitted with observational data (CO2_obs dataset). Gray curves in each panel show 1000 partial dependence curves derived from 1000 random forest models built with 1000 different subsets of CO2_obs corresponding to a forest biome-N status combination (this was done to remove the influence of random sampling on the revealed pattern). The red curves show the mean partial dependence of ∆SRN on N deposition. Panels (g, h) are density curves showing the statistical distributions of N deposition rates in global N-limited and N-saturated forests.
