Fig. 3: Change in soil P density between observations and simulations from the 1980s to the 2020s.
From: Soil phosphorus crisis in the Tibetan alpine permafrost region
a Sampling plots. b Counties. Changes in grassland, forest, and cropland are given, and each symbol in part (a) corresponds to one resampling plot. The sizes of the circles in part (b) represent the relative weights of the corresponding observations in each county. The effect of measurements on the soil P density was examined with linear mixed-effects models in which the fixed effect was the method and the random effect was the sampling plot and county. The effect of methods on soil P density was considered significant if P < 0.05. The dashed lines indicate the ordinary least-squares fit of the linear equation of changes in soil P density between the observations and simulations. The shading accompanying the dashed fitted line represents the 95% confidence interval.
