Figure 1.

The relative change of the root traits under deficiency [(X0-X1)/X1] where X0 is the value in the treatment without any addition of the nutrient and X1 is the value of the treatment with the nutrient application. np stands for the number of publications/studies considered in the calculation, and nr for the total number of observations within these publications. The line within the boxes refers to the median. ** stands for significant differences at a 0.95 confidence level. Blue dots represent the mean.