Fig. 2
From: Suppressed N fixation and diazotrophs after four decades of fertilization
a Phylogenetic tree displaying the taxonomic information on dominant soil diazotrophic phylotypes in three main ecological clusters (modules #1–3). b The standardized difference, in units of standard deviation (z-score), between observed and expected phylogenetic diversity assuming random sampling for each module. The dotted brown line represents the expected phylogenetic diversity for each treatment and the blue dashed lines represent the 95% confidence intervals. The points either above (2) or below (− 2) the blue lines represent the degree to which those ecological clusters are phylogenetically over-dispersed or clustered, respectively. Red, module #1; blue, module #2; cyan, module #3. BS: bulk soil, RS: rhizosphere soil. Fertilization treatments: control, non-fertilization; NPK fertilization, NPK (urea, superphosphate, and potassium chloride); NPK + WS, NPK with wheat straw; NPK + PM, NPK with pig manure; NPK + CM, NPK with cow manure (NPK + CM)