Leaf N:P stoichiometry across plant functional groups in the karst region of southwestern China

Key message Soil nitrogen and phosphorus are the most important factors influenced the leaf N:P ratios across plant functional groups in the karst region of southwestern China, and plant diversity are also important to certain groups. Leaf nitrogen:phosphorus (N:P) stoichiometry, which affects plant growth, nutrient cycling, and primary production in terrestrial ecosystems, is influenced by soil N and P, among other factors. However, it remains unclear how biotic and abiotic factors influence leaf N and P stoichiometry of different plant functional groups in the karst ecosystem of southwest China. We measured the leaf N and P of different plant functional groups, as well as soil total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus at 0-15 cm depth under each plant functional group. The linear mixed models (LMMs) results showed that the leaf N, P, and N:P ratios were characterized by functional groups. Higher leaf P, but lower leaf N and N:P ratios, were found in grasses than in shrubs and trees. The leaf N was higher in trees than that in shrubs. Additionally, the leaf N and N:P ratios were higher in legumes than that in nonlegumes. The LMMs results showed that the Shannon-Wiener diversity indexes (H'), soil TN, and TP significantly impacted the leaf N:P ratios (with grass-shrub-tree group as random factor), and Simpson diversity indexes (DS), soil TN, AN, and TP significantly impacted the leaf N:P ratios (with nonlegume-legume group as random factor). It suggested that soil TN and TP had major effects on the leaf N:P ratios of all the studied functional groups in the karst region, while DS and H' diversity indexes, and soil AN significantly impacted the leaf N:P ratios in several specific groups.