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

Abstract

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.