The scaling of leaf nitrogen and phosphorus along a phosphorus availability gradient in a subtropical forest

Allometric scaling of leaf nitrogen (N) and phosphorus (P) provides information on species adaptation to resource availability and nutrient limitation of primary production. Studies examining how plant functional traits vary spatially have historically used global datasets, which may blur variation at local scale and thus some of the key drivers. Global studies have observed leaf N–P scaling exponents varied across different functional groups, latitudinal zones, ecoregions, and sites. However, whether these trends are consistent in a local habitat is still unclear. Here, we capitalized on a soil P availability gradient in subtropical China to examine scaling exponents of leaf N–P. We investigated 21 woody species at P-rich and P-poor sites for two consecutive years and estimated scaling exponents of leaf N–P across P-type sites, leaf ages, plant functional types, and phylogeny. The exponents varied across the abovementioned levels from 0.356 to 0.699. Averaged across all plant species, the exponent of 0.612 was a departure from the global average of 2 / 3 (0.66) and 3 / 4 (0.75). Two types of P-sites did not affect N–P exponents of deciduous-broadleaved trees and evergreen conifers. Our findings indicated that leaf N–P scaling exponents significantly differed within plant functional types and highlighted the resource availability in shaping nutrient cycling and evolutionary processes at local scales.