ObjectiveSpecific leaf area (SLA) is a key functional trait of plants. It is affected by climate and phylogeny, and is closely associated with leaf element concentration. Therefore, the relationships between SLA and the abiotic and biotic factors are useful for understanding the strategies of plants in adaptation to environment and resource utilization. Meanwhile, trees and shrubs belong to different life forms, so we need to examine whether they differ in adaptation strategies related to SLA.

MethodThis study was based on the comparison of dominant tree and understory shrub species in sample plots along the altitudinal gradient of Changbai Mountain, northeastern China. We established a phylogenetic tree using DNA barcode sequences, and analyzed the relationships of SLA with leaf element concentrations, climatic factors and phylogeny. We examined whether the relationships between SLA and leaf element concentrations, and the influence of climate and phylogeny, were different between trees and shrubs.

Result(1) The SLA of trees and shrubs was negatively correlated with mean annual precipitation and positively correlated with thermal conditions (mean temperature of the coldest month and potential evapotranspiration). However, different from shrubs, the SLA of trees was more affected by phylogeny. (2) For both trees and shrubs, SLA was positively correlated with leaf total nitrogen (TN) and total phosphorus (TP) concentrations, but negatively correlated with total carbon (TC) concentration. Trees and shrubs differed significantly in the regression slopes of SLA with TN and TP, but did not differ in the slope of SLA with TC. (3) Climatic factors significantly affected the slope of the relationship between SLA and TC, while phylogeny affected the slope of SLA with TN and TC for both trees and shrubs. Climatic factors and phylogeny together affected the slope between SLA and TP for shrubs, but not for trees.

ConclusionThe adaptation of SLA to environment and the resource utilization strategy were similar for trees and shrubs, but there were also differences in the modulators of the relationship between SLA and TP for trees and shrubs. Compared with trees, the understory shrubs have a tendency to convergent evolution, generally with high-SLA leaves and more sensitive to climate, and may store more phosphorus in the leaves to meet the needs of survival.