Insights into the effects of simulated nitrogen deposition on leaf functional traits of Rhus Typhina

Abstract

The effects of anthropogenic nitrogen (N) deposition on successful plant invaders, particularly potential effects on their leaf functional traits, have stimulated considerable research interest. This study aims to gain insights into the leaf functional traits of the controversial invader Rhus typhina in the presence of a gradient of simulated N deposition (control, 0 g L-1; low N, 5 g L-1; medium N, 10 g L-1; and high N, 25 g L-1). Soil pH is decreased under the growth of R. typhina. The soil acidification mediated by R. typhina may be due to the positive effects of R. typhina on soil ammonium concentration and negative effects on soil nitrate concentration. Soil pH decreased under N fertilization due to the release of free H+ via the nitrification process. Leaf width, leaf chlorophyll and N concentrations, SLA, and single leaf wet weight of R. typhina increased in the presence of all N fertilizers; medium N and high N fertilization also increased leaf length and leaf thickness of R. typhina due to the fertilizing effects of the addition of exogenous N on R. typhina growth. Thus, R. typhina leaves may possess higher resource capture ability as well as higher relative growth rate by reducing material investment per unit area under exogenous N fertilization. Meanwhile, medium N fertilization exerts stronger fertilizing effects on leaf length, leaf width, leaf chlorophyll and N concentrations, single leaf wet weight, and leaf thickness of R. typhina than those of high N fertilization. This is possibly because excess N fertilization could drive some unexpected reverse phenomena on leaf growth of R. typhina. Thus, leaf growth of R. typhina may be presumably attenuated with increasing amounts of anthropogenic N deposited into ecosystems in the future, and thereby pose pronounced effects on its subsequent further invasion.