Plant traits mediate foliar uptake of deposited nitrogen by mature woody plants
Xin Wang, Jing Li, Heng Ge, Shengnan Pan, Ping Li, Lulu Guo, Lu Yang, Ziyang Peng, Bin Wang, Zhenhua Wang, Chengzhang Wang, Lingli Liu
Abstract
Abstract Increased atmospheric nitrogen (N) deposition significantly disturbs ecosystem N cycle. Although foliar interception and uptake of N deposition can provide an important alternative N supply to forest ecosystems, the mechanisms regulating foliar N uptake from wet deposition are not fully understood. Here, we selected 19 woody species with a wide range of plant traits from different functional groups and conducted a 15 N isotope labelling experiment through brushing 15 NH 4 + and 15 NO 3 − solution on canopy leaves. Our findings demonstrate that leaves can directly absorb N from wet deposition within a few hours. The average leaf 15 N recoveries were 10% and 28% under 15 NH 4 + and 15 NO 3 − treatments across species, respectively, while twig N recoveries were only 1%–7% of leaf N recoveries. Differences in foliar N uptake efficiency among species were closely associated with leaf traits but were little influenced by meteorological conditions or soil nutrient status. Specifically, plants with higher leaf N concentration, larger specific leaf area and lower wax concentration exhibited higher leaf N recovery. Our results indicated that tree canopies could directly absorb N from atmospheric deposition. We highlight the critical role of leaf traits in determining canopy foliar N uptake, which may consequently influence plant competition under elevated N deposition.