Taiki Mori;Kebin Zhou;Senhao Wang;Wei Zhang;Jiangming M

Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, People’s Republic of China;University of Chinese Academy of Sciences, Beijing, People’s Republic of China; Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, People’s Republic of Chin

Canopy exchange;Dissolved organic carbon;Nitrogen deposition;Throughfall;DISSOLVED ORGANIC-CARBON;LONG-TERM CHANGES;ATMOSPHERIC DEPOSITION;THROUGHFALL DEPOSITION;FOREST ECOSYSTEMS;SOIL RESPIRATION;OXIDE EMISSIONS;FOLIAR UPTAKE;FLUXES;RETENTIO

The impact of nitrogen (N) deposition on dissolved organic carbon (DOC) fractions in throughfall is not well understood. We performed a laboratory experiment and compared DOC leaching from canopy leaves after dipping leaves in pure water (control) and NH4NO3 solution (N-treatment) for 18h. Net changes of DOC, NH4+, NO3-, SO42-, K+, Mg2+, Ca2+ and H+ contents after dipping leaves were determined by comparing solutions with and without leaves. We recorded no differences of DOC leaching between control and N-treatment, implying that N deposition had minor impacts on canopy DOC production. This confirmed that previous experiments testing the effects of N addition on DOC dynamics without considering the effects of the canopy reaction successfully described the real situation. We also confirmed the previously-reported canopy exchange process in spite of a high background N deposition at our study site. N-treatment significantly increased base cation leaching, especially K+, and the increase was positively correlated with foliar NH4+ retention. Net leaching of H+ and SO42- was not affected by the N-treatment.