AUTHOR=Jiang Xiyan , Song Mengya , Qiao Yaqi , Liu Mengzhou , Ma Lei , Fu Shenglei 

TITLE=Long-term water use efficiency and non-structural carbohydrates of dominant tree species in response to nitrogen and water additions in a warm temperate forest

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1025162

DOI=10.3389/fpls.2022.1025162

ISSN=1664-462X

ABSTRACT=<p>Nitrogen (N) deposition tends to accompany precipitation in temperate forests, and vegetation productivity is mostly controlled by water and N availability. Many studies showed that tree species response to precipitation or N deposition alone influences, while the N deposition and precipitation interactive effects on the traits of tree physiology, especially in non-structural carbohydrates (NSCs) and long-term water use efficiency (WUE), are still unclear. In this study, we measured carbon stable isotope (δ<sup>13</sup>C), total soluble sugar and starch content, total phenols, and other physiological traits (<italic>e</italic>.<italic>g</italic>., leaf C:N:P stoichiometry, lignin, and cellulose content) of two dominant tree species (<italic>Quercus variabilis</italic> Blume and <italic>Liquidambar formosana</italic> Hance) under canopy-simulated N deposition and precipitation addition to analyze the changes of long-term WUE and NSC contents and to explain the response strategies of dominant trees to abiotic environmental changes. This study showed that N deposition decreased the root NSC concentrations of <italic>L. formosana</italic> and the leaf lignin content of <italic>Q. variabilis</italic>. The increased precipitation showed a negative effect on specific leaf area (SLA) and a positive effect on leaf WUE of <italic>Q. variabilis</italic>, while it increased the leaf C and N content and decreased the leaf cellulose content of <italic>L. formosana</italic>. The nitrogen–water interaction reduced the leaf lignin and total phenol content of <italic>Q. variabilis</italic> and decreased the leaf total phenol content of <italic>L. formosana</italic>, but it increased the leaf C and N content of <italic>L. formosana</italic>. Moreover, the response of <italic>L. formosana</italic> to the nitrogen–water interaction was greater than that of <italic>Q. variabilis</italic>, highlighting the differences between the two dominant tree species. The results showed that N deposition and precipitation obviously affected the tree growth strategies by affecting the NSC contents and long-term WUE. Canopy-simulated N deposition and precipitation provide a new insight into the effect of the nitrogen–water interaction on tree growth traits in a temperate forest ecosystem, enabling a better prediction of the response of dominant tree species to global change.</p>