Responses of functional traits to seven-year nitrogen addition in two tree species: coordination of hydraulics, gas exchange and carbon reserves

作者：Hongxia Zhang, Fenghui Yuan, Jiabing Wu, Changjie Jin, Alexandria L. Pivovaroff, Jinyuan Tian, Weibin Li, Dexin Guan, Anzhi Wang, Nate G. McDowell · 发表于：Tree Physiology · 年份：2020 · DOI：10.1093/treephys/tpaa120 · 被引用次数：37 · 研究领域：Plant Water Relations and Carbon Dynamics、Forest ecology and management、Plant responses to elevated CO2

Atmospheric nitrogen (N) deposition has been observed to impact plant structure and functional traits in terrestrial ecosystems. Although the effect of N deposition on plant water use has been well-evaluated in laboratories and in experimental forests, the linkages between water and carbon relations under N deposition are unclear. Here, we report on hydraulics, gas exchange and carbon reserves of two broad-leaved tree species (Quercus mongolica and Fraxinus mandshurica) in mature temperate forests after a seven-year experiment with different levels of N addition (control (CK), low (23 kg N ha-1 yr-1), medium (46 kg N ha-1 yr-1) and high (69 kg N ha-1 yr-1)). We investigated variation in hydraulic traits (xylem-specific hydraulic conductivity (Ks), native percentage loss of conductivity (PLC) and leaf water potential), xylem anatomy (vessel diameter and density), gas exchange (maximum net photosynthesis rate and stomatal conductance) and carbon reserves (soluble sugars, starch and total nonstructural carbohydrates (NSC)) with different N addition levels. We found that medium N addition significantly increased Ks and vessel diameter compared to control, but accompanied increasing PLC and decreasing leaf water potential, suggesting that N addition results in a greater hydraulic efficiency and higher risk of embolism. N addition promoted photosynthetic capacity via increasing foliar N concentration but did not change stomatal conductance. In addition, we found increase in foliar ...