Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Xingke Road 723, Guangzhou 510650, China.
Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Xingke Road 723, Guangzhou 510650, China; College of Life Sciences, Gannan Normal University, Ganzhou 341000, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Haibin Road 1119, Nansha, Guangzhou 511458, China.
Sci Total Environ. 2021 Jun 1;771:145415. doi: 10.1016/j.scitotenv.2021.145415. Epub 2021 Jan 27.
Plant hydraulic traits have been shown to be sensitive to changes in nitrogen (N) availability in short-term studies largely using seedlings or saplings. The extent and the magnitude of N-sensitivity of the field grown mature trees in long-term experiments, however, are relatively unknown. Here, we investigated responses of leaf water relations and morphological and anatomical traits of two dominant tree species (Castanopsis chinensis and Schima superba) to a six-year canopy N addition in a subtropical forest. We found that N addition increased leaf hydraulic conductivity in both species along with higher transpiration rate and less negative water potential at 50% loss of leaf hydraulic conductivity and at leaf turgor loss point. Examination of leaf morphological and anatomical traits revealed that increased leaf hydraulic efficiency was at least in part due to increased vessel diameter which also compromised the hydraulic safety under increased water stress. Moreover, reduced vessel reinforcement and increased thickness shrinkage index further interpreted the increases in leaf hydraulic vulnerability under N addition. Our results demonstrated that N deposition may lead to increases of plant water loss to the atmosphere as well as tree vulnerability to drought.
植物水力特性已被证明对短期研究中氮（N）可利用性的变化敏感，这些研究主要使用幼苗或幼树。然而，在长期实验中，田间生长的成熟树木对 N 的敏感性的程度和幅度相对未知。在这里，我们调查了两种优势树种（锥栗和木荷）对亚热带森林中六年树冠 N 添加的叶片水分关系以及形态和解剖特征的响应。我们发现，N 添加增加了两种物种的叶片水力传导性，同时伴随着更高的蒸腾速率和更低的负水势，即在叶片水力传导性丧失 50%和叶片膨压丧失点。对叶片形态和解剖特征的检查表明，增加的叶片水力效率至少部分是由于导管直径增加所致，这也降低了在增加的水分胁迫下的水力安全性。此外，减少的导管加固和增加的厚度收缩指数进一步解释了在 N 添加下叶片水力脆弱性的增加。我们的结果表明，N 沉积可能导致植物向大气中损失更多的水分，以及树木对干旱的脆弱性增加。
