不同气候带森林植物水分关系对大气氮沉降的响应及其调控机制

Plant water relations play a critical role in the response and adaptation of forest plants to the ever-changing environment. Exploring the response of plant water relations to increasing atmospheric nitrogen (N) deposition represents a key step towards better understanding potential adaptive strategies taken by forest plants to cope with global change. ..Previous studies on the response of forest ecosystems to atmospheric N deposition have been carried out through a direct Understory Addition of N (UAN) to the forest floor, which might ignore the impacts of important processes taking place in the canopy, such as canopy retention and absorption of N, and/or possible conversion of N from one form (Nitrate) to another (Ammonium). The Canopy Addition of Nitrogen (CAN) experimental facilities allowed a more realistic simulation of atmospheric N deposition in a monsoon evergreen broad-leaved forest and a deciduous broad-leaved mixed forest that locate in different climatic zones. ..In this project, the response of plant water relations to both UAN and CAN will be simultaneously investigated in these two forests. Employing experimental approaches of plant eco-physiology and molecular biology, key functional traits related to plant hydraulics and xylem resistance to cavitation will be determined, as well as cell membrane aquaporin expression and activity, with objectives i) to answer how UAN and CAN affect plant water transport and their vulnerability to drought; and ii) to reveal mechanisms that mediated by aquaporins underlying the response of plant water relations to atmospheric N deposition. ..Results can be anticipated to provide important clues for i) better understanding the eco-physiological adaptive strategies of forest plants in different climatic zones in response to atmospheric N deposition; and ii) more precisely forecasting the changes in structure and function of forest ecosystems under global change scenarios.

植物水分关系对森林植物响应和适应环境变化至关重要，阐明植物水分关系对大气氮沉降加剧的响应及其调控机制，是揭示氮沉降背景下森林植物生理生态适应策略的关键。以往研究森林生态系统对大气氮沉降的响应多采用林下直接施氮的方式，未能准确模拟大气氮沉降的自然过程。本项目依托“林冠模拟氮沉降”野外控制实验平台，以不同气候带森林（季风常绿阔叶林和落叶阔叶混交林）优势木本植物为研究对象，比较林冠氮沉降和林下氮添加对植物水分关系影响的差异。综合运用植物生理生态学和细胞分子生物学实验技术和方法，测定植物木质部和叶片水力功能性状，以及植物细胞膜水通道蛋白的表达和活性，阐明大气氮沉降对植物水分运输能力和干旱脆弱性的影响，揭示细胞膜水通道蛋白对植物水分关系响应大气氮沉降的调控机制，为深入了解全球变化背景下不同气候带森林植物的生理生态响应规律和适应机制，以及森林生态系统结构和功能的变化提供科学依据。

植物水分关系对森林植物响应和适应环境变化至关重要，阐明植物水分关系对大气氮沉降加剧的响应及其调控机制，是揭示氮沉降背景下森林植物生理生态适应策略的关键。以往研究森林生态系统对大气氮沉降的响应多采用林下直接施氮的方式，未能准确模拟大气氮沉降的自然过程。本项目依托“林冠模拟氮沉降”野外控制实验平台，以不同气候带森林（季风常绿阔叶林和落叶阔叶混交林）优势木本植物为研究对象，比较林冠氮沉降和林下氮添加对植物水分关系影响的差异。研究发现：1）不同物种在不同氮添加处理间叶片凌晨和正午水势均表现出显著差异；2）比叶面积、叶干物质含量和木材密度在不同物种间差异显著，然而不同氮添加方式对它们的影响不显著；3）氮添加改变了植物导管属性，进而显著增加了植物应对干旱的水力脆弱性。综上所述，本项目运用植物生理生态学实验技术和方法，测定植物木质部和叶片水力功能性状，阐明大气氮沉降对植物水分运输能力和干旱脆弱性的影响，为深入了解全球变化背景下不同气候带森林植物的生理生态响应规律和适应机制，以及森林生态系统结构和功能的变化提供科学依据。