基于功能性状的半干旱黄土小流域草地与土壤水分相互作用研究

Grassland, widely distributed in the semi-arid Loess Plateau, play an important role in ecological restoration. Water is the crucial factor influencing vegetation restoration. The interaction between vegetation and soil moisture is one of key issues in ecological restoration in the Loess Plateau and other similar areas in the world. Functional traits are characteristics relevant to the plant responses to the environment and/or their effects on ecosystem properties. They provide a powerful tool in the study of interaction between vegetation and environment. In this project, the soil moisture in depth of 0-2 m will be monitored, and a vegetation removal experiment will be conducted at a typical small watershed in the semi-arid Loess Plateau. We use a functional trait-based response-effect framework, 1) to differentiate response traits and effect traits, and analyze the response characteristics and effect processes of grassland communities on soil moisture at watershed scale; 2) to quantify the coupling relationship of functional traits and soil moisture. This study is an important part of studying the interaction mechanism between vegetation and soil moisture, and could provide scientific guidance for vegetation restoration in the Loess Plateau.

草地是半干旱黄土丘陵区分布广泛的生态系统，在区域生态恢复中占有重要地位，水分不足是这一地区植被恢复和重建的关键制约因子。植被与土壤水分的相互作用是黄土高原乃至全球干旱半干旱地区植被恢复面临的关键科学问题。功能性状是植物响应生存环境变化并（或）对生态系统功能有一定影响的属性，是研究植被与环境相互关系的可靠手段。本项目选择典型半干旱黄土小流域甘肃定西龙滩流域，通过对0-2 m深度土壤水分定位监测，结合原位去除植被实验，基于功能性状的响应-影响框架，界定草地群落的响应性状和影响性状，明确小流域尺度草地群落功能性状对土壤水分的响应特征和影响过程，构建功能性状与土壤水分的定量表达关系，是深入研究植被-土壤水分相互作用机理的重要组成部分，也为黄土高原植被恢复的合理布局提供科学指导。

水分不足是植被恢复和重建的关键限制因子。但是在水分限制地区，大规模植被恢复严重威胁了水资源安全。因而，研究植被与土壤水分的互作可为干旱区生态恢复提供科学依据，但目前对这一问题的认识还很不足。基于功能性状的响应-影响研究框架有助于深入认识植被与土壤水分的互作机制。因此，本研究通过在小流域和区域两个尺度的长期监测，基于功能性状的响应-影响研究框架，明确了土壤有效水分是半干旱区草地群落植物功能性状变异的关键性驱动因子，叶长、株高、叶面积、比叶面积、叶厚和叶干物质含量是土壤有效水分的响应性状，草地群落通过降低株高，减小叶长、叶面积和比叶面积，增加叶厚和叶干物质含量以适应土壤有效水分减少。结合原位去除植被实验，明晰了叶片大小、细根生物量、植株高度和地下生物量是土壤水分的影响性状，叶小，根系浅和植株高有利于增加表层土壤水分入渗或减少对深层土壤水分的消耗。辨识土壤水分的响应-影响性状是深入研究植被-土壤水分相互作用机理的重要组成部分，同时也为黄土高原生态恢复提供科学依据。