半干旱区沙地云杉天然林稳定性维持的水分机制研究

防护林的稳定性是保障防护林功能高效与可持续发挥的关键，天然防护林以其独特的生态稳定性，引起林学界广泛关注。水分是影响干旱半干旱地区天然防护林生长与存活的关键因子，天然防护林稳定性维持的水分机制则显得尤为重要。因此，本项目以浑善达克沙地云杉天然林为研究对象，以水分因子为主线，通过野外监测和定位试验相结合的手段，利用稳定同位素、探地雷达、激光雷达与树干液流等技术，重点开展不同年龄沙地云杉根系分布及其水分来源、树干液流特性及其与林分空间结构关系、水量平衡各分量协同变化特征及其对林分三维立体（地上与地下）空间结构的响应，明确沙地云杉根系空间分布特征及其水分利用策略，揭示沙地云杉林蒸腾耗水规律及其与林分空间结构耦合机制，确定林分水量平衡特征及其三维立体空间结构效应，阐明沙地云杉天然林稳定性维持的水分机制。研究结果将丰富防护林学，对天然林保护和管理与营建稳定人工防护林体系具有重要理论和现实意义。

Stability of protective forests is the key to guaranteeing the protective function of protective forests exerting to be effective and sustainable, and the natural protective forests grow well and have drawn great attention at forestry. Nevertheless, water is the key factor influencing the growth and survival of natural forests in semiarid and arid regions, and thus the water mechanism underlying maintenance stability of natural protective forests is to be particularly important. In this project, we select the natural Picea mongolica forests in the Hunshandake Sandy Lands as the objects of this project. Water condition is considered as the main topic in this project on basis of field monitoring and experiments. By stable isotope, ground-penetrating radar, light detection and ranging and thermal dissipation technologies, the distribution of root systems with different ages and its water use strategies, sap flow characteristics and its relationships with forest spatial structure, and coordinated variation among water balance components and its relationship with the three-dimensional structure are studied for the natural Picea mongolica forests. The specific objectives of this project are to 1) determine the spatial distribution of root systems and its water use strategies, 2) clarify transpiration characteristics and its coupling mechanism with stand spatial structure, and 3) ascertain the coordinated variations in the water balance components and its response to the stereoscopic effect of three-dimensional structure. Therefore, water mechanisms underlying the maintenance stability of natural Picea mongolica forests are revealed. Besides enriching protective forests and guiding the construction of protective forests, the results obtained in this project certainly will also have both important theoretical and practical significances for natural forest management and conservation, and construction and management of artificial protective forest systems to be stable.