胡杨树干空腐与立地条件的关系研究

Populus euphratica Oliv., as an indicator species of eco-environmental changes in arid areas, plays an irreplaceable role in maintaining the stability of regional fragile ecosystem. Currently, there is a research gap regarding the mechanism of stem cavitation formation of Populus euphratica. In this project, the stem cavitation of Populus euphratica population at the three typical transects (Yingbaza, Yingsu, Arghan) along the middle and lower reaches of the Tarim River will be studied based on the Tree Radar scanning technique (TRU) combined with field positioning observation and laboratory analysis. The research work will mainly be conducted from four aspects as following: 1) The distribution characteristics of cavity trees of Populus euphratica at different ages will be analyzed by using the cavitation survey index (number of cavities, types, height of entrance, diameter of entrance, orientation of entrance as well as rate of cavitation) and tree vitality parameters (tree height, DBH, crown size, age and crown loss), and also the probability of hollow trees appearing with different monitoring plots at each transects will be determined; 2) The effect of wood-rot fungi on stem cavitation of Populus euphratica trees will be evaluated by comparing the differences in species diversity and characteristics of wood-rot fungi in different cavity degrees of Populus euphratica trees at different transects; 3) Quantify the relationship between groundwater depth, soil physical and chemical properties as well as tree parameters (DBH, crown, age structure) and the degree of stem cavitation; 4) The mechanism and dominant factors of the stem cavitation of Populus euphratica will be revealed by analyzing the relationship between the cavitation degree and aforementioned factors comprehensively. The results of this project not only help to understand the causes of stem cavitation and its internal mechanism, but also provide scientific basis for the conservation and management of Populus euphratica forest resources.

胡杨作为干旱地区生态环境变化的指示物种，对于维持区域脆弱生态系统稳定性作用不可替代，目前针对胡杨树干空穴化形成机制研究尚属空白。本项目基于树木雷达扫描技术结合野外定位观测和室内分析，研究塔里木河中下游——英巴扎、英苏和阿拉干3个典型断面胡杨树干空穴化现象，旨在：1）利用空洞调查指标（洞口直径、空洞率）和树木长势指标（树高、胸径、冠幅、年龄、树冠疏失度）分析不同年龄级胡杨空腐分布特征，结合种群样方数据计算各断面各样地内出现空心树的概率；2）通过比较各断面各空腐程度胡杨木腐菌性质、多样性及差异，评价木腐菌对胡杨空腐的影响；3）量化地下水埋深、土壤理化性质和树木自身因素（胸径、冠幅、年龄结构）与胡杨空腐程度的关系；4）综合探究树干空腐与各因子的关系，揭示胡杨树干空腐形成机理及影响因素。本项目研究成果不仅有助于深入理解胡杨树干空穴化成因及其内在机理，同时可为珍稀胡杨林资源保育和管理提供科学依据。

树干空腐（空洞/腐朽）不仅影响树木物理、力学性能和木材质量，还会减少森林生物量而导致碳流失，使森林的生态和经济效益均有巨大损失。本项目针对塔里木河两岸天然胡杨林树干空穴化形成机制研究的欠缺和薄弱，将天然胡杨林分布区——塔里木河中、下游选为主要研究靶区，以胡杨树干空腐与立地条件的关系为研究主线，基于森林生态学、生态水文学和树木生理学等学科理论方法，利用野外定点观测（ARBOTOM应力波树木无损检测技术、生长锥、树木生长仪、小型自动气象站、测树仪器、地下水位自动监测仪、土壤湿度监测仪、土壤理化性质测定仪等）和室内分析（土壤盐分监测仪、激光粒度仪、土壤养分速测仪），获取树木外部空洞特征参数（空洞数量、类型、洞口高度、直径、方位、空洞率）、树干内部空腐程度（空腐率、空腐面积、空腐方向），树木长势（树高、胸径、树冠宽度、冠高比、冠幅面积、偏冠率、疏失度、枝下高、活力等级、年龄结构），木材物理参数（生材含水率、气干含水率、生材密度、气干密度、全干密度、基本密度），立地条件（土壤水分、含盐量、地下水位、离河道距离、坡度、坡向）等关键数据，采用数理与地学统计学相关方法手段，分析了不同年龄级胡杨随水盐梯度下的空腐空间分布特征及发生概率；量化了地下水埋深、土壤理化性质、树木自身因素与胡杨空腐程度的关系；探明了树干空腐形成及程度与各因子的关系，初步揭示了胡杨树干空腐程度及影响因素。项目研究成果将为当地林业部门保育和管理珍稀胡杨林资源提供科学依据和理论指导。在本项目执行期间，已发表学术论文10篇（其中SCI论文6篇），授权专利1项，组织一次小型项目成果交流会，参加学术会议20人次，项目负责人学术口头报告2次，项目参与人学术口头报告3次，墙报1次。已培养硕士研究生1名，本科生7名。依托本项目已获批/结题国家级大学生创新训练计划项目（SRT）1项。依托本项目后续研究，目前在培养博士生1名，硕士研究生4名，已投稿文章2篇。1名课题组成员获批国家自然科学青年基金项目1项。