干旱区绿洲城市树木健康评估及影响因素——以乌鲁木齐市为例

树木作为城市绿色基础设施重要组分，其健康直接影响城市生态系统服务及人居环境质量。城市化进程加快导致生态土地缺失，同时缺乏合理养护加之极端自然条件干扰对树木健康造成严重威胁。为揭示城市树木健康风险及影响因素，对乌鲁木齐市核心城区117个样地绿化树木进行健康评估，从4个维度12个指标构建树木健康分级体系，基于样地调查结果，分析树木组成、结构、关联性、健康状况及影响因素，揭示乌鲁木齐市不同功能区树木健康差异。旨在为研究区树木健康保护、城市绿地可持续经营及城市生态文明建设提供理论依据和数据支撑。结果表明：（1）乌鲁木齐市城市园林树木乔灌比为8.3 ： 1，树木多样性与种间关联程度较低。榆树占比高达43.87%，其中白榆占比22.62%，是主要优势树种；（2）不同树种健康程度呈现差异性，榆树类健康状况呈现圆冠榆 > 大叶榆 > 白榆 > 垂枝榆特征；（3）城市不同功能区树木健康也呈现异质性；以公园和居住小区树木健康分值较高，而行道树和学校庭院树木健康分值相对较低，且冗余分析进一步揭示地面铺装、林木配置结构、生长空间和胸径对树木健康影响程度最为显著。未来优化城市树木生境条件、提升物种丰富度、加强古树名木保育和提高园林绿化管理水平是维护和提升绿洲城市树木健康的重要举措。

Health assessment of urban trees in arid land oasis cities and its influencing factors: a case study of Urumqi

Urban green space is an important natural and heterogeneous component of urban landscape, which plays an important role in providing urban ecosystem services and improving residents'' well-being. As an important component of urban green infrastructure, the health status of urban trees directly affects urban ecosystem services and the quality of human settlement environments. The accelerated urbanization process leads to the loss of ecological land, and the lack of reasonable maintenance and the disturbance of extreme natural conditions pose a serious threat to the health of urban trees, affecting the effective development of the ecological, social and economic benefits of trees. In order to find the risk and influencing factors of urban tree health, a tree health index system was constructed from 4 dimensions and 12 indexes. Based on the survey of 117 sample plots in core urban area of Urumqi, through analyzing the tree composition, structure, association, health status and its influencing factors, the differences of tree health are revealed in different functional zones. The purpose is to provide theoretical basis and data support for tree health protection and sustainable management of urban green space in the study area, which is of great significance to play the landscape service function of green space and improve the degree of urban ecological civilization. The results show that:(1) the average ratio of trees to shrubs in core urban areas in Urumqi is 8.3:1; especially, the tree species diversity, inter and intra correlation of urban green species are low. Elm (Ulmus spp.) accounts for 43.87% of the total urban trees, of which Ulmus pumila accounts for 22.62%, which is the main dominant tree species. (2) There are some differences of the health status between different Elm species. The overall health status of the Elm species elaborates the characteristics of Ulmus densa > Ulmus laevis > Ulmus pumila > Ulmus pumila cv. pendula. (3) The tree health presents heterogeneity in different urban functional zones, which main public parks and residential areas are higher, while roadside and schools are relatively lower. The redundancy analysis further reveals that ground pavement, tree configuration structure, growth space and diameter at breast height (DBH) have the greatest contribution on the tree health. In the future, optimizing urban tree habitat conditions, improving species richness, strengthening conservation of ancient trees and improving landscape planning and management level are important measures to maintain and improve the health status of urban trees in arid land oasis cities.