Structural characteristics and health status of roadside trees in Nanchang City, China from Baidu Street view-based measurements

• 1、 Key Laboratory of Forest Plant Ecology, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin 150040
• 2、Northeast Institute of Geography and Agroecology, Chinese Academy of Science, Changchun 130102
• 3、Key Laboratory of Forest Plant Ecology, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin 150040

Abstract：As the network and skeleton of urban green space system, roadside trees play an irreplaceable role in urban residents\' life. Rapid and accurate grStructural characteristics and health status of roadside trees in Nanchang City, China from Baidu Street view-based measurementsasp of the structural characteristics and health status of urban roadside trees is conducive to the construction and management of urban forest, thus improving its ecological service function. Based on the Baidu Street View platform, this study investigated 963 quadrats, a total of 26,727 roadside trees, in Nanchang city by street view tree measurement method. Measures included indicators of street tree sizes (diameter at breast height(DBH), underbranch height(UBH), tree height(TH) and canopy size(CS)), health status ( the proportion of Tripod-supporting, the proportion of dieback, the proportion of Non-greenness leaf color and the proportion of Death trees) and vertical structure configuration of vegetation; Moreover, the spatial distribution characteristics of road trees under different administrative regions and different urbanization intensity (urban and rural gradient under the development of ring roads) are explored. The results showed that: (1) There were a high proportion of small trees in Nanchang: DBH of 10-20 cm accounted for 65%, UBH of 1.5-2.5 m accounted for 76%, TH of 4-8 m accounted for 71%, CS of 2-6 m accounted for 76%.The overall performance of the growth of street trees is healthy, the proportion of each index is small, but the leaf health is poor. In 35% of the plots, no leaf color was unhealthy, 77% of the plots had no Tripod-supporting, 76% of the plots had no Dieback and 93% of the plots had no death. T The vertical structure of vegetation is in good condition, mainly composed of arbor-shrub-herb (75% of the sample land). (2) In terms of spatial distribution, there are significant differences in the sizes index and vertical structure configuration of road trees in different administrative areas, and significant differences in health status (proportion of Tripod-supporting and proportion of Non-greenness leaf color) (p<0.05). There are urban-rural differences in the size index of road trees in different loop areas, which are manifested as 1st ring > 2nd ring > 3rd ring, the vertical structure of the outer ring is more complex, configuration grade is 1st ring < 2nd ring < 3rd ring. There were significant differences in the health status of different Ring-road (proportion of Tripod-supporting and proportion of Non-greenness leaf color) (p<0.05). To sum up, the overall health status of the roadside trees in Nanchang is good, the individual of the roadside trees is small, and they are mainly composed of multiple layers. Based on the Baidu Street View, this study makes a relatively comprehensive evaluation of the structural characteristics and health status of the roadside trees in Nanchang, which provides basic data support for the planning and management of the urban roadside trees in Nanchang in the future.

Keywords： Roadside tree Baidu Street View Vertical structure Tree sizes Forest health