Reproductive Resource Allocation Characteristics And Ecosystem Service Assessment Of Dioecious Species Fraxinus Velutina Torr.

The characteristics of reproductive resources allocation of sexual dimorphic plants is one of the core contents of plant life-history strategy.Because of the independence of gender distribution,dioecious species is an important model trees species for studying the pattern of plant resource allocation.The dioecious plant Fraxinus velutina Torr.has the characteristics of fast growth rate and strong environmental adaptability.Therefore,it is widely used in the construction of urban forests.The main ornamental part of F.velutina Tor is leaf,and the ornamental value of the fruit is low,but the seed setting rate of the female tree is high.Therefore,The study on the distribution pattern and distribution law of resources between female and male trees of F.velutina is of guiding significance for the cultivation of F.velutina and its application in urban forestry construction.In this study,F.velutina was studied in the plain forest area of Longwan Village,Yanqing District,Beijing.The phenological observation and basic characteristics of 35 male trees and 32 female trees were investigated at flowering and fruiting stages,respectively.In the field,the field samples were taken to investigate the reproductive organ biomass and vegetative organ biomass of the sample plants,and the resource allocation pattern of the F.velutina was analyzed.In order to avoid the influence of self-organization level,the study levels of shoot,branches and the whole tree.On this basis,in order to further explore the impact of resource allocation characteristics of reproductive growth and vegetative growth of dioecious plant ash on its ecological benefits,based on field investigation,i-Tree Eco is used in this paper This paper analyzes and evaluates the resource structure and ecological benefits of 1705 street trees planted on both sides of eight roads in Haidian District of Beijing.The purpose of this paper is to analyze the interaction between the resource structure of street trees of different genders,and to explore the application of i-tree model to evaluate the ecosystem service function of domestic street trees The application of tree in selection and planning provides a theoretical reference.The main results are as follows:(1)There was no significant difference in flower number,leaves number,total length of new shoot and single flower weight.At the level of shoots,there was no significant difference in the biomass of the biomass.At the level of the branches,the flower biomass of the female trees was significantly smaller than that of the male trees.At the tree level,the leaf biomass of the female trees was significantly smaller than that of the male trees.The analysis of reproductive and vegetative growth patterns of different sex plants showed that there were significant differences in the resources invested in vegetative growth and reproductive growth between female and male trees.Female trees invested significantly more resources in reproductive growth than male trees,while less resources were invested in vegetative reproduction,which means,gender had a significant impact on the distribution pattern of resources of F.velutina.(2)Using i-tree model to evaluate the ecological service function value of street trees,the ecological benefit value of eight road street trees in 2019 is 435976 yuan.Among them,the value of absorbing and fixing carbon dioxide is 217766 yuan,the value of releasing oxygen is 37283 yuan,the value of improving air quality is 171392 yuan,and the value of intercepting rainwater is 9534 yuan.(3)There was no significant difference in the ecological benefits of ash trees with DBH less than26 cm.The carbon sequestration benefit,oxygen release benefit,air purification benefit,rainwater interception benefit,total value of ecological benefit and average benefit per plant of male trees with DBH of 26-30 cm were significantly higher than that of female trees with the same diameter;the carbon sequestration benefit and oxygen release benefit of male trees with DBH of 30-34 cm were significantly higher than that of female trees with the same diameter;the carbon sequestration benefit and oxygen release benefit of male trees with DBH of 34-38 cm were significantly higher than that of female trees with the same diameter The male trees are significantly higher than the female trees of the same diameter in carbon sequestration,oxygen release and air purification benefits,and significantly higher than the female trees of the same diameter in the total value of ecological benefits and the average benefit value of a single tree.That is to say,gender has an impact on the function of the white wax street trees,which shows that the ecological benefit value of male trees is significantly higher than that of female trees.