Adaptation Of Root Functional Traits Of Landscape Tree Species To Dry And Barren Site In Stony Mountainous Area In Beijing

The root traits reflect the adaptation the tree to the growth environment,and root characteristics have an important influence on its growth.At present,the root traits were mainly based on the morphological changes of the root system under drought stress,and little research on the adaptation of plant roots under nutrient stress.Moreover,most of researches were based on field simulation experiments,and there were very few reports on the response of tree root traits to dry and barren in real environments.In this study,the main ornamental tree species in the rocky mountainous area(Cotinus coggygria,Acer truncatum,Amygdalus davidiana,Armeniaca sibirica,and Quercus variabilis)were used as the research object,and the fine roots of the trees were obtained by excavation method,and the fine root parameters were determined.Analyze the changes and differences in root functional traits of different tree species in dry and barren sites,and study the adaptation strategies of different tree species in dry and barren environments.According to the field water holding capacity and gravel content,four dry barren gradients(light,moderate,severe,extreme)were set up respectively to explore the differences in root functional traits of the five tree species in dry barren environments and their adaptive ways to dry barren stress.the result shows:(1)Both of drought and barrenness had affect on the functional traits of tree roots,among which root traits were more sensitive to drought than barrenness and interaction.The root functional traits of the five tree species changed significantly in different dry and barren environments,and the trees adjusted the root architecture to adapt to dry and barren environment.In addition,the changes of the same traits of different tree species were also different.Plant roots had shown significant differences in adapting to extreme dry and barren environments by changing root traits.(2)With the intensification of dry and barren stress,the root morphology and root stoichiometric properties of the five tree species have different changes,and the root branching patterns of different tree species are different.With the intensification of drought,the root system of Cotinus coggygria had a herringbone-like branch branching pattern,while the root systems of Acer truncatum,Amygdalus davidiana,Armeniaca sibirica and Quercus variabilis had changed from a herringbone-like branch pattern to a dichotomous branch pattern,tending to construct a compact root system configuration.With the intensification of infertility stress,the branch structure of the root system of Cotinus coggygria,Acer truncatum,and Amygdalus davidiana did not change significantly,which was between the branching pattern of Dichotomous branch and herringbone-like branch pattern.Armeniaca sibirica and Quercus variabilis used the branching pattern of herringbone-like branch to expand nutrient space.(3)Adjusting the synergy or trade-off relationship of root functional traits and realizing the efficient use of resources were important aspects for trees to cope with different soil dry and barren environments,and the synergy or trade-off relationship of root traits of the five tree species was quite different.Cotinus coggygria,Acer truncatum,Amygdalus davidiana,Armeniaca sibirica,and Quercus variabilis utilize the trade-off and synergy between different traits to improve the absorption and utilization efficiency of soil resources,and improve the resistance to barrenness.(4)Trees had certain adaptability and strategies to dry and barren stress,and could adapt to varying degrees of dry and barren stress through changes in the structure and morphology of their own root systems.By weighing carbon allocation and carbon consumption,different tree species had adopted different ecological adaptation strategies to dry and barren environments,which had obvious differences.