Comparison Of Root And Leaf Functional Traits Of 17 Tree Species In The Comman Garden Of Central Shandong Province Mountain Area

Water is an important factor that restricts the growth of trees.The selection of droughttolerant species in ecological restoration of difficult sites is an important issue in forestry.Previous studies on drought tolerance of tree species were mostly limited to short-term pot experiments on tree seedlings and lack of studies on long-term adaptive traits of trees.The functional traits of plants have strong plasticity and are the main indicators of response to environmental changes.Therefore,in homogenous territory,the study on the characters of perennial trees based on the water transport routes in trees is helpful to understand the drought tolerance mechanism and water utilization strategy of different trees,and can provide a basis for the selection of tree species for ecological restoration of difficult sites.17 species(Morus alba,Diospyros kaki,Diospyros lotus,Gleditsia sinensis,Acer truncatum,Pistacia chinensis,Ailanthus altissima,Melia azedarach,Fraxinus chinensis,Cotinus coggygria,Zanthoxylum bungeanum,Clerodendrum trichotomum,Ziziphus jujuba,Vitex negundo,Forsythia suspensa,Forsythia viridissima and Rhamnus globosa)in the Comman Garden of Central Shandong Province Mountain Area as the research object,comparing the differences and similarities of different tree species in the homogeneous habitat,discussing the relationship between different traits and water utilization,summarized its water use strategy based on trees moisture transmission route.The study found that:(1)There were significant differences in the traits of fine roots among 17 tree species(P< 0.05).The cortex thickness of Gleditsia sinensis was the largest in 1-2 order roots.In the3 rd order root,the stele diameter of Diospyros kaki was the largest but Pistacia chinensis' s was the smallest,the vessel inner diameter of Melia azedarach was the largest but Forsythia suspensa' s was the smallest,the vessel density of Acer truncatum was the largest but Melia azedarach' s was the smallest.According to the result of PCA,17 tree species were divided into 3 groups based on their traits of fine roots.The first group showed the smaller root diameter and the thinner cortex,the more compacted transport tissues(including 10 tree species,such as Morus alba,Diospyros lotus,Rhamnus globose,Ziziphus jujuba,Acer truncatum,Pistacia chinensis,Ailanthus altissima,Vitex negundo,Fraxinus chinensis andForsythia suspensa),the second showed the smaller root diameter and the thinner cortex,but the looser transport tissue(i.e.,Cotinus coggygria,Melia azedarach and Clerodendrum trichotomum),the third was of the larger root diameter and the thicker cortex,and the more compacted transport tissue(i.e.,Diospyros kaki,Forsythia viridissima,Zanthoxylum bungeanum and Gleditsia sinensis).(2)There were significant differences among vein traits of 17 tree species(P < 0.05).The midvein diameter and xylem thickness of Clerodendrum trichotomum were the largest and the midrib diameter,but the Zanthoxylum bungeanum' s were the smallest.Meanwhile,the topological parameters of the main vein of Zanthoxylum bungeanum were the largest caused the simplest branches,while the topological parameters of the main vein of Acer truncatum were the smallest caused the most complex branches.The veinlets density of Morus alba was the largest but the Zanthoxylum bungeanum was the smallest.According to the results of PCA sequencing,17 tree species of tree leaf traits can be divided into three groups,the first group has large diameter of midvein and sparse veinlet(including 12 tree species,such as Morus alba,Rhamnus globose,Gleditsia sinensis,Acer truncatum,Cotinus coggygria,Forsythia viridissima,Fraxinus chinensis,Vitex negundo,Pistacia chinensis,Ziziphus jujuba,Melia azedarach and Ailanthus altissima),the second group has large diameter of midvein and dense veinlets(including Forsythia suspensa,Diospyros kaki,Diospyros lotus and Clerodendrum trichotomum four tree species),the third group has small diameter of midvein and sparse veinlet(only 1 tree species: Zanthoxylum bungeanum).(3)The leaf traits of 17 tree species were significantly different(P < 0.05).The leaf thickness,palisade tissue thickness and sponge tissue thickness of Zanthoxylum bungeanum were the largest,which of Morus alba were the smallest.the adaxial epidermis thickness of Ziziphus jujuba was the largest,which of Fraxinus chinensis was the smallest.The abaxial epidermis thickness of Diospyros kaki was the largest,which of Cotinus coggygria was the smallest.The stomatal density was the largest in Clerodendrum trichotomum,the stomatal length of Acer truncatum was the smallest,and the stomatal length of Zanthoxylum bungeanum was the largest and the density was the smallest.According to the results of PCA sequencing,17 species of leaf traits can be divided into three groups,The first group of leaves was characterized by thin leaves,small stomatal length and high density(including 14species: Cotinus coggygria,Acer truncatum,Melia azedarach,Clerodendrum trichotomum,Fraxinus chinensis,Ailanthus altissima,Rhamnus globose,Forsythia viridissima,Forsythia suspensa,Diospyros lotus and Ziziphus jujuba),The second group was characterized by thick leaves,small stomatal length and high density(including 2 trees: Diospyros kaki Gleditsiasinensis),The third group was characterized by thick leaves,high stomatal length and low density(only tree species: Zanthoxylum bungeanum).(4)Three water utilization strategies were summarized according to the traits of 17 tree species.The first water utilization strategy is rapid water absorption,rapid water transfer,effective water separation and flexible water retention,including Morus alba,Rhamnus globosa,Pistacia chinensis,Vitex negundo,Fraxinus chinensis,Acer truncatum,Diospyros lotus,Forsythia suspensa,Forsythia viridissima,Ziziphus jujube,Ailanthus altissima,Cotinus coggygria,Melia azedarach and Clerodendrum trichotomum a total of 14 tree species.The second water use strategy is effective water seeking,rapid water transfer,effective water separation,flexible water retention,including Diospyros kaki and Gleditsia sinensis.The third water use strategy is effective water seeking,rapid water transfer,safe water distribution,effective water retention,involving only 1 species(Zanthoxylum bungeanum).The water utilization strategy of 17 tree species based on water transport route induction can better reflect the ecological adaptation strategy of trees and provide a basis for the selection of tree species with difficult ecological restoration.(5)In a homogeneous habitat,there was a systemically significant correlation(P < 0.05)or extremely significant correlation(P < 0.01)between absorptive root traits(order 1 and 2root diameter and their root cortex thickness)and leaf anatomical traits(leaf thickness,palisade tissue thickness,sponge tissue thickness,abaxial epidermal thickness),the same with stomatal traits.A series of correlation relationships reflected the coordination relationship between leaf functional traits and root traits.In terms of the function of its traits alone,it reflects the coordination relationship between the water-absorbing components and waterretaining components of woody plants in homogeneous habitat,as well as the trade-off between the water-absorbing function and water-retaining function.