Characteristics And Species Diversity Of Typical Artificial Plant Communities In The Loess Hilly Region Of Northern Shaanxi,China

In this study,we selected 111 plant communities from where sub basin of Yanan Baota District,Ansai Zhifanggou watershed,Wuqi County Jinfoping watershed,Mizhi County Gao Xigou watershed,Yichuan County Jiaozigou watershed of Shaanxi Province as study object,The characteristics and diversity of artificial plant communities in different watersheds and different site types were analyzed.The adaptability of different plant communities and environment was studied,and the succession rule of undergrowth vegetation with Robinia pseudoacacia and Apricot were explored,The dynamic characteristics of plant communities at different elevations were elucidated,and the soil quality of Robinia pseudoacacia community under different site conditions was evaluated.The main conclusions are as follows: 1.Characteristics of typical artificial plant communities in Loess Hilly Region of Northern ShaanxiThe distribution of each species is different in each watershed,the total number of genera is greater than the total number of families in each watershed,the total number of species are greater than the total number of genera.The different watersheds are mainly perennial herb and annual herb,semi-small shrubs and semi-shrubs are lesser.The world's broad branches occupy the main position in the study area,Compositae,Rosaceae are the main families of the region.The artificial economic forest take the main position at the top of Yichuan hilly.The upper,middle and lower slopes are dominated by artificial trees and shrub forests;the valley is dominated by Herbs;Yanan and Ansai watershed are dominated by herbs,the upper,middle and lower slopes are dominated by artificial trees and shrub forests,the valley is dominated by herbs;The top of the hill is dominated by artificial arbor forest,the other slope position is dominated by artificial trees and shrubs with a few herbs.There are more species in the watershed with less than 30°,and steep slope species are less.The sunny peaks of the watershed are distributed in the trees such as Robinia pseudoacacia,There are more types of communities in the semi-shady and semi-sunny slopes than the other,Ansai and Yan'an watershed are distributed with shrub.In addition to Wuqi with more herbs,the other watershed clusters are mainly woody community,The local geographical environment of Yichuan is more similar.In summary,we should consider the comprehensive effect of site factors,rational allocation of forest,so that artificial forest reaches the greatest benefit.2.Study on the diversity of different artificial plant community diversityThe species richness index and evenness index of Yichuan River Basin were higher than those of other watersheds.The Simpson index of Yan'an was higher,the Shannon-wiener index was lower,the dominant species were prominent,and the community was in the development stage.With the elevation,the community uniformity index decreased,the dominant degree is very obvious.The species richness is the highest,the vegetation diversity is the highest,and the sunny slope is the lowest,the slope is bigger,the Shannon-wiener index is higher,and the planting of Platycladus orientalis and Robinia pseudoacacia is more favorable for vegetation restoration.In the lower slope of the species within the community more uniform,middle and lower slope to create vegetation is conducive to vegetation restoration.The mid-down slope is more suitable for the construction of vegetation,while the afforestation in the sunny slope should be based on the protection and restoration of herbs community,only in the water conditions are better,to meet the growth of trees or shrubs in the micro-terrain,The appropriate proportion of Joe,irrigation,grass complex configuration rich community hierarchical structure,optimize the community ecological function.3.Succession of undergrowth plants in Artificial Robinia pseudoacacia CommunityThere are abundant resources in the succession of undergrowth plants in different Robinia pseudoacacia communities,and fewer families and single species accounted for obvious advantages in the community.Artemisia annua and Kentucky bluegrass were distributed in all successional stages,plant community species composition and distribution are effected by a number of factors.Age,plant density,soil total phosphorus and soil carbon and nitrogen ratio are the main habitat factors affecting the variation of understory species in Robinia pseudoacacia community.The factors affecting the species composition of Robinia pseudoacacia community are mainly from the interaction between plant and soil properties.4.Study on the succession of artificial apricot communities under the plantThe succession of understory plants in different retirement was closely related to the growth and development stages of the upper standings,and the composition and diversity of understory plants fluctuated with the increase of the upper standings.Undergrowth plants in young apricot community are dominated by wild alfalfa and Artemisia scoparia,species become more,plant grows well.The species were reduced,the species diversity was decreased and the plant growth was weakened when the Mountain apricot community forest arrived in the middle age.The plant species in Mountain apricot communities were dominated by Dendranthema glauca and Potentilla fruticosa,and the species increased and the diversity increased.The abundance of understory plants is mainly affected by plant density and aspect,dominance and evenness are mainly affected by slope,species diversity was mainly affected by high thoracic area and canopy closure.The succession of undergrowth plants in the apricot community was greatly affected by the growth of the apricot community.5.Changes of plant community species diversity with altitude gradient and environmental interpretationThe distribution of plants in the range of altitude are similar,they are Compositae,Gramineae,Rosaceae,Leguminosae,in which most of them are the Compositae.Compared with the low altitude,the high altitude of the four branches accounted for relatively high.The species richness of tree and shrub layer showed a single pattern,altitude is an important factor of species richness,which explained the variability of total species richness of 45.1%(P <0.01).With the increase of altitude,the species richness and species diversity increased first and then increased,the dominance and evenness of the species decreased first and then decreased,but the fluctuation was not significant.With the increase of altitude,the community similarity decreased,the species substitution rate increased.Altitude mainly affects species richness,and slope mainly affects community dominance and evenness.In summary,it is shown that the diversity of plant species in hilly loess area is influenced by various environmental factors,the low altitude and high altitude community diversity protection should be strengthen.Combined with plant characteristics,different afforestation patterns and suitable planting species should be selected for rational allocation of plants.