Biodiversity Of The Plant Community And Ecosystem Assessments At Different Scales In Alxa Deserts

Biodiversity and endangered species are abundant in the desert ecosystem,which belongs to fragile ecosystems.Deserts are home to 6% of the world's population.These population rely on desert ecology and its service to survive.Ecosystem services depend on ecosystem health,ecosystem health has the function of maintaining biodiversity and ecosystem services.Desert ecosystem protection funds and research are very scarce.Deserts are widely distributed in China,mainly in the northern provinces.This paper takes three deserts of Alxa Plateau as the research area,investigated several aspects of phytocoenosium in desert ecosystem,including diversity of species,vegetation distribution pattern and its response to soil factors,and then accomplished its biodiversity and health assessments.This research coms to the following conclusions:(1)A total of 290 sample plots in the Alxa Deserts have been set.479 quadrats and 21 transect lines show that vegetation community structure in Alxa deserts is relatively simple,with a total of 196 species(within 22 rare species,appeared twice and below in all the quadrats),under 35 families,108 genera.Among them,Compositae,Gramineae and Polygonaceae have the maximum number of species,accounting for 50.29% of the total in the study area,followed by Legumes.The plants in Badain Jaran Desert are under 26 families,73 genera,109 species.The plants in Tengger Desert are under 27 families,83 genera,118 species,and that in Ulan Buh Desert are under 12 families,39 genera,52 species.The number of species in Tengger is the most abundant,followed by that in Badan Jaran Desert,andspecies in Ulan Buh Desert are relatively few.Based on the Important Value – Sample Quadrat Matrix data,the classification result of TWINSPAN,PCA sorting combined with classical plant taxonomy reveals that the outcome of quantitative ecology method basically conform with that of the classical plant taxonomy method.The plant in Alxa deserts are divided into 5 vegetation type: desert,grassland,meadow,shrub and deciduous broad-leaved forest,15 formations.Drought-resistant and salt-tolerant plants are in majority.Spatial distribution map illustrates that the Badan Jaran Desert is dominated by Artemisia arenaria + Calligonum arborescens,Artemisia arenaria + Ephedra przewalskii deserts.The Ulan Buh Desert and Tengger Desert s are mainly Artemisia arenaria + Artemisia ordosica deserts.Therefore,the vegetation type in Alxa deserts belongs to semi-shrubs and small shrubs in temperate deserts.(2)174 representative samples for calculation of the Shannon-Wiener,Simpson,uniformity and species richness index show that the species diversity index in the study area are relatively low,shrubs,shrubs-herb have the maximum diversity indexes and minimum uniformity index,shows the characteristics of desert ecosystems.The communities with large biomass in Alxa desert are successively: Ephedra przewalskii,Reamuria soongorica,Phragmites communis,Nitraria tangutorum,Artemisia arenaria and Artemisia ordosica.They have good vegetation growth conditions.(3)2313 soil layered samples are collected under different community types,the soil moisture content,bulk density,specific gravity,porosity,particle size,organic content,total nitrogen,available phosphorus,available potassium content,pH,conductivity,and other soil properties are experimented.The soil moisture content under shrub-herb communities is maximum,4.1 %.The soil nutrients under shrub-herb communities rank only second to the Phragmites communis communities distributed around lakes and dry lakes.Through the Detrended Canonical Correspondence analysis(DCCA)of plant community species and environmental factors,Soil moisture,total nitrogen,organic matter content have great influences on the distribution of vegetation.As to the RDA analysis and Pearson correlation analysis of the Shannon-Wiener,Simpson Index,Uniformity,Species Richness and the environmental factors,there is a relatively strong positive correlation between biodiversity and soil available phosphorus content,followed by rapid availability of potassium,organic content and the conductivity again.(4)Ecosystem assessments: at the regional scale,the biodiversity in 3 deserts are evaluated and that in the Tengger Desert is relatively abundant.At the community scale,ecosystem health assessment is conducted on different community types.The health status of the Calligonum arborescens community and Phragmites communis community are “very health”.Their evaluation values are 82.93 and 80.14,which are higher than other types of vegetation communities.According to this article,it is recommended that,when necessary,species with good vegetation,soil environment and good evaluation results can be planted for desert ecosystem protection and restoration,like Calligonum arborescens,Ephedra przewalskii,Artemisia arenaria and Phragmites communis to construct Artemisia arenaria + Calligonum arborescens,Artemisia arenaria + Ephedra przewalskii,Artemisia arenaria + Artemisia ordosica deserts and Phragmites communis meadow.