Shrub Diversity In Arid And Semi-arid Desert Areas

The desertification in the northern part of China is very serious and the desert ecosystem is fragile.In the condition of global climate change,many rare species of desert plants are facing on the risk of extinction.In desert ecosystems,shrubs are im-portant species of desert vegetation due to their developed system of roots and strong resistance to stress.Therefore,the research on shrub diversity and shrub resources in desert areas is of great significance to local ecological construction,economic and social development.In this study,the research on shrub diversity,distribution pattern,flora,resource utilization and conservation in desert areas of China was carried out by collecting related literatures and investigating vegetation in the field.It will provide scientific basis for combating desertification and biodiversity conservation in arid and semi-arid regions.The main results and conclusions are summarized as the following:(1)There were 283 species of shrubs belonging to 86 genera and 28 families in arid desert areas of northern China.It was characterized by low species diversity and obvious phenomena of single genera and families.Among desert shrubs,there were more than 20 species of shrubs in 5 families,accounting for 17.86%of the total fami-lies;186 species,accounting for 65.7%of the total species.There were 17 families with single genera,accounting for 60.71%of the total families.There were 40 genera with single species,accounting for 46.51%of the total genera.There were obvious differences in species diversity of desert shrubs in different provinces.The species richness of desert shrubs in order was Inner Mongolia>Xin-jiang>Gansu>Ningxia.According to the statistical analysis of shrub species per unit area,the shrub species density in Ningxia was significantly higher than that in other areas.Meanwhile,there also were significant differences in species diversity of desert shrubs in different regions of Inner Mongolia.The species richness of desert shrubs in order was Xilinguole League,Ulanchabu League,Ikezhao League,Bayannuer League,Zhelimu League and Alashan League.There were obvious characteristics of diversification in the life type,ecological type and ecological function group of desert shrub plants.There were 6 life forms,among which shrubs accounted for 50%,semi-shrubs 27%,dwarf shrubs 15%,creep-ing shrubs 4%,erect shrubs 3%and climbing shrubs 1%.There were 7 ecological types,among which xerophytes accounted for 34%,strong xerophytes 27%,me-so-xerophytes 7%,mesophytes 16%,wet mesophytes 2%,sandy plants 12%,halo-phytes 4%.According to leaf morphological characteristics,desert shrubs were di-vided into 10 ecological functional groups,among which the type of lanceolate leaves accounted for 23%,nearly circular leaves 21%,oval leaves 18%,strip leaves 14%,linear leaves 6%,cylindrical leaves 5%,triangular leaves 3%,scaly leaves 3%,coni-cal leaves 2%,other leaves 5%.(2)Based on floristic analysis of shrubs in desert areas of northern China,the results showed that the dominant families of desert shrubs were mainly the world-wide type,including Polygonaceae,Chenopodiaceae,Rosaceae,Leguminosa,Tamaricaceae,Labiatae and Compositae.The dominant genera of desert shrubs were temperate distribution,including Salix,Calligonuml,Atraphaxis,.Salsola,Spiraea,Caragana and Artemisia.The geographical components of the genera are more repre-sentative in the desert areas of northern China.The similarity of between Inner Mongolia and Ningxia area was higher,while the similarity between Xinjiang and Ningxia area was lower by comparing the simi-larity coefficients of families,genera and species among flora in different provinces.There were some differences in the geographical composition of the dominant fami-lies of desert shrubs,among which the dominant families in Inner Mongolia are Sali-caceae,belonging to the discontinuous distribution pattern in the north temperate zone and the south temperate zone;the dominant families in Xinjiang and Ningxia were respectively Polygonaceae and Leguminosae,both belonging to the world-wide dis-tribution pattern.The dominant genera in Inner Mongolia with Caragana and Salix,Ningxia with Caragana,Spiraea and Salix,all belong to temperate geographical ele-ments.(3)There was obvious difference in the spatial distribution pattern of species di-versity of desert shrubs.The results showed that the change trend in species number of desert shrubs with longitude and latitude was a single peak curve,which first in-creased and then decreased.The areas with high species richness were Altay and Urumqi region in Xinjiang,Jiuquan and Minqin region in Gansu,Xilingol League and Ulanchabu League in Inner Mongolia,Zhongwei and Yanchi region in Ningxia.Hy-drothermal conditions are the main limiting factors affecting the distribution pattern of shrubs.The average annual precipitation was positively correlated with the number of shrub species,and the average annual temperature is negatively correlated in Inner Mongolia,Ningxia and Xinjiang.While both the average annual precipitation and temperature were negatively correlated with the number of shrub species in Gansu.(4)The species diversity in the desert area of North China is seriously endan-gered.There were 16 rare and endangered species of desert shrubs in China,of which 3 species were national grade I protected plants and 13 species were national grade ?protected plants.There were 6 endemic species of China in desert shrubs.The main protected species were of Lycium cylindricum?Tetraena mongolica?Ammopiptanthus mongolicus,A.nanus?Helianthemum songaricum?Amygdalus mongolica?Potaninia mongolica?Gymnocarpos przewalskii.