Desert Steppe Vegetation Ecology And Environmental Changes In Kumtag Desert

Kumtag desert is one of the eight deserts in China and the desertification is very serious there, and it has done harm to the surrounding environment, making the three major national natural reserve area shrink and biodiversity loss. Therefore, it is very important to carry out desert steppe vegetation ecological research in areas. The article is to explore the adaptability between desert steppe plants and ecological environments by carrying out the ecological investigation of species flora, population distribution and community diversity on the basis of comprehensive investigation to Kumtag desert and explore the desert steppe plants evolution process and its response to climate, reveal kumtag desert formation evolution process through the desert depositional environment information extraction, analysis and reconstruction of paleoclimate. The main results show that:(1)Kumtag desert steppe plant flora belongs to the typical desert area, Desert steppe plants are rare and flora structure is simple in Kumtag desert and there are 120 natural desert steppe plant species(including subspecies and varieties), which belongs to 25 families and 79 genera. Among them, the dominant families are included Chenopodiaceae, Compositae, Ttamaricaceae and Gramineae, which contains 55.70% of the total number of genera, 58.33% of the total of the species in the desert, The dominant genera is Tamarix and calligonum and the number of genera and species is not big, but the ratio of species and genera is very high. Fauna distribution is given priority to with temperate type, for the typical desert flora, the temperature of the ancient Mediterranean ingredients as an important part of flora, included in this area most of the building group of the fauna plays a very important role.(2)Haloxylon ammodendron, Populous euphratica and Tamarix taklamakanensis are the typical species, Among them,. Populations of H.ammodendron populations is an arid desert plants extensively, strippedly and continuously distributed in the south of the desert. It belongs to stabilize the growing population, has the strong adaptability to desert environment and population wide distribution diffusion, low degree of population aggregation degree is low due to the effect of population diffusion distribution. P. euphratica is a constructive species distributed in channel in closer from the water source and part of the river terraces for desert forest by riverside. Due to the smaller area like a strip and less number, the population appears as a mosaic distribution like a scattered spot and has a very high aggregation degree for the effect of water resource. T. taklamakanensis is endemic to China and distributed in the northern desert like a strip. Population is a declining type and its population aggregation degree is not high.(3)Using the level 6 taxonomic unit, kumtag desert vegetation is divided into six type class, 5 vegetation type groups, 9 vegetation type, 11 vegetation subtypes, 33 formation and10 subformation. Vegetation distribution appears circle layer distribution pattern as the center of desert from the desert landscape scale. the vegetation zonality is evident in the level of longitude change from south to north in desert vegetation and orderly distributed, namely gravel desert vegetation, sand desert vegetation and saline meadow vegetation, the distribution of vegetation in the southern margin of the desert appears a transition from the gravel desert before mountain to sand desert and the distribution in the northern margin of the desert appear a transition from meadow vegetation to sand desert in the level of longitude change..Desert vegetation on the basis of habitat is divided into the gravel desert vegetation, sand desert vegetation and saline meadow vegetation types, the vegetation community diversity level of three desert vegetation is gravel desert vegetation > saline meadow vegetation> sand desert vegetation. H value is 0.725 ~ 1.437. Desert plant community diversity in horizontal radial distribution gradually decreased with the decrease of the longitude, which is consistent with the radial degree of drought and changes in rainfall, and the level of community diversity zonal changes with the change of the surface hydrological conditions present certain distribution pattern.(4)The species and number of pollen are shortage in the quaternary of Kumtag Desert and there are totally 40 family and genera by pollen identification including the main family: Chenopodiaceae and Poaceae and other family and genera. For instance, Cyperaceae, Sparganium and Urtica ete. And these plant pollen belong to wet meadow types. the pollens from the desert quaternary show that the tendency of climate change in the desert is totally from the alternative dry and heat and the dry and wet to the dry. the most pollen number of Chenopodiacea, respective of the dry environments, account for 30. 6~50. 5% of total pollen number. The ratio of Ephedra and Artemisia, respective of the dry environment, changes from 1.0% to 2.0%. From the results, we conclude that the main climate characteristics of quaternary age in Kumtag Desert are dry and the dry degree is increasingly intensified.(5)Granularity composition of grain-size is dominated by the fine sand, which the age layer average content is 80.66 % and the content of coarse sand and coarse powder sand came next, with average value of 34.27 % and 31.90%. The grain-size composition of sand drift in the north of desert is coarse particle, the smallest particle in the east of the desert and the grain-size composition in sand drift shows the coarse particles prevail over with the increase of sedimentary layers. The main climate pattern of Kumtag Desert is the dry and strong wind, with the evident alternative course of the dry and wet by the grain composition of tamarix sedimentary layers during the 120 years.(6)The δ13C in annual stratum of Tamarix sand-hillocks is declining trend as the whole, The atmospheric CO2 concentration increasing rapidly caused the variation carbon isotope fractionation. The C13? composition in annual stratum of Tamarix sand-hillocks had a similar trend to the global climate changes. There was dry and warm climate environment for the past 120 years, which the value of C13? was reduced with the global climate warming, There was different response of the C13δ in annual stratum of Tamarix sand-hillocks under different habitats to climatic elements changes, such as the values of C13? in annual stratum restricted by several climatic factors in the high altitude area,the ?13C composition had significantly relationship with air relative humidity, precipitation and temperature, and theirs time lag effect was obvious. In contrast, at the arid desert area in high latitude and low elevation, the C13? composition had intense sensitivities to precipitation and temperature and the C13? time lag effect was not obvious.