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Gansu Agricultural University (2015)

Desert Steppe Vegetation Ecology And Environmental Changes in Kumtag Desert

张锦春;

Titre : Desert Steppe Vegetation Ecology And Environmental Changes in Kumtag Desert

Auteur : 张锦春;

Grade : Doctoral Dissertation 2015

Université : Gansu Agricultural University

Résumé
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.

Mots clés : Kumtag desert; desert steppe; floristic geographic elements; population distribution patterns; community diversity; Quaternary pollen; Tamarix sand-hillocks; age layers series; grain-size characteristics; stable carbon isotope;

Présentation (CNKI)

Page publiée le 9 octobre 2017