Study On Plant Biodiversity Of The Liangucheng National Nature Reserve In Minqin

Through investigating the vegetation growth of nation-class Liangucheng Nature Reserve in Minqin and consulting correlative data, the vegetation community of Liangucheng Nature Reserve is divided into 3 types: shrub association and shrub-grass association, desertification and meadow, in accordance with the principle and system of vegetation classification constituted in Vegetation of China, and divided into 4 vegetation forms according to its major diversities of essential live forms: defoliation-broad shrub association, desertification with shrubs, desertification with semi-shrubs and desertification meadow, and divided into 8 formation groups: salt shrub association, large desertification with shrubs, grassland-shrub desertification, desertification with desert shrubs, desertification with salt semi-shrubs and low shrubs, desertification with salt semi-shrubs and low shrubs having excessive liquor, desertification with Artemisia species, Phragmites communis meadow, in accordance with the eco-biological characteristics of dominant communities composing desertification vegetation, mainly adaptive characteristics of its assimilation organs to atmospheric and physiological droughts, and divided into 13 formations according to dominant species of communities: Tamarix ramosissima shrub association, Nitraria tangutorum shrub association, Nitraria sphaerocarpa shrub association, Ephedra przewalskii desertification, Zygophyllum xanthoxylum desertification, Oxytropis aciphylla desertification, Potaninia mongolica desertification, Caragana korshinskii desertification, Calligonum mongolicum desertification, Reamuria soongorica desertification, Kalidium foliatum desertification, Artemisia arenaria desertification, Phragmites communis meadow.Of 13 formations we set 10 quadrats of 10×10m~2 in each formation, measured overground biomass of each species by harvesting and investigated its community characteristics such as component, quantity, growth, coverage, circumstance and so on. We calculated diversity indexes of community in the quadrats such as important values, species richness, compiled lists of seed species of Liangucheng Nature Reserve in Minqin on the base of referring to the plant specimens of the Reserve and other correlative data.Analysis results show: there are 30 families, 116 genus and 198 seed species in Liangucheng Nature Reserve in Minqin, including 1 gymnosperm family (1 genus, 2 species): Ephedraceae, Ephedra, 4 monocotyledon families (25 genus, 33 species), 25 dicotyledon families (90 genus, 163 species). The result of analyzing species quantity of each family show that most of the species in the Reserve belong to few large or medium families. There are obviously diversities among floristic dominances. A sequence of dominant families ranked in the light of species quantity is: Chenopodiaceae(27 species), Leguminosae(27 species), Gramineae(26 species). Compositae(21 species), Zygophyllaceae(11 species), Polygonaceae(11 species), Tamaricaeeae(10 species), Cruciferae(9 species). Of them Zygophyllaceae and Tamaricaceae families have less species than other families, but the ratio of the quantities of them to the same species in the world is high. So, both of the families are token families of plant zone in the Reserve. Analyzing geographical components of floristic families in the Reserve, we can make out that world plant components take the most important role in the Reserve on the level of family, then the temperate zone components, including 11 families accounting for 36.67% of the total families, which reflects adaptability of the species to the climate of the Reserve. Almost all dominant families of the Reserve are families which spread over the world, which indicates asperity of the climate of Liangucheng Nature Reserve in Minqin. There are many species of the temperate zone components in the Reserve, but they can't become dominant species because of arid desertification climate. Only large families which spread over the world win in the bad surroundings of the Reserve depending on its enormous species system and adaptabilities.The species of Liangucheng Nature Reserve can be differentiated 12 distributional types and 13 transforms in term of 15 distributional types of seed plants in China differentiated by Mr. Wu-Zhengyi. Of them, the temperate zone type (44 genus, accounting for 37.93% of the total genus in the Reserve) is dominant. Distributional types of Mediterranean Sea, zone from west Asia to meddle Asia, meddle Asia (33 genus, accounting for 28.45% of the total genus in the Reserve) are important components of the floristics in the Reserve. The genus spreading over the world (21 genus, accounting for 18.1% of the total genus in the Reserve) takes an important role in the species system.The diversity indexes of 5 primary plant communities in the Reserve show that these communities have characteristics of simple species compositions, high ecological dominances, low diversity indexes, low probability of meeting each other and unbalance of species distribution in communities, which caused by resource competition among same species or different species. A sequence of species diversities is: Oxytropis aciphylla community＞Potaninia mongolica community＞Reamuria soongorica community＞Ephedra przewalskii community＞Kalidium foliatum community. A sequence of community productivities is: Reamuria soongorica community＞Oxytropis aciphylla community＞Potaninia mongolica community＞Ephedra przewalskii community＞Kallidium folianum community. Thus it can be seen that communities with higher diversity indexes have not always higher productivities. It is mainly for the intervention of annual grass. Analyzing only on the level of shrubs, diversity indexes of communities have positive correlation with its productivities. Shrub layers have higher stability and lower variability and are less affected by distributional pattern of rainfall.