Study On Floristic Phytogeography And Analysis On Regions Of Priority Conservation In Western Sichuan Province, China

Western Sichuan is located in central region of Hengduan Mountains area of Southwestern China, known for its extremely rich biodiversity,complex topography,various physiognomy types,and high elevation difference.The plant flora in this area is ancient yet young,and gets evolutioned and enriched along with the constant uplift of the Himalayas.So far,investigations of floristic phytogeography in Western Sichuan have been rarely documented both in Sichuan Province and China.In this study,the author obtained the following statistics according to 9372 shares of collected higher plant specimens and literatures,combining the field investigation in 508 tree quadrats,1157 shrub quadrats,and 1437 herbaceous quadrats.Western Sichuan harbors 7459 species of wild higher plants with 314 families and 1402 genera (including taxon units under species).Of these species,302 are bryophytes with 57 families and 150 genera;453 are ferns with 46 families and 101 genera;69 are gymnosperms with 7 families and 18 genea;6635 are angiosperms with 204 families and 1133 genera.Aquatic and vascular plants have 184 species belonging to 48 families and 90 genera in wetlands of Western Sichuan,of which 101 are emerged anchored hydrophytes,40 submerged anchored hydrophytes,16 floating hydrophytes,27 floating-leaved anchored hydrophytes;rare and endangered plants sum up to 62 species,belonging to 44 families and 52 genera;the national key protected plants have 50 species with 32 families and 38 genera; the wild terrestrial vegetations have 7 vegetation types,21 formation classes,and 185 formation groups; the wild aquatic vegetations have 62 formation groups,which can be classified,in terms of ecological types,into 30 types of emerged anchored hydrophytes,18 submerged anchored hydrophytes,6 floating hydrophytes,and 8 floating-leaved anchored hydrophytes.This study supplemented 63 new record species in Western Sichuan and 1 in Hengduan Mountains area,discovered 2 new species which belong to the genus of Gentiana and Aquilegia,respectively,and determined the distribution places of many species that have not complete description of distribution before.In this paper,Western Sichuan is analyzed as an independent unit of plant floristics,and from the three levels of family,genus and species of plant taxonomy,the bryophytes,ferns,seed plants,aquatic and vascular plants,national class protective plants in Western Sichuan were discussed,respectively. The composition,characteristics,nature,origin and geographical links of plant floristics(only species analysis to bryophyte) of Western Sichuan were analyzed to determine the basic characteristics,nature, origin of plant floristics and their relationship with other flora.The results indicated that:the higher plants of Western Sichuan,no matter what kind of plants or taxon groups,their floristics have all features of richness,complexity,antiquity,transition and uniqueness;however,a question arises,that is,which are ferns and seed plants dominant in the three levels of family,genus and species on tropical elements and temperate ones.As for fern floristics of Western Sichuan,at the level of family and genus, the tropic elements are dominant,whereas at the level of species,the main ingredients are temperate ones.To floristic elements of seed plants of Western Sichuan,at the family level,the tropical ingredients are more than temperate ones;on the contrary,at the grade levels of genus and species,temperate components are more dominant than tropical ingredients.This phenomenon was thought to be relevant with the geological uplift history of Himalayas and its surrounding regions.Western Sichuan is situated in a hot spot in the world and is one of critical areas for biodiversity conservation,facing up with the dilemma of the rational development and effective protection of biology resources.Based on the biodiversity information of Western Sichuan and the application of priority conservation theory,this paper gave priority to the protective plants,animals and ecosystems of Western Sichuan after quantitative analyses,determined areas and number of organisms for priority conservation,which are 43 species of plants,2 insects,24 mammals,5 fishes,32 birds,2 amphibians;6 categories of ecosystems including partial moist evergreen broad-leaved forest,sclerophylious evergreen broad-leaved forest,spruce forest,fir forest,larch forest,and wetland ecosystems;four areas for priority conservation include the eastern area of Liangshan(â… Zone),the area of Solar mountain and Daxue mountain(â…¡zone),the middle area of Shaluli mountain(â…¢Zone),and the area of Seda and Shiqu hilly plateau(â…£zone).