Abstract:

Wild Cymbidium tortisepalum var.longibracteatum (Orchidaceae) plants in Sichuan Province of China have become endangered due to overharvesting in recent years.In order to provide theoretical and technical basis on wild C.tortisepalum var.longibracteatum biodiversity conservation and reintroduction in a larger scale,a systematic investigation on the main habitats of populations was conducted based on representative plot survey in Parallel Ridgevalley Region of the Eastern Sichuan in 2010.The results showed that the wild C.tortisepalum var.longibracteatum distributed mainly under the mixed forest of Pinoideae and Fagaceae，Mixed Fagaceae forest and [JP2]Pinus forest where the altitude was about 680－1 900 m，[JP] and its main associated plants were composed of 34 species belonging to 15 families，28 genera in tree layer,18 species belonging to 12 families，15 genera in shrub layer and 17 species belonging to 12 families,14 genera in field layer.Among associated plants,the shade density of tree layer was from 0.2 to 0.4,and the dominant species were Pinus massoniana, Fagus longipetiolata,Pinus henryi,Pinus tabuliformis, Fagus pashanica,Lithocarpus cleistocarpus and Quercus acutissima etc.The coverage of shrub layer was from 30% to 50%,and the dominant species were Rhododendron,Coriaria sinica,Camellia japomica,Rubus orchorifolius and Pyracantha fortuneana etc.The coverage of field layer was about 40% to 80%，and its dominant species were Bryophyta，lichen,Pteridophyta.Among these plants,Pinus massoniana,Rhododendron,Bryophyta and Pteridophyta can be used as indicative plants for its high important value.Species diversity of plant community in different populations was investigated.Plants in the populations associated with suitable habitats of C.tortisepalum var.longibracteatum were prosperity and lush.Species abundance index of D was between 1.915 to 3.572 in 10 populations.Compared with others,the population of 1st,3rd and 6th had relatively low index of H′(Shannonwiener index) and E (Pielou index),and had high ecological density of C.tortisepalum var.longibracteatum,which indicated that individuals of Pinaceae and Fagaceae were more than some other species and prominent in those populations.The individual quantity of every population of wild C.tortisepalum var.longibracteatum were only from 11 to 60 individual plants per ha，which revealed that this species in Parallel Ridgevalley Region in the Eastern Sichuan had become endangered due to overharvesting.Although C.tortisepalum var.longibracteatum is rather rare,the habitat of wild C.tortisepalum var.longibracteatum were still protected well.These results,combined with other information about C.tortisepalum var.longibracteatum,may provide an important basis for proposing conservation strategies.In situ conservation will be suitable for in Parallel Ridgevalley Region of the Eastern Sichuan,especially in Tongjiang(the 1st population and 3rd population)and Nanjiang(the 6th population),while the researches about seed physiology and symbiotic germination to raise germination rate of C.tortisepalum var.longibracteatum in wild environment and the application of reintroduction in the conservation of endangered orchid should be taken into consideration to expand the population to save the endangered status