Study on Community Features of Monsoon Forest in the Dry-hot Valleys in Yuanjiang County

The state and characteristics of the monsoon forests in the dry-hot valleys in Yuanjiang County,Yunnan Province were studied based on the field data collection from the local plots.The study showed the following results: The pan-tropical elements dominated the floral composition at family and genus levels.Whereas Tropical Asia(India-Malaysia) flora dominated at species level,in which phanerophyte was the major life form,together with relatively abundant lianas.The monsoon forest in Yuanjiang County showed strong secondary status,the flora secondary index reached 56.1%.There were more secondary species in the herbaceous layer than in the arbor storey and the shrub layer.The flora secondary index of the herb layer reached 70.5% and the ecological secondary degrees reached 85.8%.There were also many secondary species among the interlayer plants.The higher biodiversity was found in areas with ample moisture and less anthropogenic disturbance.The monsoon forest in Yuanjiang County showed many characteristics of savanna shrub vegetation,such as sparse arbor layer,low living branches with large crown.The plants were generally drought tolerant,and many of the species were the major components of savanna shrub vegetation,indicating that the existing savanna shrub vegetation in Yuanjiang County was formed during the degradation of monsoon forest.The monsoon forest might be recovered from the savanna shrub vegetation if there would be no more destruction.On the contrary,the existing monsoon forest would probably degrade to be savanna shrub vegetation and grassland vegetation.