Anthropogenic disturbances and their impact on vegetation in Western Himalaya,India

The present study assesses anthropogenic disturbances and their impacts on the vegetation in Western Himalaya,India on the basis of various disturbance parameters such as density,Total Basal Cover(TBC) of cut stumps,lopping percentage and grazing intensities.On the basis of canopy cover and frequency of disturbances(%),the studied forests were divided into highly disturbed(HD),moderately disturbed(MD) and least disturbed(LD) categories.The HD forests had the lowest canopy cover,lowest density and lowest TBC and the LD had the highest canopy cover,highest density and highest TBC.The MD forests occupied the intermediate position with respect to these parameters.Species richness was least in HD forests,highest in one of the MD forests while LD forest occupied an intermediate position.The percentage of regenerating species was lowest(54%) in HD and highest(72%) in MD.The density of seedlings and saplings was higher in one of the MD forests as compared to HD and LD.We concluded that the moderate disturbances do not affect the vegetation adversely;however the increased degree of disturbance causes loss in plant diversity;affects regeneration and changes community characteristics.Construction of hydroelectric projects at various places in the study area was found to be one of the most important sources of anthropogenic disturbances in addition to the routine anthropogenic disturbances like grazing,fuelwood collection and fodder extraction.If all proposed dams in the Indian Himalaya are constructed combined with weak national environmental impact assessment and implementation,it will result in a significant loss of species.Therefore,various agents of disturbances should be evaluated in cumulative manner and any developmental activities such as hydropower projects,which trigger various natural and anthropogenic disturbances,should be combined with proper cumulative environmental impact assessment and effective implementation to minimise the anticipated loss of vegetation.

Soil seed banks along elevational gradients in tropical, subtropical and subalpine forests in Yunnan Province, southwest China

Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration.Although soil seed banks in different habitats have been reported, how soil seed banks vary with elevational gradients in different climatic zones is still unknown. This paper investigates seed density,species composition and nonconstituent species of forest soil seed banks in Yunnan Province, southwest China. Similarity between the soil seed bank and standing vegetation was also examined. We collected soil samples from sites spanning 12 elevations in tropical rain forests, subtropical evergreen broadleaved forests and subalpine coniferous forests, and transported them to a glasshouse for germination trials for species identification. The soil seed banks of tropical and subtropical forests had much higher seed densities and species richness than those of subalpine forests. Seeds of woody species dominated the soil seed banks of tropical and subtropical forests, while herbs dominated those of subalpine forests.The nonconstituent species in the soil seed banks were all herbs and were most abundant in tropical forests, followed by subtropical forests but were completely absent from subalpine forests.