Developing predictive models for climatic change and vegetation structure in Western Himalaya

Abstract

The present study deals with the impact of climate change on the structural and functional attributes (biomass and productivity) of the vegetation along an altitudinal gradient (1600-3700m asl), within watersheds and among different forest types in Garhwal Himalaya. The study provides an insight on the vegetation of Garhwal Himalaya with special reference to temperature and comparison with Kumaun Himalayan forests. Among all watersheds (Dharamganga, Dogadda, Asiganga, Bhatwari and Gangotri), 18 major forest types were identified. Out of 81 sites, most of the sites were dominated by kharsu oak (Quercus semecarpifolia) forest (# 25) followed by banj oak (Quercus leucotrichophora) forest (#8) and mixed-broadleaved, conifer-broadleaved and oak-conifer forests (each #7). The species richness and density were highest (8 and 510 trees ha-1) for horse chestnut, while the total basal area was highest for banj oak forest (74.5 m2 ha-1). The total biomass was highest for horse chestnut forests (487.0 t ha-1), productivity for oak-conifer forest (20.0 t ha-1 yr-1) followed by deciduous broadleaved forest (19.6 t ha-1 yr-1), while the litter fall for deciduous broadleaved forest (6.6 t ha-1 yr-1). The carbon allocation in biomass was highest in horse chestnut forests (243.5 t C ha-1), oak-conifer forest (10.0 t ha-1 yr-1) in productivity and deciduous-broadleaved forest (3.3 t ha-1 yr-1) in litter fall. The total carbon storage was high (196-344 t ha-1) for horse chestnut, oak-conifer, tilonj oak (Quercus floribunda), deciduous-broadleaved, silver fir and kharsu oak forests, intermediate (125-195 t ha-1) for chir pine (Pinus roxburghii), toon (Cedrella toona), mixed-broadleaved, tilonj oak-mixed, conifer-broadleaved, mixed oak and deciduous-conifer forests and low (<125 t ha-1) for alder(Alnus nepalensis), banj oak, deodar(Cedrus deodara), kai (Pinus wallichiana)l and birch (Betula utilis) forests. The carbon accumulation was extremely high (11.4-13.1 t ha-1 yr-1) in deciduous-broadleaved, oak-conifer and horse chestnut forests. Along altitudinal gradient the species richness was highest at 1800, 2300, 2400 and 2500m; density at transition place (1700m) and between 2100-2800m and total basal area at 2700 and 2800m. However, biomass between 2400-3200m, productivity between 2700-3100m and litter fall between 2700-3200m was highest. The allocation of carbon was highest for all the parameters (biomass, productivity and litter fall) was highest at 2800m (kharsu oak/oak-conifer forest) followed by altitude 2700m (kharsu oak/silverfir (Abies pindrow)/oak-conifer forests). Among watersheds, Dogadda having the highest biomass, productivity and litter fall followed by Dharamganga, while Gangotri have the least values for biomass, productivity and litter fall and allocation of carbon was following the same pattern. At a regional scale (both Kumaun and Garhwal, the relationships between temperature and structural and functional attributes are: i) the density declines at 2750m and at 11.1C MAT, ii) the total basal area declines at 2650m and at 11.5C MAT, and iii) the biomass, productivity and litter fall decline at 3050m and at 9.7C MAT.