Composition, structure and diversity of tree speciesalong an altitudinal gradient in Jammu province of north-western Himalayas, Jammu and Kashmir, India

Community structure and composition are important factors affecting diversity patterns in plant communities. Pertinently، species diversity along altitudinal and latitudinal gradient differs in different layers at different scales. Thirteen community groups characterized by different dominants in the tree layer were distinguished. These include Himalayan subtropical scrub (580-850 m asl)، Northern dry mixed deciduous forest (600-1100 masl)، Himalayan subtropical pine forest (780-1450 masl)، Lyonia / Alnus / Rhododendron forest (1250-1500 masl)، Mixed Oak forest (1300-2150 masl)، Rhododendron - Oak mixed forest (1600-2200 masl)، Pine / Oak mixed forest (1400-1750 masl)، Pure Cedrus deodara forest (1450-1700 masl)، Taxus wallichiana forest (2000-2580 masl)، Deodar / blue pine mixed forest (1900-2600 masl)، Fir / Spruce mixed forest (2700-3250 masl)، pure Betula forest (3100-3500 masl)، and alpine scrub (above 3500 masl). Distribution of importance values of dominants explicitly indicated a vertical pattern of these forest types. The sub-tropical and temperate elements of vegetation reveal predominance of closed canopy forests، wherein the sub-tropical tree species outnumber the temperate tree flora. The community analysis was performed using stratified random sampling involving 0. 01 % of the total area for each community. The pattern of plant diversity as observed by the values of species richness and diversity indices show a decreasing trend from lower to higher altitudes. The study suggests that distribution and species richness are largely regulated by physiography (altitude، latitude، slope، aspect etc.) and climatic factors.