Vegetation dry matter dynamics along treeline ecotone in Western Himalaya, India

The study aimed to assess dry matter dynamics of forests along treeline ecotone concerning environmental variability, and four representative forests, birch, kharsu oak, Himalayan fir and mixed forest along treeline ecotone (3250-3400 m asl) were selected in Kedarnath Wildlife Sanctuary, Western Himalaya. Temperature, precipitation and humidity data were recorded for complete 3 years (2008-2010). Field inventory for assessment of forest structure and dry matter was carried out in a 200 m transect in each forest along treeline using quadrats of different sizes for tree, shrub and herb layers. The biomass and net primary productivity (NPP) of woody vegetation was estimated using region-specific allometric equations and of the herb layer, by harvesting. Litter quantity and decomposition rates were assessed using litter traps and litter bags, respectively. The dry matter budget of treeline ecotone was represented using a compartment model. The mean annual temperature at treeline was recorded 6.6 +/- 0.68 degrees C with warmest month average temperature of 12.6 +/- 1.2 degrees C. The average forest biomass at ecotone was 33.27 +/- 16.97 Mg/0.1 ha, ranged between 8.87 Mg/0.1 ha in open and early successional birch forest to 44.98 Mg/0.1 ha in dense canopy mixed forest. NPP ranged from 1.49 to 2.11 Mg/0.1 ha year(-1). The birch forest exhibited the highest efficiency in annual dry matter accumulation in the canopy layer among all forests. The leaf litter decomposition rates (% weight loss) was highest for kharsu oak (74%) after 3 years. The study revealed that Western Himalayan treeline exhibit warmer summer and higher amounts of dry matter storage, production and decomposition rates. These treeline forests showed a higher dry matter assimilation rate and so the potential for carbon sequestration under a warming climate.