Effect of Different Grazing Regimes on the Growth of Quercus semecarpifolia Sm. Regeneration in Western Bhutan Himalaya (Thimphu)

Abstract

Temperate broadleaved forest of Bhutan is dominated by old-growth brown oaks (Quercus semecarpifoliaSm.) with a history of overgrazing. However, use of oak trees for firewood and practice of free range cattle grazing are being viewed as factors responsible for poor regeneration of Q. semecarpifolia in natural forests. Therefore, this research studied the response of oak seedlings under different grazing intensities in Chang and Dagala Geogs of Thimphu Dzongkhag. Three study sites of different grazing regimes (high, moderate and low) were identified using information from local people on the observed cattle number in forests around their communities. Three main plots of 20 m² were set up in each site. In every main plot, 10 sub plots of 4 m² were laid to measure the regeneration density and other parameters. There was a significant difference (p < .05) in seedling height and collar diameter between high, moderate and low grazing intensities. Grazing was strongly associated with shorter seedling height and increased seedling collar diameter. The lightly grazed area had a higher percentage of canopy cover (44.8%) followed by heavy (42.3%) and moderate grazing site (40.3%). Regeneration of Q. semecarpifolia was more in high canopy cover and controlled grazing sites.