Effect of Topography and Climate on the Radial Growth of Blue Pine (Pinus wallichiana) in the Temperate Conifer Forests of Chapcha in Western Bhutan
Sonam Wangchuk, Khwanchai Duangsathaporn, Patsi Prasomsin, Yenemurwon Omule, Karma Tenzin, and Dorji Dukpa
This article investigates the influence of topographic (altitude, slope gradient, slope position, slope shape, aspect, and solar radiation) and climatic (rainfall and temperature) factors on the radial growth of Blue Pine (Pinus wallichiana), in the temperate conifer forests of Chapcha in western Bhutan, using dendrochronological methods. At the Northern aspect, the radial growth was negatively correlated with altitude, while the correlation with other topographical variables were not significant. At the Southern aspect, the radial growth was negatively correlated with the aspect and slope, while it was positively correlated with LeAspect index, a surrogate of aspect. The radial growth was strongly correlated with rainfall during the growing season and the mean temperature during late winter in the lower and higher altitudes with pronounced effect at the Southern aspect. The radial growth did not show any significant relationship with minimum temperature, however, it was positively correlated with the maximum temperature during May-September at the Northern aspect and during August-September at the Southern aspect. The results presented in this article demonstrate the sensitivity of tree growth to the slightest of topographicclimatic variations. They highlight an important implication on the Blue Pine ecosystem under the changing climatic conditions in complex mountainous landscapes.