Modeling the diameter distribution of gymnosperm species from central Karakoram National Park, Gilgit Baltistan, and Pakistan using weibull function

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Research Paper 01/07/2014
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Modeling the diameter distribution of gymnosperm species from central Karakoram National Park, Gilgit Baltistan, and Pakistan using weibull function

Alamdar Hussain, S.S. Shaukat, Moinuddin Ahmed, Muahammad Akbar , Wajid Ali, Haleem Zaman Magsi
J. Bio. Env. Sci.5( 1), 330-335, July 2014.
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Abstract

This investigation focuses on modeling the tree diameter distribution using Weibull function of three gymnosperm species, i.e. Picea smithiana, Pinus wallichiana and Juniperus excelsa dominating the forests of Central Karakoram National Park, Gilgit-Baltistan. Various workers have attempted to model the population structure of trees in their respective study areas. A number of probability distributions have been employed to find a good fit to the observed distributions. A number of recent studies have indicated the three parameter Weibull distribution as a possible model for describing the size class structure of trees. Thus, the Weibull model was selected to describe the diameter distribution of the three conifer tree species under study. The parameters for each tree distribution were estimated by a program CumFreq that employs the maximum likelihood method. The cumulative distributions of each tree species were tested against the fitted distribution. In all cases the Weibull distribution gave excellent fit to the observed data as indicated by high efficiency coefficient R. The result showed that the tested gymnosperm species are deteriorating due to anthropogenic disturbance. The lack of recruitments alarming for future sustainability of these forests. The possible implications of these models in the management of the respective forests are discussed.

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