Characterising the diameter distribution of Sal plantations by comparing normal, lognormal and Weibull distributions at Tilagarh Eco-park, Bangladesh

Abstract

For many years foresters have been using statistical probability density functions to describe and characterise stand structure. Predicting the current and future yields of a stand is essential for successful stand and timber management. Implicit prediction of current yield is accomplished by using diameter distribution methods. All diameter distribution yield systems predict the number of trees per unit area by diameter class. In this study, the normal, lognormal and the three-parameter Weibull probability density function were compared to characterise the diameter distributions of Sal (Shorea robusta) plantations grown at Tilagarh Eco-park, Bangladesh. Data from 70 plots, established in three plantations, were used for this study. The Weibull parameters were estimated by the maximum likelihood and moments estimator methods. A one-sample Kolmogorov-Smirnov test was used for the goodness of fit for all models. The Kolmogorov-Smirnov test results showed that both lognormal and Weibull distributions were suitable to characterise the diameter distributions of Sal plantations in the study area and may be applicable for other Sal forests in Bangladesh.

Stand Structure, Allometric Equations, Biomass and Carbon Sequestration Capacity of <i>Acacia mangium</i> Wild. (Mimosaceae) in Côte d’Ivoire

“…This diameter structure is typical of even forest stands with high regeneration capacity (Rollet, 1974). This diameter distribution structure was consistent with the study of Deb et al (2014) that found normal distribution in a Shorea robusta plantation in Bangladesh. It was also consistent with the study of Ribeiro et al (2014) which found the same structure in a plantation of Eremanthus erythropappus.…”

The impact of climate change on the distribution of two threatened Dipterocarp trees

“…Although Sal is listed as a “least concern” species in the IUCN Red list (IUCN Species Survival Commission, ), recurrent anthropogenic disturbances such as overexploitation, deforestation, and encroachment combined with climate change, are major threats to Sal forests (Kushwaha & Nandy, ). Results from previous work suggest that the natural distribution of Sal has contracted very rapidly over the last few decades, and it is thus highly vulnerable to climate change (Chitale & Behera, ; Deb, Salman, Halim, Chowdhury, & Roy, ; Sarker, Deb, & Halim, ). Garjan is a “critically endangered” (IUCN Species Survival Commission, ) commercially important Dipterocarp tree naturally distributed in the tropical evergreen, semievergreen, and deciduous forests of Bangladesh, India, Myanmar, Thailand, Cambodia, and Vietnam (Ashton, ).…”