Journal of Environment and Sociobiology

N. C. Nandi ¹, Sumanta Pasari ²

Affiliations
1 Social Environmental and Biological Association, Kolkata, IN
2 Birla Institute of Technology and Science Pilani, Pilani Campus, Jhunjhunu, Rajasthan, IN

Abstract

The non-timber forest products (NTFP) in India have gained enormous attention to the forest ecologists and environmentalists due to their importance in rural livelihood enhancement, biodiversity conservation and sustainable forest management. The present case study thus aims to document detail information of various forest-based resources in the Garhbeta forest of West Medinipur district in West Bengal. These resources include medicinal plants, mushrooms, wild honey, kendu-patta (leaves of Diospyrous melanoxylon tree, useful in preparing Indian beedi), fruits, barks, ischolar_mains and herbs for the chemical and herbal production, and diverse usages of sal tree (Shorea robusta) in sal leave plate and bowl production, resin, oil-cake, lamp oil, and vegetable cooking oil preparation. The dry leaves of sal tree, kendu tree and eucalyptus trees are also used as traditional cooking fuel for domestic usages throughout the year by almost all the local communities neatly stacking in the shade close to their household for future use. To this end, various NTFP resources, the provincial resource availability, cost-benefit analysis, and seasonal NTFP harvesting patterns will be analysed as an attempt to promote optimal resource management and participatory conservation of wild medicinal/herbal plants towards community economic development in the study region. In addition, discussions will be made to encourage alternative earning options in the tribal community by introducing regional forest-based handicrafts and sustainable animal husbandry in the wide but uninterrupted sal coppice forest of Garhbeta region.

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Sumanta Pasari ¹, N. C. Nandi ²

Affiliations
1 Birla Institute of Technology and Science Pilani, Pilani Campus, Jhunjhunu, Rajasthan, IN
2 Social Environmental and Biological Association, Kolkata, IN

Abstract

In forestry, statistical modelling has long been an effective tool in quantitative assessment of tree sizes using various probability distributions on tree diameters at breast height (dbh). It is however still unclear that which family of probability distributions, viz., symmetric, skewed, or heavy-tailed models are more flexible to this end, especially in forests within a small area like Garhbeta sal (Shorea robusta) coppice forest of West Medinipur district, West Bengal. Here we provide a comprehensive analysis of several descriptive and inferential statistics to identify the best-fit probability distribution in tree diameter estimation. Our sample data set comprises tree diameters (22-44 cm) of 80 randomly selected sal trees, aged between 40-50 years. Twelve candidate probability distributions, namely, exponential, exponentiated exponential, Frechet (inverse Weibull), gamma, Gaussian, inverse Gaussian, Levy, lognormal, Maxwell, Pareto, Rayleigh and Weibullare were used in this study. The Maximum Likelihood Estimation (MLE) method is applied for the parameter estimation, whereas the Fisher Information Matrix (FIM) based surrogate approach is used for uncertainty analysis. We determine the best-fit distribution(s) from two goodness-of-fit tests: Akaike Information Criterion (AIC) and Kolmogorov-Smirnov (K-S) minimum distance criterion. Results reveal that (i) the exponentiated exponential distribution provides the best fit, (ii) the Frechet, gamma, Gaussian, inverse Gaussian, lognormal and Weibull distributions provide the intermediate fit and (iii) the rest, namely exponential, Levy, Maxwell, Pareto and Rayleigh distributions fit poorly to the observed tree diameters in the study area. Finally, we discuss some theoretical issues related to the selection of appropriate models. However, further studies encompassing multi-variable tree diameter data are recommended to arrive at a reasonably acceptable probability model useful for assessing timber production in forests.

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Sumanta Pasari ¹, N. C. Nandi ²

Affiliations
1 Birla Institute of Technology and Science, Pilani, Jhunjhunu, Rajasthan, IN
2 Social Environmental and Biological Association, Kolkata, IN

Abstract

In forestry, statistical modelling has long been an effective tool in quantitative assessment of tree sizes using probability distributions on tree diameters at breast height (dbh). It is however still unclear that which family of probability distributions, viz., symmetric, skewed, or heavy-tailed models are more flexible to this end, especially in forests within a small area like Garhbeta sal (Shorea robusta) coppice forest of Paschim Medinipur district, West Bengal. Thus, a comprehensive analysis of several descriptive and inferential statistics is provided here to identify the best-fit probability distribution in tree diameter estimation. The sample dataset comprises tree diameters (22 cm-44 cm) of 80 randomly selected sal trees, aged between 40-50 years. Twelve candidate probability distributions are evaluated in this study. The Maximum Likelihood Estimation (MLE) method is used for parameter estimation. Results from two goodness-of-fit criteria reveal that (i) the exponentiated exponential distribution provides the best fit, (ii) the Frechet (inverse Weibull), gamma, Gaussian, inverse Gaussian, lognormal and Weibull distributions provide the intermediate fit, and (iii) the rest, namely, exponential, Levy, Maxwell, Pareto and Rayleigh distributions fit poorly to the observed tree diameters in the study area. Finally, some theoretical issues related to the selection of appropriate models are discussed. However, further studies encompassing multi-variable tree diameter data are recommended to strengthen the modelling results towards commercial timber production assessment in forests.

Keywords

Garhbeta Forest, Probability Distributions, Diameter Modelling, Model Selection.

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