Comparing normal,lognormal and Weibull distributions for fitting diameter data from Akashmoni plantations in the north-eastern region of Bangladesh

Statistical probability density functions are widely used to model tree diameter distributions and to describe stand structure. The objective of this study was to compare the performance of normal, logarithmic-normal and three-parameter Weibull distributions for fitting diameter data from Akashmoni (Acacia auriculiformis A. Cunn. ex Benth.) plantations grown in the north-eastern region of Bangladesh. Data from 96 plots, established in 24 plantations in north-eastern Bangladesh and ranging in age from 1 to 6 years, were used for this study. The parameters of the Weibull distribution were calculated using maximum likelihood estimation (MLE) and moment estimation (ME) methods. The goodness of fit of normal, lognormal, Weibull MLE and Weibull ME were tested using one-sample Kolmogorov-Smirnov (KS) tests. The KS test results showed that both lognormal and Weibull distributions were equally effective for describing the diameter distributions of these Akashmoni plantations grown in the north-eastern region of Bangladesh.     

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

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.     

轮换种植对孟加拉国吉大港山区土壤中真菌和细菌群落的影响

在孟加拉国吉大港山区选择两块研究地,研究轮换种植对土壤中真菌和细菌群落的影响。两块研究地均包含轮换种植和本地社区管理的乡村森林,第一块研究地点选择在兰加马蒂地区,第二块研究地点选择在吉大港的班多尔班地区。在两个地点和不同用途的地块中,其表面土（0-10cm）和地表下土（10-20cm）的土壤质地不同,分别为砂壤和粘土。轮作地的土壤pH和含水量比乡村森林的低。研究结果表明：在兰加马蒂和班多尔班地区,大多数情况下,轮作地的表面土和地表下土壤中的真菌和细菌群落数量比乡村森林的低。在兰加马蒂和班多尔班地区的轮作地中,炭疽菌属（CoHetrotrichum）和镰孢菌属（Fusarium）真菌稀少,而两个地方的不同用途地块中均有细菌球菌属（Coccus）,芽孢杆菌属（Bacillus）和链球菌属（Streptococcus）。在两个地方的不同用途地块中常见的真菌有曲霉属（Aspergillus）、根霉属（Rhizopus）、木霉属（Trichoderma）和青霉菌属（Penicillium）。在其它的土壤区系中,由于轮换种植导致土壤环境退化的程度还需要进一步的研究。     

Feed technology and production performance of Thai koi (Anabas testudeneus) in Bangladesh

ABSTRACT

Thai koi farming is relatively new in the aquaculture industry of Bangladesh. Costly industrial feed pellets is the main factor influencing the productivity of Thai koi (Anabas testudineus). Two types of feed, namely, floating and sinking, are commercially available in the country. The ingredients of both types of feed are more or less the same. Floating feed requires high technology, high pressure and temperature and hence is more expensive than sinking feed. Most of the Thai koi farmers use either floating or sinking feed, while some farmers use a mix of both types of feed. This article investigated the effects of these three feed types on Thai koi productivity using primary data collected from the Mymensingh district of Bangladesh. The performance of different feed types on productivity was investigated using the Cobb-Douglas production function and propensity score matching (PSM) methods. Floating feed led to the highest daily mean weight gain of fish, feed conversion ratios, and net returns. The regression and PSM results revealed that farmers using floating feed produced significantly higher quantity of fish per unit compared to those using the other feed types. The cost of feed per hectare was higher in the farms using the floating feed, but these farms earned extra return from the additional investment, compared with the farms that use the other feed types. Thai koi farmers are advised to use floating feed to reap higher production and returns on investment.     

SOCIOECONOMIC ASPECTS OF SMALL-SCALE FRESHWATER PRAWN MARKETING SYSTEMS IN MYMENSINGH,BANGLADESH

An investigation was carried out in Mymensingh region of Bangladesh to understand current practices of freshwater prawn (Macrobrachium rosenbergii) marketing systems. Prawn marketing is almost exclusively maintained by the private sector, where the livelihoods of a considerable number of people are associated with prawn distribution and marketing systems. The market chain from producers to consumers passes through a number of intermediaries. The prawn is a highly valued product in international markets; most of the prawns (60%) are therefore exported, particularly to the USA, Japan and Europe. The rest (40%) of the under-sized prawns are sold to local markets in Mymensingh. The price of prawn depends on quality, size and weight, and grade. In spite of marketing constraints, livelihood outcomes are positive and most of the households of traders (75%) have improved their social and economic conditions through prawn marketing activities. However, concerns arise about the long-term sustainability of prawn marketing due to poor road and transport facilities, inadequate supply of ice, lack of money and credit facilities, and poor market infrastructure. It is therefore necessary to provide institutional, organizational, and government support for a sustainable prawn market.     

Impacts of decentralized fish fingerling production in irrigated rice fields in Northwest Bangladesh

Rice field‐based fish seed production (RFFSP) has become established in parts of Northwest Bangladesh (NWB) as part of promoting improved rice‐based livelihoods. The impact of RFFSP on adopting households in terms of interactions of assets and other activities was assessed in a comparison of seed‐producing (RF; n = 60) and non‐seed‐producing (NRF; n = 58) households that were sampled randomly and ranked as poor, intermediate and better‐off. Adoption of RFFSP was not constrained by illiteracy of the household head, the size or ownership status of ponds, or lack of ownership of land or an irrigation pump. Poorer and intermediate households had smaller RF plots and lower production of fingerlings (kg per household) compared with the better‐off, although production efficiency (kg ha^?1) was higher. Restocking of fingerlings in RF household ponds increased productivity by 60% over NRF. Fish consumption of better‐off RF households exceeded NFR by 50%. Among the poor, seasonal benefits of income from sales and subsistence consumption of fingerlings were significant. Rice production in irrigated, and income in both irrigated and rain‐fed seasons was higher, and production costs lower, in riceplots producing fish than in rice‐only plots. Implications for supporting the innovation networks promoting and establishing RFFSP among rice growers, are discussed.     

Study on soils under shifting cultivation and other land use categories in Chittagong Hill Tracts, Bangladesh

Soil samples were collected and analyzed from 25 sites of three hilly regions (Rangamati, Banderban and Khagrachari) for an understanding of the impact of denudation and land use on soils in Chittagong Hill Tracts, Bangladesh. There were natural forests, bushy land, slashed sites, slashed and burnt sites, and the sites prepared for shifting cultivation, one year after shifting cultivation and two years after shifting cultivation. The soils were generally yellowish brown to reddish brown, sandy to sandy clay loam, strongly acid, and well to excessively drained on steep slopes with considerable variation among the sites and land use categories. Bulk density was the highest in sites of one year after shifting cultivation (1.52 g·cm-3) and the lowest in forested sites (1.38 g·cm-3). Water holding capacities were, however, statistically similar in all sites. Organic carbon varied from 0.54% (slashed and burnt sites) to 1.55% (forested sites) and total N ranged from 0.05% (shifting cultivation for one year) to 0.13% (forested sites). Available phosphorus (Bray & Kurtz-2 P) was the maximum in forested sites (12.32 mg·kg-1), and it did not differ significantly in other sites. Contents of available Ca, Mg and K were also higher in the bushy lands and forested sites than cleared and shifting cultivated sites.     

NTFP income contribution to household economy and related socio-economic factors: Lessons from Bangladesh

Exploring extent and pattern of non-timber forest product (NTFP) income contribution to livelihoods of forest-adjacent people and the income related socio-economic factors is crucial in designing any development and conservation initiative. This paper examines NTFPs' role in contributing to the household economy and how different socio-economic factors may influence this contribution. Field methods involved quantitative and qualitative data collection of forest-adjacent households of Chittagong Hill Tracts in Bangladesh. Results show that the contribution of different types of NTFPs to household economy varies in terms of subsistence and cash income. However, overall NTFP income is much higher than income from timber or firewood which indicates a larger dependence of the households on NTFPs. Income data analysis also finds that the poor households are relatively more dependent on NTFPs for their subsistence and cash income than the better-off households. Moreover, the study reveals that there are many other socio-economic factors at the household level such as number of members in household and total value of household implements and furniture that are significantly correlated with the NTFP income. More site-specific applied research on NTFP income and influential factors is necessary to generalize the findings for other parts of the world with similar socio-economic and environmental settings.     

Production risk of pangas (Pangasius hypophthalmus) fish farming

Pangas is a relatively new and fast-growing fish species that has great potential for production and export growth in Bangladesh. However, production variability exists from farm to farm and location to location, which indicates that production risk may be a problem in pangas farming. Research on production risk is therefore of great importance, especially for small-scale farming systems in developing countries, where farmers are more vulnerable to risk. This study investigates the production risk of pangas farming in selected areas of Bangladesh. A Just–Pope stochastic production function is chosen to estimate the mean and risk functions. The test result shows that significant production risk exists in pangas farming, and that the risk differs between small and large farms.