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Tree Species Diversity and Productivity Relationship in the Central Region of Bangladesh

Niamjit Das
Department of Forestry and Environmental Science, School of Agriculture and Mineral Sciences, Shahjalal University of Science and Technology, Sylhet, Bangladesh.

Swapan Kumar Sarker
Department of Forestry and Environmental Science, School of Agriculture and Mineral Sciences, Shahjalal University of Science and Technology, Sylhet, Bangladesh, Division of Environmental & Evolutionary Biology, Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, UK.

Abstract/ Executive Summary:

The diversity - productivity relationship has received considerable attention during the past two decades, largely because of the continuous loss of biodiversity. The positive relationship between species diversity and productivity is significant as a credible argument for the conservation of biodiversity. This research was conducted in the central region of Bangladesh to exemplify the relationship between tree species diversity and stand productivity at four mixed plantations. In total 112 sample plots (size - 0.09 ha/plot) of four different mixed species plantations were systematically selected for data collection. After that, regression analysis was explained significantly positive relationship be tween tree species diversity and productivity at four mixed plantations. This research suggests that having more tree species generally raises plantation productivity. Therefore, this result indicates that mixed species plantations could be the better choice in the degraded and fallow forest lands of Bangladesh.

Keywords: Species diversity, Stand productivity, Acacia auriculiformis, Acacia mangium, Swietenia mahagoni, Gmelina arborea, Mixed species plantations

Location: Bhawal Sal forest and Madhupur tract

Start Date:

End Date:

Program Area: Conservation and Biodiversity

Commodity: Tree

Objectives:

To investigate the nature of the relationship between tree species diversity and productivity at a different mixed species plantation across the region.

Methodology:

The Bhawal Sal forest is situated 40 km north of Dhaka on the Madhupur tract in the central region of Bangladesh and it lies between 24º 5^/44.98 ^// North latitude and 90º 24^/ 14.4 ^// East longitude. The field work was conducted at the Bhawal National Park (BNP) on this forest that was established in 1982 comprising an area of 5,022 ha of reserved forests through the Bangladesh Wildlife (Preservation) Order, 1973. The park is a tropical, moist - deciduous forest that mainly originated from seedlings and coppices with Sal ( Shorea robusta ) as the dominant tree species. Its forest of partial area planted of the different mixed species plantation includes Acacia auriculiformis, Acacia mangium, Swietenia mahagoni, Gmelina arborea and so on. The soil belongs to the bio - ecological zone of Madhupur Sal Tract. The soils have a moderate to strong acidic reaction. The soils are also characterized by low organic matter and low fertility. Climatic condition is moderate, annual rainfall of 2030 - 2290 mm, annual temperature of 10 - 37°C, humidity between 60 and 86%. The Bhawal National Parkwas selected on the basis of different mixed species plantation forest at this regional. In total 112 sample plots (sample size – 30 m × 30 m) were systematically selected for data collection. Four different mixed plantations of S. mahagoni, A. auriculiformis, G. arborea, A. mangium were selected in this research. Systematic sampling was adopted for selecting plots within these mixed plantations. Afterward, 28 sample plots of size 30 m × 30 m were established in each mixed species plantation.Standard forestry growth measurements were made on each plot with the following information recorded: tree species identity, diameter over bark at 1.3 m (breast height - DBH) and total height data from all sample plots (10.08 hectares). In each plot, all trees ≥7.6 cm in diameter at breast height (DBH) was identified and it was measured by tree calipers. These measurements were used to calculate biodiversity (as species richness and Simpson’s biodiversity index) and production (calculated as basal area (m² ha^-1). Simpson’s biodiversity index was used to represent biodiversity after testing found that it was closely related to both species richness and the Shannon – Weaver index. This choice is supported by who, in a detailed analysis of different biodiversity indices, suggests that the Simpson’s biodiversity index can be a more reliable measure than the Shannon – Weaver index or species richness. Therefore, accurate biomass estimates would have been problematic, so plantation productivity was measured by stand basal area, which were derived from DBH and plot measurements. Subsequently, nondestructive methods were found user friendly, less expensive, and can give accurate different part of tree productivity estimates. Moreover, basal area is nevertheless highly correlated with tree volume and biomass and is used as the measure of plantation productivity widely. The Regression analysis suggests the simplest expressions of linear relationship between species diversity and productivity, were retained as the best models explaining variation in the data. We used R statistical software version 3 for data analysis.

Source of Information: Journal of Forests, 2015, 2(2): 24-33, ISSN(e): 2409 -3807/ISSN(p): 2413-8398

Article Link (Online Journal): DOI: 10.18488/journal.101/2015.2.2/101.2.24.33

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The consequences of this result showed that high species diversity usually raises productivity in mixed species plantations. These results should encourage the planting of a wider variety of species across this region. Extensive research is also required to incorporate the management factors in the diversity - productivity research for surpassing the effects of compounding factors. Though, tropical mixed species plantation could be the better choice in the degraded and fallow forest lands in the central region of Bangladesh.

Knowledge Management: Journal