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Patterns of Tree Buttressing at Lawachara National Park, Bangladesh

Md. Abu Hanifa Mehedi
Department of Forestry and Environmental Science, Shahjalal Univer-sity of Science and Technology, Sylhet-3114, Bangladesh

Chandan Kundu
Department of Forestry and Environmental Science, Shahjalal Univer-sity of Science and Technology, Sylhet-3114, Bangladesh

Md. Qumruzzaman Chowdhury
Department of Forestry and Environmental Science, Shahjalal Univer-sity of Science and Technology, Sylhet-3114, Bangladesh

Abstract/ Executive Summary:

We describe patterns of buttress formation and development in eleven tree species at Lawachara National Park, Bangladesh. Forty-five percent of trees of these 11 species had buttresses. Artocarpuschaplasha Roxb. showed maximum (87%) buttress formation, whereas Alstonia scholaris (L.) R. Br. did not show any buttress. Buttresses were recorded in 20%−40% of trees of six species and 40%−60% of trees in three species. Mean length and height of buttress varied among the species and ranged from 0.37−1.37 m and 0.71−2.13 m, respectively. Buttress height, mean buttress length, total buttress length, and total length plus length of secondaries increased with DBH (diameter at breast height) and tree height. Buttress number did not increase with DBH or tree height. Under-storey and mid-canopy trees produced less developed buttresses than did emergent trees (p<0.01). Wood density showed moderate effects on buttress characters (p<0.05), while the slope of the land did not. Canopy category was a primary regulating factor for tree buttressing, suggesting that buttresses are mechanical adaptations of trees to counter physical stresses.

Keywords: Buttresses; Tree architecture; Canopy category; Slope of the ground; Wood density

Location: Lawachara National Park

Start Date:

End Date:

Program Area: Conservation and Biodiversity

Commodity: Plant

Objectives:

Our objective was to explore the patterns of tree buttressing and their relationships with tree architectural parameters (DBH and tree height) at Lawachara National Park, Bangladesh. We also analyzed the effects of canopy category (under-storey, mid-canopy and emergent), wood density, and land slope on buttress characteristics.

Methodology:

Study area The study was conducted at Lawachara National Park, which was once under west Bhanugach Reserve Forest under Sylhet Forest Division of Bangladesh and is situated 60 km south of Sylhet city in the Komalgonj Upajila of Moulvibazar District. The forest is managed by the forest department as a protected area covering 1,250 ha with the remaining 281 ha under West Bhanugach Reserved Forest. The forest is semi-evergreen (Fee-roz and Islam 2000), and lies between 24°30'−24°32' N and 91°37'−91°39' E. The study area has a monsoonal climate with one dry and one wet season. Average annual rainfall in the study area is about 4,000 mm, and the temperature varies on average from a minimum of 26.8°C in February to a maximum of 36.1°C in June (NSP 2006). Sampling and field measurements We collected data from 10 randomly selected plots (50 m × 20 m). Plots were established only in the natural portion of the for-est. To demarcate plot boundaries, two meter tapes were used and the plot boundary was defined by four poles in four corners. Plot locations were recorded using a GPS (Magellan® TritonTM2001) from the approximate middle point of the plot. We measured numbers of buttresses, lengths of all buttresses, and lengths of secondary projections coming off from the main buttresses, heights of all buttresses, tree heights, and DBH for eleven species (DBH > 10 cm). Each tree was categorized as emergent, mid-canopy and under-storey according to tree height (Chapman et al. 1998). Tree height (m) was measured by Sunntu Clinometer (Suunto PM5-360) and DBH (cm) of each tree was measured by a diameter tape above the buttresses. Buttress numbers were counted for each tree. Buttress length (m) was measured by meter tape from the bole of the tree to the uppermost surface of the buttress where it first entered the ground. Buttress height (m) was measured by meter tape from the ground to the point where the but-tress became even with the trunk of the tree. Wood samples were collected by an increment woodborer (Haglöf Sweden®), and the slope of the ground was measured by Sunntu Clinometer. Measurement of wood density Wood samples were collected from outer into the inner portion of the trunk of standing trees. Each tree (DBH > 10 cm) was sampled from the selected plot area. A wood core was extracted from each sample tree at a point above the buttress from the periphery to the inner portion of the trunk with increment borer. Samples were placed immediately in an airtight container to prevent drying out for measurements of green volume. Wood volume was determined by assuming that the core is cylindrical, with πr2h, where r is the radius (2.1 mm) and h is the length of the core sample, which was measured with a digital caliper (Chave et al. 2006). Basic density was measured using the oven-dry method (Chowdhury et al. 2009). Statistical Analysis Data was analyzed by SPSS Software (SPSS, ver. 17, Chicago, IL, USA). Relationships between tree diameter and height versus buttress characteristics (e.g., buttress number, height and length) were determined by liner and non-linear regression analysis, respectively. The effects of canopy category, land slope, and wood density on buttress characteristics were reflected by multiple regression analysis. In multiple regression analysis, the canopy category was used as a dummy variable (e.g., 0, 1 & 2). Comparisons among the canopy categories (under-storey, mid-canopy and emergent) were done by analysis of variance (ANO-VA) followed by post-hoc (Games-Howell) test.

Source of Information: Journal of Forestry Research (2012) 23(3): 461-466

Article Link (Online Journal): DOI 10.1007/s11676-012-0285-x

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Buttress formation varied by species at Lawachara National Park. Mean buttress height and length varied between tree species from 0.47−1.37 m and 0.71−21.3 m, respectively. For 11 tree species, buttress characteristics except for numbers of buttresses (buttress height, mean buttress length, total buttress length, and total plus length of secondaries) were strongly related with tree architectural parameters (e.g., DBH and tree height). Wood density showed moderate relationship (p<0.05) with buttress height and mean buttress length. Land slope did not show any relation-ship with buttress characteristics. Canopy category (under-story, mid-canopy and emergent) was strongly related to buttress characteristics in our study area (p<0.01), and the under-storey and mid-canopy trees had less developed buttresses to counter physical stresses.

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