Forest and agro-ecosystem productivity in Bangladesh: a climate vegetation productivity approach

The aim of the study was to assess spatial and temporal variation in productivity with respect to climate factors in Bangladesh in different forest ecosystems and agro-ecological zones. A climate vegetation, and productivity index (CVPI) for different vegetation types of Bangladesh were measured for years ranging between 1990 and 2010. Data were gathered from 11 meteorological stations sporadically distributed throughout the country. The range of CVPI at different vegetation zones of the country shows values between 1223 and 2800 (this index has no unit). Spatial distribution of values indicates that CVPI is lower in northwestern and southwestern agro-ecological zones of the country, whereas it is higher in eastern zones. This may be due to less rainfall and higher atmospheric temperature in the western part than the eastern part. CVPI in the central part of Bangladesh also decreases while the temporal scenario also varies significantly. There was a peak in the index during the year 1998 when the country faced extreme precipitation followed by devastating floods. Both spatial and temporal variation depicts that vegetation productivity would increase or decrease with respect to climatic parameters such as mean monthly temperature, precipitation, and solar radiation received at the site. For major types of forested woodland, tropical evergreen and semi-evergreen types cover the range of 2150-2800, moist Sal forest covers 1223-1896, dry Sal forest covers 1277-1280, Sundarbans covers 1307, and coastal plantations cover 1946-2531 CVPI. This value greatly depends on the spatial coordinates of the meteorological stations. From Paterson's regression, forest timber productivity was calculated which was found to be higher for evergreen, semi-evergreen, and coastal plantation (about 10-11 m(3) ha(-1) yr(-1)), where deciduous Sal and Sundarbans has lower productivity (about 8-9 m(3) ha(-1)yr(-1)) than hill forests. Thus, climatic factors, as well as altitudinal and latitudinal differences, may pose divergence in forest productivity. Hence, climate is the key factor in forest productivity and distribution.