EFFECT OF HIGHWAY’S ON BHAWAL SAL FOREST AREAS OF BANGLADESH

Abstract

The tropical moist deciduous Sal (Shorea robusta) forest ecosystem of central Bangladesh is currently in a critical situation due to Dhaka-Mymensingh highway passing over the forest. The present study is an attempt to determine the major problems of Bhawal Sal forest arises due to Dhaka-Mymensingh highway by assessing soil properties and to evaluate the impact upon adjacent vegetation. The study was conducted in three different locations (selected purposively) along Dhaka-Mymensingh highway with different distances like 202m, 152m, 102m, 52m and 2m on both sides of the highway during the period of July 2017 to July 2018. Height and DBH were measured from the sample plots (10m×10m) and 500 g soil samples from the surface soil (0―20 cm) were taken and tested in laboratory. The study revealed that in Bhawal Sal forest the soil moisture content (5.87% to 12.65%), soil pH (4.2 to 5.5), soil organic carbon (0.98% to 2.41%), soil organic matter (1.68% to 4.14%), soil exchangeable nitrogen (0.03% to 0.063%), soil exchangeable phosphorous (0.11 ppm to 0.41 ppm), soil exchangeable potassium (0.12meq/100g to 0 meq/100g all the parameters were decreased with the decreasing distance from the forest to the highway and soil bulk density (1.17g/cc to1.94 g/cc) increased with the decrease in distance from the forest to the highway. Relationship between tree growth variables of Sal forest and chemical properties were found positive and they were strongly correlated with respect to each other. Again it was also observed that if the distance increases from the road to the inside of the forest, trees with increasing height and DBH were found. The Sal forest is under tremendous human interference from all sides and day by day this problem is becoming acute. So for the betterment of the degraded area, it should recover the raised problem related to highway construction.