Effects of forest encroachment on tree stock parameters and soil nutrient status in the Madhupur Sal (Shorea robusta C.F. Gaertn) forest of Bangladesh

Abstract

Tree stock parameters and soil nutrient status were affected due to forest encroachment in the Madhupur Sal forest of Bangladesh from September 2015 to April 2016. The study was investigated through 120 sample plots of 10 m × 10 m in sizes taken randomly from three sites such as high, medium, and low encroached forest. Prior to objective, tree stock parameters were measured having a diameter at breast height (dbh) ≥ 10 cm and necessary soil samples were collected. The collected soil samples were analyzed in the laboratory to determine the organic matter, total N, available P, exchangeable K, available Ca, Mg, S, Fe, B and Zn. The results revealed that the tree stock parameters such as stand density, basal area and dbh were measured the highest (650 trees/ha, 30.17 m2/ha and 26 cm) in the low encroached forest and the lowest (75 trees/ha, 4.47 m2/ha and 21 cm) in the high encroached forest sites. Accordingly, the higher content of organic matter (1.60%), total N (0.18%), available P (12.97 ppm), exchangeable K (0.25 ppm), available Ca (3.38 ppm), Mg (1.47 ppm), S (20.34 ppm), Fe (234.06 ppm), B (0.68 ppm) and Zn (2.3 ppm) were found in soils from low encroached forest site and lower (0.65%), (0.09%), (8.09 ppm), (0.10 ppm), (1.09 ppm), (0.92 ppm), (10.60 ppm), (180.85 ppm), (0.28 ppm) and (1.22 ppm) in the high encroached forest site soils. Therefore, it can be concluded that tree stock parameters and soil nutrients status were remarkably affected due to the forest encroachment in the Madhupur Sal forest of Bangladesh.