VOLUMES IN SELECTED FOREST RESERVES IN ONDO STATE, NIGERIA

Abstract

This study assessed the impacts of logging on tree species diversity and abundance, soil physicochemical properties, and Volumes yield. Data collection took place in logged and unlogged forest of Oluwa Forest Reserve and Akure Forest Reserve. The systematic line transect method was used in plot laying where tree variables are collected for biodiversity assessment. Two parallel transects of 200m apart were laid and two equal sample plots (50x50m) were laid in alternate direction on each transect. All trees with DBH ≥10cm were tagged, measured and classified into family and their frequency of occurrence were determined to ascertain tree species diversity and abundances. Tree variables such as the Db, Dbh, Dm, Dt and total height of all trees encountered on the plots were measured for Volume estimation. Soil samples were collected for soil physicochemical properties assessment and Biodiversity indices were generated to assess the tree species diversities and abundance and evenness of species, Soil physicochemical properties were analyzed and volumes yield of logged and unlogged forests were compared. A total of 117.25 stems per hectare were encountered in all the study areas. The logged and unlogged plots of Oluwa Forest Reserve had a total of 53 and 150 stems per hectare respectively while 98 stems and 168 stems per hectare were encountered in the logged and unlogged plots of Oluwa Forest Reserve. The logged forest of Oluwa Forest Reserve had a high Shannon-Wiener index (3.50) when compared to the logged plots (2.97) and 3.46 when both portions were pooled together. A high Shannon-Wienner index (3.0) was also recorded for the unlogged plots of Akure Forest Reserve when compared to the logged forest (2.78) and 3.19 when both portions were pooled together. This is an indication that unlogged portion has the highest varieties of species. A high volume and basal area per hectare were recorded in unlogged Forest Reserve when compared to the logged Forest Reserve. There were significant differences (P<0.05) in the tree growth variables obtained in the logged and unlogged sites of each of the Forest Reserves. The results of soil analysis revealed that the chemical properties unlogged forest of both Forest Reserves were high during mean separation but no significant difference was observed except in the sodium content. The high Shannon Wienner index, volumes and nutrients recorded in the unlogged forests were attributed to conservation. The results of the study further revealed that continuous and excessive exploitation could lead to loss of tree species biodiversity and reduction in tree yield as well as quality of the physicochemical soil properties.