Assessment of Tree species in the Faculty of Agriculture and Forestry, University of Ibadan, Nigeria

Abstract

Sustainable tree and/or forest management require information on the growing stock. Such information guides the resource manager in appropriate valuation and efficient utilization of the resources. However, where the objective of management is not timber production, little or no emphasis has been placed on the adequate assessment of the growing stock. For timber production, estimates of the growing stock are often expressed in terms of timber volume, which can be estimated from measurable characteristics of the trees. This study assessed the yield, diversity and abundance of tree species in the Faculty of Agriculture and Forestry, University of Ibadan, Nigeria. Total enumeration of all the tree species in the faculty was carried out. Tree species diversity, stem volume and the relationships among growth variables were investigated. All the trees encountered were grouped into species, diameter and height classes and their basal area and tree stem volume were computed. Stem volume equations were developed for the tree species in the area. The variables used for the equations consisted of basal area; diameters at breast height, merchantable height, crown length and tree total height. The species were distributed among 14 genera and 8 families. Eucalyptus camadulensis had the highest population of trees in the study area. The family Myrtaceae has the highest number of observation (32.7%) with only one species belonging to the group. This is followed by the Papilionaceae (12.7%) with five species. The third in the series being the families of Meliaceae and Verbenaceae with 12.7% each of the species encountered in the study area. The family of Caesalpiniaceae had 9.1% of the total observations while Bignoniaceae, Pinaceae and Sapindaceae had 1.8% each. The diameters at breast height (Dbh) ranged between 14.0cm and 128.2cm while tree total height ranged between 7.0m and 30.5m. About 33% of the tree species falls into the middle diameter class (40-60cm). This is followed by the diameter class 60-80cm with about 24%. The diameter class 20-40cm was made up of about 22%. The fifth diameter class (>80.0m) ranked fourth, with about 18% of tree frequency in the study area. The least represented diameter class is 0-20cm with 3.6% of the species encountered in the study area. The best volume equation obtained was (R2 = 95.4%; SEE = 0.3). All the models generated are adequate and are recommended for stand volume assessment in the study area.