Crown ratio assessment for Prosopis africana (Guill. and Perr.) Taub species in Makurdi, Nigeria

Abstract

Information on tree crown is prerequisite for sustainable utilization of forest tree resources, as it is the site for physiological activities that lead to tree growth and development. Crown ratio (CR) is an index of tree stability; it indicates tree vigour and is a useful parameter for assessing forest condition. This study aimed at assessing crown ratio for improved silvicultural management of naturally grown Prosopis africana species within the University of Agriculture Makurdi, Nigeria. Nine temporary sample plots (TSPs) of size 100 m x 100 m were established using simple random sampling method. Diameter at breast height (Dbh), total height (Ht) and crown diameter (Cd) and height to live crown base (HCB) were measured for all living P. africana trees with Dbh > 10 cm within the 9 TSPs. Data collected were subjected to descriptive and bivariate correlation analysis. The trees were further classified based on their Crown ratio as high vigour (CR>0.50), moderate vigour (CR= 0.30-0.50) and low vigour (CR<0.30). The result revealed that CR had strong negative correlation with Ht and HCB. Tree diameter attributes showed low positive correlation with CR. However, about 69% of the trees are within moderate CR class and only 3% areof the low CRclass. This implies that majority of the P. africana species in the study area are of moderate and high vigour. Hence, appropriate silvicultural Treatment such as thinning is recommended for trees with CR <0.3 to ensure moderate, better stand stability and sustainability of the species benefits.

Keywords: Correlation; Crown ratio; Economic trees; Tree growth characteristics; Prosopis africana