Effects of canopy structure on the diversity and structure of tree species in omo biosphere reserve, Ogun state, Nigeria

Abstract

This study assessed the effects of canopy structure on tree species diversity and forest structure in Omo Biosphere Reserve. Landsat imagery was used; supervised maximum likelihood classification was used to classify the reserve into two canopy structures (closed and open canopies). Random sampling technique was used to delineate 10 sample plots of 30m x 30m in each canopy type. Tree species with a diameter at breast height (Dbh) ≥10cm were enumerated in each sample plot. Shannon Weiner and Simpson’s indices were used to assess the tree diversity, while diameter and height stratification were used to evaluate the forest structure. Shannon Weiner and Simpson’s indices were 3.507 and 0.953, respectively, in open canopy structure (OCS) and 3.396 and 0.951, respectively, in closed canopy structure (CCS). Species richness and population were higher in OCS (64 and 575, respectively) than in CCS (56 and 531, respectively). Milletia thonningii and Strombosia pustulata were the dominant tree species in OCS and CCS, respectively. The mean Dbh and height in OCS were 40.09cm and 22.86 cm; and 50.21cm and 23.05cm in CCS, respectively. The basal area was 110.01m²/ha in OCS and 207.97m²/ha in CCS. The volume yield per hectare in OCS was 343.35m³/ha and 842.49m³/ha in CCS. The OCS was dominated by younger trees than the CCS. Canopy structure affects tree species richness, population, and diversity, as well as tree attributes.