The present study was conducted in El- Nour Natural Forest Reserve to assess the effects of lightning, winds, illicit cutting and overgrazing as unfavorable factors affecting the natural regeneration in addition to tree species diversity in El-Nour Natural Forest Reserve. For data collection and depending on species and soil types more than 200 samples (205) were taken covering the whole forest area. In each sample plot, diameters at breast height over bark (dbh) were measured for all mature trees by using tree caliper and diameter tape for large trees (more than 95cm), and total tree height (h) for the largest four trees by using Suunto Clinometer. Damages by man, wind, lightening, domestic animals, insects and diseases were also monitored, counted and recorded in each sample plot. The collected data were analyzed using Computer Packages SPSS 16, past program and Microsoft Excel of Office 2013. Average of diameter at breast height (dbh), height (h), basal area (b) and volume (V) were calculated as well as relative frequency (RF), relative abundance (RA) and relative dominance (RD) for each species. Scattered plots and trend graphs were fitted to examine the effect of different selected agents on the natural regeneration and distribution of tree species in this forest. The occurrence of species within a sampled area shown a considerable variation where relative frequency change in descending order for the following species, Acacia seyal var seyal, Combretum hartmannianum, Terminalia laxiflora, Terminalia brownii, Sterculia setigera, Anogeissus leiocarpus, Sterculia africana and Acacia seyal var fistula respectively. Man represents the most damaging agent for most trees particularly those used for charcoal production as it represent a source of income generation. Lightening and winds damaged mainly Combretum hartmannianum, Anogeissus leiocarpus, Sterculia africana and Sterculia setigera as tallest trees in the forest. The severity of damages caused by animal and insects were less than that of former agent, however, it alter the new regeneration in the forest floor. One of the important new finding of the study was the crown damage (new shoot removal) of Sterculia setigera and Sterculia africana as fodder for domestic animals. This new deviation may referred to the obvious increase in domestic animals around the forest as well as, the considerable numbers of nomads that passing through the forest and sometime camping inside the forest for many days and damaged it stock. The study recommends that, intensive awareness program for local people around the forest is necessary to reduce this increasable pressure on the forest, as well the participation of local people in forest activities. Also some damaged compartments in the forest should be fenced against domestic animals to facilitate the natural regeneration.
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