Effect of Forest Fires on Tree Diversity and some Soil Properties

The effect of forest fire was studied after one year in three natural forests in Al Baha region (south-west Saudi Arabia). Three sample plots (100 m(2) each) were selected randomly inside the burned and the immediately neighboring unburned area in each forest (Al Hilia, Al Kahla & Ragdan). The effect of fire on tree species recovery, regeneration and some soil physical and chemical properties was investigated. Regeneration of Acacia origena increased significantly after fire and dominated the burned areas. Most of the trees in these areas either resprouted completely or partially. In contrast, Juniperus procera was very sensitive to fire and most burned trees failed to recover or regenerate. Olea spp., were intermediate in their reaction to fire, but generally they were negatively affected by fire in terms of recovery and regeneration. Fire had no effect on soil texture. Soil pH increased significantly, whereas (EC) significantly decreased in the burned sites as compared to unburned areas. Organic matter and total N decreased significantly in the burned areas, whereas available P and K increased significantly after fire. Micronutrients such as Mo, Co, Ni and Pb, varied in their response to fire and no pattern was recorded. It appears that A. origena might succeed other associated tree species after fire. (C) 2011 Friends Science Publishers