Forest structure of a protected east african coastal forest: a case study of kaya muhaka forest, Kenya

Agricultural expansion continues to be the biggest threat facing the Coastal Forests of East Africa. Due to poor soil quality and an increasing population trend, subsistence agriculture as well as commercial farming continue to consume more and more of the region's natural habitat. The study assessed the forest structure of the Kaya Muhaka forest and the adjacent agro-ecosystems at the Kenyan Coast. Two 3 km parallel transects running through the agroecosystem and Kaya Muhaka forest from East to west and three 1 km parallel transects running from north to south of the forest were set up. 20 m x 20 m quadrats were laid out every 250 m along transects. The vegetation structure of the forest was assessed by identifying and recording all trees with a Diameter at Breast Height (DBH) of 5 and above within each quadrat. The DBH was measured using a diameter tape measure in the following class intervals; 5-9 cm, 10-14 cm, 15-19 cm, 20-24 cm, 25-29 cm,30-34 cm, 35-39 cm, 40-44 cm, 45-49 cm and >50cm. Most forest species occupied the lowest DBH class of 5-9cm, with the overall DBH class distribution exhibiting an inverse letter J indicating regeneration. The canopy cover and height within the three life form layers (herb shrub and tree) were estimated in each plot by ocular estimates. The tree layer cover was estimated in three sub canopy layers namely; upper stratum (>20m height), middle stratum (5-10m height), lower stratum (5-10m height).The canopy cover estimation involved the imaginary projection of the aerial shadow of each vegetation layer on the ground and estimation of its percentage area. The total percentage cover of each area was assumed to be 100%. Tree height measurement was done by use of a suunto clinometer and the tree height was calculated trigonometrically. In all the sampled transects, the upper stratum was the least represented while the lower stratum dominated the forest canopy. These results were interpreted to mean that the forest has experienced significant disturbance from the surrounding smallholder farmers and is under a regeneration process.