The Effects Of Fires On Plants And Wildlife Species Diversity And Soil Physical And Chemical Properties At Aberdare Ranges, Kenya

Abstract

More than 220,000 forest fires occur every year around the world resulting in more than 6 million hectares of forests burnt. Fires are a frequent phenomenon in Kenyan forests especially during the dry seasons. In the Aberdare ranges fires occur every year during the dry season as the vegetation is usually dry and there are strong winds which make it easy for any fire started spread very fast. Fire can initiate changes which affect the composition, structure, and pattern of vegetation on the landscape. These changes also affect animal habitation and utilization of the forests. It can also change the soil properties which in turn can affect the vegetation growing there. This study was conducted to determine the effects of fires on plants, animals, birds and soil physical and chemical properties at the Aberdare Ranges forest. Data was collected on five sites that experienced fires in 2002, 2009, 2012, 2013, and 2014. In every site, data was collected from both burnt and un-burnt areas for comparison. For the woody vegetation sampling, Point Centered Quarter method was used and for herbaceous vegetation sampling, quadrat method was used. Foot count was done for animal census and point count for birds. In every site, soil was sampled at three depths from three points chosen randomly in every site and the soil samples were taken to soil laboratory for analysis. The data showed that woody species diversity did not differ significantly between burnt and un-burnt sites for all fire episodes at all sites. This could be because most fires do not totally burn the trees but just affect the Diameter at Breast Height, height and the canopy of the trees. There was no significant difference in woody species diversity (F 1, 8 =0.001; P˃0.05). However, the herbaceous vegetation in burnt sites had significantly higher species diversity than the un-burnt sites in the areas that experienced fire prior to 2014. The mean number of species in all burnt site was 34.6±5.215 and the mean number of species in all un-burnt sites was 24.8±5.215. Fire had triggered the regeneration of the herbaceous plants. There was a significant difference between the percentage cover of the burnt sites and the un-burnt sites with the burnt sites having a higher percentage cover (F 1,128=5.360; P˂ 0.05). Fire has immediate negative effect on the population of animals as demonstrated on the site burnt on 2014. No single animal was found on the site one week after the fire when data was collected. xiii The site that was burnt in 2013 also had fewer animals compared to the un-burnt site. All the other sites which had been burnt prior to 2013 had more animals compared to the un-burnt sites. The animal diversity was directly proportional to the vegetation density caused by the vegetation regeneration due to fires. The areas with more vegetation had more animals. Fire had negative effect on birds and all the burnt sites had fewer birds than the un-burnt sites. The site burnt in 2014 had the least number of birds. The number of birds in the sites burnt before 2014 had increased although they were still fewer than the population in the un-burnt sites. Effects of fires were evident in the upper layer (0-15cm) of the soil for all the soil properties under study. There was no significant difference at 15-30cm and 30-45cm in soil properties between the burnt sites and un-burnt sites. Burning caused increase in pH, potassium, organic carbon and cation exchange capacity. Fire was found to decrease nitrogen and phosphorus content. The study demonstrated that fires lead to an immediate negative effect on vegetation, wildlife and soil chemical properties. Post fire management is important on sites that have recently experienced fires in order to rehabilitate them. Since the reduced herbaceous vegetation makes it easy for the humans to access the forest, this can lead to further destruction of the forest. Authorities responsible for the management of forests should ensure that people are kept out of those sites to allow vegetation to regenerate without interference. Reforestation can also be done on the burnt sites so as to increase vegetation and habitat for the wildlife. Key words: Animal diversity, Birds, Fire, Plant diversity, Soil properties