Effects of anthropogenic disturbances on natural regeneration and population structure of gum arabic tree (Acacia senegal)in the woodlands of Lake Baringo ecosystem, Kenya  

作　　者：Stephen F. Omondi David W. Odee George O. Ongamo James I. Kanya Damase P. Khasa 

机构地区：[1]Kenya Forestry Research Institute,P.O. Box 20412,00200 Nairobi,Kenya [2]School of Biological Sciences,University of Nairobi,P. O. Box 30197-00100,Nairobi,Kenya [3]Centre for Forest Research and Institute for Systems andIntegrative Biology,Universite′ Laval,Sainte-Foy,QC G1V 0A6,Canada

出　　处：《Journal of Forestry Research》2017年第4期775-785,共11页林业研究（英文版）

基　　金：supported by Kenya Forestry Research Institute(KEFRI/FBEM 2014_2015/2.3);International Foundation for Science(IFS D5452-1)

摘　　要：Despite the ecological and economic importance of Acacia senegal, little is known about the effects of anthropogenic disturbances on its natural regeneration patterns and population structure. We investigated the effects of these factors within the Lake Baringo woodland ecosystem. Data was collected from 60 plots of 20 m × 20 m systematically distributed in four A. senegal-dominated populations within the Lake Baringo woodland. Sample populations spanned a degradation gradient measured by a population disturbance index (PDI). Trees were measured for diameter at breast height (DBH) and categorized by growth stages: seedling, sapling and adult tree. Higher seedling and sapling densities were recorded in lightly than heavily disturbed populations, but only sapling density was significantly different between the two disturbance levels (P = 0.02). Lightly disturbed populations revealed a reversed J-shape size-class distribution (SCD) indicative of stable structure unlike the heavily disturbed populations. The quotient and permutation indices indicated unstable populations with episodic recruitment and mortality. Our study reveals that natural regeneration and population structure of A. senegal were affected majorly by selective harvesting and heavy browsing. Suitable management strategies to control livestock grazing and illegal tree harvesting within the woodland is required to promote conservation of the species genetic resourcesDespite the ecological and economic importance of Acacia senegal, little is known about the effects of anthropogenic disturbances on its natural regeneration patterns and population structure. We investigated the effects of these factors within the Lake Baringo woodland ecosystem. Data was collected from 60 plots of 20 m × 20 m systematically distributed in four A. senegal-dominated populations within the Lake Baringo woodland. Sample populations spanned a degradation gradient measured by a population disturbance index (PDI). Trees were measured for diameter at breast height (DBH) and categorized by growth stages: seedling, sapling and adult tree. Higher seedling and sapling densities were recorded in lightly than heavily disturbed populations, but only sapling density was significantly different between the two disturbance levels (P = 0.02). Lightly disturbed populations revealed a reversed J-shape size-class distribution (SCD) indicative of stable structure unlike the heavily disturbed populations. The quotient and permutation indices indicated unstable populations with episodic recruitment and mortality. Our study reveals that natural regeneration and population structure of A. senegal were affected majorly by selective harvesting and heavy browsing. Suitable management strategies to control livestock grazing and illegal tree harvesting within the woodland is required to promote conservation of the species genetic resources

关 键 词：Anthropogenic disturbance Population dynamics Renewal rate Selective harvesting Tropical woodland 

分 类 号：S718.5[农业科学—林学]