An Ecological Study Of The Vegetation Of The Ravenna Forest

An ecological study of the vegetation of the Harennarnforest was performed from April 1986 to October 1986. Datarnon the vegetation and environmental factos were collected,rni.e. enumeration of tree and shrub species, an estimate ofrncover abundance value for herbs, epiphytes and lianes, alti~rntude, edaphic factors and topography.rnThe program GROUPAGE 'las used to summarlze -the vef,eta-tionrndata. The program CHECK 'las employed to analyse speciesrndiversity. Five homogeneous clusters of vegetation were re~rncognized using the presence-absence and quantitative data.rnThe clusters obtained were compared for the mean values ofrnthe environmental factors using the statistic t-test.rnThe highest number of significant contrasts among thernclusters were observed to result from variation in altitude.rnAnalysis of species diversity showed that with increasingrnal ti tude, tree and shUl'b species decrease >I11ile herbaceousrnspecies, epiphytes and lianes increase in number. As a result,rnin the area of the Harenna forest, the main vegetationrngradient is caused by differences in altitude associated 'lithrnvariation in moisture. The moisture gradient is accompaniedrnby gradients in soil physical and chemical properties andrntopography.

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