Postfire Influence On Erica Shrubland Within The Afroalpine Vegetation

The aim of the study was to compare variations in size, density, and concentration of the floristicrncomposition, soil seed bank and soil nutrient concentration respectively between recently and previouslyrnburnt blocks within the lower and upper boundary of the Erica shrubland community, in the upperrnAfroalpine vegetation zone of the BMNP, Southeast Ethiopia. A stratified-systematic sampling design wasrnused to collect data on each block, each comprising three quadrats having equal size of 20m by 20mrn(400m2). Accordingly, a total of twelve quadrats were laid out along two transect lines: one passingrnthrough the recently burnt areas and the other one passing through the previously burnt areas; givingrnfour conditions, two on the lower boundary and the other two on the upper boundary on fire-affectedrnEricaceous species, Erica arborea L., and other associated plant communities such as herbs and grassesrnincluding sedges. As a result, variations in species composition and abundance were significant betweenrnblocks; species richness was higher on the lower than upper boundary. Differences in speciesrncomposition and abundance were greater between blocks within the upper than lower boundary afterrndisturbances by fire. A total of 51native species were identified in the study site. Of the total speciesrnidentified, herbs and grasses dominated the above-ground vegetation cover. Herbaceous and woody plantrnspecies accounted 88% and 12% respectively. Alchemilla haumannii Rothm was the single most abundantrnand frequent species encountered in the study site. Analysis and interpretation of soil seed bank datarnshowed, at least 24 species were identified in the 0 – 9cm soil layer, of which woody plants were unlikelyrnto germinate from seeds even buried deep in the soil bank which may be due to frequent and/o lessrnfrequent but intensive fires. The total average number of germinated seedlings ( per meter square) were:rn1487 on the lower recently burnt block, 1911 on the lower previously burnt block, 1687 on the upperrnrecently burnt block, and 1961 on the upper previously burnt block for herbs and, 810, 884, 943, and 962rnfor grasses including sedges in these corresponding blocks stated for herbs. Generally, herbs dominatedrnin average density deeper in the soil bank on the lower boundary, while on the upper boundary, deeperrnsoil layers were dominated by grasses including sedges. In addition, significant variation was observedrnalong similar soil depth layers, except for 5.5 – 6.0cm. In the same token, only few group of individualsrnunder Rosaceae family use soil bank as an alternative means for regeneration, and hence survival in thisrnfire-affected Erica shrubland. Analysis and interpretation of soil nutrient pool showed, significantrnvariation was observed only for soil permanent wilting point, bulk density, and particle density along thern0 – 10cm depth layer, while significant variation was observed solely for soil organic carbon along the 0rn– 50cm depth layer. Hence, fire plays a vital role in maintaining species diversity, succession and localrncarbon balance in the Erica shrubland of the Afroalpine vegetation.rnKey words: Fire, species composition and abundance, density and concentration

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