Abstract
Detail study on soil seedbank composition and regeneration potential is needed for Ethiopian forests. In present work, soil seedbank assessment of woody plant species was made in Hgumbirda national forest priority area so as to evaluate composition and estimate their regeneration status. A total of 36 quadrates were established in selected four sites of the forest. The quadrates (20 m x 20 m) were laid along line transects. Soil samples were collected from sub-quadrates measuring 10 cm x 10 cm. Composition and status were determined by direct count and seedling emergence technique. Results showed the presence of seeds of 19 plant species in the soil. Juniperus procera had the highest viable seed density. Only Afrocarpus falcatus seeds were non-viable although very abundant (266.7seeds/m2). Except Cupressus lusitanica, no exotic woody species were found. The Shannon diversity index demonstrated low value for soil seedbank in Hgumbirda NFPA (H’=1.763). There was also significant variation of seed distribution between soil layers of the four selected forest sites (p<0.05). Jaccard’s coefficient of similarity between the standing vegetation and soil seedbank showed low value (JCS = 0.21 - 0.43). From the results, appropriate management strategies including preparation of nursery sites for selected indigenous plant species is suggested. Keywords : Soil, Seedbank, Woody species, Viable seeds, Afromontane, Hgumbirda forest, Regeneration, Ethiopia.
Highlights
Deforestation and conversion of land to permanent cultivation is the primary cause for dwindling tropical biodiversity and the practice has already threatened a number of plant species (IBC, 2005)
Out of the 54 standing woody plant species, 35 were exclusively represented by above ground flora and the rest 19 species were found in soil seedbank flora (17 from seed count and 2 from seedling emergence). This finding of only two woody species from the seedling emergence method is consistent with the findings of other authors such as Tinsae Assefa (2011) who worked on the seed bank composition of Bezawit forest at Abay Millennium Park, Ethiopia
Similar to other Ethiopian afromontane forests reported by different authors (Feyera Senbeta and Demel Teketay, 2002; Getachew Tesfaye et al, 2004; Mulugeta Lemenih and Demel Teketay, 2006; Reubens et al, 2007) most of these rare woody species recorded from seedbank flora belonged to shrubs and trees but no climbers except in Ksadaider (Fig.2)
Summary
Deforestation and conversion of land to permanent cultivation is the primary cause for dwindling tropical biodiversity and the practice has already threatened a number of plant species (IBC, 2005). One widely used option is creating exclosures, i.e. demarcated land areas under strict conservation management where intruders are excluded, often controlled by a local community In these areas, cultivation, unmanaged collection of fuel wood and grazing are forbidden whereas harvesting of grass is strictly controlled in order to allow spontaneous forest regeneration from soil seedbank (Reubens et al, 2007). In Ethiopia, as described by Mulugeta Limehih and Demel Teketay (2006), little was known about the survival of seeds of forest species in the below ground vegetation and their ecological implication for biodiversity. A study on underground vegetation (the soil seedbank) is very important to evaluate the regeneration status of the vegetation This enables policy makers and the community to make appropriate interventions in managing this ecologically important afromontane forest. This study was designed to abridge the prevailing gap on the seedbank flora and relate it with the above ground vegetation
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