Effects of environmental factors on floristic diversity and composition of vascular plants in the remnant moist Afromontane forest in Wondo Genet, South Central Ethiopia Mamo Kebede 1, Eshetu Yirdaw, Olavi Luukkanen, Mulugeta Lemenih 1 Viikki Tropical Resources Institute (VITRI), Department of Forest Sciences, University of Helsinki

Introduction Ethiopia is endowed with diverse vegetation types ranging from Afroalpine vegetation in the central highlands to arid lowlands in the east, and rainforests in the west (Friis et al., 2010) The country has the fifth largest flora in Africa (EPA, 1997) Wondo Genet forest in the south central highlands, where this study was conducted, is classified as Moist evergreen Afromontane Forest (Friis et al., 2010) The forest cover of the area declined from 16% to 2.8% in three decades (Dessie, 2007).

Objectives of the study  To examine the floristic diversity and composition of vascular plants  To assess the structural diversity and population structure of the forest  to analyze regeneration characteristics and soil seedbank pool in the forest and compare with the standing stock  To study reproductive phenology of selected four native tree species with population structure at risk

Study questions  What is the extent of the vascular plant species diversity in this remnant forest as influenced by environmental gradients ?  what is the current status of structural diversity of tree and / or shrub species ?  Which species maintained regeneration and soil seed bank pool for potential replacement of the standing crop ?  Do the selected native tree species have adequate reproductive phenology in terms of the presence of flowering mature trees, flower visitors and seed production ?

Introduction … Generating information to assist planning for conservation and restoration of this forest is crucially important. The aim of this study was to: (i)Describe species richness, abundance and plant community types of Wondo Genet Afromontane forest (ii)Ascertain the pattern of species richness and abundance with elevation, slope and aspect, and (iii)Carry out floristic similarity (Sørensen’s) comparison of the Wondo Genet forest with other Afromontane forests of Ethiopia and with some Eastern African countries.

Materials and Methods Wondo Genet is situated in the south-eastern central highlands of Ethiopia, about 263 km from Addis Ababa, at 7 o 5’N latitude and 38 o 36’ E longitude on the eastern slope of the Rift Valley escarpment The altitude ranges from 1800 m to 2500 m. The mean annual rainfall is about 1200 mm and it is bimodal. Rain can be expected from March to April and June to August. The period from November to February is relatively dry. The soils are young and of volcanic origin, characterized by well-drained loam or sandy loam, and it is shallow at steep convex slopes but deeper at lower altitudes (Eriksson and Stern, 1987). The current land use is predominantly smallholder agriculture with an average landholding size of less than one hectare per household

Materials and Methods … Systematic plot sampling was conducted in four transects and seventy-five 20 x 20 meter quadrats The first quadrat was located randomly, and after that the quadrats were established at 100 m intervals along transects. Transects were spaced 350 m apart. In each quadrat, all species with DBH (Diameter at Breast Height) ≥ 2 cm and height ≥ 2 m were identified and counted. The presence of epiphytes, herbs, grasses, sedges and ferns was recorded for floristic compilation. Herbarium vouchers were collected and Plant identification was done in the National Herbarium, Addis Ababa University. Environmental parameters including slope, elevation, exposition, and coordinates were measured on plot basis.

Data Analysis Diversity Analysis Species diversity was measured using Shannon diversity (H’), H’max, and Shannon evenness (J’), Simpson index (D) ((Magurran, 2004 ) Cluster Analysis Hierarchical cluster analysis of the data was done using PC-ORD for Windows version 5 (McCune and Mefford, 2006). Ordinations Ordination was also computed using a Nonmetric Multidimensional Scaling (NMDS) (McCune and Grace, 2002). The species abundance and environmental matrices containing elevation (meter a.s.l), slope (%), and aspect were used for the ordination Phytogeographic comparison A similarity analysis was carried out to evaluate the relationship between the forest based on the presence of trees and shrubs. Sørensen’s similarity was used for comparison with Mafi in Tanzania (Lyaruu et al., 2000) and Mt. Elgon in Kenya, (Hitimana et al., 2004) and other Ethiopian Afromontane forests.

Results A total of 240 plant species including nine endemic plant species were found representing 91 families and 210 genera, of which trees constitute 23.8%, shrubs 25%, herbs 35%, lianas 11.3% and ferns 5%. Cluster and indicator species analyses revealed five plant communities described as: C1 - Teclea nobilis-Calpurnia aurea, C2- Erythrococca trichogyne-Millettia ferruginea, C3 - Croton macrostachyus-Vernonia hochstetteri, C4 - Protea gaguedi-Rhus retinorrhoea and C5 - Dodonaea angustifolia-Hypericum quartinianum community.

CommunityElevationSpecies richnessEvenness Shannon diversity (H')H'MaxEvenness (J)SimpsonBerger I (6.51)0.354 (0.18)2.89 (0.44) (0.11)0.90 (0.12)0.17(0.15) II (4.19)0.468 (0.13)3.026 (0.44) (0.10)0.932 (0.12)0.142 (0.16) III (7.67)0.402 (0.14)3.20(0.42) (0.08)0.931(0.07)0.163 (0.11) IV (3.64)0.45(0.13)3.017(0.39) (0.07)0.926 (0.09)0.185(0.12) V (4.35)0.46 (0.18)2.836(0.43) (0.11)0.897(0.09)0.26 (0.14) Over all (6.04)0.52 (0.17)3.63 (0.43) (0.10)0.96(0.10)0.079(0.143)

Dendrogram

Results

Results… The five communities identified were: A. schimperi-F. indica community, E.-M. ferruginea community, C. macrostachyus- V. hochstetteri community, P. gaguedi- R. retinorrhoea community ; D.angustifolia – H. quartinianum community Ten combinations of pair-wise T-test comparisons were conducted and showed a significant difference (P = 0.001). From the analysis, the T- value statistic for the five groups is (P = 0.001) and the agreement statistic A is The test statistic T describes the separation between groups. The more negative T values, the strongest the separation The agreement statistics A describes chance corrected for within-group homogeneity, compared to random expectation and lies between 0 and 1 ( when all items are identical.

Results…. r = y = x r = y = x r = y = x r = y = x

Results ( Sørensen’s similarity)… Forest N a (common)b (WG)cSs Jibat Chilimo Menagesha Wof-washa Yayu Mena Angetu Mafi (Tanzania) Mt. Elgon (Kenya)

Conclusion and recommendations Wondo Genet remnant forest contains a substantial amount of Afromontane plant species composition and diversity. The high diversity, coupled with the presence of some endemic species calls for immediate conservation strategies with the involvement of the government and local communities that would lead to the restoration and rehabilitation of this remnant forest Detailed ecological studies are vital concerning the species composition, diversity and distribution of the possible plant community types in relation to other environmental factors such as soil properties, moisture regime, temperature fluctuation, frost occurrence, and the like, which were not the subject of this study. Ethnobotanical studies should be conducted to harness the indigenous knowledge on the uses of plant resources contained in the forest.