Eshetu Yirdaw

Diversity of naturally-regenerated native woody species in forest plantations in the ethiopian highlands

Woody species diversity and ground layervegetation cover were studied in plantations ofPinus patula, Cupressus lusitanica,Grevillea robusta, and Juniperusprocera, and in surrounding natural forests inWondo Genet, Ethiopia. In the understory of theplantations, a total of 53 naturallyregenerated tree and shrub species belonging to31 families were recorded. Important indigenoustimber species were also represented. Treesaccounted for 72% of all naturally-regeneratedwoody plant species. On the average, 78% ofthe woody species found in plantations werealso found in the natural forest. There was nosignificant variation in understory woodyspecies richness among plantations. C.lusitanica plantations had a significantlyhigher abundance of woody species than those ofP. patula, but the difference wasnot significant in relation to J. procera,G. robusta and the adjacent natural forest.The herbaceous ground cover percentage in G. robusta and P. patula stands wasconsiderably higher than in C. lusitanicaand J. procera stands. Relative toplantations of other species, plantations ofthe native tree species J. procera hadhigher understory species richness, mediumwoody species abundance and low ground cover.Although there was a marked variation inoverstory plantation density, its effect onunderstory species richness and abundance wasnot significant. The density ofnaturally-regenerated woody species inplantations was over three times the usualplanting density in Ethiopia, indicating a highpotential of forest plantations for restoringthe natural forest ecosystems on degraded landsat a comparatively low cost.

Indigenous woody species diversity in Eucalyptus globulus Labill. ssp. globulus plantations in the Ethiopian highlands

The naturally regenerated native woody species diversity was studied ineucalypt plantations at Menagesha, where there was remnant natural forest, and atChancho, where natural forests were absent. A total of 22 and 20 woody speciesbelonging to 18 and 17 families were found, and of these species, treesaccounted for 68 and 55% at Menagesha and Chancho, respectively. About 83% ofthe woody species found in the adjacent natural forest, including importanttimber species were represented in the eucalypt understory at Menagesha.However, the relative abundance of species in eucalypt plantations and theadjacent natural forest varied considerably. Woody species richness andabundance of sample plots at Menagesha were on average 2.4 times and 5.7times higher, respectively, than the sample plots at Chancho. This resultdemonstrates the crucial role of the remnant small patches of natural forest,as a source of diaspores for the restoration of the woody species diversity indegraded areas of the Ethiopian highlands. There was no significant differencein woody species diversity between the eucalypt stand margin and centre. Theunderstory woody species density in eucalypt plantations was up to 8325stems/ha, indicating that the numerous eucalypt stands have a highpotential for restoring the woody species diversity in the Ethiopian highlands.In order to fully re-establish the diverse and economically valuable naturalforest, complementary measures such as enrichment planting of missing primaryforest species may be required.

Seed germination responses of four afromontane tree species to red/far-red ratio and temperature

The germination response of Cordia africana, Juniperus procera, Acacia abyssinica, and Faidherbia albida seeds to continuous exposure of various red to far-red ratios (R/FR) and constant-temperatures of 15, 20, 25 and 30 °C were studied. Germination of C. africana seeds was strongly inhibited at low R/FR and it appears that this species has evolved a light quality sensing mechanism that prevents seed germination beneath leaf canopies. The germination probability of C. africana increased as temperature increased from 15 to 30 °C. R/FR, temperature, and their interaction significantly affected germination of J. procera. Seeds of this species displayed a complex dormancy mechanism and germinated only in a narrow range of temperatures and R/FR. The effect of R/FR on germination of J. procera was most pronounced and the highest germination probability was recorded at 20 °C. The germination probability of F. albida seeds increased with rising temperature (from 15 to 30 °C), but there was no significant effect of light. At high temperatures, mean germination time in this species decreased with increasing R/FR, but increased with rising R/FR at low temperatures. Neither R/FR, temperature, nor their interaction had a significant effect on the germination of A. abyssinica seeds. The results suggest that deep sowing of J. procera and especially C. africana seeds, as well as covering and shading of their seed beds with leaf litter in nurseries, should be avoided. By proper regulation of light and temperature conditions, prolonged nursery germination of J. procera seeds can be reduced.

Vegetation structural characteristics and topographic factors in the remnant moist Afromontane forest of Wondo Genet, south central Ethiopia

For forest ecosystem management to be effective, knowledge of the horizontal and vertical structural diversity of a forest is essential. The moist Afromontane highlands of Wondo Genet in south-central Ethiopia present an opportunity to restore and rehabilitate and enhance the ecosystem services to be obtained from this forest sustainably. We focused on the forest structural characteristics to better understand the current forest conditions to assist in the sustainable management of this resource. A total of 75 (20 m × 20 m) quadrats were sampled and diameter at breast height (DBH) ≥ 2 cm and stem height ≥ 2 m were measured. Species identity and abundance, elevation, slope, and aspect were recorded for each plot. Structural characteristics were computed for each plot. Relationship of topographic factors with vegetation characteristics was conducted using R-Software. A total of 72 woody species was recorded. Whereas, the overall diameter distribution shows an inverted J-shaped curve, the basal area followed a bell-shaped pattern. Five types of population structures are revealed. The mean tree density and basal area was 397.3 stems·ha−1 and 31.4 m2·ha−1, respectively. Only 2.8% of the tree species have densities of >25 stems·ha−1 and the percentage distribution of trees show 56.2% in the DBH class 2–10 cm, indicating that the forest is dominated by medium-sized trees. Celtis africana (8.81 m2·ha−1) and Pouteria adolfi-friedericii (5.13 m2·ha−1) make the highest contribution to the basal area and species importance value index. The families/species with the highest importance value index are Ulmaceae, Fabacea and Sapotaceae. Species abundance (r2 =0.32, p <0.001) and species richness (r2 =0.50, p <0.001) are positively related with tree density. Tree density is negatively related with elevation (r2 =−0.36, p <0.001), slope (r2 =−0.15, p <0.001) and aspect (r2 =−0.07, p <0.05). While basal area is negatively related with elevation (r2 =−0.14, p <0.001), it has a positive relationship with tree density (r2 =0.28, p <0.001 and species richness (r2 =0.098). Species with poor population structure should be assisted by restoration tasks and further anthropogenic disturbance such as illegal logging and fuel wood extraction should be restricted.

Plant community analysis and effect of environmental factors on the diversity of woody species in the moist Afromontane forest of Wondo Genet, South Central Ethiopia

Abstract Floristic diversity and the composition of vascular plants are described for the moist Afromontane forest (MAF) of Wondo Genet, south-central Ethiopia. A total of 75 (20 x 20 m) quadrats were sampled and data on species identity, abundance, elevation, slope and aspect were recorded. Different diversity indices and ordination techniques were used to analyze the data. A total of 240 plant species including seven endemic plant species were found representing 94 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: Teclea nobilis-Calpurnia aurea, Erythrococca trichogyne-Millettia ferruginea, Croton macrostachyus-Vernonia hochstetteri, Protea gaguedi-Rhus retinorrhoea and Dodonaea angustifolia-Hypericum quartinianum. Elevation (R2=0.48, P<0.001), slope (R2=0.14, P<0.001) and aspect (R2=0.04, P<0.01) correlated significantly and negatively with species richness, whereas only elevation (R2=0.30, P<0.001) and slope (R2=0.13, P<0.001) related significantly and negatively with abundance. Sørensen’s similarity coefficient indicates that the forest of Wondo Genet is similar to moist montane forests of southwestern and southeastern Ethiopia. Given the high diversity, coupled with the existence of endemic species, ecosystem conservation and restoration strategies with further research are warranted.

Species Diversity Based on Vertical Structure as Indicators of Artificial Restoration for Coniferous Forests in Southwest China

Five indices of species richness, species diversity and species evenness were used to assess α diversity of four types of coniferous forests undergone different artificial regeneration time. The study was based on the vertical structure of forests, involving growth-forms of total plants as well as vertical layers of woody plants. The results showed that, except for the fourth layer of woody plants, the vertical structure of the four forests exhibited significant difference in terms of their species richness, species diversity and species evenness, suggesting that α species diversity index provided more detailed information and was a better index reflecting the regeneration processes in this region It was recommended that silvicultural management of artificially regenerated forests should be strengthened to conserve the biodiversity of the forests, optimize forest structure and, in the long run, promote sustainable development of forest ecosystems.