Mulualem Tigabu

Millettia ferruginea (Hochst.) Baker is a potential agroforestry species endemic to Ethiopia. No documented information exists about genetic variation in this species, thus baseline information is needed to initiate improvement program. Here, we quantified variations in seed size, germination and seedling growth at nursery stage based on seeds collected from six sites across the natural range of distribution of the species in Ethiopia. All seed- and seedling-related traits exhibited highly significant differences among seed sources (P < 0.01), and the magnitude of genetic variation was substantially higher (77–99%) than the environmental variation. The genetic advance as percent of the mean was higher for germination capacity (69.4%) and seed weight (31.7%) than for other traits, suggesting that the population means for these traits may be changed considerably by selecting the superior 5% of the genotypes. There were strong phenotypic (rp = 0.81) and genotypic (rg = 0.89) correlations between seed width and seed weight, so also between seedling height and root collar diameter (rp = 0.95 and rg = 1.00). In conclusion, the results reveal the existence of substantial genetic variation, which can be utilized to initiate tree improvement program of the species and for gene conservation in seed banks.

Patterns of genetic variation in Cordia africana, a tropical timber species, were evaluated at the population level. Bulk seed samples were collected from six natural populations in Ethiopia and examined for variations in seed morphometric traits, seed germination, and seedling growth at nursery stage. Analysis of variance revealed significant differences among provenances in all studied attributes except root collar diameter after 4 months of growth. The provenance effect, as determined by broad sense heritability, was 71–98% for seed morphometric traits, 80% for germination capacity, 42% for germination energy, 57–58% for seedling height and 3–13% for root collar diameter. Seed weight showed a significant positive correlation with altitude and negative correlation with mean annual temperature of seed origin. Germination energy was significantly correlated with longitude and mean annual rainfall. Seedling parameters and geo-climatic variables of seed origin were fairly correlated. A significant intercharacter correlation was found between seed length and seed weight, between root collar diameter at the age of 4 months and seed length and weight, as well as between seedling height after 4 and 8 months of growth. It can be concluded that the observed patterns of variation will have implications for genetic resources conservation and tree improvement.

The floristic composition and diversity of tropical dry deciduous and gallery forests were studied in Chacocente Wildlife Refuge, located on the Pacific coast in Nicaragua during 1994 and 2000. Density, dominance and frequency as well as species and family important values were computed to characterize the floristic composition. A variety of diversity measures were also calculated to examine heterogeneity in each forest community. A total of 29 families, 49 genera and 59 species were represented in 2 ha dry deciduous forest. In the gallery forest, the number of families, genera and species recorded in 2000 inventory was 33, 48 and 58, respectively and slightly higher than the 1994 inventory. The number of stems ⩽ 10 cm dbh varied from 451 to 489 per hectare in the deciduous forest, and from 283 to 298 per hectare in the gallery forest. The basal area was much larger for species in the gallery than dry deciduous forest. Fabaceae, sub family Papilionoideae, was the most specious family in the deciduous forest while Meliaceae was the dominant family in the gallery forest. Similarity in species composition and abundance between deciduous and gallery forests was low. In terms of species diversity, the gallery forest was found more diverse than the deciduous forest using Fisher's diversity index. Both forest communities were characterized by a typical inverse J shape. Therefore, emphasis should be given to the protection of rare species, i.e. as the forests are still under continued human pressure, an immediate action should be taken to conserve the remaining flora.

Sustainable forest production demands a continuous supply of high quality seeds for the production of seedlings in the nursery or for direct sowing. Here, we demonstrated the potential of near infrared spectroscopy as a rapid technique to discriminate viable and empty seeds of Pinus patula Schiede & Deppe. Near infrared spectra were collected from single seeds in transmittance and reflectance modes. To discriminate viable and empty seeds, multivariate classification models were developed with partial least squares (PLS) regression using the digitized spectra as a regressor and a y-vector of artificial values (1 for viable and −1 for empty seeds) as a regressand. Viable and empty seeds were perfectly distinguished by PLS models computed on full and selected transmittance spectroscopy data, while those derived from ‘full’ NIR reflectance spectra recognized 96 % of viable and 88 % of empty seeds. Analyses made on selected NIR reflectance spectra improved the classification rate of empty seeds to 100%. Difference spectra and PLS weights indicated that the origin of spectral differences between viable and empty seeds was attributed to differences in fatty acids and proteins that were totally absent in empty seeds. The result shows the prospect of developing rapid filter-based sorting equipment that can easily be automated.

Diversity and regeneration of woody species were investigated in two ecological niches viz. gap and intact vegetation in old-growth seasonally dry Shorea robusta (Gaertn. f.) forests in Nepal. We also related varieties of diversity measures and regeneration attributes to gap characteristics. Stem density of tree and shrub components is higher in the gap than in the intact vegetation. Seedling densities of S. robusta and Terminalia alata (B. Heyne ex Roth.) are higher in the gap than in the intact vegetation, while contrary result is observed for T. bellirica (Gaertn. ex Roxb.) and Syzigium cumini (L. Skeels) in term of seedling density. The complement of Simpson index, Evenness index, and species-individual ratio in the seedling layer are lower in the gap than the intact vegetation. Gap size can explain species richness and species establishment rate. Gaps created by multiple tree falls in different years have higher seedling density of S. robusta than gaps created by single and/or multiple tree falls in the same year. In conclusion, gaps maintain species diversity by increasing seedling density, and favor regeneration of Sal forests. In addition to gap size, other gap attributes also affect species diversity and regeneration.

Predispersal seed predation among individual Acacia macrostachya trees over two sites in Burkina Faso was assessed. In addition, the effects of seed predation on seed viability; germination responses to scarification (mechanical, hot water at 60, 70 and 80°C, and sulphuric acid for 10, 20 and 30 min) and dry heat (at 60, 70 and 80°C for 15, 30 and 60 min each) treatments were investigated under laboratory conditions. The results indicated a large difference in predation intensity among individual trees, as well as between sites. Predispersal predation significantly decreased seed germination, particularly when the number of insect larvae per seed increased. Scarified and unscarified seeds germinated equally well, except for hot water treatments of high temperature. This indicates lack of physical dormancy and dispersed seeds can readily germinate provided that conditions for germination are conducive. Seeds exposed to dry heat treatments also germinated close to 97% under low intensity and short exposure times. This suggests that fire, under natural condition, plays a key role in triggering germination of A. macrostachya seeds.

There is growing evidence that population pressure on the land has become the most intractable problem in the developing countries where demand for food exceeds the food production capacity of the land. Southern Burkina Faso has experienced rapid population growth, mostly driven by immigration of farmers. This study was carried out in Sissili Province and used satellite images acquired over 31-year period, census and survey data to capture migration patterns and its impacts on land use change. Results showed that migrant population which accounted for only 3 per cent in the study area in 1976 shifted to 57 per cent in 2007. Migrant people were using improved technology to progressively convert forest land to cropland. Cropland increased at an annualized rate of 0·46 per cent to the detriment of the dense forest and woodland which decreased at 0·57 per cent per annum. Population growth was highly correlated with increasing area of cropland (r2 = 0·95, p = 0·014) and declining dense forest (r2 = 0·78) and woodland (r2 = 0·95) covers. It can be concluded that rural migration, driven by the relatively good soil and rainfall conditions in the recipient area, is accounted for deforestation in the study area. If rural migration is not checked, it will seriously degrade the environment. Copyright © 2009 John Wiley & Sons, Ltd.

Annual early fire, selective tree cutting and exclusion of grazing are currently used as management tools in the Sudanian savanna of Burkina Faso although their long-term effects on seedling recruitment are poorly documented. A factorial experiment involving fire, grazing and cutting, each with two levels, was established in 1992 to study the effects of these management regimes and their interactions on the regeneration of woody species, and examine whether their effects varied temporally. Species richness, density and the morphology of seedlings were assessed in 1997 and 2002, and their relative changes were determined. The change in species richness of multi-stemmed individuals was significantly higher (P = 0.018) on plots that received fire × cutting treatment than the control plots. Significantly more species with single-stem were found on unburnt than on burnt plots (P < 0.001). Grazing tended to reduce the change in total density while fire (P < 0.001) and grazing (P = 0.029) significantly reduced the change in density of single-stemmed individuals. Selective cutting did not affect the total seedling density, but tended to reduce the change in single-stemmed seedling density. Principal component analysis revealed species-specific responses to treatments, particularly the relatively high abundance of lianas compared with other species.Les feux annuels précoces, la coupe sélective d’arbres et l’exclusion du pâturage sont des moyens actuellement utilisés dans la gestion de la savane soudanienne du Burkina Faso, mais leurs effets à long terme sur le recrutement de jeunes plants sont encore mal documentés. Une expérience factorielle impliquant le feu, le pâturage et la coupe, chacun à deux niveaux, a été mis en place en 1992 pour étudier les effets de ces régimes de gestion et leurs interactions sur la régénération d’espèces ligneuses et pour voir si ces effets variaient de façon temporelle. La richesse spécifique, la densité et la morphologie des jeunes plants furent évaluées en 1997 et en 2002, et l’on a leurs changements relatifs déterminés. Le changement de la richesse spécifique des individus multicoles était significativement plus important (P = 0.018) dans les parcelles qui avaient subi le traitement feu × coupe que dans les parcelles témoins. On a trouvé significativement plus d’espèces à tige unique dans les parcelles non brûlées que dans les parcelles brûlées (P < 0.001). Le pâturage avait tendance à réduire le changement de densité totale alors que le feu (P < 0.001) et le pâturage (P = 0.029) réduisaient significativement le changement de densité des individus à tige unique. La coupe sélective n’affectait pas la densité totale des jeunes plants mais avait tendance à réduire le changement de la densité des plants à tige unique. L’analyse en composantes principales a révélé que les réponses aux différents traitements étaient spécifiques aux espèces, particulièrement l’abondance de lianes, relativement grande par rapport aux autres espèces.

Seeds of Juniperus procera collected from five provenances across its geographic range in Ethiopia were subjected to cold-moist stratification at 5°C or 10°C for 6–12 weeks. The effect of aqueous smoke solution in overcoming the light requirement for germination, and the potential of visible (VIS) and near infrared reflectance (NIR) spectroscopy for sorting sound and insect-damaged seeds were also investigated. Highly significant differences in germination were detected among provenances (P < 0.0001) and stratification periods (P <  0.0001), but not between temperature regimes (P=0.111). Seeds from the south and southeast distribution ranges had higher percentage germination after 6 weeks of stratification than seeds collected from north, northwest and central ranges of distribution. The smoke treatment did not affect germination regardless of whether the seeds were exposed to light. Exposure to light increased germination capacity three fold. Sound and damaged seeds were distinguished with 90% accuracy using VIS + NIR spectroscopy. It can be concluded that dormancy in juniper seeds varies with provenances, and cold stratification for 6 weeks alleviates dormancy in some seed lots. Tentatively, smoke treatment seems ineffective in overcoming photo-dormancy in juniper seeds. VIS + NIR spectroscopy has demonstrated a great potential for sorting damaged seeds, thereby upgrading seed lot purity.

Near infrared spectroscopy was used for simultaneous detection of filled, empty and insect-infested seeds of Larix decidua Mill., Larix gmelinii Rupr. and Larix sukaczewii Dyl. Near-infrared spectra, expressed in the form of log (1/T), were collected from single seeds with 1225 Infratec analyzer from 850–1048 nm at 2 nm interval. Discriminant models were developed with partial least squares (PLS) regression using the normalized digital spectra as a regressor and a y-vector of artificial values (1 for filled and −1 for empty and infested seeds) as a regressand. The result showed a 100% recognition of infested and empty seeds in the test set by 3-factor PLS models computed based on calibration sets of each species and combined spectra of all species. The recognition rate of filled seeds was 90–100%; the highest being for L. sukaczewii, followed by L. decidua and L. gmelinii respectively. A similar recognition rate for empty and infested seeds was achieved by discriminant models derived from selected absorption bands, while the recognition rate of filled seeds differed slightly. Difference spectra and PLS weights indicated that the origin of spectral differences between filled versus empty and insect-infested seeds were attributed to differences in lipids and proteins.

The IDS (Incubation, Drying and Separation) method was tested on Schinus molle L. seeds collected from Ethiopia in an attempt to sort non-viable from viable seeds. Seeds were incubated for 24 h followed by one, three, four, five, six, nine and twelve hours of drying and then separated in water. All IDS treatments gave 80.5–93.5% germination in the sunken fraction compared with 61% for untreated seeds. The mean germination time of sunken seeds reduced from 11.2 (control) to 8.9–9.2 days (IDS-treated). Specific gravity separation in water of untreated seeds was also tested, and the germination capacity of sunken fraction was 83.5% with a mean germination time of 9.3 days. IDS method can, therefore, be used to enhance both percentage and rate of germination of a seed lot of Schinus molle, which is desirable to produce uniform and vigorous seedlings in the nursery or out in the field.

• Seedling density and the regeneration mechanisms of five tree species, Anogeissus leiocarpa, Combretum aculeatum, Combretum micranthum, Combretum nigricans, and Pteleopsis suberosa were investigated in relation to latitudinal gradient across the Sahelo-Sudanian zone of West Africa. • Data were collected on 461 quadrats (2 m × 5 m) laid out every 30 m on transect lines through Combretaceae communities at four latitudinal positions. Regeneration mechanisms were determined by excavating the below ground root system and assessing basal and aerial sprouts. • The results showed a significant species × latitudinal position effect on the total density of seedling populations, and the density of single- and multi-stemmed individuals (p < 0.001). C. aculeatum and C. micranthum were abundant in the North-Sahelian sector, C. nigricans and P. suberosa in the Sudanian sector and A. leiocarpa across a wide range from the South-Sahelian to South-Sudanian sectors. In general, 58% of the seedlings were regenerated asexually (as coppice, water sprout, layer, and root sucker) while 42% were sexual recruits (as true seedling and seedling sprouts). The proportion of vegetatively propagated seedlings increased with increasing latitude for all species except C. micranthum, for which a clear decreasing trend was observed. The relative importance of the different regeneration mechanisms varied among species: seedling sprouts were important for A. leiocarpa, C. aculeatum and C. nigricans, coppice for C. micranthum and sucker for P. suberosa • The significant interaction observed between species and latitudinal position highlights the importance of accurate species-site matching to ensure successful restoration of degraded areas in the Sahelo-Sudanian zone. Inter-species differences in regeneration mechanism could be related to their biology and ecological adaptation to the site-specific biotic and abiotic factors. • La densité de semis et les mécanismes de régénération de cinq espèces d’arbres, Anogeissus leiocarpa, Combretum aculeatum, Combretum micranthum, Combretum nigricans, et Pteleopsis suberosa ont été étudiés par rapport au gradient latitudinal dans la zone sahélo-soudanienne de l’Afrique occidentale. • Les données ont été recueillies sur 461 quadrats (2 m × 5 m) disposés tous les 30 m sur des lignes de transects à travers les communautés de Combretaceae dans quatre positions latitudinales. Les mécanismes de régénération ont été déterminés par l’excavation du sol en dessous du système racinaire et par l’évaluation des pousses basales et aériennes. • Les résultats ont montré l’importance de l’effet position latitudinale × espèces sur la densité totale des populations de semis, et la densité des individus à fût simple ou multiples (p < 0,001). C. aculeatum et C. micranthum étaient abondants dans le secteur nord-sahélien, C. nigricans et P. suberosa dans le secteur Soudanien et A. leiocarpa dans une large aire du secteur Sud-sahélien au secteur sud-soudanien. En général, 58 % des plants ont été régénérés par voie végétative (taillis, gourmands, marcottes et drageons), alors que 42 % étaient des recrues sexuées (vrais semis et baliveaux). La proportion de jeunes plants issus de la multiplication végétative s’est accrue avec l’augmentation de la latitude, pour toutes les espèces, sauf C. micranthum, pour laquelle une tendance claire à la baisse a été observée. L’importance relative des différents mécanismes de régénération a varié selon les espèces: les baliveaux sont importants pour A. leiocarpa, C. aculeatum et C. nigricans, les taillis pour C. micranthum et les drageons pour P. suberosa. • L’interaction significative observée entre les espèces et la position en latitude met en évidence l’importance de veiller à une bonne correspondance des espèces et des sites pour assurer le succès de la restauration des terres dégradées dans la zone sahélo-soudanienne. Des différences interspécifiques dans les mécanismes de régénération pourraient être liées à leur biologie et à leur adaptation écologique aux spécificités stationnelles des facteurs biotiques et abiotiques.

The germination of Casuarina equisetifolia Forst seed lots is low (40–50%) even when freshly collected. This study aimed at upgrading the germination performance by removing non-germinable seeds using petroleum flotation technique. Seeds collected from 19 individual trees in seedling seed orchards in India were assessed using X-ray to determine the proportion of different seed lot fractions. The feasibility of petroleum ether as a separation medium was tested. Morphological characters of floating and sunken seeds were further studied using image analysis technique to examine their effects on the separation efficiency. The X-ray analysis revealed a large quantity of shrivelled, empty and insect-damaged seeds, altogether accounting 50%, which were the causes of low percentage germination of un-graded seed lots (48%). Petroleum flotation resulted in 90% germination in the sunken fraction and 4% in the floating fraction. The separation was distinct for most seed lots, except few seed lots that had relatively low germination in the sunken fractions and more than 10% germination in the floating fractions. As a whole, petroleum flotation appears to be a feasible technique to upgrade the germination of C. equisetifolia seed lots, and its efficacy is influenced by wing surface area, seed density and wing quotient of filled and empty seeds.

The fruit of Vitellaria paradoxa is an ideal raw material in cosmetic, pharmaceutical and confectionery industries. There are no accurate data on annual fruit yield due to the lack of objective assessment tools. The objectives of this study were to develop fruit yield prediction models based on dendrometric and fruiting variables, to examine variations in these variables between upland and lowland populations in Burkina Faso, and associations between these variables. A total of 191 fruiting trees were selected according to crown accessibility, and 17 dendrometric and fruiting variables were recorded. The fruit yield, expressed in number of fruits per tree, fresh and dry weights of fruits, was assessed by collecting fruits dropped overnight until the end of the fruiting period. Fruit yield prediction models were derived for each population using partial least squares regression. The results showed significant differences in dendrometric and fruiting variables between populations (P < 0.01). The lowland population had the highest values for most of the dendrometric variables while fruiting variables were the highest for the upland population. A strong significant correlation (P < 0.01) was found between number of shoots and fruiting variables. Within individual trees, fruit yield was lowest for the bottom part of the crown and the section of the crown with north-east orientation. Fruit yield parameters were successfully predicted based on selected dendrometric and fruiting variables (prediction error = 0.092 and 0.125 for upland and lowland populations, respectively). All fruiting variables, number of shoots and crown attributes had the highest influence on the models.

The potential of visible (VIS) and near infrared (NIR) spectroscopy for identifying seed sources and parents of Pinus sylvestris L. was studied. Seeds of a single family (clones AC1005 × BD1178) collected from three localities in Sweden—Sävar (north), Röskär (central) and Degeberga (south)—and seeds from four maternal (clone no. BD1032, AC1014, BD1178 and AC1005) and four paternal (Y3020, BD1178, AC1014 and BD1032) parents were used to evaluate the method. VIS and NIR reflectance spectra were recorded on individual seeds using a NIRSystems Model 6500 spectrometer from 400 to 2,498 nm with a resolution of 2 nm. The VIS + NIR spectroscopic data were pre-treated with multiplicative signal correction, and analysed by soft independent modelling of class analogy (SIMCA) and partial least squares-discriminant analysis (PLS-DA). The computed models were later applied to classify samples in the external test sets. The results show that seed sources were identified with 100% classification accuracy using PLS-DA models in the VIS + NIR, VIS and NIR regions. The average classification accuracy for maternal parents ranged from 92% to 96%, while paternal parents were identified with 91.2–96% accuracies. The classification accuracy using the SIMCA approach was relatively low for seed sources as well as maternal and paternal parents. It can be concluded that VIS + NIR spectroscopy could be employed as a rapid and non-destructive method for monitoring putative seed sources. The result underscores the prospect of the technique for characterizing seeds based on genotype, thereby serving as a tool in tree improvement and breeding.

Seeds of Strychnos nux-vomica have slow and erratic germination; thus different presowing treatments were applied to enhance the germination of its seeds collected from Tamaraikulam, Tamil Nadu, India. In addition, the effects of desiccation and different storage conditions on the germination of S. nux-vomica seeds were investigated. The results show that soaking in 500 ppm gibberellic acid (GA3) for 24 h, incubation of seeds at 40 °C for 3 days and alternate water soaking (16 h) and drying (8 h) for 14 days significantly increased the percentage germination compared to the control. Desiccation of seeds down to 10% moisture content resulted in better germination. Germination of S. nux-vomica seeds differed significantly between different storage periods, moisture contents of the seed and for first and second order interactions (p<0.001). The highest germination (92%) was achieved when seeds with 10% moisture content were stored at ambient temperature for 30 weeks. Evidence from the present study indicates that S. nux-vomica seeds possess physiological dormancy that can be broken effectively by after-ripening. As seeds of S. nux-vomica are found to be desiccation tolerant, dry seed (10% moisture content) can be hermitically stored at ambient temperature for 30 weeks without losing their viability.