On-farm tree species diversity and management in semi-arid of Lemo district,Southern Ethiopia

Agroforestry Systems - Despite the emerging and promising of on-farm trees to the biodiversity conservation, economic and ecological importance, there is still a dearth of empirical scientific...     

To prune or not to prune Faidherbia albida: competing needs for water,wheat and tree products in semi-arid Ethiopia

Faidherbia albida is one of the scattered trees commonly intercropped with most cereals in Ethiopia due to its positive impacts. The tree is pruned for various purposes including for fencing and fuelwood. In this study, the impact of pruning on water relations of F. albida and on understorey wheat productivity was investigated. The on-farm study was conducted in Ejerssa Joro, semi-arid Ethiopia. Six mature trees were selected; three were fully pruned and three were left unpruned. Sap flow and leaf water potential were measured on these trees. Crop gas exchange, aboveground biomass and grain yield were measured under and outside tree canopies. The highest and the lowest sap volumes, recorded from unpruned F. albida, during the dry period, were 153 L day^?1 and 20 L day^?1, respectively. The highest and the lowest sap volumes were 13.4 L day^?1 and 0.04 L day^?1 recorded during the wet period. Wheat CO₂ assimilation was highest (7.8 µmolm^?2 s^?1) at 1 m distance and declined away from the tree trunk under unpruned trees. Aboveground biomass and grain yield under unpruned treatments were significantly (P?<?0.05) higher than outside of canopy of same tree and outside canopies of pruned trees. Pruning reduced aboveground biomass and grain yield by 30% and 27%, respectively; despite the higher water uptake by unpruned trees. We recommend that intensive pruning of F. albida be discouraged and propose further studies on optimal pruning for increased food production and provision of tree products to meet farmers’ needs.

     

Fruit production ofAcacia tortilis andA. nilotica in semi-arid Ethiopia

Dry, dehiscent fruits ofAcacia tortilis provide important fodder for pastoral livestock in dry seasons on the central Borana Plateau, fruits ofA. nilotica may also be useful during drought. Information was needed on fruit yield to assess what these species could contribute to improved calf feeding systems based on local resources. Fruit production of 10 mature trees per species was measured at five sites for seven months during 1988–9 (n=50 per species). Fruit yields varied according to site, season and species x site (each atP<0.001), but there was no main effect of species (P=0.13). Yields were not correlated with trunk diameter at breast height (DBH) or canopy area within or across species (P>0.05 in all cases). Yields ranged from 0 to 40 kg DM per tree overall, with an average of 5.3 kg DM per tree (or 65 g DM/m² of canopy area). This average tree had a DBH of 26 cm and a canopy area of 81 m². Low and highly variable fruit yields appear to constrain enhanced use of these species here. These species warrant further attention in research and development, however, given their strategic value as forage resources in pastoral systems and their ability to persist in variable environments.     

Factors affecting adoption of hedgerows and other biodiversity-enhancing features on farms in California, USA

Although hedgerows, windbreaks, and other biodiversity-enhancing farm edge features offer the potential for ecosystem benefits without occupying much crop space, relatively few farms in California, USA include such features. Our study identified the practices currently used to manage non-cropped edges of fields, ponds, and watercourses in a case study area in California. We also identified social, economic, and agronomic incentives and constraints to installing biodiversity-enhancing edge features. More than one-third of the study farmers had installed native hedgerows, windbreaks, and/or grassed edges. Interviews demonstrated the importance of socially influential farmers working in tandem with public and private agencies to build initial interest in these practices. However, these features occupied less than four percent of all possible edge length. Constraints to increasing adoption included high costs, fear of harbouring weeds and rodents, and lack of certainty about ecosystems benefits, highlighting the need for cost-share programs and more regionally-focused agroecological research.     

Effects of livestock exclusion on tree regeneration in church forests of Ethiopia

In Ethiopia, forests near churches, are the last remnant forest patches. These forests are currently under threat, probably due to diminishing areas of the forest itself and repeated grazing for extended periods by cattle. We assessed the effect of livestock exclusion on the regeneration of four indigenous tree species in two church forests. The four species have a high abundance and socioeconomic value, but limited regeneration in the two forests. We investigated the effect of grazing and trampling on seed germination, seedling survival, and seedling growth. Livestock grazing had a strong negative effect on germination, seedling growth and mortality. In fenced plots, more seeds germinated, seedling survival was higher and seedlings grew faster. Seed germination was higher inside the forest than in the adjacent open area for all species. Seedling survival was not different between forest interior and open fields, except for unfenced plots in the open fields where survival was lower because of the higher grazing pressure. In unfenced plots, no seedlings survived until the end of the year, indicating that grazers destroyed the seedling bank in and around the forest. The significant interaction between fencing and species on seed germination and seedling survival revealed that the magnitude of damage due to grazing can vary with species.     

Microclimate patterns on the leeside of single-row tree windbreaks during different weather conditions in Florida farms: implications for improved crop production

Florida citrus and vegetable crops generate billions of dollars in revenue every year. However, wind, freezing temperatures, hurricanes, and diseases negatively impact production. Windbreaks located perpendicular to the prevailing wind can increase farm production simply by reducing wind and modifying microclimate. Windbreaks can also help in managing pathogens such as citrus canker (Xanthomonas campestris pv. citri). To study the modification of wind speed, temperature, and relative humidity on the leeside of single-row tree windbreaks in southern Florida, automated weather stations were installed in 2007/2008 at 2 m above the ground along transects perpendicular to a eastern redcedar (Juniperus virginiana) and three cadaghi (Corymbia torelliana) (WB1–WB3) windbreaks. All windbreaks reduced wind speed, with minimum wind speed (~5% of the open wind speed) at two times the distance of windbreak height (2H, where H = windbreak height in m) on the leeside of a E. redcedar (~17% porosity) and at 4H (~3–30% of the open wind speed) and 6H (<50% of the open wind speed) on the leeside of cadaghi windbreaks WB1 (~22% porosity) and WB2 (~36% porosity), respectively, when the wind direction was nearly perpendicular to the windbreaks. Wind speed reduction was observed up to 31 times the windbreak height (31H). Cadaghi windbreaks reduced wind speed on the leeside even during a tropical storm event. Temperatures on the leeside of the windbreaks were warmer during the day and cooler near the windbreaks at night compared to temperature in the open fields. This study demonstrates that single-row tree windbreaks can reduce wind and modify the microclimate to enhance crop production for Florida growers.     

Planning tree species diversification in Kenya based on differences in tree species composition between farms. I. Analysis of tree uses

Concerns exist about the limited diversity of tree species in agricultural landscapes. Complete tree inventories were carried out on 201 farms from four villages in western Kenya to establish whether significant differences in tree species composition existed between farms, and if so their magnitude and implications for new introductions and plantings. Tree species composition was interpreted to encompass elements of both tree identity and abundance. Tree identity was viewed from both taxonomic and function (e.g. fruit, timber, medicine) perspectives. Novel types of ordination using the Hellinger ecological distance and polynomial Redundancy Analysis indicated wide heterogeneity between farms with respect to tree species composition. For the 12 most prevalent functions of trees, the analyses showed significant differences (p<0.05). Partitioning of variance identified that village location explained much of the differences between farms suggesting that farmers share tree species within villages more than between villages. Differences between farms were assessed on two-dimensional ordination graphs. For five important tree functions, including beverage, charcoal, construction, fodder and medicine, two species dominated the compositional differences. For these functions, diversification can be achieved by village-to-village sharing even in the absence of any new species introductions. A general process to determine the degree of tree diversity at farm and landscape levels and steps to increase it are discussed.     

Growth performance of some multipurpose trees and shrubs in the semi-arid areas of Southern Ethiopia

Growth performances of some multipurpose trees and shrubs have been studied for five years at two locations in the semi-arid areas of Southern Ethiopia. The best performance in terms of rates of survival and growth rates (height and diameter growth) has been attained byAcacia nilotica, A. Cyanophylla, A. seyal, Cassia siamea andProsopis juliflora. Given the ecological limitations of semi-arid areas, growth rates of these species is promising and this indicates that sustainable production system can be realized using proper agroforestry technologies in the semi-arid areas of Southern Ethiopia and similar area types elsewhere.     

Planning tree species diversification in Kenya based on differences in tree species composition between farms. II. Analysis of tree niches.

Concerns exist about the limited diversity of tree species in agricultural landscapes. Complete tree inventories were carried out on 201 farms from four villages in western Kenya to establish whether significant differences in tree species composition existed between farms, and if so their magnitude and implications for new introductions and plantings. Novel types of ordination using the Hellinger ecological distance and polynomial Redundancy Analysis indicated wide heterogeneity between farms with respect to tree species composition of five niches, including homestead, cropland, fallow, woodlot, and external boundary (p ≤ 0.05). Multiple regression analysis confirmed the ordination results using the abundance of dominant species as the response variable. The relationship between location and species composition differed with those of two previous surveys. Methodological differences in sampling intensity, locations and time of sampling between these surveys could have caused the difference. The maps of spatial distribution of compositional types provided in the previous surveys were not confirmed, whereas villages were found to contain several farms with a species composition that was not typical of their village. Meaningful results about the species composition of a landscape should include several farms per village and use a sampling grid finer than 5×5 km².     

Drivers of adoption of eucalypt tree farming by smallholders in Thailand

Eucalypt (Eucalyptus spp.) tree farming is a source of income for many smallholders in developing and emerging countries and critical to the resource supply of many pulp and paper companies. These companies rely on smallholders adopting tree farming, sometimes by offering a contract. This paper reports a study from four regions of Thailand, where smallholder eucalypt tree farming is important, which investigated what characteristics of smallholders were associated with greater adoption of tree farming. A total of 461 eucalypt tree farmers and 171 non-tree farmers were randomly selected and surveyed in these regions, using a door-to-door household survey. A logit analysis corroborated hypotheses about the drivers of adoption. Qualitative analyses were used to inform interpretation of the quantitative results and shed light on the role of eucalypt tree farming in smallholders’ livelihood. Results demonstrate that those with suitable land available are more likely to adopt eucalypt tree farming than others. In addition, perception of land tenure security matters in the adoption of tree growing, but holding a formal land tenure document does not. Adoption of eucalypt tree farming in Thailand is not part of a land use intensification strategy. Instead, eucalypts are used as an alternative crop for low productivity land, on which eucalypts are the most profitable crop. Eucalypt tree farming also gives smallholders an opportunity to diversify their income. In addition, this alternative land use has the advantage of requiring low labour inputs between planting and harvest. This is particularly advantageous for many tree growers who have off-farm income or rely on hired labour for farming their land.     

Growth stress patterns in tree stems

Growth stresses originate in maturation strains, induced in cambial layers during the differentiation and the maturation of new cells, impeded by the mass of the whole trunk. To predict stresses in a stem, one must add successive incremental stresses at successively created points of the growing trunk. Usual measurements of released strains at the surface of a stem do not give the evolution of maturation strains with growth. As the assumption that states that maturation strains are constant since the beginning of secondary growth leads to singularities near the pith, an empiric pattern of variation of maturation strains along the radius is proposed, using observations about relationships between released longitudinal strain and microfibril angle. Furthermore, assuming an elastic, orthotropic behavior law and a cylindrical, sufficiently long stem, residual stresses are computed and discussed.For hardwoods, far enough from the pith, patterns of computed longitudinal and tangential stresses agree with distributions already stated by other authors although these stress components are limited near the pith. Computed radial stresses have lower levels than commonly admitted. On the other hand, stress-distributions in young softwoods are found very different, especially near the pith where the longitudinal component appears tensile and the tangential one compressive.     

Farmer-led approaches to increasing tree diversity in fields and farmed landscapes in Ethiopia

Agroforestry Systems - Increasing tree cover and managing trees better on farms in Ethiopia supports livelihoods and the environment but most tree-planting schemes promote only a few species. This...     

Socioeconomic factors affecting the adoption potential of improved tree fallows in Africa

In many parts of Africa, farmers periodically fallow their land, which is allowing land to lie idle for one or more seasons primarily to restore its fertility. This paper assesses the feasibility, profitability, and acceptability of improved tree fallows, which are the deliberate planting of trees or shrubs in rotation with crops to improve soil fertility. Improved tree fallows are assessed at different stages of intensification, drawing on farmers' experiences in three different settings. In extensive systems where land is plentiful and existing fallows with natural regeneration of vegetation restore soil fertility (southern Cameroon), farmers have little incentive to invest labor in establishing improved fallows. Where population density is higher and fallow periods are decreasing and farmers perceive a decline in soil fertility (eastern Zambia), improved fallows have great potential. In intensive systems where land is unavailable and cropping is often continuous (western Kenya), many farmers find it difficult to fallow land. Even here, there is scope for introducing improved fallows, especially among farmers who have off-farm income. Labor constraints and institutional support were found to greatly influence the feasibility of improved fallows. In intensive systems, low returns to cropping, low base yields, and a high opportunity cost of labor increase the returns to improved fallows. Principal factors associated with acceptability include past perception of soil fertility problems, past use of measures for improving soil fertility, current fallowing, economic importance of annual cropping, and wealth level. Adoption potential may be increased by reducing fallow periods, intercropping trees and crops during the first season, reducing establishment costs, producing higher value by-products, and by encouraging farmers to test improved fallows on high-value crops.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effects of tree species diversity on leaf litter decomposition process in semi-arid Mediterranean oak forests

European Journal of Forest Research - Many studies have been conducted on the effects of changes in plant diversity and species composition on ecosystem functioning and plant productivity due to...     

Influence of fly ash mixtures on early tree growth and physicochemical properties of soil in semi-arid tropical Alfisols

The beneficial effects of planting mixtures comprising of fly ash at the rate of 66%, 33% and 17% by soil volume were assessed for the early growth of two economic tree species, teak (Tectona grandis) and leucaena (Leucaena leucocephala) in rainfed Semi-Arid Tropical (SAT) Alfisols in India. Measurements of tree growth were made at six monthly intervals over a 3-year period. Fly ash at 66% by soil volume of the planting pit significantly increased the diameter of teak at breast height (dbh). In leucaena, application of fly ash at 17% by soil volume was found to be effective in increasing dbh during most of the study period. Changes in soil physicochemical properties (bulk density, water retention at 0.033 and 1.5 MPa, profile moisture content, pH, soluble salt content and organic carbon) were simultaneously studied. Among these soil properties, plant available water (PAW) and organic carbon (OC) contents explained variations in diameter at breast height (dbh) in teak during most of the sampling period, while none of the soil properties significantly explained dbh in leucaena. The highest dose of fly ash applied (66% by volume) decreased bulk density (BD) and increased PAW in teak and to an extent in leucaena during the first 2 years of tree growth. Higher profile moisture content was noted in pits treated with 66% fly ash during the dry period of November (after the end of seasonal rainfall which occurred from June to October) during the first and second year after application. An erratum to this article can be found at     

Land-use legacy of historical tree harvesting for charcoal production in a semi-arid woodland

Historical processes may have longer lasting effects in arid forest and woodlands because of slow rates of succession. We investigated the influence of historical tree harvesting upon contemporary spatial dynamics of pinyon-juniper woodland in the western United States. Despite intensive and widespread harvesting of woodland by the charcoal industry during the late 19th century, the role of afforestation has seldom been addressed as a potential mechanism for the dramatic expansion of pinyon-juniper woodlands over the past century. Spatial models of disturbance processes are one way to ascertain effects of such historical influences. We developed a process-based spatial model to estimate the historical tree harvest pressure according to a parsimonious set of rules and constraints. The model used a convection-diffusion approach that incorporated the influences of topography, transportation, and mining production. We used a combination of field-surveyed, archaeological, historical, and GIS data sets to calibrate, validate, and compare the alternative mathematical models. Model results were consistent with the historical harvest evidence (AUC > 0.66), with high harvest intensity closer to the mining districts, quickly decreasing at the maximum distance of influence. Performance was improved by including the local terrain. Harvesting initially showed radial patterns emanating from the significant mining districts, and then gradually expanded northward with development of the railway system. Our spatial modeling approach provides a means to assess the pattern and magnitude of historical tree harvesting in semi-arid woodlands. The general approach can be applied to explore the importance of other historical disturbance and cultural processes, whose effects may no longer be evident, in forests and woodlands worldwide.     

Implications of national land legislation and customary land and tree tenure on the adoption of alley farming

Increasing population in the forest zone of Cameroon has led to reduction of fallow periods and to diminution of per capita cropping land area. Alley farming is a promising technology for the zone; however, its large scale adoption depends on host of factors of which an important one is tree and land tenure. For this reason, a study was conducted in 1990 to determine implication of national land legislation and customary land and tree tenure on the adoption of alley farming in the forest zone of Cameroon.Despite national laws purposing to regulate land and tree use, ownership rights to land and trees are largely determined by customary tenure rules. According to the forest zone customs, land is passed on from father to son when the father dies. Owners of inherited lands have full rights on lands and these rights are rarely revoked. Women do not own lands but are allowed to crop any piece of their husband's land as long as they stay married. Despite the lack of land ownership, women might still readily adopt alley farming because they are primarily concerned about food crop production and the amount of land to be given to their sons in the future.Study funded by the International Livestock Center for Africa (ILCA), Addis-Abeba, Ethiopia, and technically supervised by the Land Tenure Center (LTC), University of Wisconsin, Wisconsin USA.     

Ethnobotanical study of forage/fodder plant species in and around the semi-arid Awash National Park,Ethiopia

We undertook ethnobotanical study of forage/fodder plant species used by the Afar and Oromo （Kereyu and lttu） Nations in and around the semi=arid Awash National Park （ANP）, Ethiopia. The study aimed at investigating and documenting indigenous knowledge （IK） on forage/fodder plant species and threats to their survival. Ninety-six in= formants between 20 and 80 years old were selected using prior informa- tion. Data were collected using semi-structured interview, guided field wail discussion and field observation. Preference ranking, Jaccard＇s coefficient of similarity and priority ranking were used for data analysis. One hundred twenty-six forage/fodder species of 90 genera and 43 fami- lies were collected in the study area. More than 88% of the species were reported with their vernacular names, where 68% were reported by the Afar Nation and 70% by the Oromo Nation. Family Poaceae was repre- sented by 25 species （20%）, followed by Fabaceae 18 （14%）. Preference ranking for the most preferred forage grasses as perceived by key informants revealed that Chrysopogon plumulosus was the most important forage/fodder species. Overgrazing was the major threat in the study area, scoring 22%.     

半干旱地区主要造林树种蒸腾耗水特点的研究进展

文章对半干旱地区主要造林树种杨树、油松、樟子松蒸腾的日变化和生长季变化及影响因子和各树种的耗水量进行了探讨,认为3种树种的蒸腾强度日变化和生长季变化以单峰型为主,蒸腾强度最大的是杨树。影响蒸腾强度的因子主要有光照强度、气温、相对湿度、土壤水分。