Journal of the Drylands 1(1), 2006

Journal of the Drylands 1(1) (full issue)

Special Issue "THE CHALLENGE OF DRYLAND FOREST REHABILITATION IN ETHIOPIA, VOLUME 1: Ecology and rehabilitation techniques"

The ecology and silviculture of dryland forest rehabilitation in Ethiopia

Special issue - introduction

The role of forest rehabilitation in poverty alleviation in drylands

Though poverty exists also in urban areas, it is perhaps most prevalent in rural areas. Of all rural areas, it is the drylands that experience destitution the most. This is so because droughts are the most frequent and intense in these areas, though because of global warming, these vagaries of nature are now globally more common. Forest rehabilitation helps mitigate the impact of drought for several reasons. Afforestation attracts more rain and improves the microclimate of a dry area. It also decreases both wind and rain erosion. It builds up soil organic matter, increases soil fertility, moisture holding capacity and resistance to erosion. Consequently, both crop and animal production increase in good years. The impact of droughts also decreases making some production possible even in bad years. The improved woody biomass and animal and crop production provide cash income to both farmers and pastoralists. This enables them to buy food when droughts strike. It also enables them to send their children to school and to obtain medical care. Afforestation, therefore, helps alleviate poverty directly by yielding cash, and indirectly by improving both crop and animal production.

Comparative floristic study on Mt. Alutu and Mt. Chubbi along an altitudinal gradient

A comparative study of the dryland forest floristic composition on Mt. Alutu and Mt. Chubbi along an altitudinal gradient was performed in the main rift valley of central Ethiopia. Seventy-one 20 m x 20 m sample plots, thirty-seven from Mt. Alutu and thirty-four from Mt Chubbi were selected systematically and presence/absence of all plants in the stands were recorded. Cover-abundance (%) value for trees, shrubs, and herbs was estimated. In addition trees and shrubs were counted. Environmental factors including altitude, slope and aspect were measured. The vegetation data from both mountains were merged and analysed using the program SYNTAX. A utility program was employed to analyse species diversity. Eight homogenous clusters of stands were recognized. The resulting clusters were interpreted as community types and given provisional names after two or three dominant species. The clusters of the stands were compared for their averaged environmental factors using Tukey's family error rate test. The clusters of sample plots were found to show the highest degree of contrast due to variation in altitude. In the present study sites altitude and slope to a lesser extent were found to be the major determinants of vegetation variation, whereas, aspect was less important. Recovery of the dryland forest vegetation in the area seems to be possible if appropriate land use systems and area closure approach are applied.

Water and nutrient relations of selected indigenous and exotic tree species of Ethiopia and the implications for their use in land rehabilitation

Considering the need for planting trees to rehabilitate dry and nutrient deficient sites in Ethiopia, this paper provides an overview of the water and nutrient relations of three indigenous deciduous tree species of Ethiopia: Cordia africana Lam., Croton macrostachyus Del. and Millettia ferruginea (Hochst.) Baker and two widely used exotic tree species: Eucalyptus camaldulensis Dehnh and Eucalyptus globulus Labill. Glasshouse experiments show that the deciduous species grow comparable to the eucalypts when sufficient moisture is available. Growth of the eucalypts exceeds that of the deciduous species under prolonged water stress. However, seedlings of eucalypts are more vulnerable to severe drought compared to the deciduous species. Leaves of C. macrostachyus and C. africana transpire more water and plants have lower water use efficiencies compared to M. ferruginea and the eucalypts. Stomatal closure, leaf shedding, allocation of more biomass to roots and leaf re-orientation are some of the identified mechanisms employed to cope with water stress depending on the species. Whereas the deciduous species accumulate more nitrogen (N) and phosphorus (P) compared to the eucalypts, the latter show superior growth in N and P-deficient soils. M. ferruginea uses N efficiently. C. macrostachyus and C. africana produce extensive lateral roots that may deplete surface soil nutrients. However, field studies show positive impacts on soil nutrients due to their short leaf lifespan, high leaf nutrient content and rapid decomposition to release nutrients. E. camaldulensis produced extensive roots with negative impact on adjacent croplands. The implications of these findings for using the studied species in land rehabilitation as components of agroforestry or in plantations are discussed.

Forest regeneration without planting: the case of community managed forests in the Bale mountains of Ethiopia

The participatory forest conservation approach adopted by the forest dwellers associations, hereafter referred to as user groups, in Adaba-Dodola forest priority area has substantially reduced illegal utilization and further degradation of the forests. However, the forests were already degraded before they were handed over to the user groups due to illegal logging. Therefore, to make the conservation efforts of the user groups more beneficial there is a need to improve the production potential of the forests. The present study assessed the potential of the forests to be transformed into semi-natural productive forests based on potential crop tree focused management. A diagnostic survey conducted in the year 2003 in the forests managed by the three user groups revealed that more than 30 % of the total area had a sufficient number of potential crop trees per hectare to start the transformation process. In this area forest rehabilitation seems to be feasible without replanting. However, a rotating grazing system has to be introduced to enable the establishment of highly palatable species like Hagenia abyssinica (Bruce) JF Gmel.

Ecological restoration and church forests in northern Ethiopia

Disturbance of ecosystems by humans is of all times. The extent, however, has increased drastically over the last decades, leading to many degraded areas. Restoration of these areas is highly needed and should be based on sound knowledge of successional pathways of existing ecosystems and how people can tune-in into these pathways by directed restoration activities. Conceptual frameworks are available to help understand the process. We try to use these for developing restoration activities for church forests in northern Ethiopia. For the church forests studied we may conclude that (a) diversity and forest area protected are important, (b) each church forest fragment has its own unique species composition, (c) they harbour good wood stock compared to some of the natural state forests, (d) population structures suggest at least two major types of plants: species able to regenerate in the forest understory and species with difficulties to reproduce, (e) church traditions to conserve forest resources: tree seeds collection, traditional medicine and contemplation are permitted, while collection of fuel wood, construction wood and fodder are forbidden for the community, and (f) there is a high respect and trust of the local community with respect to the church organisation and their activities and rules. These results can be used as points of departure for restoration of the church forests themselves as well as for restoration of areas surrounding these forests.

Effects of fencing and ground cultivation on natural regeneration of Boswellia papyrifera in Metema Wereda, Ethiopia

Dryland woodlands have significant economic and ecological functions in Ethiopia. Boswellia papyrifera woodland provides commercial frankincense in which over thirty specialized enterprises are currently involved. Scarce natural regeneration is more serious in B. papyrifera woodlands and urgent action is needed if sustainable utilization of the species is to be assured. A factorial experiment in a completely randomized block design consisting six treatment combinations of fencing and ground cultivation has been set up with the objective of improving natural regeneration. Ground cultivation seems to affect the natural regeneration negatively. Seedling height does not show significant difference among treatments (p<0.939). Apparently, although not statistically significant (p<0.304), fencing appears to be beneficial in facilitating regeneration recruitment and maintaining healthy seedlings. Further inspection to the data disclosed that majority of seedlings are growing closer to the nearest mother trees. About 78% of the B. papyrifera regeneration was found nearer than 2m from the nearest mother trees. This pattern of regeneration triggered us to further investigate the phenomenon, and eventually it was discovered that root sucker was the major origin of natural regeneration of B. papyrifera in the study area. It should be mentioned however that the amount of regeneration is extremely low (50 seedlings/ha) and needs further research to initiate more root suckers and improve overall regeneration.

Agroforestry practices and tree planting constraints and opportunities in Sekota district of Amhara Regional State

Informal Survey was conducted in Sekota district in the year 2000. The objectives of the surveys were to describe agroforestry practices, to characterize major tree species in the district, and to identify and prioritize major constraints related to tree planting. To conduct the informal survey, the district was first divided in to two homogenous target groups (TGs): TG-I and TG-II. To identify target groups, criteria like vegetation cover, types of crops grown, soil type, livestock production, etc were used. In the survey, PRA tools like individual and group discussions, and transect walk and observations were employed. A total of 20 and 12 different tree/shrub species were identified in TG-I and TG-II, respectively. The common agroforestry practices at both target areas are scattered trees on farmlands, along rivers and around home gardens. Among the agroforestry practices, the most widely practiced in TG-I is leaving deliberately of naturally grown trees on cropland. Farmers prefer to have zizyphus spp. on croplands as compared to other tree species, as it is easy to manage and does not have considerable negative impact on yield of the crops grown beneath the tree. In TG-II, farmers are not willing either to plant or to leave trees on croplands except Zizyphus though they know some benefits of trees like shading. Farmers believe that trees on cropland serve as the home for birds, which damages their crops. In both TGs farmers, moisture stress, theft, population pressure, termite, woodborers and livestock are the most important factors that affect tree planting practices and /or that contribute for forest resource degradation. Due to moisture stress in the area the survival of most seedlings were very low. Therefore, it is important to gear research to select the best adaptable species under moisture stressed condition and also that are preferred by most farmers. Moreover developing appropriate moisture-conserving techniques that improve the survival of most of the seedlings are necessary.

Survival of planted African wild olive seedlings in northern Ethiopian exclosures depends on planting season and shrub cover

Vegetation such as shrubs and grass tussocks is usually considered to present a competitive barrier for seedlings planted in reforestation programs. However, shrubs also have the ability to facilitate the establishment of seedlings of woody species under their canopy, especially in ecosystems under high abiotic stress. In 2003, an experiment was set up in exclosures in northern Ethiopia to test the use of shrubs as nurse plants for reforestation. Seedlings of African wild olive Olea europaea ssp. cuspidata were planted in three microhabitats: (1) bare soil between shrubs, (2) under individuals of the dominant thorn shrub Acacia etbaica, and (3) under individuals of Euclea racemosa, a fruit-bearing evergreen shrub which supports the majority of naturally established olive seedlings. Experimental seedlings were planted during the short spring rains (March&#8211;April) and long summer rains (June&#8211;September). The present study reports early seedling survival, i.e. until the end of the first winter (February 2004). Olive survival was significantly higher when planted under shrub cover as compared to open areas, especially under Euclea canopies, but spring rain enrichment planting showed high mortality in all three microhabitats due to drought stress soon after planting. Reduction of solar radiation by shrub canopies and thus control of soil-water evaporation and seedling transpiration most likely controlled the observed facilitation. We conclude that planting under shrubs during aboveaverage summer rains, as occuring during La Niña episodes, may have important advantages in assisting natural regeneration of dry Afromontane vegetation, and that conserving the pre-existing shrubs at the same time reduces the risk of erosion and keeps levels of indigenous biodiversity high.

Expediting ecological restoration with the help of foster tree plantations in Ethiopia

The biophysical degradation of land and its formidable impediment to sustainable rural and economic development in Ethiopia has been discussed for several decades. What is required is to develop and implement scientific solutions to the problem. Obviously, in a country like Ethiopia, where vast degraded ecosystems and a rapidly growing human population occur, and where still all livelihood and economic development emerge from agriculture and biological resources, the restoration of the productive capacity of the degraded ecosystems will have a valid and crucial role to bring about sustainable development. A key question, however, is how to successfully and quickly restore the degraded landscapes in the country. An ecological management tool that is receiving considerable attention in recent years for enhancing ecological restoration in the tropics is the use of tree plantations as foster ecosystem. (Re)forestation of heavily degraded lands with fast growing tree species has been shown to expedite the recovery of soil fertility as well as the rehabilitation of a diverse native flora and fauna faster than sites that are left bare or unplanted. In this paper information is collected by reviewing primary literature. Ample evidence is presented from wide geographical areas, both from outside and from inside Ethiopia, to substantiate this potential of tree plantations. It is also known that several factors related to the design and management of plantation forests affect their usefulness in restoration ecology. These issues that require special attention in using tree plantations in restoration ecology are discussed in detail. The paper concludes that, supported with sound silvicultural management, tree plantations can be employed as one effective method capable of reversing soil, biomass and biodiversity degradation, while providing diverse socio-economic services.

Population structure and morphology of the frankincense tree Boswellia papyrifera along an altitude gradient in Eritrea

In Eritrea, the frankincense tree Boswellia papyrifera is a multipurpose plant. Human induced factors such as land clearing for agriculture, overgrazing by livestock and overtapping of resin are threatening its distribution. Against this background, a study was carried out to investigate the species current population structure and tree morphology in five Boswellia areas along an altitude gradient (range 800 - 2000 m a.s.l.). In each area sample plots of 20 by 20 m were inventoried; a total of 144 plots were studied. The population structure analysis showed that there was an overall absence of juvenile trees between 1 and 8 cm DBH. Natural regeneration was found only in two areas in which trees were not tapped for resin and inaccessible to livestock. Tree height, DBH, crown depth and crown diameter decreased with increasing altitude. In the lowland areas trees were about two times taller (10 to 12 m) with deeper crowns than those growing in the highland areas. This indicates that the species grows better in the warm moist lowlands than in the moist and dry highlands. To promote natural regeneration and seedling establishment in existing Boswellia woodlands control measures are needed including proper tapping procedures and controlled grazing.

Guidelines for authors

POLICY AND GUIDELINES IN WRITING ARTICLES IN JOURNAL OF THE DRYLANDS