Reforestation of the Ethiopian Highlands using mixtures of indigenous tree species (CARBOPART-II)
Background of the Project
In Ethiopia, large areas of land either have very sparse shrub/tree vegetation or are degraded communal grazing land, which may be reforested to stop erosion, increase carbon sequestration and provide sustainable income from wood products. These afromontane forests in the highlands of Ethiopia have very high soil C stocks that are the results of 1000s of years of accumulation and are probably a result of the high species and trait biodiversity of these sites. However, removal of the tree cover and conversion to crop or grassland results in loss of ca 60% of the soil C stores within 50 years. Associated with the loss of soil organic C is a high loss of soil fertility due to loss of N and organic P stores. Replanting with Eucalyptus leads to a recovery of soil C stocks, but not the level of the original natural forests. Exclosure however does not lead to rapid recovery of soil C. Modelling results suggest that even if natural forest cover and structure are restored recovery of soil C stocks may take 100 to 1000 of years.
Afforestation programs are needed to avoid further erosion, meet the local demands for fuelwood and timber and address the climate goals within the REDD+ framework. As a result, the current Ethiopian REDD+ implementation strategies focus on reforestation of grass land and shrub land areas, enhancing agroforestry practice with indigenous species and sustainable management of the remaining natural forests (Arbonaut, 2016; MEFC, 2017). Any forest recovery program should be based on tree mixtures to maintain ecological stability and should include sustainable management as the demand for fuel wood and timber is high and still increasing due to the fast growing population. Ethiopian Government has set a target to reforest 7 million ha by the year 2030. The aim is to decrease current CO2 emissions (53 Mt CO2 in 2010) mainly due to land-use change. Without this intervention emission are expected to increase to 88 Mt CO2 by 2030. Afforestation schemes require that re/afforested areas are initially protected from grazing. Experience from establishment of exclosures has shown that protection from grazing can be obtained in co-operation with local farmers if the afforested or protected sites deliver some form of ecosystem service such as fodder or honey production delivering an intermediate income stream. Considering these fundamental issues, the current project frame-works have been initiated to develop the foundation for a large scale afforestation scheme using herbaceous pre-cultures, nurse trees and mixtures of indigenous Ethiopian tree species.
The overall project goal of the project Carbopart 2 is to lay the foundation for large scale reforestation in Ethiopia. We will use the knowledge gained in the previous project (Carbopart 1) to develop large scale reforestation schemes using ecologically stable tree mixtures as opposed to non–ecologically stable monocultures. Further we will develop a program based on ecological forest monitoring, forest growth modelling and forest planning/management to establish sustainable harvesting routines based on species mixture thinning and regeneration options. The established forest sites will be used for educating farmers in sustainable forest management with the goal to (i) avoid erosion and thus loss of soil fertility, (ii) ensure continued supply of fuel wood and other timber and non-timber products, and thus (iii) generate income and (iv) to promote further planting programs within REDD+ program activities.
A central common garden demonstration site (Koga) and two regional plantation sites (Bezewit and Worken) have been selected on the basis of soil quality, altitude and land degradation representing the landscape of the region. Three reforestation sites correspond to three major land-forms of the Amhara Regions viz. low land of the Blue Nile basin, degraded grazing land and high mountain:
1. Koga (Latitude: 11°24ʹ25.94ʺN, Longitude: 37°05ʹ22.85ʺE): Irrigated, lowlands site with good growing conditions, can be used as Central demonstration plots for different indigenous tree species. The site allows us to observe the growth characteristics of the different species.
2. Bezawit (Latitude: 11°34'10.32"N and Longitude: 37°24'39.74"E): Severely degraded and eroded site, heavily grazed and rocky landscape. Challenging for landscape restoration and management approaches.
3. Worken (Latitude: 11°50ʹ14.4ʺN, Longitude: 38°05ʹ29.3ʺE): Large surface (several hectares) at top of the hill, covered by grass and few shrubs species, suitable for highland tree species.
Forest establishment is being carried out using pre-cultures of herbaceous species such as wheat (Triticum aestivum) or vetches (Vicia sp.), fast growing nurse tree species and mixtures of target tree species. The objectives of this system is to produce a constant intermediate harvest in the form of fodder for stock feeding from the pre-culture herbaceous species, and a woody supply from the thinning of the fast growing nurse tree species, allowing the development of the target tree mixtures. The mixtures will be designed using tree trait data obtained in Carbopart 1. This will include traits such as growth rate, light requirements, position in ecological succession, leaf and root morphology and chemistry, symbiotic associations. At the sites, the development of the tree stands will be followed to measure productivity of the mixtures and individual species, and restoration of soil fertility and SOM stocks.
For the work a number of tree species have been selected based on tree traits (i.e. fast/slow growing, N-fixing, and endangered species etc.) and availability the targeted species are: Acacia albida, Acacia abyssinica, Podocarpus falcatus, Olea africana, Cordia africana, Milletia ferruginea, Hygenia abyssinica, Prunus africana, Albizia gumifera, and Juniperus procera. Protection of planted seedlings and survival rate are the most challenging issues in Ethiopia with its’ huge livestock population. Construction of fences at the plantation sites and protection barrier for individual seedling are essential against animal browsing.
Training: Within the framework of the Bahir Dar University new agroforestry program, staff form BOKU will make an active contribution to teaching and program development. This will lead to the development of local forest managers trained in concepts and practical skills of multipurpose mixed forest management. It is planned that BOKU will also offer short courses on forest management to ensure the long term sustainable management of the established forest sites and the long term benefits of reforestation.