Management Interventions to Assist Restoration of Degraded Dry Afromontane Forest N. Ethiopia
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Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 SUMMARY Tropical deforestationcontinues to threaten biodiversity and forest-based livelihoods. In thiscontext, management of the remaining forests is becoming an increasinglyimportant component of sustainable land management options. This isparticularly evident in the dry afromontane regions of Ethiopia where there isnear to complete biomass dependence of the population against a background ofcontinuous expansion of agriculture. Moreover, the remaining forests arechallenged by resource limitation due to continuous degradation and drought,and associated loss of biodiversity. The challenge is to identify managementinterventions able to sustain their existence and ability to provide ecosystemservices.A common goal forrestoration of any natural ecosystem is to recover autogenic processes to thepoint where assistance from restorationists is no longer needed. Therefore, themajor challenge to sustainably manage degraded afromontane forests is torestore the forest habitat and microclimate by facilitating naturalregeneration or performing enrichment planting of the existing forests species.In addition, silvicultural treatments to improve resource allocation, growthand productivity, have seldom been integrated in the management of Ethiopianforests, particularly in natural afromontane forests. This research aims atcontributing with observational and experimental work to the conservation andrestoration of dry afromontane forests. The study was conducted in DesaaForest, the emblematic last large natural dry afromontane forest of northernEthiopia. The observational work focussed on assessing the soil, vegetation,and traditional use of the forest by local communities and the experimentalwork evaluated the effects of fencing and silvicultural treatments on survivaland growth of natural regenerated seedlings, planted saplings, and the remainingtree population in an ambitious long-term experimental site. The work included a large variety ofmonitoring techniques ranging from ethnobotanical household interviews todendrometer measurements in permanent plots. Desaa Forest, as most ofthe forests in the semi-arid tropics has a large potential of providingprovisioning, regulating and cultural services to local communities.Integrating local communities needs in forest management is an essentialelement in striving towards sustainability of the forest. One option of doingthis is by providing economic alternatives. An ethnobotanical study wasconducted to investigate the variety of medicinal plants occurring in theforest, their uses and conservation by people living in and around the forest. Information was collected usingsemi-structured interviews and focus group discussions in seven villageslocated close to and inside the forest. In the area, local communities useforest based plants (74.4 % trees and shrubs) as remedies for human and livestocktreatments. Thirty-four medicinal wild plants used as cure for 35 human andlivestock ailments were documented. It was observed that the practice ofcultivating medicinal plants is very poor in the study area, which may be dueto sufficient wild availability of medicinal plants thus far. Focus should be given to domestication and insitu conservation of the existing medicinal plants and the associatedindigenous knowledge, which are both at risk. This may offer the people analternative income-generating activity and contribute to the creation of aforest friendly community in Desaa Forest. Anthropogenic pressuresstrongly hamper natural regeneration of the tropical dry forests, which bringsthe continuity of the forests at stake. The experiment in Desaa Forest allowedstudying the growth establishment, survival and growth response of naturalregeneration in response to four silvicultural treatments, Pruning (P),Thinning (T), Pruning and Thinning (P&T), and No treatment (C), combinedwith two levels of fencing, with and without fencing, using a split plotarrangement. Periodic measurement (Dec. 2009 Jan. 2013) of seedlingregeneration, survival and growth (root collar diameter and height) wereundertaken in 5 x 5 m plots established inside every 40 x 40 m treatmentplot. Fencing improved survival ofnatural regeneration by 21 %. The response could have been stronger had it notbeen for Olea europaea whichmaintains its root stock even under grazing pressure. Olea europaea dominates the regeneration profile with 46.8 %,other 19 species covering 0.2 to 9 %.Juniperus procera was found to have a serious problem with naturalregeneration though performs well in enrichment plantings. Fencing has broughta significant contribution to height growth of regenerating seedlings with meangrowth of 0.065 ±0.011 cm cm-1 yr-1 for fenced and -0.002±0.015 cm cm-1 yr-1 for unfenced plots. Though it isclearly seen that fencing has a strong impact on relative height growth ofseedlings, it is much amplified when combined with silvicultural treatments.The P & T treatment has brought a negative growth in relative height ofseedlings without fencing (-0.005 ± 0.23 cm cm-1 yr-1). In general, from the overall trend, withfencing, silvicultural treatments have the potential to bring an increase inmean height growth. Fencing did not bring any significant change in diametergrowth of seedlings whereas treatments had a marginal effect on their diametergrowth. Performanceof planted seedlings in a forest restoration process may vary widely betweendifferent establishment techniques, with important impact on the success offorest restoration. Enrichment planting is one promising technique of forestrestoration where natural regeneration is assumed insufficient. In our experiment,we tested planted Olea europaea L.subsp. cuspidata, Juniperus procera, and Dodonaea angustifolia seedlings fortheir survival and growth under three levels of natural forest cover and withor without artificial shelters. A total of 72 one-year-old seedlings of eachspecies were monitored over 30 months (July 2010February 2013). All plantedspecies showed good survival rates averaging 68 %, with a slightly higher valuefor Juniperus procera (72 %).Artificial sheltering improved overall survival significantly by 18 %, in caseof Olea even by 31 %. Better diameter growth was registered withlow natural canopy cover (0.233 ± 0.014 cm cm-1 yr-1),with Juniperus achieving thestrongest growth, followed by Olea andDodonaea. Olea and Juniperus were significantlydifferent from Dodonaea concerningtheir relative height growth, with Olea attainingthe strongest growth (0.2 ± 0.02), followed by Juniperus (0.15 ± 0.023) and Dodonaeathe weakest (0.057 ± 0.026 cm cm-1 yr-1). Artificialsheltering offered a significantly stronger relative height growth (0.2 ±0.023) than without artificial shelter (0.075 ± 0.023). Olea achieved significantly higher relative height growth withartificial shelter (0.31 ± 0.03) followed by Juniperus (0.17 ± 0.033) and Dodonaea(0.12 ± 0.037). From this comparative study of planted seedlings, we can seethe variation in survival and growth among habitats differing in canopyopenness and artificial shelter with interesting implications for futureenrichment planting schemes. In addition toanthropogenic factors, tropical dry forests are challenged by high potentialevapotranspiration combined with limited water resources, for which specificmanagement interventions could be needed to sustain their existence. In thiscontext common management practices like pruning and thinning may not onlyincrease the commercial quality of the standing timber resource, but are alsoimportant means to regulate access to light and water as to improve resourcedistribution, microclimate, growth and productivity of the ecosystem. Wecompared the effect of four silvicultural treatments, Pruning, Thinning,Pruning and Thinning, and No treatment, combined with two levels of fencing,with and without fencing on the growth of individual trees and stands. Periodicmeasurement (Dec. 2009 Jan. 2013) of height and diameter growth of trees wasundertaken using calipers and dendrometers over a period of three years. Onaverage 12.3% of monitored stems disappeared from the forest, mainly because ofillegal logging, especially (46 %), in the unfenced plot with dense vegetation.Both height (H) and diameter at breatsheight (DBH) growth were significantlyaffected by fencing treatment where there is a net decrease in height and anincreased DBH growth in unfenced plots and an increase in height growth infenced plots. Silvicultural treatments did not bring significant difference inboth height (H) and diameter at breats height (DBH) growth though in both casesthere is an indication that the combined application of pruning and thinninghave a trend towards a positive response with time. In general, fencing with some level of pruning and thinningprovides relatively safe sites for seedlings to establish and grow stronger. Atleast temporary exclosure of areas in regeneration during a period of 5-10years has to be considered as part of a future management plan, creatingprotected restoration areas inside the forest. This would temporary decreasethe available forest area for some ecosystem service provision to communitieswith a few percent of the total area, but would guarantee continued provisionof forest ecosystem services over the longer term. The problematic regenerationof J. procera still needs furtherresearch on site specific seed, germination characterstics, and large scaleenrichment scheme. In dry areas where seedling establishment is constrainedmainy due to moisture stress, the possibility of manipulating the forest canopyand use of artificial shelters would help in successful establishments of plantedseedlings. Medium levels of silvicultural treatments have showes a positiveeffect on growth of seedlings and trees though it will need time to see itseffect very clearly. These will also have a potential to improve the foresthealth and productivity there by positively influencingflowering, seed production and regeneration. We concluded that, in the courseof our four year experiment, 1) trees persisted but hardly grew; 2) fencingbrought positive effect on survival and growth of both seedlings and trees; 3)natural regeneration was poor especially for J. procera; 4) plantedseedlings were able to survive and grow given adequate protection (fencing andshelter); 5) the overall slowness of ecological processes in these dry forestscalls for much longer scientific attention to monitor the effect ofsilvicultural treatments. It is highly recommended to maintain the establishedexperimental site in Desaa Forest as a permanent observatory to investigateslow-acting ecological processes and changes, and for evaluating theconsequences of rare events, because this kind of basic ecological informationis commonly missing for the dry afromontane forests of the tropics.Finally, it is recommended to increase the national and internationalprotection status of Desaa forest, like that of UNESCO biosphere reserve forwhich an application is being processed, to implement this conservation statuswith a participatory management plan where the ideas and recommendations fromthis work could be part of.