Fire and grazing in subalpine heathlands and forests of Bale Mountains, Ethiopia

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https://hdl.handle.net/20.500.12703/84
Fire and grazing in subalpine heathlands and forests of Bale Mountains, Ethiopia. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2013:14

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    Fire and grazing in subalpine heathlands and forests of Bale Mountains, Ethiopia
    (Institutionen för skogens ekologi och skötsel, Sveriges lantbruksuniversitet, 2013-01-25) Johansson, Maria U
    Pastoralists frequently depend on fire to produce forage for their livestock, but traditional burning is often banned, despite being essential for livelihoods and ecosystem maintenance. In the subalpine heathlands of Bale Mountains traditional fire management is still practiced. This offered a rare opportunity to analyze fire ecology and traditional fire knowledge in a fire-managed shrub system. My aim was to disentangle the interactions between livestock, fuels and vegetation in the heathlands and the forests below, through a combination of experimental and observational studies. My results show that the subalpine forests had a low fire potential due to lack of good surface fuels. In contrast, the Erica-dominated heathlands produced highly flammable fuel complexes. Here anthropogenic burning resulted in a regime of high-intensity fires with an average fire return interval of ~10 years. However, the grazed heathlands were non-flammable the first ~4 years post fire, due to lack of fine dead fuels and a discontinuous fuel bed. This helps create a patchy landscape in which young vegetation patches act as fire breaks, limiting the extent of subsequent fires. Interviews with pastoralists revealed three objectives for burning: to improve pasture, to remove an insect pest and to reduce livestock loss to predators. The informants were well aware of the critical relations between fuel structure, weather and fire behaviour, showing intimate knowledge of fire as a management tool. Cattle exclusion had relatively little impact on the vegetation and fuel development in both heathland and forest. Cattle browsing, however, dramatically altered the competitive balance between the two co-dominant shrubs E. arborea and E. trimera, favouring E. arborea. In the heathland the return to a flammable state was somewhat faster when cattle were excluded, but in the forest a denser field layer developed which did not increase flammability. Vegetative regeneration dominated after both fire and mechanical disturbance, despite a large seed bank in the top 10 cm of soil in both heathland and forest sites. In heathland sown Hagenia tree seedlings grew extremely poorly, probably due to unsuitable soil conditions. Neither did Hagenia seedlings survive in the forest zone, except in exclosures in large canopy gaps, showing that cattle exclusion alone is not sufficient for tree regeneration. Thus, the present division between heathland and forest is stabilized by the lack of fire potential in the forest and lack of potential for tree expansion into heathland. My results suggest that fire exclusion is not a viable option for the heathlands. It would destroy the pasture quality and is also unlikely to succeed, since huge tracts of highly flammable vegetation would soon develop. To successfully protect these ecosystems and pastoralist livelihoods, I recommend that a joint management plan is created that allows burning, but with defined prescriptions with regard to both fire intervals and fire weather.
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