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  • 1. Gil-Romera, Graciela
    et al.
    Adolf, Carole
    Benito, Blas M.
    Bittner, Lucas
    Johansson, Maria U.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Grady, David A.
    Lamb, Henry F.
    Lemma, Bruk
    Fekadu, Mekbib
    Glaser, Bruno
    Mekonnen, Betelhem
    Sevilla-Callejo, Miguel
    Zech, Michael
    Zech, Wolfgang
    Miehe, Georg
    Long-term fire resilience of the Ericaceous Belt, Bale Mountains, Ethiopia2019In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 15, no 7, article id 20190357Article in journal (Refereed)
    Abstract [en]

    Fire is the most frequent disturbance in the Ericaceous Belt (ca 3000-1300 m.a.s.l.), one of the most important plant communities of tropical African mountains. Through resprouting after fire, Erica establishes a positive fire feedback under certain burning regimes. However, present-day human activity in the Bale Mountains of Ethiopia includes fire and grating systems that may have a negative impact on the resilience of the ericaceous ecosystem. Current knowledge of Erica-fire relationships is based on studies of modern vegetation, lacking a longer time perspective that can shed light on baseline conditions for the fire feedback. We hypothesite that fire has influenced Erica communities in the Bale Mountains at millennial time-scales. To test this, we (1) identity the tire history ot the Bale Mountains through a pollen and charcoal record from Garba Guracha, a lake at 3950 m.a.s.l., and (2) describe the long-term bidirectional feedback between wildfire and Erica, which may control the ecosystem's resilience. Our results support fire occurrence in the area since ca 14 000 years ago, with particularly intense burning during the early Holocene, 10.8-6.0 cal ka BP. We show that a positive feedback between Erica abundance and fire occurrence was in operation throughout the Lateglacial and Holocene, and interpret the Ericaceous Bolt of the Ethiopian mountains as a long-term fire resilient ecosystem. We propose that controlled burning should be an integral part of landscape management in the Bale Mountains National Park.

  • 2.
    Johansson, Maria U.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Frisk, Carl A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nemomissa, Sileshi
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Disturbance from traditional fire management in subalpine heathlands increases Afro-alpine plant resilience to climate change2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 7, p. 2952-2964Article in journal (Refereed)
    Abstract [en]

    Species are often controlled by biotic factors such as competition at the warm edge of their distribution range. Disturbances at the treeline, disrupting competitive dominance, may thus enable alpine species to utilize lower altitudes. We searched for evidence for range expansion in grazed, fire-managed Ethiopian subalpine Erica heathlands across a 25-year chronosequence. We examined vascular plant composition in 48 plots (5x5m) across an altitudinal range of 3,465-3,711m.a.s.l. and analyzed how community composition changed in relation to increasing competition over time (using a Shade index based on Erica shrub height and cover) and altitude. Species habitats and altitudinal ranges were derived from literature. Time since fire explained more variation (r(2)=.41) in species composition than altitude did (r(2)=.32) in an NMDS analysis. Community-weighted altitudinal optima for species in a plot decreased strongly with increasing shade (GLM, Standardized Regression Coefficient SRC=-.41, p=.003), but increased only weakly with altitude (SRC=.26, p=.054). In other words, young stands were dominated by species with higher altitudinal optima than old stands. Forest species richness increased with Log Shade index (SRC=.12, p=.008), but was unaffected by altitude (SRC=-.07, p=.13). However, richness of alpine and heathland species was not highest in plots with lowest Shade index, but displayed a unimodal pattern with an initial increase, followed by a decrease when shading increased (altitude was not significant). Our results indicate that disturbance from the traditional patch burning increases the available habitat for less competitive high-altitude plants and prevents tree line ascent. Therefore, maintaining, but regulating, the traditional land use increases the Afro-alpine flora's resilience to global warming. However, this system is threatened by a new REDD+ program attempting to increase carbon storage via fire suppression. This study highlights the importance of understanding traditional management regimes for biodiversity conservation in cultural landscapes in an era of global change.

  • 3.
    Johansson, Maria U.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Senay, Senait D.
    Creathorn, Emma
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kassa, Habtemariam
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Change in heathland fire sizes inside vs. outside the Bale Mountains National Park, Ethiopia, over 50 years of fire-exclusion policy: lessons for REDD2019In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 24, no 4, article id 26Article in journal (Refereed)
    Abstract [en]

    In flammable shrublands fire size often depends on local management. Policy and land use change can drastically alter fire regimes, affecting livelihoods, biodiversity, and carbon storage. In Ethiopia, burning of vegetation is banned, but the burn ban is more strongly enforced inside the Bale Mountains National Park. We investigated if and how policy and land use change have affected fire regimes inside/outside the park. The park was established in 1969, and both studied areas have been part of a new REDD+ project since 2013. Our hypothesis is that burnt heath-land stands are nonflammable and act as fuel breaks, and hence that reduced ignition rates leads to larger fires. To quantify change we analyzed remote-sensed imagery from 10 fire-seasons between 1968 and 2017, quantifying sizes of resprouting Erica stands and recording their postfire age. To elucidate underlying mechanisms of change we interviewed 41 local smallholders. There was a five order of magnitude variation in patch size (< 0.01- > 1000 ha). A significant interaction was found between year and site (inside/outside park) in explaining patch size, indicating that the park establishment has affected fire size. Inside the park there was a tendency of patch size increase and outside a clear decrease. Especially the largest fires (> 100 ha) increased in numbers inside the park but not outside. Respondents confirmed that large fires have increased in frequency and attributed this mainly to lack of fuel breaks and the fact that fires today are ignited in a more uncontrolled manner later in the dry season. Outside the park respondents explained that fires have become smaller because of increased ignition and intensified grazing. Both situations degrade pasture and threaten Erica shrub survival. For flammable ecosystems, REDD+ fire-exclusion policies need updating, and in this case complemented with a community-based fire management program making use of the vivid local traditional fire knowledge.

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