Bracken fern facilitates tree seedling recruitment in tropical fire-degraded habitats Silvia C. Gallegos a,b,c,⇑ , Isabell Hensen a,d , Francisco Saavedra a,b,c , Matthias Schleuning a,b a Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle-Wittenberg, Am Kirchtor 1, D-06108 Halle, Germany b Biodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, D-60325 Frankfurt (Main), Germany c Herbario Nacional de Bolivia (LPB) – Instituto de Ecología – MNHN, Universidad Mayor de San Andrés, Campus Universitario Cota Cota, La Paz, Bolivia d German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, D-04103 Leipzig, Germany article info Article history: Received 30 June 2014 Received in revised form 7 November 2014 Accepted 11 November 2014 Keywords: Clusia Facilitation Forest recovery Litter Montane forest Pteridium arachnoideum abstract Tropical forest regeneration is hindered by human-induced fires. After deforestation by fires, Pteridium spp. (bracken fern) often colonizes and dominates the vegetation for long time periods, presumably inhibiting the succession. Tree species from mature forests are rare in the degraded areas, potentially due to the lack of seed dispersal and unfavourable abiotic conditions. Here, we experimentally assess the effect of bracken presence, in terms of litter and shade, on seedling recruitment of three native, shade-tolerant tree species in the tropical mountains of Bolivia. In a spatially blocked design at eight sites, we compared seedling recruitment, survival and growth three months and one year after sowing between experimental litter and vegetation treatments and among habitat types (forest interior, degraded habitats close and far from the edge) and species (Clusia sphaerocarpa, Clusia lechleri and Clusia trochiformis). We found that species differed in their recruitment success and habitat preferences, but responded similarly to experimental treatments. Litter removal increased temperature and reduced humidity on the ground and vegetation removal increased canopy openness. Seedling recruitment was consistently reduced by litter and vegetation removal, and their interaction had a deleterious negative effect. Seedling survival and growth were also reduced by litter removal. Our results highlight the over- looked facilitative effects of bracken by ameliorating harsh abiotic conditions and increasing the proba- bility of Clusia seedling recruitment and potentially other shade-tolerant tree species in degraded habitats. To enhance forest regeneration in fire-degraded areas, we recommend spreading seeds of shade-tolerant tree species into the bracken vegetation. This method is less costly and might be more effi- cient than previous methods that involved repeated bracken removal. Recruitment of late-successional species in the bracken vegetation is likely to promote the restoration of tropical forest; however, long- term studies are needed to test the success of such efforts. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Deforestation in tropical forests has created vast areas of degraded habitats dominated by pastures and ferns. Forest recov- ery in these areas is limited by the lack of seed dispersal (Holl, 1999). Furthermore, the stressful microclimatic conditions, limited soil nutrients and competition between grasses and ferns and the recruiting tree seedlings have been suggested to inhibit tree regen- eration (Aide and Cavelier, 1994; Holl, 2002; Holl et al., 2000). One of the main weeds that dominates huge degraded lands worldwide is the bracken fern (Pteridium spp.). Bracken accumulates dead fronds (i.e., fern ‘‘leaves’’) and ground litter that are highly inflam- mable, but it rapidly colonizes and re-establishes after fire (McGlone et al., 2005; Ramírez-Trejo et al., 2010). Bracken main- tains its dominance by: (i) producing a dense frond canopy that shades other species; (ii) a deep litter layer that prevents the colo- nization of other species; (iii) a large rhizome system that is highly persistent and resilient; and (iv) chemicals in defence of herbivores that could also have allelopathic effects (reviewed by Marrs et al., 2000). Although Beck and collaborators (2008) state that tree spe- cies are rarely found in bracken-dominated vegetation and fast regeneration of forest is unlikely, some studies have shown that certain tree species can naturally, albeit slowly, establish in bracken vegetation (e.g., Günter et al., 2009; Lippok et al., 2013; Ribeiro et al., 2013). http://dx.doi.org/10.1016/j.foreco.2014.11.003 0378-1127/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Herbario Nacional de Bolivia (LPB) – Instituto de Ecología – MNHN, Universidad Mayor de San Andrés, Campus Universitario Cota Cota, La Paz, Bolivia. Tel.: +591 2 2770962. E-mail address: silvia.gallegos.a@gmail.com (S.C. Gallegos). Forest Ecology and Management 337 (2015) 135–143 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco