A first look at the impediments to forest recovery in bracken-dominated clearings in the African Highlands

Ssali, Fredrick; Moe, Stein R.; Sheil, Douglas

doi:10.1016/j.foreco.2017.07.050

Cited by 22 publications

(36 citation statements)

References 39 publications

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“…We also found roughly similar stem‐size density ratios in both forest and bracken in our 10 transects and a markedly lower ratio of saplings to large seedlings in bracken than in forest. The low abundance of seedlings appears to be largely a result of limited recruitment or poor survival rather than rapid development as the abundance of more mature life stages is lower or similar to those seen in forest (see also Ssali et al., ). The difference for tree seed rain was 1.7 times (forest 1605 ± 335 vs. bracken 949 ± 582 vs. tree seeds m −2 year −1 ), and for the seed bank was 0.9 times (264 ± 99 vs. 304 ± 236 viable tree seeds/m 2 ).…”

Section: Discussionmentioning

confidence: 99%

“…The forest canopy is open in many areas due in part to extensive clearings dominated by bracken fern Pteridium aquilinum (Ssali et al., ). The clearings have been created by past fires, landslides, timber cutting, and cultivation (Babaasa, Eilu, Kasangaki, Bitariho, & McNeilage, ; Olupot, Barigyira, & Chapman, ; Ssali et al., ). Other understorey species dominate other areas both in the continuous forest and in the open clearings.…”

Section: Methodsmentioning

confidence: 99%

“…Temperate studies have suggested that bracken, Pteridium aquilinum , interferes with forest regrowth due to the effects of shade, pathogens, allelopathy, deep litter or perhaps seed removal (den Ouden, ; Dolling, ; Facelli & Pickett, ; Gaudio et al., ; Ghorbani, Duc, Mcallister, Pakeman, & Marrs, ; Priewasser, ). However, how these factors and mechanisms might operate singly or in combination has seldom been examined especially in equatorial Africa (but see Ssali, Moe, & Sheil, ).…”

Section: Introductionmentioning

confidence: 99%

“…Successful establishment requires the arrival and persistence of viable seeds, germination, and seedling survival. Our initial exploration showed that bracken‐dominated areas are persistent and indicated that species with longer seed dormancy and greater growth potential are better suited to establish in bracken than are species lacking these characteristics (Ssali et al., ). However, how seed limitation and establishment limitation, that is, seed rain, soil seed bank, and seed removal, influence tree regrowth in bracken clearings remains poorly understood despite the existing literature (from temperate and neotropical regions, see Marrs & Watt, ; Priewasser, ; Royo & Carson, ).…”

Section: Introductionmentioning

confidence: 99%

“…In the Bwindi Impenetrable National Park (“Bwindi”) in Uganda, forest recovery in bracken‐dominated clearings is slow (Ssali et al., ). Our hypothesis here is that the limited forest recovery in bracken compared to forest is related to differences in recruitment limitation (namely seed arrival, persistence, and predation).…”

Section: Introductionmentioning

confidence: 99%

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Tree seed rain and seed removal, but not the seed bank, impede forest recovery in bracken (Pteridium aquilinum (L.) Kuhn)‐dominated clearings in the African highlands

Ssali

Moe

Sheil

2018

Ecology and Evolution

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Considerable areas dominated by bracken Pteridium aquilinum (L.) Kuhn occur worldwide and are associated with arrested forest recovery. How forest recovery is impeded in these areas remains poorly understood, especially in the African highlands. The component processes that can lead to recruitment limitation—including low seed arrival, availability and persistence—are important determinants of plant communities and offer a potential explanation for bracken persistence. We investigated key processes that can contribute to recruitment limitation in bracken‐dominated clearings in the Bwindi Impenetrable National Park, Uganda. We examined if differences in seed rain (dispersal limitation), soil seed bank, or seed removal (seed viability and persistence) can, individually or in combination, explain the differences in tree regeneration found between bracken‐dominated areas and the neighboring forest. These processes were assessed along ten 50‐m transects crossing the forest–bracken boundary. When compared to the neighboring forest, bracken clearings had fewer seedlings (bracken 11,557 ± 5482 vs. forest 34,515 ± 6066 seedlings/ha), lower seed rain (949 ± 582 vs. 1605 ± 335 tree seeds m−2 year−1), comparable but sparse soil seed bank (304 ± 236 vs. 264 ± 99 viable tree seeds/m2), higher seed removal (70.1% ± 2.4% vs. 40.6% ± 2.4% over a 3‐day interval), and markedly higher rodent densities (25.7 ± 5.4 vs. 5.0 ± 1.6 rodents per 100 trapping sessions). Camera traps revealed that rodents were the dominant animals visiting the seeds in our seed removal study. Synthesis: Recruitment limitation contributes to both the slow recovery of forest in bracken‐dominated areas, and to the composition of the tree species that occur. Low seed arrival and low persistence of unburied seeds can both explain the reduced density of seedlings found in bracken versus neighboring forest. Seed removal, likely due to rodents, in particular appears sufficient to constrain forest recovery and impacts some species more severely than others.

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Section: Discussionmentioning

confidence: 99%