Predação de sementes ao longo de uma borda de Floresta Ombrófila Mista e pastagem

Abstract

RESUMO -(Predação de sementes ao longo de uma borda de Floresta Ombrófila Mista e pastagem). Este estudo teve como objetivo avaliar o processo de predação de sementes em três árvores nativas (Mimosa scabrella Bentham, Prunus sellowii Koehne e Myrsine laetevirens Mez.) ao longo de uma borda de Floresta Ombrófila Mista e pastagem, na Floresta Nacional de São Francisco de Paula, RS, Brasil. Grupos de sementes foram distribuídos em dez pontos aleatórios nas distâncias: 0m, 25m, 50m, 100m e 250m da borda para dentro da floresta e 5m e 50m da borda para dentro da pastagem. As sementes foram monitoradas até a predação total ou até esgotado o tempo para germinação. Houve redução nas taxas de predação de sementes até 50m da borda para dentro da floresta em relação ao interior da floresta e da pastagem. M. scabrella e M. laetevirens apresentaram redução nas taxas de predação de sementes na pastagem próxima à borda da floresta. Os resultados indicam que houve decréscimo na atividade de predadores de sementes nas proximidades da borda florestal estudada, podendo ocorrer maior regeneração de plantas próximo à borda e um avanço da floresta na pastagem adjacente.Palavras-chave: predadores de sementes, efeito de borda, recrutamento de plântulas, floresta com Araucária ABSTRACT -(Seed predation along an edge gradient between Araucaria forest and pasture). This study aims to evaluate how seed predation of three native tree species (Mimosa scabrella Bentham, Prunus sellowii Koehne, and Myrsine laetevirens Mez.) could be altered along an edge between Araucaria forest and pasture at the National Forest of São Francisco de Paula, Rio Grande do Sul, Brazil. Groups of seeds were placed at ten random points in each of the following distances from the forest edge: 0m, 25m, 50m, 100m, and 250m from the edge into the forest, and 5m and 50m from the edge into the pasture. Seeds were monitored until total predation or until their time for germination was over. Seed predation rates decreased from the edge up to 50m inside the forest in relation to the forest interior and open pasture. M. scabrella and M. laetevirens showed a reduction in seed predation rates in pasture points that were located at the vicinities of the forest. The results indicated a decrease in the activity of seed predators near the forest edge, which could enhance plant community regeneration at the edge, and promote the expansion of the forest towards the adjacent pasture.

Changes in plant community diversity and composition across an edge between Araucaria forest and pasture in South Brazil

“…Second, we found a high density of E. horridum in the pasture, and this species is known to be very abundant, and outcompete previously existing species in situations where fields are managed with fire (Boldrini 1997). Third, other works performed at the study area have found high seed predation rates of woody plant species colonizing this abandoned pasture, indicating that post dispersal hazards may limit tree establishment (Baldissera & Ganade 2005).…”

Biodiversity, Species Interactions and Ecological Networks in a Fragmented World

“…. Furthermore, recruitment and predation of seeds in the forest interior might decrease relative to edges (Baldissera and Ganade, 2005;Fleury and Galetti, 2006;Jules and Rathcke, 1999;Vargas, 1999, but see Cunningham, 2000;Guimarães and Cogni, 2002). Besides the capability of a species to perceive suitable habitat fragments and the connectivity of the landscape, its persistence in a fragmented landscape depends on its ability to cross the edge between fragment and matrix (Morris, 1997;Stamps et al, 1987a;Stevens et al, 2006).…”

Pre-dispersal seed predation and abortion in species of Callisthene and Qualea (Vochysiaceae) in a Neotropical savanna

“…It is of note that seed predation was greatest in areas such as the PARNASC and PESCAN, which are larger and more well-preserved. Conservation status and area size can influence seed predators, because species richness and disturbance can affect those specialized interactions (Janzen 1975;Ehrlén 1996;Pizo 1997;García et al 2000;Baldissera & Ganade 2005). Janzen (1971b;1978) suggested that mother plants increase fruit and seed production as a strategy to satiate predators and guarantee a reliable seed supply, thereby ensuring germination and consequently recruitment.…”

“…Studies comparing populations in terms of the occurrence of abortion and predation can further understanding of the ecological consequences to plant reproduction and persistence (Bradford & Smith 1977;Ehrlén 1996;Pizo 1997;Crawley 2000;García et al 2000García et al , 2001Steffan-Dewenter et al 2001;Leimu et al 2002;Baldissera & Ganade 2005;Marino et al 2005;Figueiredo et al 2008). In the Cerrado of Brazil, one of the most well-represented and characteristic families of woody plants is the Vochysiaceae, some species of which are among the most common and widespread in the Biome (Haridassan & Araújo 1988;Ratter et al 1996;Appolinário & Schiavini 2002;Lopes et al 2011).…”