Tree Regeneration and Understory Woody Plants Show Diverse Responses to Forest-Pasture Edges in Costa Rica

Abstract

Edge effects along tropical forest-pasture margins are thought to cause a shift toward early successional characteristics of the understory forest vegetation. We tested this idea by sampling vegetation at five forest sites in northeast Costa Rica each of which had edges that were established over 20 yr earlier. Four of these sites had been selectively logged. We sampled woody plants 4 0.2 and 1.3 m height in 54 m 2 within 0.2 ha plots at edges (N = 14), and at 150 m (N = 11) and 300 m from edges (N = 9). Composition and diversity did not vary with edge distance. Abundance of tree regeneration, mainly of canopy and emergent species, increased at edges. Abundance of lianas and slow-growing tree species did not differ significantly across the sampling locations. Weighted mean wood density varied little, with a reduction at edges for canopy species. Palms were less abundant at edges, but not less species rich. At edges, these plant assemblages maintain many of the characteristics of forest interior vegetation, though the changes observed may indicate ongoing functional change. Degradation of forest-pasture edges is not a universal feature of tropical forest fragmentation, and forests with high rates of natural turnover might have a high capacity to maintain themselves within forest edges alongside pasture.Foreign language abstract is available in the online version of this article.

The Nature of Seedling Assemblages in a Fragmented Tropical Landscape: Implications for Forest Regeneration

“…, Sánchez‐Gallen et al . ) and in northeast Costa Rica (Bouroncle & Finegan , for seedling and saplings). This study, however, suggests that changes in seedling assemblages may be more drastic and persistent than previously reported.…”

Predicted trajectories of tree community change in Amazonian rainforest fragments

“…Forest edges experience elevated wind turbulence (Somerville , Laurance and Curran ) and altered microclimate conditions (Camargo and Kapos , Chen et al , Didham and Lawton , Ewers and Banks‐Leite ) that are linked with increases in canopy dessication (Stevenson and Coxson , Briant et al ) and tree mortality (Chen et al , Brando et al , Badano et al , Hallinger et al ), and those mortality rates increase even more for sites that are close to multiple edges (Laurance et al ). High mortality rates open canopy gaps and create opportunities for seedlings and saplings to recruit into the population, so it is no surprise that recruitment rates are also higher near forest edges than deep inside forest interiors (Chen et al , Laurance et al , Bouroncle and Finegan ). The species traits associated with increased mortality and recruitment are non‐random, with a set of slower‐growing tree species with high wood density tending to decline in abundance whereas faster‐growing tree and liana (woody vine) species with lower wood density are increasing (Laurance et al , Pütz et al , Benchimol and Peres ).…”

Coupled social and ecological outcomes of agricultural intensification in Costa Rica and the future of biodiversity conservation in tropical agricultural regions

“…This region has a mean annual temperature of 26.5 8C and annual precipitation ranging from 3000 to 4500 mm (Grieve et al, 1990;McDade et al, 1994), and lies within a wet tropical forest life zone (sensu Holdridge et al, 1975). Old-and second-growth forest remnants currently cover an important proportion of the land area (Morse et al, 2009;Fagan et al, 2013; Section 4 in this paper), retaining high tree species diversity and showing quick regeneration rates (Guariguata et al, 1997;Schedlbauer et al, 2007;Chazdon et al, 2009b;Norden et al, 2009;Sesnie et al, 2009;Bouroncle and Finegan, 2011). Soil types are generally acidic (pH $4.5), primarily Inceptisols and Ultisols (Sollins et al, 1994).…”

“…The study region is a critical conservation area where 43.8% forest cover is maintained with demonstrated resilient forest dynamics despite population growth and a modernizing agricultural landscape (Letcher and Chazdon, 2009;Norden et al, 2009;Schedlbauer et al, 2007;Bouroncle and Finegan, 2011;Fagan et al, 2013). These factors make the SJLS region an appropriate site to assess the effects of NTAE-based agricultural intensification on rural economies and biodiversity conservation, and to explore the tradeoffs between parallel agricultural growth and conservation objectives.…”

“…Previous studies document that forest directly adjacent to agricultural land uses suffers from ''edge effects'', which drive changes in forest microclimate, tree mortality, and in the abundance and distribution of animal species; the severity of edge effects vary depending on the type of adjacent land use (Fischer and Lindenmeyer, 2007;Schedlbauer et al, 2007;Bouroncle and Finegan, 2011;Laurance et al, 2011). FRAGSTATS metrics such as core area (CORE), which describes the patch area free of edge effects, and edge contrast indices (TECI), which describe the proportion of forest edge in maximum contrast (Table A1), are useful metrics for assessing the impact of edge effects.…”