Urban or rural areas: which types of surrounding land use induce stronger edge effects on the functional traits of tropical forests plants?

Abstract

AbstractQuestionsWhich types of land use adjacent to Atlantic Tropical Forests induce the strongest edge effects in terms of the functional responses of arboreal and understorey plants? Which functional traits respond to stress imposed by each land‐use type in the two forest layers?LocationFull‐protection conservation areas in the metropolitan region of Recife, Pernambuco State, Brazil.MethodsWe calculated the proportions of species and individuals of woody plants in terms of their functional traits (seed size, maximum height, dispersal syndrome and regeneration strategy) along the edge and in the interior of tropical Atlantic Forest remnants exposed to different degrees of adjacent urbanization along their borders (urban, suburban and rural) by establishing 120 sampling points (60 plots considering the arboreal components and 60 subplots considering woody understorey plants).The degree of urbanization adjacent to the edges of the remnant forests were determined by mapping the sites based on satellite images. The intensities of the edge effects on functional composition, and the differences in the functional traits were assessed using multivariate analysis.ResultsFunctional composition along the edges and within the forest interiors of remnants with the highest densities of urban areas around them demonstrated the greatest variability of both the arboreal and understorey components. The arboreal component of the forest sites adjacent to rural areas (intense agricultural activities) tended to demonstrate intermediate intensity edge effects. Species showing shade intolerance, with smaller maximum heights, producing small seeds and with abiotic dispersion were present in high proportions in forests bordering heavily urbanized areas. Biotic dispersal predominated in the arboreal component of the rural remnant.ConclusionsFrom a functional point of view, the forest with the most highly urbanized border is more impacted by edge effects than forests bordering on suburban or rural areas. Nonetheless, in an urban–rural gradient, intense agricultural activity was observed to create intermediate pressure in terms of the intensities of its edge effects. These edge effects differentially impact the functional traits of the arboreal and understorey components, influencing different traits, depending on the type of border.