Alternative functional trajectories along succession after different land uses in central Amazonia

Abstract

The recovery capacity and the successional pathways of tropical forests after anthropogenic disturbance vary considerably and may depend on prior land-use type and intensity. It is still unclear if forests subjected to high intensity impact, such as periodically burned pastures, are capable of restoring their original functional properties. This study analysed the functional trait dynamics of the dominant species in successional trajectories following two land uses, pasture or clear-cut, north of Manaus. Fourteen years of demographic data from the Biological Dynamics of Forest Fragments Project were used to determine the dominant species of the two successional trajectories, for which leaf area, leaf dry mass content, specific leaf area and wood density were collected, whereas seed mass was obtained from literature. Community weighted mean of each trait was weighted by basal area determined annually along succession. Prinicpal components analysis was used to analyse the extension and direction of the functional trajectories of plots. Forests regenerating from pastures increased in wood density through successional time, but other traits did not change significantly. Succession after clear-cut exhibited increasing leaf dry mass content and seed mass, and decreasing leaf area over time, but no change in wood density. Functional trajectories of plots after clear-cut were more extensive and directional than those of pasture-derived plots. Synthesis and applications. We demonstrate how central Amazonian secondary forests subjected to different land uses show differences in functional trait trajectories, in ways parallel to previously shown changes in biomass, floristic diversity and forest structure. These results indicate that natural recovery of forest functional traits is affected by prior land-use history, with implications for management and restoration. Thus, natural recovery of forests on abandoned pastures is much slower than clear-cuts, even though seed sources from mature forests are very close to these areas, and the former may need intervention to counteract the diverted succession. © 2019 The Authors. Journal of Applied Ecology © 2019 British Ecological Society