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Chloé Debyser

McGill University
Long-term biomass and community composition dynamics following forest fragmentation in Central Amazonia

Chloé Debyser, William Laurance, Ana Andrade, Susan Laurance, José Luís Camargo, Thomas Lovejoy, Andrew Gonzalez

Tropical forest fragmentation often triggers rapid changes in forest ecology and functioning, including collapses in tree biomass in small fragments within a few years of the disturbance. Here we investigate the long-term legacy of forest fragmentation. We ask: Do tropical tree communities recover from the fragmentation disturbance in the long-term? We analyse tree monitoring data collected between 1980 and 2009 at the Biological Dynamics of Forest Fragments Project (BDFFP), a long-term and large-scale forest fragmentation experiment located in the Brazilian Amazon. Tree biomass within sixty-eight BDFFP permanent forest plots is estimated from repeated tree diameter at breast height measurements, for 4-8 time-points in the three decades following experimental fragmentation. Our results corroborate previous findings of a biomass collapse in BDFFP forest fragments in the first 5 years after the disturbance, and we identify fragment area as the most parsimonious predictor of these dynamics. We also detect a full biomass recovery of forest plots starting ~14 years after experimental fragmentation. However, the tree community composition of plots having experienced a biomass collapse remained significantly different from that of controls up to >25 years after the disturbance. Collapse plots presented a shift towards smaller stems and towards species of earlier-successional status, and their species composition exhibited greater divergences from their pre-treatment compositions compared to control plots. Our results suggest a nuanced outlook on the long-term recovery of fragmented Amazonian forests, with, given appropriate management practices, a potential for full biomass recovery to occur despite greater limits on compositional recovery.