Data from: Interaction between extreme weather events and mega‐dams increases tree mortality and alters functional status of Amazonian forests

1. Forest responses to changes in drought frequency is a critical unknown
for the future of Amazon forests under climate change, but equally
important is the much less studied response to large floods, which may
also increase tree mortality and change forest functionality. Further,
forest vulnerability to flood is being exacerbated by large hydroelectric
dams on Amazon rivers that put upland environments not adapted to flood at
unique risk. 2. To address this critical knowledge gap, we evaluated the
synergistic effects of the extreme 2014 rainfall coupled with the newly
constructed Jirau hydroelectric dam on tree survival and forest
functionality, in the upper Madeira River basin. We used surveys of
campinarana white-sand forests (stems >1 cm in seven 1 ha plots)
conducted before and after the extreme flood to test trait-based
ecological theory predictions of the impact of drought on overall
community function. 3. We found that flooding increased mortality by
nearly five-fold (from 3.2% to 15.1%), mostly in smaller trees. This large
mortality induced significant and consistent shifts in community function,
towards species with conservative life strategies: direct comparison of
trait differences between surviving and dying trees showed that survivors
had smaller, high density stomata, and higher leaf dry matter content,
wood density and root tissue density. Size and density of stomata and root
tissue density were the most important predictors of species mortality
rates. 4. Synthesis and applications. Although focused on a single event
in one type of forest, this work highlights the general importance, and
need for further study, of synergism between climate change and
development in Amazon forests. In particular, we expect that continued
expansion of hydroelectric dams in Amazonia will likely intensify the
impact of large floods on forests made newly vulnerable by these dams,
with substantial effect on future forest functionality in expanded
floodplain areas across the Basin.16-Aug-2019