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Scaling from individuals or species to ecosystems is a fundamental challenge of modern ecology and understanding tropical forest response to drought is a key challenge of predicting responses to global climate change. We here synthesize our developing understanding of these twin challenges by examining individual and ecosystem responses to the 2015 El Niño drought at two sites in the central Amazon of Brazil, near Manaus and Santarem, which span a precipitation gradient from moderate (Manaus) to long (Santarem) dry seasons. We will focus on how ecosystem water and carbon cycling, measured by eddy flux towers, emerges from individual trait-based responses, including photosynthetic responses of individual leaves, and water cycle responses in terms of stomatal conductance and hydraulic xylem embolism resistance. We found the Santarem forest (with long dry seasons) responded strongly to drought: sensible heat values significantly increased and evapotranspiration decreased. Consistent with this, we also observed reductions in photosynthetic activity and ecosystem respiration, showing levels of stress not seen in the nearly two decades since measurements started at this site. Forests at the Manaus site showed significant, however, less consistent reductions in water and carbon exchange and a more pronounced water deficit. We report an apparent community level forest composition selecting for assemblies of traits and taxa manifest of higher drought tolerance at Santarem, compared to the Manaus forest (short dry seasons) and other forest sites across Amazonia. These results suggest that we may be able to use community trait compositions (as selected by past climate conditions) and environmental threshold values (e.g. cumulative rainfall, atmospheric moisture and radiation) as to help forecast ecosystem responses to future climate change. 

Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, toSphagnumbog underlain by permafrost, toEriophorum‐dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi‐decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi‐continuous measurement of CO₂and CH₄exchange, and 21 core profiles for²¹⁰Pb and¹⁴C peat dating. Year‐round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m⁻² y⁻¹for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO₂uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO₂fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial‐scale levels (17–29 g C m⁻² y⁻¹) to moderate aCAR of the past century (72–81 g C m⁻² y⁻¹) to higher recent aCAR of 90–147 g C m⁻² y⁻¹. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO₂sink, but this CO₂sink is increasingly offset by rising CH₄emissions, dominated by modern carbon as determined by¹⁴C. The higher CH₄emissions result in higher net CO_{2‐equivalent}emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate.