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Doughty C.E.,University of Oxford | Metcalfe D.B.,Lund University | Girardin C.A.J.,University of Oxford | Amezquita F.F.,National University of Costa Rica | And 13 more authors.
Nature | Year: 2015

In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO 2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the absence of growth. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots. © 2015 Macmillan Publishers Limited.

Almudi T.,IPAM Institute Pesquisa Ambiental da Amazonia | Berkes F.,University of Manitoba
Local Environment | Year: 2010

How do nation states accommodate people who live in regions declared as protected areas (PAs)? In Brazil's Peixe Lagoon National Park, established in 1986, eviction of fisher communities has been occurring gradually through license non-renewal and ill-treatment of fishers by Parks authorities. We examined fishers' interactions with other groups and the role of partnerships and linkages in fighting for fishing rights. Results show that the new national law on PAs (SNUC) approved in 2000 could be used to enable this particular group of fishers to safeguard their culture and livelihoods. However, fishers and their representatives considered themselves weak and disempowered. Existing partnerships were sufficient to fight eviction in the short term, but not to safeguard resource access rights in the long term. We identified obstacles to empowerment in the form of "missing linkages" and institutions, specifically with respect to service and support functions to build capacity to defend rights to remain physically within the park and politically in the conservation process. © 2010 Taylor & Francis.

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