Effect of 7 yr of experimental drought on vegetation dynamics and biomass storage of an eastern Amazonian rainforest

Costa, Antonio; Galbraith, David; Almeida, Samuel; Portela, Bruno Takeshi Tanaka; Costa, Mauricio da; Silva, João de Athaydes; Braga, Anna Rafaela Cavalcante; Gonçalves, P. H. L.; Oliveira, Alex Santos de; Fisher, Rosie A.; Phillips, Oliver L.; Metcalfe, Daniel B.; Levy, Peter E.; Meir, Patrick

doi:10.1111/j.1469-8137.2010.03309.x

Cited by 322 publications

(437 citation statements)

References 74 publications

(168 reference statements)

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“…The plot data clearly show short-term peaks in the size of dying trees during the anomalously dry years 2005 and 2010 (Extended data figure 5c). These are consistent with results from rainfall exclusion experiments in Amazonia 20,21 and observations 4 showing that large tropical trees are vulnerable to drought stress 20 . However, our data lack the signature expected if drought were the dominant driver of the increasing loss of biomass due to mortality in Amazonia.…”

supporting

confidence: 80%

Long-term decline of the Amazon carbon sink

Brienen¹,

Phillips²,

Feldpausch³

et al. 2015

Nature

904

910

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Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades1, 2, with a substantial fraction of this sink probably located in the tropics3, particularly in the Amazon4. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity5. The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale1, 2, and is contrary to expectations based on models. (Résumé d'auteur

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supporting

confidence: 80%

Long-term decline of the Amazon carbon sink

Brienen¹,

Phillips²,

Feldpausch³

et al. 2015

Nature

904

910

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“…ecosystem photosynthetic capacity is at its maximum . Soil water availability strongly impacts wood productivity as directly observed in tropical forests (Wagner et al, 2012;Nath et al, 2006;Baker et al, 2003) and as deduced from experimental forest droughts (Nepstad et al, 2002;Lola da Costa et al, 2010). (ii) Wood production could be indirectly linked to irradiance via a shift in resource allocation from wood to leaves during the peak of irradiance in the early dry season (Fig.…”

Section: Wood Productionmentioning

confidence: 99%

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Wagner

Rossi²,

Stahl

et al. 2013

Biogeosciences

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Abstract. The fixation of carbon in tropical forests mainly occurs through the production of wood and leaves, both being the principal components of net primary production. Currently field and satellite observations are independently used to describe the forest carbon cycle, but the link between satellite-derived forest phenology and field-derived forest productivity remains opaque. We used a unique combination of a MODIS enhanced vegetation index (EVI) dataset, a wood production model based on climate data and direct litterfall observations at an intra-annual timescale in order to question the synchronism of leaf and wood production in tropical forests. Even though leaf and wood biomass fluxes had the same range (respectively 2.4 ± 1.4 and 2.2 ± 0.4 Mg C ha −1 yr −1 ), they occurred separately in time. EVI increased with leaf renewal at the beginning of the dry season, when solar irradiance was at its maximum. At this time, wood production stopped. At the onset of the rainy season, when new leaves were fully mature and water available again, wood production quickly increased to reach its maximum in less than a month, reflecting a change in carbon allocation from short-lived pools (leaves) to long-lived pools (wood). The time lag between peaks of EVI and wood production (109 days) revealed a substantial decoupling between the leaf renewal assumed to be driven by irradiance and the water-driven wood production. Our work is a first attempt to link EVI data, wood production and leaf phenology at a seasonal timescale in a tropical evergreen rainforest and pave the way to develop more sophisticated global carbon cycle models in tropical forests.

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“…This implies several consequences for future ecosystem function and biodiversity. The fact that drought has a more detrimental impact on their growth and mortality suggests a greater drought-driven feedback to the carbon cycle than if their drought sensitivity were equal to the average community response 4,20,29 . In addition, large canopy trees can account for a greater proportion of ecosystem-level transpiration than smaller trees 8 and their drought-related decline could imply reduced latent cooling of the land surface and transpiration contributions to cloud formation 21 .…”

mentioning

confidence: 99%

“…Either way, drought disproportionately reduces carbon sequestration in the biomass of large trees and further reduces ecosystem-level carbon stocks associated with large size classes through higher mortality. The few studies that have quantified the implications of greater drought sensitivity of large trees on ecosystem-level productivity or carbon stocks demonstrate that the greater drought sensitivity of large trees has disproportionate impacts on the ecosystem carbon cycle 4,20,29 .…”

mentioning

confidence: 99%

Larger trees suffer most during drought in forests worldwide

et al. 2015

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The frequency of severe droughts is increasing in many regions around the world as a result of climate change [1][2][3] . Droughts alter the structure and function of forests 4,5 . Site-and region-specific studies suggest that large trees, which play keystone roles in forests 6 and can be disproportionately important to ecosystem carbon storage 7 and hydrology 8 , exhibit greater sensitivity to drought than small trees 4,5,9,10 . Here, we synthesize data on tree growth and mortality collected during 40 drought events in forests worldwide to see whether this size-dependent sensitivity to drought holds more widely. We find that droughts consistently had a more detrimental impact on the growth and mortality rates of larger trees. Moreover, drought-related mortality increased with tree size in 65% of the droughts examined, especially when community-wide mortality was high or when bark beetles were present. The more pronounced drought sensitivity of larger trees could be underpinned by greater inherent vulnerability to hydraulic stress 11-14 , the higher radiation and evaporative demand experienced by exposed crowns 4,15 , and the tendency for bark beetles to preferentially attack larger trees 16 . We suggest that future droughts will have a more detrimental impact on the growth and mortality of larger trees, potentially exacerbating feedbacks to climate change.Climate change has been linked to water deficits in many parts of the world, and future climate projections suggest that droughts are likely to increase in severity because of changes in the timing and magnitude of precipitation and rising temperature 1,2,14,17 . Across a wide range of biomes, drought leads to changes in forest composition, structure, productivity and climate interactions 5,18,19 . Drought has many important consequences for forest communities, as species composition and dominance are shaped by water availability and can change rapidly in response to drought 19,20 . Drought-induced forest decline results in climate feedbacks including reduced CO 2 uptake, reduced carbon stocks, increased albedo and decreased evapotranspiration 21 . The impact of drought on forest structure and function depends on which trees are most adversely affected; greater mortality of small trees may modify future forest succession whereas mortality of large trees causes disproportionate losses of carbon and ecosystem function 5-7 . It has not been clear whether large or small trees would suffer more under drought stress. Several studies have documented a greater impact of drought on large trees at a single site 4,9,10 , and a synthesis of data from the humid lowland tropics revealed a tendency for greater drought-related mortality increases in large trees 5 , but these patterns have never been systematically reviewed for forests worldwide.Here, we perform a meta-analysis of data from 40 drought events at 38 forest locations worldwide, ranging from semi-arid woodlands to tropical rainforests, to address whether trees of different size (seedlings excluded) respond differe...

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Effect of 7 yr of experimental drought on vegetation dynamics and biomass storage of an eastern Amazonian rainforest

Cited by 322 publications

References 74 publications

Long-term decline of the Amazon carbon sink

Long-term decline of the Amazon carbon sink

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Larger trees suffer most during drought in forests worldwide

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