Suchergebnisse

Indonesia and Peru harbor some of the largest lowland tropical peatland areas. Indonesian peatlands are subject to much greater anthropogenic activity than Peru's, including drainage, logging, agricultural conversion, and burning, resulting in high greenhouse gas and particulate emissions. To derive insights from the Indonesian experience, we explored patterns of impact in the two countries, and compared their predisposing factors. Impacts differ greatly among Indonesian regions and the Peruvian Amazon in the following order: Sumatra > Kalimantan > Papua > Peru. All impacts, except fire, are positively related to population density. Factors enhancing Indonesian peatlands' susceptibility to disturbance include peat doming that facilitates drainage, coastal location, high local population, road access, government policies permitting peatland use, lack of enforcement of protections, and dry seasons that favor extensive burning. The main factors that could reduce peatland degradation in Peru compared with Indonesia are geographic isolation from coastal population centers, more compact peatland geomorphology, lower population and road density, more peatlands in protected areas, different land tenure policies, and different climatic drivers of fire; whereas factors that could enhance peatland degradation include oil and gas development, road expansion in peatland areas, and an absence of government policies explicitly protecting peatlands. We conclude that current peatland integrity in Peru arises from a confluence of factors that has slowed development, with no absolute barriers protecting Peruvian peatlands from a similar fate to Indonesia's. If the goal is to maintain the integrity of Peruvian peatlands, government policies recognizing unique peatland functions and sensitivities will be necessary.

Understanding the relationship between photosynthesis, net primary productivity and growth in forest ecosystems is key to understanding how these ecosystems will respond to global anthropogenic change, yet the linkages among these components are rarely explored in detail. We provide the first comprehensive description of the productivity, respiration and carbon allocation of contrasting lowland Amazonian forests spanning gradients in seasonal water deficit and soil fertility. Using the largest data set assembled to date, ten sites in three countries all studied with a standardized methodology, we find that (i) gross primary productivity (GPP) has a simple relationship with seasonal water deficit, but that (ii) site-to-site variations in GPP have little power in explaining site-to-site spatial variations in net primary productivity (NPP) or growth because of concomitant changes in carbon use efficiency (CUE), and conversely, the woody growth rate of a tropical forest is a very poor proxy for its productivity. Moreover, (iii) spatial patterns of biomass are much more driven by patterns of residence times (i.e. tree mortality rates) than by spatial variation in productivity or tree growth. Current theory and models of tropical forest carbon cycling under projected scenarios of global atmospheric change can benefit from advancing beyond a focus on GPP. By improving our understanding of poorly understood processes such as CUE, NPP allocation and biomass turnover times, we can provide more complete and mechanistic approaches to linking climate and tropical forest carbon cycling. ; Fieldwork was funded by grants from the UKNatural Environment Research Council (NE/D01025X/1 andNE/D014174/1) the European Union Framework 7 projectGEOCARBON (283080), and the Gordon and Betty Moore Foun-dation. YM is supported by the Jackson Foundation and by aEuropean Research Council Advanced Investigator Award. OPis supported by an ERC Advanced Grant and a Royal SocietyWolfson Research Merit Award.

UK Natural Environment Research Council ; European Research Council Advanced Investigator Award (GEM-TRAIT) ; Nature Conservancy-Oxford Martin School Climate Partnership ; NERC ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Gordon and Betty Moore Foundation ; Sime Darby Foundation ; Project USA-NAS/PEER ; Project ReFlor FAPEMAT ; Empresa Brasileira de Pesquisa Agropecuaria - Embrapa ; European Research Council (H2020-MSCA-RISE-2015) ; UK government Darwin Initiative ; Nature Conservancy ; UK Natural Environment Research Council (NERC) ; Jackson Foundation ; UK Natural Environment Research Council: NE/P001092/1 ; European Research Council Advanced Investigator Award (GEM-TRAIT): 321131 ; NERC: NE/I014705/1 ; NERC: NE/K016369/1 ; NERC: NE/F005776/1 ; NERC: NE/K016385/1 ; NERC: NE/J011002/1 ; CNPq: 457914/2013-0/MCTI/ CNPq/FNDCT/LBA/ESECAFLOR ; CNPq: 403725/ 2012-7 ; CNPq: 441244/2016-5 ; CNPq: 457602/2012-0 ; Project USA-NAS/PEER: PGA-2000005316 ; Project ReFlor FAPEMAT: 0589267/2016 ; CNPq: 574008/2008-0 ; Empresa Brasileira de Pesquisa Agropecuaria - Embrapa: SEG: 02.08.06.005.00 ; European Research Council (H2020-MSCA-RISE-2015): 691053-ODYSSEA ; UK government Darwin Initiative: 17-023 ; UK Natural Environment Research Council (NERC): NE/F01614X/1 ; UK Natural Environment Research Council (NERC): NE/G000816/1 ; UK Natural Environment Research Council (NERC): NE/K016431/1 ; UK Natural Environment Research Council (NERC): NE/P004512/1 ; : PQ-2 ; Meteorological extreme events such as El Nino events are expected to affect tropical forest net primary production (NPP) and woody growth, but there has been no large-scale empirical validation of this expectation. We collected a large high-temporal resolution dataset (for 1-13 years depending upon location) of more than 172 000 stem growth measurements using dendrometer bands from across 14 regions spanning Amazonia, Africa and Borneo in order to test how much month-to-month variation in stand-level woody growth of adult tree stems (NPPstem) can be explained by seasonal variation and interannual meteorological anomalies. A key finding is that woody growth responds differently to meteorological variation between tropical forests with a dry season (where monthly rainfall is less than 100 mm), and aseasonal wet forests lacking a consistent dry season. In seasonal tropical forests, a high degree of variation in woody growth can be predicted from seasonal variation in temperature, vapour pressure deficit, in addition to anomalies of soil water deficit and shortwave radiation. The variation of aseasonal wet forest woody growth is best predicted by the anomalies of vapour pressure deficit, water deficit and shortwave radiation. In total, we predict the total live woody production of the global tropical forest biome to be 2.16 Pg C yr(-1), with an interannual range 1.96-2.26 Pg C yr(-1) between 1996-2016, and with the sharpest declines during the strong El Nino events of 1997/8 and 2015/6. There is high geographical variation in hotspots of El Nino-associated impacts, with weak impacts in Africa, and strongly negative impacts in parts of Southeast Asia and extensive regions across central and eastern Amazonia. Overall, there is high correlation (r = -0.75) between the annual anomaly of tropical forest woody growth and the annual mean of the El Nino 3.4 index, driven mainly by strong correlations with anomalies of soil water deficit, vapour pressure deficit and shortwave radiation. This article is part of the discussion meeting issue 'The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

Funding Information: The analysis undertaken here was largely funded by the NERC-funded TREMOR project (NE/N004655/1) to D.G., R.J.W.B., E.G. and O.L.P. A.E.-M. was funded by TREMOR and by two ERC awards (T-FORCES 291585, TreeMort 758873). D.G. acknowledges further support from a Newton-funded consortium award (ARBOLES, NE/S011811/1). O.L.P. was supported by an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. T.A.M.P. was funded by the ERC award TreeMort 758873. This is paper number 47 of the Birmingham Institute of Forest Research. T.R.F., L.E.O.C.A. and O.L.P. were supported by NERC NE/N011570/1. Support for RAINFOR has come from the Natural Environment Research Council (NERC) Urgency Grants and NERC Consortium Grants AMAZONICA (NE/F005806/ 1), TROBIT (NE/D005590/1) and BIO-RED (NE/N012542/1), a European Research Council (ERC) grant T-FORCES (291585), the Gordon and Betty Moore Foundation (#1656), the European Union's Seventh Framework Programme (282664, AMAZA-LERT) and the Royal Society (CH160091). This is paper #47 of the Birmingham Institute of Forest Research (BIFoR). ; The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality. ; Publisher PDF ; Peer reviewed