| 1. |
- Aguirre-Gutierrez, Jesus, et al.
(författare)
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Long-term droughts may drive drier tropical forests towards increased functional, taxonomic and phylogenetic homogeneity
- 2020
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Tropical ecosystems adapted to high water availability may be highly impacted by climatic changes that increase soil and atmospheric moisture deficits. Many tropical regions are experiencing significant changes in climatic conditions, which may induce strong shifts in taxonomic, functional and phylogenetic diversity of forest communities. However, it remains unclear if and to what extent tropical forests are shifting in these facets of diversity along climatic gradients in response to climate change. Here, we show that changes in climate affected all three facets of diversity in West Africa in recent decades. Taxonomic and functional diversity increased in wetter forests but tended to decrease in forests with drier climate. Phylogenetic diversity showed a large decrease along a wet-dry climatic gradient. Notably, we find that all three facets of diversity tended to be higher in wetter forests. Drier forests showed functional, taxonomic and phylogenetic homogenization. Understanding how different facets of diversity respond to a changing environment across climatic gradients is essential for effective long-term conservation of tropical forest ecosystems. Different aspects of biodiversity may not necessarily converge in their response to climate change. Here, the authors investigate 25-year shifts in taxonomic, functional and phylogenetic diversity of tropical forests along a spatial climate gradient in West Africa, showing that drier forests are less stable than wetter forests.
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| 2. |
- Aragão, Luiz E. O. C., et al.
(författare)
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21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Tropical carbon emissions are largely derived from direct forest clearing processes. Yet, emissions from drought-induced forest fires are, usually, not included in national-level carbon emission inventories. Here we examine Brazilian Amazon drought impacts on fire incidence and associated forest fire carbon emissions over the period 2003-2015. We show that despite a 76% decline in deforestation rates over the past 13 years, fire incidence increased by 36% during the 2015 drought compared to the preceding 12 years. The 2015 drought had the largest ever ratio of active fire counts to deforestation, with active fires occurring over an area of 799,293 km(2). Gross emissions from forest fires (989 +/- 504 Tg CO2 year(-1)) alone are more than half as great as those from old-growth forest deforestation during drought years. We conclude that carbon emission inventories intended for accounting and developing policies need to take account of substantial forest fire emissions not associated to the deforestation process.
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| 3. |
- Cuni-Sanchez, Aida, et al.
(författare)
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High aboveground carbon stock of African tropical montane forests
- 2021
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 596:7873, s. 536-542
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Tidskriftsartikel (refereegranskat)abstract
- Tropical forests store 40–50per cent of terrestrial vegetation carbon. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests. Owing to climatic and soil changes with increasing elevation, AGC stocks are lower in tropical montane forests compared with lowland forests. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4megagrams of carbon per hectare (95% confidence interval 137.1–164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network4 and about 70per cent and 32per cent higher than averages from plot networks in montane and lowland forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa8. We find that the low stem density and high abundance of large trees of African lowland forests is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to helpto guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse and carbon-rich ecosystems.
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| 4. |
- Davies, Stuart J., et al.
(författare)
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ForestGEO: Understanding forest diversity and dynamics through a global observatory network
- 2021
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207. ; 253
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Tidskriftsartikel (refereegranskat)abstract
- ForestGEO is a network of scientists and long-term forest dynamics plots (FDPs) spanning the Earth's major forest types. ForestGEO's mission is to advance understanding of the diversity and dynamics of forests and to strengthen global capacity for forest science research. ForestGEO is unique among forest plot networks in its large-scale plot dimensions, censusing of all stems ≥1 cm in diameter, inclusion of tropical, temperate and boreal forests, and investigation of additional biotic (e.g., arthropods) and abiotic (e.g., soils) drivers, which together provide a holistic view of forest functioning. The 71 FDPs in 27 countries include approximately 7.33 million living trees and about 12,000 species, representing 20% of the world's known tree diversity. With >1300 published papers, ForestGEO researchers have made significant contributions in two fundamental areas: species coexistence and diversity, and ecosystem functioning. Specifically, defining the major biotic and abiotic controls on the distribution and coexistence of species and functional types and on variation in species' demography has led to improved understanding of how the multiple dimensions of forest diversity are structured across space and time and how this diversity relates to the processes controlling the role of forests in the Earth system. Nevertheless, knowledge gaps remain that impede our ability to predict how forest diversity and function will respond to climate change and other stressors. Meeting these global research challenges requires major advances in standardizing taxonomy of tropical species, resolving the main drivers of forest dynamics, and integrating plot-based ground and remote sensing observations to scale up estimates of forest diversity and function, coupled with improved predictive models. However, they cannot be met without greater financial commitment to sustain the long-term research of ForestGEO and other forest plot networks, greatly expanded scientific capacity across the world's forested nations, and increased collaboration and integration among research networks and disciplines addressing forest science.
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| 5. |
- Devisscher, Tahia, et al.
(författare)
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Anticipating future risk in social-ecological systems using fuzzy cognitive mapping : The case of wildfire in the Chiquitania, Bolivia
- 2016
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Ingår i: Ecology and Society. - 1708-3087. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- Understanding complex social-ecological systems, and anticipating how they may respond to rapid change, requires an approach that incorporates environmental, social, economic, and policy factors, usually in a context of fragmented data availability. We employed fuzzy cognitive mapping (FCM) to integrate these factors in the assessment of future wildfire risk in the Chiquitania region, Bolivia. In this region, dealing with wildfires is becoming increasingly challenging because of reinforcing feedbacks between multiple drivers. We conducted semistructured interviews and constructed different FCMs in focus groups to understand the regional dynamics of wildfire from diverse perspectives. We used FCM modelling to evaluate possible adaptation scenarios in the context of future drier climatic conditions. Scenarios also considered possible failure to respond in time to the emergent risk. This approach proved of great potential to support decision making for risk management. It helped identify key forcing variables and generate insights into potential risks and trade-offs of different strategies. The “Hands-off” scenario resulted in amplified impacts driven by intensifying trends, affecting particularly the agricultural production under drought conditions. The “Fire management” scenario, which adopted a bottom-up approach to improve controlled burning, showed less trade-offs between wildfire risk reduction and production compared with the “Fire suppression” scenario. Findings highlighted the importance of considering strategies that involve all actors who use fire, and the need to nest these strategies for a more systemic approach to manage wildfire risk. The FCM model could be used as a decisionsupport tool and serve as a “boundary object” to facilitate collaboration and integration of different perceptions of fire in the region. This approach also has the potential to inform decisions in other dynamic frontier landscapes around the world that are facing increased risk of large wildfires.
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| 6. |
- Devisscher, Tahia, et al.
(författare)
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Deliberation for wildfire risk management : Addressing conflicting views in the Chiquitania, Bolivia
- 2019
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Ingår i: Geographical Journal. - : Wiley. - 0016-7398 .- 1475-4959. ; 185:1, s. 38-54
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Tidskriftsartikel (refereegranskat)abstract
- Wildfires are increasingly affecting forest landscapes around the world. In the Bolivian Chiquitania, southern Amazonia, large wildfires during recent droughts have intensified public debate around more systemic solutions to address the possible root causes. While the integration of different forms of fire knowledge is gaining acceptance as an approach to dealing with increasing wildfire risk, little attention has been given to this integration in the Amazonia. In fact, mismatches between policy, science and local realities have curtailed the success of fire risk strategies in the region. To address this challenge, we conducted interviews and focus group discussions with a wide range of actors in the Chiquitania to examine different forms of knowledge and views of fire, and the extent to which these were integrated in prevalent wildfire risk strategies. We found that the risk strategies were in tension between two conflicting understandings of fire. A conceptual framework was developed to capture the configuration of knowledge underpinning this tension. Adopting a more integrated and inclusive approach to manage wildfire risk will require overcoming first this tension through a more open deliberation process within a reflexive governance framework. We proposed three “deliberation arenas” to facilitate this process, which could ultimately support more systemic, inter-cultural fire management in the Chiquitania and other landscapes with conflicting views in the Amazonia.
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| 7. |
- Doughty, Christopher E., et al.
(författare)
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What controls variation in carbon use efficiency among Amazonian tropical forests?
- 2018
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Ingår i: Biotropica. - : Wiley. - 0006-3606. ; 50:1, s. 16-25
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Tidskriftsartikel (refereegranskat)abstract
- Why do some forests produce biomass more efficiently than others? Variations in Carbon Use Efficiency (CUE: total Net Primary Production (NPP)/ Gross Primary Production (GPP)) may be due to changes in wood residence time (Biomass/NPPwood), temperature, or soil nutrient status. We tested these hypotheses in 14, one ha plots across Amazonian and Andean forests where we measured most key components of net primary production (NPP: wood, fine roots, and leaves) and autotrophic respiration (Ra; wood, rhizosphere, and leaf respiration). We found that lower fertility sites were less efficient at producing biomass and had higher rhizosphere respiration, indicating increased carbon allocation to belowground components. We then compared wood respiration to wood growth and rhizosphere respiration to fine root growth and found that forests with residence times <40 yrs had significantly lower maintenance respiration for both wood and fine roots than forests with residence times >40 yrs. A comparison of rhizosphere respiration to fine root growth showed that rhizosphere growth respiration was significantly greater at low fertility sites. Overall, we found that Amazonian forests produce biomass less efficiently in stands with residence times >40 yrs and in stands with lower fertility, but changes to long-term mean annual temperatures do not impact CUE.
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| 8. |
- Fisher, Joshua B., et al.
(författare)
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African tropical rainforest net carbon dioxide fluxes in the twentieth century
- 2013
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Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 368:1625, s. 9-20120376
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Tidskriftsartikel (refereegranskat)abstract
- The African humid tropical biome constitutes the second largest rainforest region, significantly impacts global carbon cycling and climate, and has undergone major changes in functioning owing to climate and land-use change over the past century. We assess changes and trends in CO2 fluxes from 1901 to 2010 using nine land surface models forced with common driving data, and depict the inter-model variability as the uncertainty in fluxes. The biome is estimated to be a natural (no disturbance) net carbon sink (−0.02 kg C m−2 yr−1 or −0.04 Pg C yr−1, p < 0.05) with increasing strength fourfold in the second half of the century. The models were in close agreement on net CO2 flux at the beginning of the century (σ1901 = 0.02 kg C m−2 yr−1), but diverged exponentially throughout the century (σ2010 = 0.03 kg C m−2 yr−1). The increasing uncertainty is due to differences in sensitivity to increasing atmospheric CO2, but not increasing water stress, despite a decrease in precipitation and increase in air temperature. However, the largest uncertainties were associated with the most extreme drought events of the century. These results highlight the need to constrain modelled CO2 fluxes with increasing atmospheric CO2 concentrations and extreme climatic events, as the uncertainties will only amplify in the next century.
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| 9. |
- Girardin, Cécile A J, et al.
(författare)
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Seasonal trends of Amazonian rainforest phenology, net primary productivity, and carbon allocation
- 2016
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Ingår i: Global Biogeochemical Cycles. - 0886-6236. ; 30:5, s. 700-715
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Tidskriftsartikel (refereegranskat)abstract
- The seasonality of solar irradiance and precipitation may regulate seasonal variations in tropical forests carbon cycling. Controversy remains over their importance as drivers of seasonal dynamics of net primary productivity in tropical forests. We use ground data from nine lowland Amazonian forest plots collected over 3 years to quantify the monthly primary productivity (NPP) of leaves, reproductive material, woody material, and fine roots over an annual cycle. We distinguish between forests that do not experience substantial seasonal moisture stress (“humid sites”) and forests that experience a stronger dry season (“dry sites”). We find that forests from both precipitation regimes maximize leaf NPP over the drier season, with a peak in production in August at both humid (mean 0.39 ± 0.03 Mg C ha−1 month−1 in July, n = 4) and dry sites (mean 0.49 ± 0.03 Mg C ha−1 month−1 in September, n = 8). We identify two distinct seasonal carbon allocation patterns (the allocation of NPP to a specific organ such as wood leaves or fine roots divided by total NPP). The forests monitored in the present study show evidence of either (i) constant allocation to roots and a seasonal trade-off between leaf and woody material or (ii) constant allocation to wood and a seasonal trade-off between roots and leaves. Finally, we find strong evidence of synchronized flowering at the end of the dry season in both precipitation regimes. Flower production reaches a maximum of 0.047 ± 0.013 and 0.031 ± 0.004 Mg C ha−1 month−1 in November, in humid and dry sites, respectively. Fruitfall production was staggered throughout the year, probably reflecting the high variation in varying times to development and loss of fruit among species.
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| 10. |
- Householder, John Ethan, et al.
(författare)
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One sixth of Amazonian tree diversity is dependent on river floodplains
- 2024
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Ingår i: NATURE ECOLOGY & EVOLUTION. - 2397-334X.
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Tidskriftsartikel (refereegranskat)abstract
- Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.
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