| 1. |
- 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. ; 8, s. 901-911
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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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| 2. |
- Luize, Bruno Garcia, et al.
(författare)
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Geography and ecology shape the phylogenetic composition of Amazonian tree communities
- 2024
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Ingår i: JOURNAL OF BIOGEOGRAPHY. - 0305-0270 .- 1365-2699. ; 51:7, s. 1163-1184
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and v & aacute;rzea forest types, the phylogenetic composition varies by geographic region, but the igap & oacute; and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R-2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R-2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.
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| 3. |
- ter Steege, Hans, et al.
(författare)
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Mapping density, diversity and species-richness of the Amazon tree flora
- 2023
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Ingår i: COMMUNICATIONS BIOLOGY. - 2399-3642. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution. A study mapping the tree species richness in Amazonian forests shows that soil type exerts a strong effect on species richness, probably caused by the areas of these forest types. Cumulative water deficit, tree density and temperature seasonality affect species richness at a regional scale.
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| 4. |
- Peripato, Vinicius, et al.
(författare)
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More than 10,000 pre-Columbian earthworks are still hidden throughout Amazonia
- 2023
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Ingår i: Science (New York, N.Y.). - 1095-9203. ; 382:6666, s. 103-109
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Tidskriftsartikel (refereegranskat)abstract
- Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.
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| 5. |
- Aronsson, Daniel, et al.
(författare)
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EU FP7 INFSO-ICT-247223 ARTIST4G, D3.4 Relay configurations
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The following document contains proposals for innovations on relay configurations made by partners involved in the Artist4G project WP3, Task 3.3. The different relay configurations are for in-band and out-band relays, multi-hop relays, and moving relays. For each innovation, a description, the potential deviation from a defined baseline architecture, and simulation results (as far as available) are included. Important issues regarding the innovations impact on the architecture are pointed out and analysed in detail. This analysis will also be forwarded to WP4.
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| 6. |
- Bonneville, Hervé, et al.
(författare)
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EU FP7 INFSO-ICT-247223 ARTIST4G, D3.2 Advanced Relay Technical Proposals
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The following document contains technical proposals for advanced relays that have been developed so far by the partners in Task 3.1 of WP3. The proposals are grouped according to the respective activity in Task 3.1 and contain a description of the innovation and all deviations from the baseline assumptions listed for state-of-the-art relay-enhanced systems in the first part of this document. For each innovation, analytical derivations and/or simulation results are provided, as well as an outlook on future work within WP3.
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| 7. |
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| 8. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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Advanced Relaying Concepts for Future Wireless Networks
- 2012
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Ingår i: Future Network and Mobile Summit (FUNEMS 2012), Berlin, Germany, July 2012. - 9781905824298
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Konferensbidrag (refereegranskat)abstract
- Relaying is undoubtedly a key technology for future wireless networks as it can be applied to provide coverage extension and capacity increase in a cost-effective manner. This paper presents an outline of the major advanced relaying concepts that will be part of future systems from the viewpoint of the ARTIST4G European project. These concepts can be divided into three categories, those pertinent to type-1 relays, type-2 relays and moving relays. The characteristics of each of these concepts are presented and the challenges related to their implementation are discussed. Furthermore the paper proposes a set of solutions to address the discussed challenges. For type-1 relays, the paper presents solutions for the allocation of resources to the backhaul and the access links, the inter-relay interference mitigation, and the multi-hop transmission mode. For type-2 relays, our focus is on the design of distributed hybrid automatic repeat request (HARQ) protocols. More specifically we propose that the conventional HARQ schemes are adapted to exploit the potentially better channel conditions provided by the relays. Moreover distributed turbo coding solutions are introduced for increasing transmission reliability with the aid of relays. Finally, moving relays are presented as an efficient solution to the ever-growing demand for wireless broadband by users within public transportation vehicles. We show that moving relays can very effectively overcome vehicle penetration losses and boost the achievable capacities of the moving users. Overall, we conclude that the presented advanced relaying concepts are very promising and can significantly enhance the user experience in future wireless networks.
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| 9. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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Pass it on: Advanced Relaying Concepts and Challenges for Networks Beyond 4G
- 2014
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Ingår i: IEEE Vehicular Technology Magazine. - 1556-6080 .- 1556-6072. ; 9:2, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- Relay nodes (RNs) will be a key feature of future wireless networks. RNs can extend coverage, increase network capacity, and provide more uniform quality-of-service (QoS) across the cell area in a cost-effective manner. Therefore, not surprisingly, relaying techniques have attracted a significant amount of attention from the wireless industry and standards. The Third-Generation Partnership Project (3GPP) release 10 has considered RNs that act as base stations (BSs), known as type-1 RNs, aiming only for coverage extension. However, RNs can be employed in different ways, and several challenges have to be addressed to attain the theoretical gains. This article presents an overview of the relaying concepts related to the 3GPP long-term evolution (LTE) road map, i.e., concepts related to type-1, type-2, and moving RNs. The implementation challenges are outlined, and a number of promising solutions for each RN type are discussed. More specifically, for type-1 RNs, this article focuses on the allocation of resources to the backhaul and access links. For type-2 RNs, the focus is on designing distributed hybrid automatic repeat request (HARQ) protocols that involve RNs. Moving RNs are presented as an efficient solution to the ever-growing demand for wireless broadband by vehicleborne users. Overall, the presented relaying concepts and solutions can significantly improve the user experience and can play an important role in the future.
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