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  • 1
    In: Global Ecology and Biogeography, Wiley, Vol. 31, No. 8 ( 2022-08), p. 1571-1588
    Kurzfassung: Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Location Lowland Amazonian forests. Time period 1971–2019. Methods We used 344 long‐term inventory plots distributed across Amazonia to analyse the effects of long‐term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil‐water and edaphic properties. Results Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth  〈 5 m) had 18% less above‐ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit 〈 −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table. Main conclusions We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland ( terra‐firme ) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change.
    Materialart: Online-Ressource
    ISSN: 1466-822X , 1466-8238
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2022
    ZDB Id: 1479787-2
    ZDB Id: 2021283-5
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Ecography, Wiley, Vol. 2022, No. 11 ( 2022-11)
    Kurzfassung: Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well‐drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1‐ha non‐flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community‐weighted wood density mean (CWM‐wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well‐drained soils. CWM‐wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central‐Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures.
    Materialart: Online-Ressource
    ISSN: 0906-7590 , 1600-0587
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2022
    ZDB Id: 2024917-2
    ZDB Id: 1112659-0
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    In: Global Ecology and Biogeography, Wiley, Vol. 32, No. 1 ( 2023-01), p. 49-69
    Kurzfassung: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser‐availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource‐availability hypothesis). Time period Tree‐inventory plots established between 1934 and 2019. Major taxa studied Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree‐inventory plots across terra‐firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance‐weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra‐firme forests (excluding podzols) compared to flooded forests. Main conclusions The disperser‐availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types.
    Materialart: Online-Ressource
    ISSN: 1466-822X , 1466-8238
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2023
    ZDB Id: 1479787-2
    ZDB Id: 2021283-5
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    In: Global Change Biology, Wiley, Vol. 29, No. 17 ( 2023-09), p. 4861-4879
    Kurzfassung: For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of diversity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species diversity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The diversity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regions and forest types. Environmental variables associated with disturbances, for example, the lightning flash rate and wind speed, as well as the fraction of photosynthetically active radiation, tend to govern the diversity of large trees. Upland rainforests in the Guiana Shield and Roraima regions had a high diversity of large trees. By contrast, variables associated with resources tend to govern tree diversity in general. Places such as the province of Imeri and the northern portion of the province of Madeira stand out for their high diversity of species in general. Climatic and topographic stability and functional adaptation mechanisms promote ideal conditions for species diversity. Finally, we mapped general patterns of tree species diversity in the Brazilian Amazon, which differ substantially depending on size class.
    Materialart: Online-Ressource
    ISSN: 1354-1013 , 1365-2486
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2023
    ZDB Id: 2020313-5
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    In: Frontiers in Ecology and the Environment, Wiley, Vol. 21, No. 1 ( 2023-02), p. 24-32
    Kurzfassung: Amazon forests are being degraded by myriad anthropogenic disturbances, altering ecosystem and climate function. We analyzed the effects of a range of land‐use and climate‐change disturbances on fine‐scale canopy structure using a large database of profiling canopy lidar collected from disturbed and mature Amazon forest plots. At most of the disturbed sites, surveys were conducted 10–30 years after disturbance, with many exhibiting signs of recovery. Structural impacts differed in magnitude more than in character among disturbance types, producing a gradient of impacts. Structural changes were highly coordinated in a manner consistent across disturbance types, indicating commonalities in regeneration pathways. At the most severely affected site – burned igapó (seasonally flooded forest) – no signs of canopy regeneration were observed, indicating a sustained alteration of microclimates and consequently greater vulnerability to transitioning to a more open‐canopy, savanna‐like state. Notably, disturbances rarely shifted forests beyond the natural background of structural variation within mature plots, highlighting the similarities between anthropogenic and natural disturbance regimes, and indicating a degree of resilience among Amazon forests. Studying diverse disturbance types within an integrated analytical framework builds capacity to predict the risk of degradation‐driven forest transitions.
    Materialart: Online-Ressource
    ISSN: 1540-9295 , 1540-9309
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2023
    ZDB Id: 2161292-4
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    In: Biological Reviews, Wiley, Vol. 98, No. 2 ( 2023-04), p. 662-676
    Kurzfassung: Naturally regenerating forests or secondary forests (SFs) are a promising strategy for restoring large expanses of tropical forests at low cost and with high environmental benefits. This expectation is supported by the high resilience of tropical forests after natural disturbances, yet this resilience can be severely reduced by human impacts. Assessing the characteristics of SFs and their ecological integrity (EI) is essential to evaluating their role for conservation, restoration, and provisioning of ecosystem services. In this study, we aim to propose a concept and indicators that allow the assessment and classification of the EI of SFs. To this end, we review the literature to assess how EI has been addressed in different ecosystems and which indicators of EI are most commonly used for tropical forests. Building upon this knowledge we propose a modification of the concept of EI to embrace SFs and suggest indicators of EI that can be applied to different successional stages or stand ages. Additionally, we relate these indicators to ecosystem service provision in order to support the practical application of the theory. EI is generally defined as the ability of ecosystems to support and maintain composition, structure and function similar to the reference conditions of an undisturbed ecosystem. This definition does not consider the temporal dynamics of recovering ecosystems, such as SFs. Therefore, we suggest incorporation of an optimal successional trajectory as a reference in addition to the old‐growth forest reference. The optimal successional trajectory represents the maximum EI that can be attained at each successional stage in a given region and enables the evaluation of EI at any given age class. We further suggest a list of indicators, the main ones being: compositional indicators (species diversity/richness and indicator species); structural indicators (basal area, heterogeneity of basal area and canopy cover); function indicators (tree growth and mortality); and landscape proxies (landscape heterogeneity, landscape connectivity). Finally, we discuss how this approach can assist in defining the value of SF patches to provide ecosystem services, restore forests and contribute to ecosystem conservation.
    Materialart: Online-Ressource
    ISSN: 1464-7931 , 1469-185X
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2023
    ZDB Id: 1423558-4
    ZDB Id: 1476789-2
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    In: Journal of Ecology, Wiley, Vol. 108, No. 4 ( 2020-07), p. 1311-1321
    Kurzfassung: In tropical rainforest, most vascular plants have some capacity to resprout, and lianas are often effective resprouters after canopy fall. However, the diversity of resprouting responses of liana species and the consequence for plant persistence are poorly understood. We hypothesized that variation in regeneration among liana species causes differences in liana species abundance in tropical rainforest through differential resprouting capacity, such that liana species with higher densities produce more resprouts after canopy falls. We applied a manipulative field experiment investigating the effect of different levels of disturbance on the production of resprouts and adventitious roots in 10 liana species of the tribe Bignonieae (Bignoniaceae) with contrasting abundances in central Amazonia. We selected 15 individuals of each species and assigned the lianas to three distinct conditions: (a) total canopy fall with lianas severely damaged and detached from trees; (b) partial fall of lianas, without visible damage; and (c) intact lianas (control). We tested whether liana species regeneration patterns were related to species density. Liana species density was calculated using previous research on liana species distribution in 30 1‐ha plots systematically distributed in a 6 × 6 km 2 grid at the Ducke Reserve. The number of aerial resprouts produced by lianas under the total canopy fall treatment was twice that of plants under lower levels of disturbance, while the production of adventitious roots did not differ among treatments. Liana species showed different intensities of resprouting, and species with higher average densities on the forest landscape had more resprouts after the total canopy fall treatment. Synthesis . Our results shed new light on the factors that influence liana species abundance, highlighting the role of resprouting after canopy fall and its variation among liana species. Resprouting mitigates the negative effects of canopy damage, suggesting that the impact of increased tree fall disturbances over time, which has been attributed to Amazonian forests in the literature, may increase already abundant liana species with effective resprouting capacity. We identify liana species that are more resilient to disturbance and may alter forest dynamics during climatic change.
    Materialart: Online-Ressource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2020
    ZDB Id: 3023-5
    ZDB Id: 2004136-6
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    In: New Phytologist, Wiley, Vol. 237, No. 3 ( 2023-02), p. 714-733
    Kurzfassung: See also the Commentary on this article by Chitra-Tarak & Warren 237 : 703–706.
    Materialart: Online-Ressource
    ISSN: 0028-646X , 1469-8137
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2023
    ZDB Id: 208885-X
    ZDB Id: 1472194-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    In: Global Ecology and Biogeography, Wiley, Vol. 29, No. 9 ( 2020-09), p. 1495-1514
    Kurzfassung: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in 〉 80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests.
    Materialart: Online-Ressource
    ISSN: 1466-822X , 1466-8238
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2020
    ZDB Id: 1479787-2
    ZDB Id: 2021283-5
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    In: Journal of Ecology, Wiley, Vol. 108, No. 5 ( 2020-09), p. 2070-2082
    Kurzfassung: The intensity and frequency of severe droughts in the Amazon region have increased in the recent decades. These extreme events are associated with changes in forest dynamics, biomass and floristic composition. However, most studies of drought response have focused on upland forests with deep water tables, which may be especially sensitive to drought. Palms, which tend to dominate the less well‐drained soils, have also been neglected. The relative neglect of shallow water tables and palms is a significant concern for our understanding of tropical drought impacts, especially as one‐third of Amazon forests grow on shallow water tables ( 〈 5 m deep). We evaluated the drought response of palms and trees in forests distributed over a 600 km transect in central‐southern Amazonia, where the landscape is dominated by shallow water table forests (SWTF). We compared vegetation dynamics before and following the 2015–2016 El Nino drought, the hottest and driest on record for the region (−214 mm of cumulative water deficit). We observed no change in stand mortality rates and no biomass loss in response to drought in these forests. Instead, we observed an increase in recruitment rates, which doubled to 6.78% year ‐1  ± 4.40 ( M  ±  SD ) during 2015–2016 for palms and increased by half for trees (to 2.92% year ‐1  ± 1.21), compared to rates in the pre‐El‐Nino interval. Within these SWTF, mortality and recruitment rates varied as a function of climatic drought intensity and water table depth for both palms and trees, with mortality being greatest in climatically and hydrologically wetter environments and recruitment greatest in drier environments. Across our transect, there was a significant increase over time in tree biomass. Synthesis . Our results indicate that forests growing over shallow water tables—relatively under‐studied vegetation that nonetheless occupies one‐third of Amazon forests—are remarkably resistant to drought. These findings are consistent with the hypothesis that local hydrology and its interactions with climate strongly constrain forest drought effects, and has implications for climate change feedbacks. This work enhances our understanding of integrated drought effects on tropical forest dynamics and highlights the importance of incorporating neglected forest types into both the modelling of forest climate responses and into public decisions about priorities for conservation.
    Materialart: Online-Ressource
    ISSN: 0022-0477 , 1365-2745
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2020
    ZDB Id: 3023-5
    ZDB Id: 2004136-6
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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