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Anthropogenic and climatic variables combine to alter river flow regimes worldwide, which can influence shifts in species composition. Exacerbation of drought events in southeastern United States floodplains may have varying impacts on survival and regeneration of high bottomland, low bottomland, and swamp forest species, causing distribution shifts between these forest types. We tested 7-month-old seedlings of the swamp species water tupelo (Nyssa aquatica), Ogeechee tupelo (Nyssa ogeche), and pop ash (Fraxinus caroliniana), and the low bottomland species overcup oak (Quercus lyrata) and water hickory (Carya aquatica) in a controlled experiment with increasing drought treatment. We compared timing to 95% mortality and determined lethal soil moisture thresholds for species. Swamp species were no more vulnerable to mortality under increasing drought than low bottomland hardwood species found in neighboring wet floodplain habitats, suggesting that duration of drought may not be a main driver of compositional shifts between these forests. Study Implications : Natural flows of river systems around the world have been altered by humans and a changing climate. Increased intensity of drought events can affect tree species growing adjacent to rivers and influence their ability to reproduce, thus changing the composition of floodplain forests. We tested the drought tolerance of three swamp species accustomed to frequent flooding and two low bottomland hardwood species accustomed to less frequent flooding to see which species might be more affected by drought. We observed no differences between these two groups, suggesting that greater flood tolerance may not imply greater drought intolerance. [ABSTRACT FROM AUTHOR]

Introduction: Trees from flooded forests have to adjust their xylem hydraulic structure to face the annual flooding and the climatic conditions of the atmosphere. Usually, this adjustment of anatomical tissues in the tropics is driven by drought events inducing conservative behavior and can be recorded annually in tree rings. However, how the flood pulse and the climatic conditions influence the xylem hydraulic structure in floodplain trees is unknown. Methods: To fill this gap, we explore if flooded periods and monthly climate variation affect the annual tree growth and xylem anatomy structure for the tree species Hydrochorea corymbosa (Fabaceae) from the varzea flooded forest in the Central Amazon. We developed a 41-year ring width chronology (1971-2018) and a 30-year time series of xylem anatomy parameters (1988-2018) as mean hydraulic vessel diameter (Dh), vessel frequency (VF), and parenchyma quantity (PQ). We correlated the series with monthly hydrological and climatic data. Results: The hydrological regime did not correlate with annual tree growth in that species as we previously expected but showed correlations with the xylem anatomical structure. High flood levels during the end of the flooding period induced conservative patterns of the anatomical structure, with a negative correlation with Dh (rho June = -0.40, p < 0.05) and a positive correlation with the PQ (rho September/October = 0.42, p < 0.05). These responses show that these trees are responding to flooding similar to the tree responses to drought. Regarding the climatic variation, the annual tree growth showed a negative correlation with the vapor pressure deficit (VPD), after the second half of the flooded period with the strongest correlation happening during the non- flooded period (rho December = -0.66, p < 0. 01). These conservative patterns in tree behavior also happened when the maximum temperature negatively affected the vessel diameter (rho September = -0.42, p < 0.05). Discussion: In that case, we recognized two different moments that the environment is inducing conservative patterns in the xylem structure of those trees: 1) increasing the flood levels and 2) the high evaporative demand during the non-flooded period. In this way, the intensification of the hydrological regime, as well as the strong drought conditions during the non-flooded periods, can be a risk for H. corymbosa in the Central Amazonian floodplains. [ABSTRACT FROM AUTHOR]

IntroductionTrees from flooded forests have to adjust their xylem hydraulic structure to face the annual flooding and the climatic conditions of the atmosphere. Usually, this adjustment of anatomical tissues in the tropics is driven by drought events inducing conservative behavior and can be recorded annually in tree rings. However, how the flood pulse and the climatic conditions influence the xylem hydraulic structure in floodplain trees is unknown.MethodsTo fill this gap, we explore if flooded periods and monthly climate variation affect the annual tree growth and xylem anatomy structure for the tree species Hydrochorea corymbosa (Fabaceae) from the várzea flooded forest in the Central Amazon. We developed a 41-year ring width chronology (1971–2018) and a 30-year time series of xylem anatomy parameters (1988–2018) as mean hydraulic vessel diameter (Dh), vessel frequency (VF), and parenchyma quantity (PQ). We correlated the series with monthly hydrological and climatic data.ResultsThe hydrological regime did not correlate with annual tree growth in that species as we previously expected but showed correlations with the xylem anatomical structure. High flood levels during the end of the flooding period induced conservative patterns of the anatomical structure, with a negative correlation with Dh (rho June = −0.40, p < 0.05) and a positive correlation with the PQ (rho September/October = 0.42, p < 0.05). These responses show that these trees are responding to flooding similar to the tree responses to drought. Regarding the climatic variation, the annual tree growth showed a negative correlation with the vapor pressure deficit (VPD), after the second half of the flooded period with the strongest correlation happening during the non-flooded period (rho December = −0.66, p < 0. 01). These conservative patterns in tree behavior also happened when the maximum temperature negatively affected the vessel diameter (rho September = −0.42, p < 0.05).DiscussionIn that case, we recognized two different moments that the environment is inducing conservative patterns in the xylem structure of those trees: 1) increasing the flood levels and 2) the high evaporative demand during the non-flooded period. In this way, the intensification of the hydrological regime, as well as the strong drought conditions during the non-flooded periods, can be a risk for H. corymbosa in the Central Amazonian floodplains.

Key message: Tree species in a temperate floodplain forest had leaf turgor loss point values similar to those of upland forest trees, suggesting physiological drought tolerance in this generally non-water-limited system. Leaf turgor loss point (TLP) is a key plant trait associated with drought tolerance. In the bottomland hardwood (BLH) forests that grow in floodplains of the southeastern USA, drought stress is generally low but may increase with climate change. To address drought tolerance among BLH trees, we measured TLP among 20 species in a BLH forest in Louisiana, USA. We tested whether (1) TLP is higher in BLH tree species than in upland temperate-zone trees; (2) lower TLP is associated with higher drought tolerance among BLH species; (3) TLP drops during the growing season within BLH trees; and (4) within species, TLP is lower in more water limited, non-flooded BLH habitats than in seasonally flooded habitats. Among BLH tree species, TLP was −2.23 ± 0.28 (mean ± SD) and, contrary to our hypothesis, weakly positively correlated with drought tolerance. Within BLH species, TLP was lower in non-flooded habitats than seasonally flooded habitats and TLP decreased between the early and late growing season, more so in the non-flooded habitat. Overall, our results show that TLP among BLH trees is relatively low and plastic for a system that is generally not water limited, which may contribute to drought tolerance in future scenarios. [ABSTRACT FROM AUTHOR]

Forest tree species reproduction is a key factor in maintaining the genetic diversity of future generations and the stability of forest ecosystems. The ongoing ash dieback disease could affect the reproductive ecology of Fraxinus excelsior L. and have a major impact on the quantity and quality of pollen and seeds. In this study, we investigated pollen production and viability of pollen and seeds of ash trees with different health status from 2018 to 2022. Inflorescences were collected from 105 trees (pollen production), pollen from 125 trees (pollen viability), and seeds from 53 trees (seed quality) in two seed orchards and in one floodplain forest in southern Germany. Not all parameters were examined at every site every year. The average pollen production per tree was estimated at 471.2 ± 647.9 billion pollen grains. In addition, we found that a high number of inflorescences did not equate to high pollen production per inflorescence. Pollen production of healthy and diseased trees did not differ significantly, although only 47% of severely diseased male trees (vs. 72% for healthy trees) produced flowers. With regards to pollen viability, the TTC test showed an average viability of 73% ± 17%. Overall, there was a slight tendency for diseased trees to have less viable pollen. However, a significant difference could only be calculated for trees in the floodplain forest. The percentage of germinable seeds in 2018 was 38% in the floodplain forest and 57% in one of the seed orchards. The percentage of viable seeds (TTC test) ranged from 17 to 22% in the orchards in 2020. Non-viable seeds were usually heavily infested by insects. In general, seed quality was not significantly different between healthy and diseased trees. Our results indicate that ash dieback affects flower formation and pollen viability but not pollen production or seed quality. Nevertheless, the fact that hardly any flowering was observed, especially for trees that were seriously affected, suggests a negative effect of ash dieback on reproductive performance. Thus, severely diseased trees will transfer their genes to a smaller extent to the next generation. [ABSTRACT FROM AUTHOR]

The extent of bottomland hardwood forests in the Lower Mississippi Alluvial Valley (LMAV) has diminished, and federal programs like the Conservation Reserve Program provide incentives to afforest marginal agricultural areas with oaks to provide ecosystem services. Remote sensing technologies, like light detection and ranging (LiDAR), can be used to estimate biomass of these stands to potentially allow landowners to take advantage of carbon markets, but data are expensive to collect. Therefore, we determined whether freely available low-density LiDAR data could capture variability in tree- and stand-level characteristics in the LMAV, including aboveground biomass. We found that multiple regression LiDAR models captured more variability in tree-level than stand-level parameters and including soil type generally improved models. Model r2 values predicting tree and stand parameters including tree height, height to the live crown, quadratic mean diameter, crown area, trees per hectare, stand basal area, and stand biomass ranged from 0.34 to 0.82 and root mean square percent error (RMSPE) ranged from 7% to 36%. Specifically, models for stand biomass had an RMSE of about 19 Mg/ha or about 19% of mean values across sites. Therefore, freely available LiDAR data was useful in evaluating afforested bottomland oak sites for tree- and stand-level structural components in the LMAV. [ABSTRACT FROM AUTHOR]

The physical and biological structure of riparian vegetation fundamentally influences floodplain roughness, and thus the flood velocity and flood levels of a river. The study aims to provide detailed spatial data on the vegetation density of a floodplain, and to model the effect of the actual vegetation and various scenarios on flow conditions. LiDAR data were applied to evaluate the density and roughness of the submerged understory vegetation over the densely vegetated floodplain of Lower Tisza, Hungary. Then, HEC–RAS 2D modelling was applied to analyse the effect of the actual vegetation on flow conditions. Further scenarios were also created to predict the effect of (i) invasive plant control, (ii) no maintenance, and (iii) riparian vegetation restoration (meadows). According to the results, since the 19th Century, the increased vegetation density is responsible for a 17-cm flood level increase, and if the vegetation grows even denser, a further 7 cm could be expected. As the vegetation density increases, the overbank flow velocity decreases, and the crevasses and flood conveyance zones gradually lose their function. Simultaneously, the flow velocity increases in the channel (from 1 m/s to 1.4 m/s), resulting in an incision. Applying LiDAR-based 2D flow modelling makes it possible to plan sustainable riparian vegetation maintenance (e.g., forestry, invasive species clearance) from both ecology and flood control perspectives. [ABSTRACT FROM AUTHOR]

In 2022, four small-scale protected areas (SPA) within Litovelské Pomoraví Protected Landscape Area were surveyed for terrestrial molluscs. All localities are floodplain forest fragments with oxbow lakes, pools and marshes in the Morava river catchment. The most species-rich SPA was Hvězda Natural Monument (NM), with 38 species recorded. The threatened species Cochlicopa nitens (Endangered), known from this area from previous surveys, was not recorded despite high sampling effort. This sensitive hygrophilous species disappeared probably due to droughts occurring in earlier years. However, other sensitive hygrophilous species such as Euconulus alderi (Nearly Threatened) and Vertigo antivertigo were recorded. The latter was also found in Plané loučky Nature Reserve (NR; 27 spp. in total) and Častava NM (19 spp. in total). Relatively common floodplain forest species Perforatella bidentata was recorded in Plané loučky NR and Hvězda NM; however, it was absent in Častava NM and Kurfürstovo rameno NM (20 spp. in total). The partial absence of this species and the complete absence of substantially declining floodplain species Pseudotrichia rubiginosa (Nearly Threatened) and other sensitive taxa indicate habitat degradation caused mainly by stream regulations and water level decrease and manipulation. The presence of invasive plant species known to decrease terrestrial mollusc species diversity and abundance are of the essence as well. Highly invasive species Arion vulgaris was the most abundant species in all of the surveyed SPAs, except for Hvězda NM, where it was present in lower numbers. Over some twenty years, this species spread from anthropogenic areas to natural habitats to become one of the most prominent features of floodplain biocoenoses in Litovelské Pomoraví and elsewhere. To improve the habitat conservation status, it is important to maintain favourable water level in streams and water bodies adjacent to SPAs, especially during the critical periods of summer droughts. Furthermore, it is advised to focus the management on neophyte extirpation.

Anthropogenic impact has largely altered the estuarine environment. Today, Nature-based solutions (NbS) are required to respond to challenges such as flooding that affect both the human population and estuarine ecosystems. Estuarine ecosystems such as saltmarshes and floodplain forests provide valuable services, and wetland restoration for flood control is suggested. Recently, flow velocities attenuating the effects of juvenile floodplain willows and wave attenuation through White willow trees under extreme conditions have been found. Services in flood control seemed promising. However, large woods do not bend and may cause turbulence. On the contrary, complex and flexible woody vegetation bends in response to currents and reduces velocities, thereby inducing lower turbulence, but knowledge of the diversity and structure of tidal willow floodplain forests (TWFF) is lacking. Thus, first, an observational study on the occurrence of TWFF in European estuaries along the North Sea was carried out. Based on findings in aerial images, only small TWFF fragments were confirmed in the field for the Elbe, Ems, Dutch delta, and the Scheldt estuary. Based on these findings and the analyses of management plans, the restoration of TWFF was planned, implemented, and studied, including a long-term study at the Elbe estuary upstream stretch. The results of the restoration efforts are provided, including the long-term study (2012–2022) on a restored TWFF in the Elbe estuary, which could serve as a pilot for TWFF restoration and adapting estuarine communities to climate change via NbS. [ABSTRACT FROM AUTHOR]

Trees can contribute to the reduction of atmospheric CO2 concentrations, but they do so at varying rates. The carbon sequestration rate (CSR) of trees is influenced by many factors including tree age, forest density, site conditions, and extreme events such as droughts and floods. This research reconstructs past carbon stocks of Pedunculate oak (Quercus robur) trees in floodplains with different hydrological conditions (low and high active floodplain, the seepage water zone of the former floodplain, and the tributary floodplain). We used increment tree cores and allometric equations and compared the annual changes in stocks as a way of assessing CSR. Furthermore, we used time series data on floods and droughts to analyze possible effects of extreme events on CSR. The aims of this study are to (a) compare the CSR of dominant Q. robur in young plantations to dominant trees in old forest stands, (b) compare the CSR of old Q. robur trees under different hydrological conditions, and (c) analyze how drought and flood events influence the CSR of Q. robur in different hydrological conditions. From 2009 to 2018, old Q. robur trees on the low active floodplain had an average CSR of 18.4 ± 1.1 (SE) Kg tree−1 year−1, while young trees had an average CSR of 8.7 ± 0.6 (SE) Kg tree−1 year−1. From 1976 to 2018, the overall CSR of Q. robur was highest on the high active floodplain (18.6 ± 1.7 (SE) Kg tree−1 year−1) and lowest on the seepage water zone of the former floodplain (13.1 ± 1.1 (SE) Kg tree−1 year−1). CSR was higher during flood years in all hydrological conditions, but was significantly reduced by drought only on active floodplains with a comparatively high elevation. Floodplains are well-suited areas for reforestation as natural climate solutions because the dominant trees in these areas have a high CSR even under severe conditions which are predicted to become more common with climate change in the future.

Little is known about the life history and environmental factors that regulate the growth rate of hyperdominant trees in flooded Amazonian forests. Pentaclethra macroloba is a hyperdominant tree, and it is widely explored in the Amazon, because its seed oil is a powerful herbal medicine. We evaluated the demographic structure and growth patterns of P. macroloba and tested the effect of the Amazon River flood pulse on its growth. We modeled the growth and determined the age of P. macroloba by analyzing the growth rings of 30 monitored trees in relation to hydroclimatic variables. We also inventoried 240 juvenile and 2072 adult trees arranged in a clustered pattern. The diametric distribution pattern of the juvenile and adult trees was exponential and log‐normal, respectively. The trees were found to be up to 102 years old, and 47% of them grew freely toward the canopy. Peak growth in height and diameter occurred at 24 (61.7 cm year‐1) and 46 (9.38 mm year‐1) years, respectively. Pentaclethra macroloba showed cambial dormancy during the seasonal peak of rainfall (R2 = 0.41; t = −2.62; p < 0.01) and flooding of the Amazon River (R2 = 0.47; t = −3.01; p < 0.01). Increases in rainfall and flood level of the river in the rainy season control the growth rate of P. macroloba, making it a seasonal process. The demographic and growth patterns of P. macroloba respond to the environmental heterogeneity of the estuarine floodplain forest and also reflect its life history over time. [ABSTRACT FROM AUTHOR]

Floodplain forests have become rare in Europe due to anthropogenic changes. A critical aspect of their restoration is reintroducing flooding via dike relocation, as implemented at the Elbe River near Lenzen/Germany. How forest development is influenced by dike relocation is still unclear and difficult to predict. Inside the dike relocation area at the Elbe River, most trees were planted. Due to high tree mortality, we asked if the relative elevation of the planted trees and thus the number of flooding days inside the relocation area was comparable to the prevailing flooding regime in the surrounding active floodplain. Therefore, the positions of Ulmus laevis, Quercus robur, and Crataegus monogyna individuals were recorded using a DGPS and merged with a digital terrain model. Subsequently, relative elevations and numbers of flooding days per year and growing season (averages for 2011–2017) were calculated. The most flooding tolerant species, U. laevis, occurred at the lowest sites and tolerated the highest number of flooding days, followed by Q. robur, and finally by the least flooding tolerant species C. monogyna. All three species occurred at lower sites inside the dike relocation area and were exposed to longer flooding durations compared to sites outside the area. This was due to the complex morphology of this area and its special flooding and flow dynamics, which differed from the conditions in the surrounding active floodplain. Although the mean flooding duration was within the growth range of hardwood floodplain forests (Ficario‐Ulmetum), most individuals may not have established at the planted sites under natural conditions. Therefore, we recommend not relying only on plantings but also allowing natural succession. Then, species that can cope with the hydrological site characteristics may also establish in the long term. [ABSTRACT FROM AUTHOR]

Environmental conditions influence forest ecosystems and consequently, its productivity. Thus, the quantification of forest CO2 exchange is a critical requirement to estimate the CO2 balance of forests on a local and regional scale. Besides interpreting the annual CO2 exchange corresponding to environmental conditions over the studied years (2015–2020) at the floodplain forest in Lanžhot, Czech Republic (48.6815483 N, 16.9463317 E), the influence of below-above canopy air mass decoupling on above canopy derived CO2 exchange is the focus of this study. For this purpose, we applied the eddy covariance (EC) method above and below the forest canopy, assessing different single- and two-level flux filtering strategies. We focused on one example year (2019) of concurrent below and above canopy EC measurements. We hypothesized that conventional single-level EC flux filtering strategies such as the friction velocity (u*) filtering approach might not be sufficient to fully capture the forest CO2 exchange at the studied ecosystem. Results suggest that decoupling occurs regularly, but the implication on the above canopy derived EC CO2 fluxes appears to be negligible on an annual scale. We attribute this to the open canopy and flat EC tower surrounding terrain which inhibits horizontal removal of below-canopy respired CO2. [ABSTRACT FROM AUTHOR]

Japanese hops (Humulus japonicus) is an invasive vine that establishes in open areas in riverine habitats and suppresses tree regeneration and native vegetation. This study evaluated the use of herbicides and tree plantings to control and manage Japanese hops on five Mississippi River islands over a four-year period. Herbicide treatments included a preemergent (sulfometuron methyl), a postemergent (glyphosate), and a combination of both. Tree plantings used containerized and bareroot American sycamore (Platanus occidentalis) and eastern cottonwood (Populus deltoides) trees. Japanese hops biomass was significantly lower in all herbicide treatments in 2012 and 2015, but the preemergent treatment was less effective than other treatments in 2012 and 2014. After two years, average survivorship of containerized trees was 20%–42%, whereas bareroot seedlings had near 100% mortality. Results indicate that postemergent treatments are effective for short-term control, but large floods reestablish Japanese hops in treated areas. Reforestation, if combined with herbicide treatments and active management, may be a promising approach in large river floodplains that experience frequent flooding, but low tree survivorship presents challenges to reforestation. [ABSTRACT FROM AUTHOR]

Abstract Background This article presents, from an ethnoecological perspective, the worldviews, traditional knowledge, and cultural practices of Amazonian riverine people involved in the extraction of miriti fruits (Mauritia flexuosa L.f.), in a context of increasing market demand for miriti fruits and of pressure for the intensification of açaí (Euterpe oleracea Mart.) production on the Sirituba island, in Abaetetuba, Brazil. Methods Methods used were participant observation and non-directive interviews with 22 extractive families of miriti from the Santa Maria and Costa Sirituba communities, on Sirituba Island, in Abaetetuba, Pará, Brazil. Non-structured interviews were used to analyze the knowledge about the species, history of miriti extraction, the traditions, and innovations related to this activity over time. Participant observation took place when riverine individuals were working with miriti fruits, in order to grasp the “codes” that permeate the human-nature relationships embedded in this production system. Results It was verified that the riverine peoples have a great knowledge about the palm tree, which is reflected in their own classification systems and management practices that allow the sustainable extraction of the fruits, avoiding, for example, cutting the miriti palms. In addition, a reciprocity relationship was observed between riverine peoples and miriti palm that are personified and preserved, contributing to the conservation of the species in the floodplain, even with the intensification of açaí (Euterpe oleracea Mart.) production. Another important aspect is the collective work involving all the members of the family, which allows the appropriation of the knowledge about the extraction of miriti by the young, allowing the resistance of the tradition that remains strong, contributing to the sustainability of the practice and conservation of biodiversity in the Amazonian floodplain. Conclusion The k-c-p complex inherent to the riverine universe allows, even in face of the growing commercial demand for miriti fruits and the unchallenged increase in the extraction of this product, the conservation of floodplain biodiversity. Thus, we emphasize the importance of traditional knowledge and practices for biodiversity preservation, and they use them to guide public policies and natural resource management systems, aiming for sustainable ways to manage and use biodiversity.

Abstract Species richness is a frequently used measure of biodiversity. The compilation of a complete species list is an often unattainable goal. Estimators of species richness have been developed to overcome this problem. While the use of these estimators is becoming increasingly popular, working with the observed number of species is still common practice. To assess whether patterns of beetle communities based on observed numbers may be compared among each other, we compared patterns from observed and estimated numbers of species for beetle communities in the canopy of the Leipzig floodplain forest. These patterns were species richness and the number of shared species among three tree species and two canopy strata. We tested the applicability of the asymptotic Chao1 estimator and the estimate provided by the nonasymptotic rarefaction–extrapolation method for all tree species and both upper canopy and lower canopy. In the majority of cases, the ranking patterns of species richness for host tree species and strata were the same for the observed and estimated number of species. The ranking patterns of the number of species shared among host tree species and strata, however, were significantly different between observed and estimated values. Our results indicate that the observed number of species under‐represents species richness and the number of shared species. However, ranking comparisons of published patterns based on the number of observed species may be acceptable for species richness but likely not reliable for the number of shared species. Further studies are needed to corroborate this conclusion. We encourage to use estimators and to provide open access to data to allow comparative assessments.

Anthropogenic impact has largely altered the estuarine environment. Today, Nature-based solutions (NbS) are required to respond to challenges such as flooding that affect both the human population and estuarine ecosystems. Estuarine ecosystems such as saltmarshes and floodplain forests provide valuable services, and wetland restoration for flood control is suggested. Recently, flow velocities attenuating the effects of juvenile floodplain willows and wave attenuation through White willow trees under extreme conditions have been found. Services in flood control seemed promising. However, large woods do not bend and may cause turbulence. On the contrary, complex and flexible woody vegetation bends in response to currents and reduces velocities, thereby inducing lower turbulence, but knowledge of the diversity and structure of tidal willow floodplain forests (TWFF) is lacking. Thus, first, an observational study on the occurrence of TWFF in European estuaries along the North Sea was carried out. Based on findings in aerial images, only small TWFF fragments were confirmed in the field for the Elbe, Ems, Dutch delta, and the Scheldt estuary. Based on these findings and the analyses of management plans, the restoration of TWFF was planned, implemented, and studied, including a long-term study at the Elbe estuary upstream stretch. The results of the restoration efforts are provided, including the long-term study (2012–2022) on a restored TWFF in the Elbe estuary, which could serve as a pilot for TWFF restoration and adapting estuarine communities to climate change via NbS.

Abstract: The aim of this study was to describe the morphology of fruit, seeds and seedlings, as well as the anatomy of the seed and the seedling of Pentaclethra macroloba (Willd.) Kuntze. Morpho-biometry was performed on fifty fruit samples and one hundred seeds. To describe the sequences of the morphological events of the germination stages, ten seeds were placed to germinate. Anatomical analysis was performed in a scanning electron microscope with seed samples and seedling leaves. The species has leguminous type fruit of 16.1 to 45.2 cm length and 4.1 to 7.3 cm width; seeds have a pleurogram and are eurispermic, ovoid, deltoid to elliptical and measure from 3.8 to 6.1 cm length and 2.5 to 5.7 cm width. Anatomically, the cotyledons are composed of thin-walled parenchyma cells with various oil cells. The seedlings have bipinnate leaves, with waxes and simple trichomes at the margins of the adaxial surface and paracytic stomata on the abaxial surface. The epicotyl is slightly twisted, with caducous cataphylls and a first pair of alternate eophylls. Germination is of the phanero-hypogean-reserve type. Taxonomic recognition of this species is possible in the field through the external morphological traits and can help in identification of saplings.

Floodplain forests provide a highly suitable environment for wild boar, especially because they offer a sufficient quantity of good-quality food across the seasons. Combined with year-round additional feeding and treatment, wild boar enjoy ideal living conditions in floodplain forests, which should have a positive effect on reproduction and, in turn, an increase in population. We expected the high carrying capacity of the floodplain forest environment to be reflected in young boar showing greater body weight and have a higher layer of subcutaneous fat, young females being in their first heat earlier, and females of all ages having more young. This was verified on a sample of wild boar females collected in Czechia’s largest floodplain forest, which extends above the confluence of the Morava and Dyje Rivers and which is fenced off and used for breeding hoofed ruminant mammals. In addition to determining body characteristics and examining reproductive tracts, food quality was also analysed based on an analysis of stomach contents. Body and reproductive characteristics were compared with available data for the South Moravia. It has been confirmed that, in the floodplain forest, wild boar have a sufficient quantity of good-quality food all year round, yet they reach a smaller body size across all age classes. Piglets ovulated more eggs, while in contrast older females ovulated fewer. That is also why they gave birth to fewer piglets per litter. Wild boar in the floodplain forest gave birth later, with a birthing peak in May–June. This delay can be explained by the adaptation of wild boar populations in floodplain forests to the annual floods that come in March. We estimate that wild boar are able to respond flexibly not only to the food conditions of their environment, but also to the risk of possible mortality and other significant stressors, and to adapt their reproductive strategy accordingly. [ABSTRACT FROM AUTHOR]

We investigated the pre-breeding intersexual foraging habitat preferences of the great spotted woodpecker Dendrocopos major in six old, unmanaged riparian forest stands in Central Hungary, which are composed mainly of the invasive North American green ash Fraxinus pennysylvanica and boxelder Acer negundo, and native poplar Populus sp. and willow Salix sp. trees in lower abundances. With the influence of river management, the two invasive species have usurped native tree species in numerous Central European riparian forests. We studied the intersexual utilization of tree species, tree condition, stem diameter, foraging height, horizontal sections, substrate diameter, substrate condition, and foraging technique. The birds showed intersexual segregation in numerous studied variables despite the high niche overlap between sexes. Similar patterns were also found in other woodpecker species as well. We think that the most important part of this segregation could be the difference revealed in the choice of tree species, as males tended to be more specialized for native softwood tree species with rougher bark structure. Despite the high abundance of invasive tree species, neither sex preferred them. The further population decrease of native tree species could increase within-species competition and negatively affect the studied bird species. [ABSTRACT FROM AUTHOR]

The bryophyte flora of Acarlar Lake (Sakarya-Karasu), Karacabey Floodplain Forests (Bursa) and Samanlı Mountains (Sakarya-Akyazı) was studied in Turkey between 2016 and 2017. As a result of these bryofloristic studies, we determined for the first-time records of Dicranella staphylina from three different localities in Turkey. Site descriptions, illustrations, diagnostic characters and comparisons with morphologically similar taxa are presented. [ABSTRACT FROM AUTHOR]

Between February and July 2015, the composition of mammalian assemblages of the Santa Elena River island, located at the lower basin of the Orinoco River in the department of Vichada, Colombia, was thoroughly assessed. Complementary sampling methods were implemented including plots, camera traps, mist nets and ad libitum observations. In order to test for the effect of spatial stability on mammalian species distribution within the island, we reclassified and scored satellite images of the island, corresponding to scenarios of lower and higher flooding, according to the spatial stability in the sampling period. We report the presence of 31 mammal species in seven orders and 14 families. Considering that 118 mammal species have been recorded in the department, these results corroborate the impoverishment condition of island systems, previously documented in analogous studies. Significant differences are reported in mammal species richness between habitats in the Santa Elena insular system. These differences were represented by higher species richness in stable habitats less affected by flooding, compared to those more affected habitats that accumulated a lower number of species, a phenomenon herein named as "core island effect". Finally, the results suggest that the spatial distribution of mammalian species richness within the island is a selective process mediated by: a) spatial stability of the island, and b) species dispersal and establishment capability. [ABSTRACT FROM AUTHOR]

Large wood (LW) found in both the river channel and the floodplain significantly influences geomorphic processes in the fluvial corridor and plays a vital role in ecological processes. In this study, we investigate the spatial distribution, characteristics, and sources of LW within the entire fluvial corridor of the actively meandering Odra River in Czechia. This region has been subject to long-term human influences on the riverine landscape. We observed notable variations in LW volume throughout the studied fluvial corridor. The highest LW volume was detected in hardwood forested areas in the high floodplain segments, registering at 39.35 m³/ha. This volume was approximately four times greater than the average LW volume found in other areas, including softwood forested patches and low floodplain segments. In contrast, the lowest LW volume was recorded in the low-flow channel, at 4.32 m³/ha. A significant portion of the floodplain LW originated in-situ, as opposed to being deposited during flooding or through beaver activities; these latter two sources typically contributed smaller pieces of LW. The spatial analysis of LW distribution indicated higher densities in the high floodplain within hardwood floodplain forests, especially in regions affected by bank erosion. Additional hotspots of LW occurrence were identified in the low floodplain, which are primarily associated with sites where LW is preferentially deposited during high-flow events, or with spatially-limited areas impacted by beaver activity. The study also offers guidelines for LW management in the fluvial corridors of large meandering rivers, focusing on increasing floodplain geodiversity and addressing potential flood risks associated with the recruitment and subsequent transport of floodplain LW. • Large wood (LW) distribution examined in the fluvial corridor of a meandering river. • The highest LW volume was detected in hardwood forests in high floodplain. • Majority of in-situ LW recruitment, contrasting smaller pieces delivered by floods. • The highest LW densities noted in hardwood forests near the river channel. • Guidelines for LW management in the fluvial corridors are provided. [ABSTRACT FROM AUTHOR]

Altered river hydrology caused by anthropogenic and climatic influences is a global issue causing riparian vegetation species shifts and decline. To help inform efforts to mitigate forest composition shifts through floodplain flow restoration, we tested the first-year responses of three common swamp species, water tupelo (Nyssa aquatica), Ogeechee tupelo (Nyssa ogeche), and pop ash (Fraxinus caroliniana), and two common bottomland hardwood species, overcup oak (Quercus lyrata) and water hickory (Carya aquatica), against twelve moisture treatments through one typical growing season of the Apalachicola River system. Species were grown from seed in a full sun environment under ambient conditions with alteration of soil moisture through treatments varying in timing and duration of ambient precipitation, saturation, or flood. Observations of total emergence, cumulative emergence, total mortality, and final height allowed assessment of responses to treatments and associated stresses. Swamp species emerged quickly early in the growing season compared to bottomland species whose emergence was more gradual. Early-season stresses caused greater mortality of light-seeded swamp species compared to heavier-seeded bottomland species that had ample carbohydrate reserves allowing recovery. Bottomland species were more vulnerable to moisture deficit experienced later in the season. Saturated soil conditions limited the total emergence and rate of emergence of overcup oak. The observed responses to variable stresses can assist forest and restoration managers in developing achievable goals and actions that promote establishment and survival of target species. • Lighter-seeded species emerged more quickly compared to heavier-seeded species. • Emergence rate and total emergence of overcup oak was reduced in saturated soil. • Early season stress significantly impacted mortality of first-year swamp seedlings. • Heavier-seeded bottomland species were more adapted to survive early-season stress. • Saturated soil did not accelerate height growth of swamp species. [ABSTRACT FROM AUTHOR]

A critical review of reports from European localities reveals that the herein newly described Populus erratica Sachse, nom. nov. was previously treated under a variety of names. Due to its stratigraphical range from the late Oligocene to early Miocene, it might be a useful tool for age determinations in the terrestrial record. So far it is known only from warm-temperate floodplain forests in Central Europe – possibly even restricted to the alpine area. The taxonomic relationships to some morphologically similar species from other localities cannot be entirely clarified here.

With ongoing climate change, episodes of severe flooding are predicted to become more frequent despite a general trend towards increasing summer drought. We investigated how wood growth of adult trees of two species characteristic of floodplain forests in Central Germany (Fraxinus excelsior L., Quercus robur L.) and two less-typical species (Acer pseudoplatanus L., Carpinus betulus L.) responded to both maximum stream water level and climate, with a special focus on the effects of the extraordinary flood of the Saale River in June 2013 and the extreme drought in summer 1976. Tree-ring widths were measured on wood cores, and standardized ARSTAN tree-ring chronologies were produced. Using variance partitioning as well as linear mixed-effects models, we compared the effects of monthly values for maximum water level, temperature and precipitation sum on tree-ring width. Further, we calculated resistance, resilience and recovery of the tree species to the extreme events of flooding in 2013 and drought in 1976. Wood growth of all species studied, and particularly of F. excelsior, responded positively to the extraordinary flooding in June 2013. However, in the best models for the characteristic floodplain forest species (F. excelsior and Q. robur), mainly precipitation (F. excelsior) or a combination of precipitation and wood growth of the previous year (Q. robur) acted as drivers of wood growth of the current year. In contrast, growth of the less habitat-specific species (A. pseudoplatanus) mainly showed a significant response to the combination of temperature and wood growth of the previous year. C. betulus was the only species studied that benefited from the extreme drought in 1976. However, two years afterwards, only the wood growth of A. pseudoplatanus was still reduced, while F. excelsior and Q. robur fully recovered. In comparison to other regions in Central Europe, the moderate flood regime of the Saale River seems to have the potential to mitigate effects of summer drought in this region, which is one of the driest in Germany. Thus, increased flooding frequency might, to some degree, reduce drought effects brought about by climate change as well.

In many countries worldwide, measures have been taken in floodplains for flood prevention and nature rehabilitation. In the Netherlands, floodplains are lowered by excavating to enlarge the discharge capacity and to create opportunities for development of river habitats such as forest. As forest can obstruct the water flow through the floodplain, their development has to be controlled in some cases. In many floodplains, vegetation development is controlled by cattle and horses. We carried out an exclosure experiment over a twelve year period in a partly excavated and year-round grazed floodplain along a lowland river in the Netherlands. We focussed on the thorny shrub hawthorn (Crataegus monogyna Jacq.) as it plays an important role in the obstruction of the water flow and in the wood-pasture cycle. Most hawthorn shrubs established on the excavated part of the floodplain with low cover of tall herbs. The total number of established hawthorn was negatively related to inundation on the lower parts of the excavated sites and positively related to inundation on the higher parts of the excavated sites. The herbivores negatively affected establishment and growth of hawthorn. Although lowering the floodplain by excavation will increase discharge capacity of the floodplain in the short term, it will decrease in the long term as excavation also increases opportunities for floodplain forest. If flood prevention and nature rehabilitation are both goals to be achieved in a floodplain, hawthorn encroachment can be controlled by a clever design of the measures and grazing management is needed.

This article brings new information about phenomenon of the growth of floodplain forest without influence of floods over 50 years. Floodplain forest and its hydrogeological regime are under detail research for 10 years and detail 10 years data from hydrogeological well is used in this study. The area of interest belongs to nature reserve Plackuv les what together with brook Satava represents a unique relic of a floodplain forest in the confluence area of the rivers Svratka and Jihlava in southern Moravia (South‑Moravian Region). The damming of the channel of the river Svratka has caused the end of floods. Despite the anthropogenic regulations performed, the hydrogeological conditions have remained preserved at the site. Stream channel was rised due to the regulation at the above the level of the existing ground; this eliminated its drainage functions for groundwater. The contact between the base of floodplain loams and the groundwater Tab. is not lost and the capillary rise in them remains preserved. Analysis of groundwater level confirmed multi‑component refilling of the hydrogeological structure, which is drained in Plackuv les and the river Satava. All last 10 years, the maximum of the groundwater level measured is from July to September. It means, that groundwater reaches the highest level in the period, when the minimum flow rates are recorded on the surface flows. In this period, the locality displays the maximal infiltration of the precipitation from the last hydrological year from distant infiltration area. Because of the absence of floods, groundwater at this site is the most significant resource of water, and it represents a key‑factor which enables the growth and thriving of the floodplain forest ecosystem.

This paper presents an evaluation of full-area floristic investigation of floodplain forests in Soutok forest district (Židlochovice Forest State Enterprise) based on an individual forest stand inventory. The study area encompasses 5103 ha of forests, where 1186 segments were inventoried, and 71 223 single records about presence of vascular plant species were done. We found 761 taxa (species, subspecies and hybrids), out of which 655 were herbs, 106 woody plants, 156 were endangered species and 177 adventive species. The average area of a segment was 4.3 ha. The mean number of species per segment was 64.42 in a range of 4–180.

Environmental conditions influence forest ecosystems and consequently, its productivity. Thus, the quantification of forest CO2 exchange is a critical requirement to estimate the CO2 balance of forests on a local and regional scale. Besides interpreting the annual CO2 exchange corresponding to environmental conditions over the studied years (2015–2020) at the floodplain forest in Lanžhot, Czech Republic (48.6815483 N, 16.9463317 E), the influence of below-above canopy air mass decoupling on above canopy derived CO2 exchange is the focus of this study. For this purpose, we applied the eddy covariance (EC) method above and below the forest canopy, assessing different single- and two-level flux filtering strategies. We focused on one example year (2019) of concurrent below and above canopy EC measurements. We hypothesized that conventional single-level EC flux filtering strategies such as the friction velocity (u*) filtering approach might not be sufficient to fully capture the forest CO2 exchange at the studied ecosystem. Results suggest that decoupling occurs regularly, but the implication on the above canopy derived EC CO2 fluxes appears to be negligible on an annual scale. We attribute this to the open canopy and flat EC tower surrounding terrain which inhibits horizontal removal of below-canopy respired CO2.

Co-variation among vegetation structural layers occurs in some forests but has been minimally found in forested wetlands. We assessed co-variation in six vegetation layers (three size classes of trees, tree seedlings, shrubs, and herbs) in 39 forested wetlands including in five before and after invasion by the beetle emerald ash borer (Agrilus planipennis; EAB) in northwestern Ohio, USA. Across the 39 wetlands, cover of wetland herbs requiring full sunlight was negatively related to tree density, while herbs tolerant of shade minimally co-varied with tree layers. Several wetlands contained both large trees and regeneration (small trees and seedlings) of the same tree species, but often distributions of large trees and regeneration were disjointed. Variation in plant community quality (e.g., non-native cover, floristic quality) for understory layers was partly modeled (34–75% of variance) using multivariate combinations of tree layers. Low-density pin oak (Quercus palustris) flatwoods, which contained species-rich, high-quality understories, drove much co-variation in vegetation layers, suggesting that coupling of layers might occur on only segments of landscape gradients. Another factor was that nearly every site had a different dominant herbaceous species, producing extreme compositional heterogeneity (94% dissimilarity among plots), limiting possible co-variation, but creating high beta diversity. On the five long-term EAB sites, shrub and herb composition co-varied before EAB invasion, but not 14 years later after shrub cover doubled. High diversity in vegetation layers among sites suggests that conserving forested wetlands, including sites that individually might not have high floristic quality, can be a major contributor to landscape diversity. [ABSTRACT FROM AUTHOR]

Background: This article presents, from an ethnoecological perspective, the worldviews, traditional knowledge, and cultural practices of Amazonian riverine people involved in the extraction of miriti fruits (Mauritia flexuosa L.f.), in a context of increasing market demand for miriti fruits and of pressure for the intensification of açaí (Euterpe oleracea Mart.) production on the Sirituba island, in Abaetetuba, Brazil. Methods: Methods used were participant observation and non-directive interviews with 22 extractive families of miriti from the Santa Maria and Costa Sirituba communities, on Sirituba Island, in Abaetetuba, Pará, Brazil. Non-structured interviews were used to analyze the knowledge about the species, history of miriti extraction, the traditions, and innovations related to this activity over time. Participant observation took place when riverine individuals were working with miriti fruits, in order to grasp the "codes" that permeate the human-nature relationships embedded in this production system. Results: It was verified that the riverine peoples have a great knowledge about the palm tree, which is reflected in their own classification systems and management practices that allow the sustainable extraction of the fruits, avoiding, for example, cutting the miriti palms. In addition, a reciprocity relationship was observed between riverine peoples and miriti palm that are personified and preserved, contributing to the conservation of the species in the floodplain, even with the intensification of açaí (Euterpe oleracea Mart.) production. Another important aspect is the collective work involving all the members of the family, which allows the appropriation of the knowledge about the extraction of miriti by the young, allowing the resistance of the tradition that remains strong, contributing to the sustainability of the practice and conservation of biodiversity in the Amazonian floodplain. Conclusion: The k-c-p complex inherent to the riverine universe allows, even in face of the growing commercial demand for miriti fruits and the unchallenged increase in the extraction of this product, the conservation of floodplain biodiversity. Thus, we emphasize the importance of traditional knowledge and practices for biodiversity preservation, and they use them to guide public policies and natural resource management systems, aiming for sustainable ways to manage and use biodiversity. [ABSTRACT FROM AUTHOR]

Species richness is a frequently used measure of biodiversity. The compilation of a complete species list is an often unattainable goal. Estimators of species richness have been developed to overcome this problem. While the use of these estimators is becoming increasingly popular, working with the observed number of species is still common practice.To assess whether patterns of beetle communities based on observed numbers may be compared among each other, we compared patterns from observed and estimated numbers of species for beetle communities in the canopy of the Leipzig floodplain forest. These patterns were species richness and the number of shared species among three tree species and two canopy strata.We tested the applicability of the asymptotic Chao1 estimator and the estimate provided by the nonasymptotic rarefaction–extrapolation method for all tree species and both upper canopy and lower canopy. In the majority of cases, the ranking patterns of species richness for host tree species and strata were the same for the observed and estimated number of species. The ranking patterns of the number of species shared among host tree species and strata, however, were significantly different between observed and estimated values.Our results indicate that the observed number of species under‐represents species richness and the number of shared species. However, ranking comparisons of published patterns based on the number of observed species may be acceptable for species richness but likely not reliable for the number of shared species. Further studies are needed to corroborate this conclusion. We encourage to use estimators and to provide open access to data to allow comparative assessments. [ABSTRACT FROM AUTHOR]

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Policy makers are interested in managing forests to store carbon. Optimizing this strategy requires understanding how carbon storage varies across environmental gradients. We explored variation in tree growth rate, tree longevity, and surface soil organic matter across 135 Connecticut River riparian forest plots. Tree growth rate did not vary significantly with climate but rather increased with sediment accretion rate, soil pH and decreased with plot elevation, where elevation was measured relative to the stage of the 2-year flood. By contrast, surface soil organic matter was negatively related to pH and tree growth rate. Tree species longevities were greater at higher elevations with coarser soils. The faster growth rates at lower elevations allow for restoring forest structure rapidly, whereas flood intolerant but longer-lived tree species allow more durable carbon sequestration at higher elevations. The close associations of growth rate, sediment accretion, and pH suggest that riverine nutrient inputs are important to maintaining the exceptionally high productivity of floodplains. Environmental assessments of river dams should consider impacts of intercepting sediments and reducing flooding on downstream floodplain fertility and productivity. Restoration of riparian locations with high deposition of sediments and associated nutrients may be an opportunity to maximize both nutrient and carbon sequestration. [ABSTRACT FROM AUTHOR]

Vertical stratification and host tree species are factors with a high influence on the structure of communities of xylobiont beetles. However, little is known about how this influence varies between common and rare species. Based on estimated species richness, we compared alpha and beta diversity patterns of common and rare species in the canopy of the Leipzig floodplain forest to assess their response to vertical stratification and tree species. We used two measures of rarity: threat level in red lists and abundance based on octaves. The understory displayed a significantly higher number of common species than the canopy strata. Conversely, the canopy strata harbored a higher number of rare species. Turnover was always dominant over richness differences in beta diversity partitions. Using Raup–Crick null models and non-metric multidimensional scaling, we found that the vertical strata accounted for 19% of the overall beta diversity of common species and for 15% of the overall beta diversity of rare species. The tree species accounted for 7% of the overall beta diversity of the common species and 3% of the beta diversity of the rare species. Our results indicate that studies carried out in the understory alone do not allow drawing conclusions regarding the biodiversity in the canopy strata, and thus regarding the overall community structure of xylobiont beetles in the canopy.

Floodplain forests are very complex, productive ecosystems, capable of storing huge amounts of soil carbon. With the increasing occurrence of extreme events, they are today among the most threatened ecosystems. Our study's main goal was to assess the productivity of a floodplain forest located at Lanžhot in the Czech Republic from two perspectives: carbon uptake (using an eddy covariance method) and stem radius variations (using dendrometers). We aimed to determine which conditions allow for high ecosystem production and what role drought plays in reducing such production potential. Additionally, we were interested to determine the relative soil water content threshold indicating the onset and duration of this event. We hypothesized that summer drought in 2018 had the most significant negative effects on the overall annual carbon and water budgets. In contrast with our original hypothesis, we found that an exceptionally warm spring in 2018 caused a positive gross primary production (GPP) and evapotranspiration (ET) anomaly that consequently led in 2018 to the highest seasonal total GPP and ET from all of the investigated years (2015–2018). The results showed ring-porous species to be the most drought resistant. Relative soil water content threshold of approximately 0.45 was determined as indicating the onset of drought stress. This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'. [ABSTRACT FROM AUTHOR]

Charcoal analysis, applied in sediment facies analysis of the Pecora river palaeochannel (Tyrrhenian southern Tuscany, Italy), detected the occurrence of past fire events in two different fluvial landforms at 800–450 BC and again at AD 650–1300. Taking place in a central Mediterranean district adequately studied through palaeoenvironmental and archaeological research, the investigation determined land changes, time phases and socio-economic driving forces involved in dynamic processes of fire. The fire sequences had purely anthropogenic origins and were linked to forest opening and reduction by local communities. Introduced by the Etruscans, fires dated to 800–450 BC involved mainly the forest cover on the hilly slopes, ensuring agricultural exploitation. From AD 650, fires contributed to Medieval upstream reclamation and vegetation clearing of flat swamplands. From AD 850 to 1050, the use of fire spread over a wider area in the river valley, increasing arable lands. Between AD 1150 and 1300, fires belonged to a regional forest clearance phase. Medieval fire episodes had a paramount importance in shaping and determining the character of the Tuscan Mediterranean landscape. From AD 850, Medieval fire clearing influenced regional vegetation history contributing to the decline of the dominant deciduous Quercus woodland. Open habitats became the new form of a clearly detectable agricultural landscape from AD 950. The use of fire clearing and the resulting landscape changes in the Pecora river valley depended on the political strategies adopted by Medieval authorities and marked, in fact, the progression of a cultural landscape still characterizing central Tyrrhenian Italy. [ABSTRACT FROM AUTHOR]

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Floodplain forests of large rivers in the midwestern United States are naturally fragmented by sloughs, backwaters, wetlands, and shrub carr. On the highly altered Upper Mississippi River (UMR), resource managers want to protect and manage floodplain forests to benefit forest "interior" bird species. To discover bird relations with interior and edge floodplain forest, we characterized bird assemblages during spring migration and breeding season in 3 forest types: habitat in the interior of forest areas > 100 m from an edge, edges associated with interior areas, and other areas of forest not associated with an interior area (random sites) on the UMR between Hastings and Red Wing, Minnesota. The random sites represent the majority of UMR floodplain forest area because only a small percentage of forest occurs >100 m from edge. Estimated habitat characteristics did not differ among interior, edge, and random sites. Bird relative abundance, species richness, diversity, assemblage composition, and detections of all but one species (in spring) did not differ among interior, edge, and random sites during both seasons. Our results suggest a homogeneous bird assemblage across UMR floodplain forest in the study area during spring migration and the breeding season, and that individual forest bird species do not seem to be more abundant in interior or edge areas as we defined them. [ABSTRACT FROM AUTHOR]