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Abstract: Stomatal regulation plays a critical role in controlling tree water loss and mediating atmosphere–vegetation–soil water coupling, yet the implications of species-specific differences in stomatal regulation on this coupling remain poorly understood. Drimys species possess primitive leaf anatomy with limited stomatal closure capacity, while Nothofagus exhibits more effective stomatal control. We compared multi-year sap flux data from these two co-occurring Southern Chilean species to evaluate how stomatal traits influence water-coupling dynamics across timescales. Using boosted regression tree modeling and wavelet coherence analysis, we found that while both species showed similar functional responses to environmental drivers, the relative importance of these drivers differed between them. Both Drimys and Nothofagus responded to VPD, but Drimys sap flux was more strongly influenced by soil moisture, particularly during early season wet periods and late-season drought. In contrast, Nothofagus showed greater dependence on light and vapor pressure deficit (VPD), reflecting tighter stomatal regulation. Wavelet coherence analyses further confirmed stronger soil moisture control of sap flux in Drimys, especially at weekly to sub-seasonal timescales, and provided evidence that stomatal regulation can either buffer or amplify late-season soil moisture deficits. These findings suggest Drimys follows a high water use, low-conservation strategy closely tied to soil moisture, whereas Nothofagus demonstrates more conservative water use governed by atmospheric conditions. The strong soil moisture dependence of Drimys may increase its vulnerability to future warming and drying trends, with implications for forest composition and hydrological modeling in a changing climate. PubDate: 2025-06-30
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Abstract: Intensive forest management simplifies habitat structure, reducing capacity to support a diverse range of species. Eucalyptus plantations can be managed by two approaches; ‘regrowth’, where stems are cut to stumps to allow regeneration which maintains understory vegetation, or by ‘seedling’ establishment following clearfell and suppression of understory vegetation. We proposed that regrowth stands, which have enhanced structural complexity in understorey layers, positively influence taxon and functional diversity. We predicted functional redundancy in seedling stands as they will be composed of a few tolerant species sharing a limited number of functional traits, whereas regrowth stands will also demonstrate functional redundancy by supporting multiple functional trait combinations and multiple species. Taxonomic diversity was measured by counts of birds and spider webs and collection of ground-dwelling spiders and ants using pitfall traps. Functional diversity was measured using trait data for each species. Understorey forest management was an important driver of diversity and functional redundancy, but responses were not consistent across taxonomic groups. Species-trait relationships, representing the specific requirements of the various organisms, were driving each response. Therefore, management that promotes vegetation complexity has the potential to improve the capacity of homogenous forest environments to support resilient communities and ultimately to ensure sustainability of the economically important global forest resource. PubDate: 2025-06-26
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Abstract: Burrowing crab engineers can affect the biological structure and sediment conditions of their environments. However, it is challenging to predict when and where burrow effects will manifest, as they are often site- and habitat-specific. We used a tidal marsh restoration chronosequence to explore crab burrow effects on plant communities (for example, percent cover, biomass, stem heights) and sediment characteristics (for example, bulk density, organic matter, carbon and nitrogen stocks) through early succession. In a field survey, we compared plants and sediments between plots with high and low crab burrow densities within three habitat zones: mud flat (that is, 0–1 years old), young marsh (that is, ~ 1–6 years old), and old marsh (that is, ~ 6+ years old). In a manipulative experiment, we tested the physical effects of crab burrows on plants and sediments at the mud flat-young marsh ecotone using burrow mimics. In our field survey, crab burrow density did not influence plants or sediments. Rather, plant biomass and stem heights, as well as sediment bulk density, organic matter, carbon, and nitrogen, differed between habitat zones, following expected marsh successional trajectories of development over time. However, in our manipulative experiment, crab burrow mimics had a strong positive effect on plants at the ecotone, suggesting crab burrows can facilitate plant expansion into unvegetated mud flats. Thus, crab burrow effects on plant performance appear to peak in early successional ecotones where burrowing mediates environmental stressors and promotes vegetative growth, with implications for the recovery of biological structure and sediment properties following restoration. PubDate: 2025-06-25
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Abstract: Identifying and understanding the response of tree species to climate variability and drought events is a key challenge in addressing climate change in the Andean ecosystems of southern South America. This study aims to: (1) determine the main temporal patterns of radial growth of three Nothofagus species (N. pumilio, N. dombeyi, and N. alpina) on the northwest slope of the Choshuenco volcano, around 40°S, (2) examine the relationship between radial growth and environmental variables, as well as climatic forcings, and (3) evaluate the resilience of these species across an altitudinal gradient in the Valdivian Andes. The chronologies of the three Nothofagus species were assessed using principal component analysis, correlation analysis between the chronologies and environmental variables, and resilience analysis for drought years. The Nothofagus chronologies reveal an increased common signal in radial tree growth since the 1980s. At the beginning of the growing season (November) all chronologies exhibit a negative relation with precipitation and some chronologies positive relations with mean air temperature and the 0 °C isotherm height. These findings suggest that the persistence of snow cover during spring may be crucial for the onset of the tree growth. Previous year hydroclimate appears to have an important role favoring tree growth, with most chronologies exhibiting positive relations with summer soil moisture, and circulation patterns forced by the Antarctic oscillation that favors wet mild and summers. The response to drought varies among species, with N. alpina notably exhibiting high resistance, recovery and resilience, likely due to its location near the southern limit of its distribution. Integrating analyses of temporal growth patterns, growth-environment variables relationships, and drought resilience enhances understanding of how Nothofagus species have responded to climatic variability in recent decades in the Valdivian Andes forests. PubDate: 2025-06-25
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Abstract: Water use efficiency (WUE) represents the trade-off between carbon uptake and water consumption in terrestrial ecosystems. Utilizing eddy covariance, digital camera, and synchronous meteorological measurements at an underrepresented hyper-arid grassland, this study investigated the seasonal variations in WUE and evaluated its responsiveness to environmental and biological variables across different phenological periods. Additionally, we explored the response of WUE to drought events. Results showed that WUE exhibited opposite seasonal patterns compared to gross primary production (GPP) and evapotranspiration (ET), with peaks occurring during the senescence period. The annual mean WUE was 1.15 g C kg−1 H2O. Seasonal variations of WUE were more controlled by the biophysical factors acting on ET than on GPP. Air temperature (Ta) and surface conductance (gs) were the most important factors regulating WUE. Annually, WUE was markedly different between the dry and wet years, with values of 0.94 and 1.13 g C kg−1 H2O, respectively. Seasonally, precipitation patterns exerted more pronounced effects on WUE than precipitation totals. Additionally, the seasonal processes of carbon and water coupling were highly related to vegetation phenology. Lastly, under varying moisture conditions, GPP and ET exhibited a significantly positive correlation, with decreasing slopes as soil water content increases, indicating heightened carbon–water coupling under drought stress. Under drought stress, both stomatal and non-stomatal factors governed WUE, with VPD directly regulating WUE or indirectly affecting gs. This study enhances our knowledge of ecohydrological processes and the coupled dynamics between carbon and water cycles in hyper-arid grassland ecosystems. PubDate: 2025-05-30
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Abstract: Water is an important dispersal vector for seeds of riparian plants, but little is known on how this form of dispersal, called hydrochory, varies throughout seasons and through geomorphically different areas. Therefore, we trapped seeds in 25 x 25 Astroturf mats along a free-flowing boreal river for an entire year. Sites mirrored the full range of geomorphic variation in the area and traps were emptied before and after the annual peak flow. The traps collected 2,062 seeds before the spring flood and 16,157 during the spring flood. While most of the seeds were deposited in the summer-low water traps (from now on “water edge”) before the spring flood, they were distributed more equally in the riparian traps (defined as the level 40 cm above the water edge; from now on “riparian zone”) during the spring flood. We found 77 species in total, of which 71 were at least recorded during the spring flood. Species numbers were higher at the water edge than at the riparian zone before and during the spring flood. Only 6.6% of the seeds, from 26 species, were viable. Most viable seeds were found in the water edge traps and, during the spring flood, in the riparian zone traps. While species that are primarily dispersed by water were not the most abundant among the viable seeds, they were the most species-rich group. This means that hydrochory is an important dispersal mechanism for riparian vegetation and an important contributor to riparian plant diversity in free-flowing rivers, and that changes in flow regimes, such as by flow regulation, can affect riparian vegetation composition. PubDate: 2025-05-29
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Abstract: The assessment of the qualitative and quantitative structure of microbial communities is vital for recognizing the role that microorganisms play in aquatic ecosystems. We investigated microbial communities using high-throughput sequencing of the 16S rRNA gene, and the population activity, using fluorescent markers. Three lakes (oligotrophic, eutrophic, and hypertrophic) were studied in spring, summer, and autumn 2021 in the Zaborski Landscape Park, northern Poland. The results showed that dead bacterial cells dominated in the tested water samples. Their distribution was mainly related to the trophic status of the studied lakes. Bacteroidetes, Proteobacteria, Cyanobacteria, Verrucomicrobia, and Actinobacteria predominated in bacterioplankton. At lower taxonomic levels, certain groups were associated specifically with the eutrophic Lake Niedźwiedzie, mainly bacteria of the Flavobacterium and Rheinheimera genera, which in spring accounted for 14.4% and 11.95% of the population, respectively. Our analyses demonstrated that the structure of bacterial communities (β-diversity) was strongly correlated with the trophic status of the studied lakes. This study indicates that the environmental gradient has a strong influence on the functional and taxonomic structure of bacterioplankton. Our study demonstrates that the assessment of the activity and spatial structure of bacterial communities can be a useful tool for determining differences in the ecological state of waterbodies. Moreover, knowledge about the factors shaping the structure of microbial communities can be helpful in responding to any disturbances in the functioning of lake ecosystems. PubDate: 2025-05-28
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Abstract: The Loess Plateau is the most typical loess platform worldwide and has experienced heavy restoration since 1999, costing hundreds of billions of Chinese Yuan. However, there has been a long-lasting and huge controversy about how to restore and manage different ecosystem types in the Loess Plateau. A primary reason is the lack of a clear idea of how major biological components—biocrusts (a mixture of soil particles, cyanobacteria, fungi, lichen, and moss), grasses, and shrubs coexist together therein and of system equilibrium behavior, which will significantly affect our understanding about restoration efforts. To that end, this study integrated field surveys, literature review, and environmental data analysis to identify determining factors and coexistence patterns of biocrust and vascular plants (grass and shrub) in the Loess Plateau. We found that precipitation, surface temperature, and solar radiation were the most important determining factors of biocrust, grass, and shrub cover in the Loess Plateau. Three coexistence patterns were identified based on these key environmental factors, namely a high biocrust-grass mixed state under high annual rainfall and surface temperatures of 10–12 °C, a biocrust-dominated state under low rainfall conditions, and a low biocrust-grass mixed state under low surface temperature and strong solar radiation situations. More importantly, we found that these three coexistence patterns appeared to be alternative stable states along the annual precipitation gradient. This study, for the first time, discovered coexistence patterns of biocrust-vascular plants in the Loess Plateau and can guide future restoration and conservation in the region, which is crucial for achieving sustainable development and ecological safety in North China. PubDate: 2025-05-20
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Abstract: Anthropogenic activities add more reactive nitrogen (N) to the environment than all natural sources combined, and the fate of this N is of environmental concern. If N that is deposited on terrestrial ecosystems through atmospheric deposition is retained in plant tissues or soil organic matter, it could stimulate carbon (C) storage in plant biomass or soils. However, added N also could increase soil inorganic N concentrations and leaching, potentially polluting watersheds, particularly in areas with low-N soils and/or a high propensity for leaching, such as sandy or arid areas. Here, we assessed N allocation and retention across a 13-year experimental N addition gradient in a temperate grassland. We found that N accumulation decreased significantly at mid- to high levels of N addition compared to the Control, such that ecosystem N pools were equivalent across a 10 g m−2 year−1 range of annual N addition rates (0–10 g N m−2 year−1), which spans most of the global range of N deposition. Nitrogen addition increased plant tissue percent N, but the total pool of N did not increase because of reduced plant biomass, particularly in roots. Nitrogen addition also increased soil inorganic N concentrations. Our results indicate that N addition is unlikely to increase grassland N pools, particularly in sandy or low-fertility ecosystems with a high potential for leaching because high application rates lead to N saturation, and additional inputs are lost. PubDate: 2025-05-20
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Abstract: Alpine and subalpine grasslands experience strong seasonal climatic variations, with snow cover for over six months maintaining steady soil temperature and moisture. This seasonal structure limits plant growth and strongly influences microbial activity, which together control key ecosystem functions like soil organic matter (SOM) inputs, mineralization, and greenhouse gas fluxes, ultimately influencing the composition and quantity of SOM. In our study, we monitored soil pedoclimate (temperature and moisture) and net ecosystem exchange (CO2 flux) at both plot and local footprint scales, using discrete measurements and flux tower, to characterize the seasonal context of alpine and subalpine grasslands. Meanwhile, we investigated the seasonal properties of topsoil organic matter (SOM) at six key times throughout the hydrological year: before snow cover, before snowmelt, after snowmelt, during the growing season, at vegetation peak, and during senescence. SOM properties were analyzed through the combination of methods including DRIFT spectroscopy, RockEval® thermal analysis, water-extractable organic carbon and permanganate-oxidizable carbon (POxC). Finally, soil incubations were conducted to assess microbial respiration sensitivity to temperature and moisture across these six periods, enhancing our understanding of seasonality’s impact on microbial features. Our study integrates in situ and in vitro measurements across multiple scales (soil sample, plot, and landscape), traditionally analyzed separately. This approach bridges microbial mechanisms with SOM quality and links them to ecosystem-scale carbon exchanges. Our findings highlighted a clear seasonality in SOM properties, offering valuable insights into the functioning of these grasslands. We identified a labile seasonal pool of SOM that persists through the winter due to low temperatures and low-carbon outputs, maintaining its availability for mineralization at the onset of the growing season—when primary producers have the highest nutrient demand. This labile pool decreases over the growing season, as microbial activity peaks and organic matter inputs decline. Additionally, seasonal shifts in microbial responses to temperature and humidity indicate functional acclimations: enhanced cold tolerance in winter, waterlogged tolerance during snowmelt, and increased capacity to degrade complex organic molecules during the growing season. PubDate: 2025-05-16
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Abstract: Alpine tundra at the top of high mountains and the treeline ecotone are both highly sensitive to modern climate change. In the Southern Urals alpine tundra occupies relatively small areas as the mountain ranges are quite low, while the treeline there is relatively high. The summit Dalniy Taganay, due to its marginal position in the mountain range and the direct onsite long-term monitoring, gives unique data on the intensity of upward expansion of woody vegetation for the last century and its consequences on the ecosystem level. By comparing old topographic maps and satellite images, repeated landscape photographs, and analyzing the age structure of forest stands it was determined that since the 1960s the upward expansion of open and closed forests had resulted in 72% decrease of unforested areas including alpine tundra. The intrusion of junipers to alpine tundra communities has been detected as well. Since 1990 the changes in various types of alpine tundra have been revealed by repeated observations. Since 2008 at the summit of Dalniy Taganay the ground-dwelling invertebrates have shown a significant decrease in the abundance of certain species and the endemic ground beetle Carabus karpinskii Kryzhanovskij & Matveev has not been recorded since 2022. Only the number of red ants in alpine tundra has shown a fourfold increase and typical forest beetles appeared. We could trace in detail not only the movement of forest higher into the mountains but also the changes in alpine and treeline ecotone’s vegetation and animal communities with local extinction of specific species. The presented results can be used to adjust the models of climate-driven transformation for other similar mountains, where the area of alpine meadows or tundra is critically small. PubDate: 2025-05-14
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Abstract: It is widely recognized that soil microorganisms undergo adaptation in response to phosphorus (P)-depleted tropical soils by enhancing the abundance of phosphatases, as evidenced by an increase in the maximum rate of substrate conversion (Vmax) of an assemblage of phosphatases. Conversely, the question remained unclear as to whether soil microorganisms adapt to P-poor conditions by producing “high-quality” enzymes, characterized by an increased affinity in the produced phosphatases, as indicated by a lower Michaelis constant (Km). Through an integrated analysis that encompasses both previously published data from 10-year P-fertilized forests and newly acquired data from a eucalyptus-dominated planted forest in a 6-year P-fertilized forest, we have demonstrated that soil microorganisms adapt to P-deficient conditions by increasing Vmax, rather than by producing high-quality phosphatases (phosphomonoesterases). In response to this, we have proposed a novel hypothesis, termed "the enzyme degradation hypothesis," which effectively elucidates why microorganisms prioritize quantity over quality of phosphatases. Producing a small quantity of high-quality phosphatases is less advantageous, as proteolytic degradation has a greater impact in this strategy compared to producing a large quantity of low-quality phosphatases. This is because, as the availability of phosphatases—the substrate for proteases—decreases, the proportion of degraded phosphatases relative to the total phosphatase pool increases, due to the upward convexity of the enzyme reaction described by the Michaelis–Menten equation. This hypothesis requires further validation in other forest ecosystems, including different types of tropical forests. PubDate: 2025-04-24
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Abstract: Aboveground litter not only is an important nutrient source for soil microbes but also regulates the microclimate in topsoil, and consequently affects microbial activities and related ecological processes. Here, we used a three-year experiment manipulating litterfall inputs to soil in a coniferous–broadleaf mixed forest in Central China to assess how soil microbial community and respiration responded to litter-derived carbon (C) change. Our results showed that litter addition increased gram-positive (GP) bacteria abundance by increasing soluble C content, decreased fungi abundance by increasing the ratio of dissolved organic carbon to available nitrogen and decreasing soil pH, but had no effect on gram-negative (GN) bacteria abundance. Litter exclusion decreased GP abundance but had little effect on GN and fungi abundance. Our study highlights the crucial roles of the ratio of substrate carbon to nitrogen in regulating bacterial and fungal communities and soil pH in regulating fungal communities. The shifts in microbial communities have crucial effects on microbial respiration. Litter addition increased microbial respiration by enhancing GP abundance and decreasing fungal abundance, while litter exclusion decreased microbial respiration by reducing GP abundance. Our findings suggest that identifying and describing soil dissolved organic carbon are key for understanding microbial community composition because of their significant relationships with ecosystem C emission processes. PubDate: 2025-03-31
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Abstract: Small coastal watersheds ( PubDate: 2025-03-31
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Abstract: Riparian forests influence stream ecosystems by controlling light availability, nutrient inputs and adding large wood (LW). While many functions of in-stream LW are well studied, there is limited research on their carbon storage potential, especially in eastern North America. Due to forest recovery following historic clearing regionally, riparian forest structure is changing, with implications for LW recruitment, accumulation and carbon dynamics. To better understand the LW carbon pool and relationships with riparian forest structure, we collected data on the forest and in-stream LW in headwater streams in the mature, northern hardwood Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA. To understand how in-stream carbon storage will change as these second-growth forests develop, we collected comparison data at streams in old-growth forests of the Adirondacks of New York State. Streams at the HBEF contained 7.5 Mg C/ha in LW (SD = 5.8 Mg C/ha), exhibiting substantial variation within and between sites. This variation is linked to heterogeneity in riparian forest structure, especially the large tree basal area. Our data suggest the storage potential of stream LW will increase as riparian forests age, with old-growth stands storing 23.8 Mg C/ha as LW (SD = 9.8). This provides a first assessment of the LW carbon pool in the region and the biotic factors that influence this storage. The positive relationship between LW carbon and large trees, and the increased storage in old-growth forests supports conservation and management that promote large trees and old forests in riparian zones. Such practices may improve the value of in-stream LW carbon as a natural climate solution. Graphic Abstract PubDate: 2025-03-27
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Abstract: Trophic interactions determine food web structure and influence biodiversity, community structure, ecosystem functioning, and food web responses to global change. These interactions are highly flexible, changing on temporal scales from diurnal to evolutionary times due to phenotypic plasticity, rapid evolution and species sorting. Small-scale experimental and theoretical studies of plankton interactions have demonstrated a high relevance of this flexibility for community dynamics and ecosystem processes in small, simplified communities. However, the extent to which this flexibility affects larger-scale systems, for example, global ocean dynamics and their responses to global change, is still poorly understood. Differences in methodology, focus and terminology between research disciplines limit our ability to project established effects of flexible trophic interactions onto larger spatial and temporal scales. We propose to bridge this gap with a general framework for upscaling knowledge from small-scale research to large-scale models. Building on examples from plankton communities, we use this framework to show how mechanisms demonstrated in small-scale studies can be linked to ecosystem functions relevant at large scales. We argue for incorporating flexibility in large-scale process-based models to improve their realism and predictive power, and discuss challenges and ways forward for achieving this. Finally, we suggest several concrete ways for upscaling small-scale studies to make their findings more relevant for large-scale research, to close existing knowledge gaps and to improve our understanding of how flexible trophic interactions affect dynamics and processes across scales. PubDate: 2025-03-24
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Abstract: The balances of nitrogen (N) and phosphorus (P) in plants are important for numerous fundamental ecological processes. These balances are vulnerable to global change drivers, including extreme drought, yet it remains largely unknown whether plant N:P imbalances are reversible. This issue is even more complex at the community level, where the recovery of community composition and its influence on N:P ratio pose significant challenges. We examined the responses of green and senesced leaf N:P ratios at both species and community levels to a 4-year extreme drought and their subsequent recovery over two years in a temperate steppe. Drought increased leaf N:P ratios of most dominant species and the dominance of grasses, which have higher N:P ratios than forbs, resulting in stronger leaf N:P imbalances at the community level. The increased community N:P ratios can recover within two years after drought cessation, largely due to the reduced soil N concentration caused by plant overgrowth during the post-drought period. Our results indicate that drought-induced N:P imbalances in plant community are reversible and highlight the role of community compositional changes in driving plant N:P stoichiometric responses to drought and recovery. PubDate: 2025-03-13
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Abstract: While the direct effects of white-tailed deer (Odocoileus virginianus) on vegetation have been intensively studied, less is known about the indirect and interactive effects of herbivory on lower trophic levels, such as soil microbes and their processing of carbon pools. We explored how carbon dynamics shift with release from over-browsing by white-tailed deer in two mature stands of oak and hemlock trees. We measured soil carbon pools (for example, soil organic matter, carbon stocks, litter biomass, and litter stabilization) and fluxes (for example, soil respiration, methane uptake, microbial substrate use, and litter decomposition) using a spatially balanced survey design inside and outside two 24-year-old deer exclosures, one in each forest stand. Soil carbon pools were higher inside the exclosures than in deer-browsed plots in both forest stands, but the effect of deer herbivory on fine-scale spatial patterning of soil carbon pools and mean carbon fluxes varied by forest type. Release from deer herbivory in the oak stand increased the patchiness of soil pools and led to higher litter decomposition, soil respiration, and methane uptake rates. Release from deer herbivory in the hemlock stand did not affect the spatial structure of soil pools, had little effect on methane uptake, and had negative effects on litter decomposition and soil respiration. These differences may be due in part to the interactive effects of two herbivores, deer and the hemlock woolly adelgid (Adelges tsugae), that appear to be limiting regeneration and promoting the proliferation of monodominant hay-scented fern (Dennstaedtia punctilobula) in the hemlock-dominated stand. Our work suggests that future efforts consider multiple zoogeochemical stressors simultaneously, in addition to variation in environmental templates, to explain uncertainties in carbon pools and fluxes in temperate forested ecosystems. PubDate: 2025-02-27
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Abstract: Amazonian floodplains are the most extensive and biodiverse riverine habitat on Earth. They currently face unprecedented fire regimes as climate change increases the frequency and intensity of drought. While it is clear that fire impacts on floodplain ecology can be severe, fire regimes and their effect on forest ecosystems have yet to be fully examined across the considerable spatial and ecological heterogeneity of Amazonian floodplains. We used the MODIS burned area product to map fire occurrence across Amazonian floodplain forests. Next, we assessed forest recovery after burning using NDVI values from LandSat images. We specifically focused on differences in wildfire dynamics and forest recovery after burning across floodplains associated with the three main river types in the Amazon basin (black-, clear-, and white-water rivers). We found that the occurrence of forest fires in floodplains is strongly associated with ENSO events and increases as land-use intensity increases, dry seasons get longer, soils become sandier, and the synchrony between flooding and precipitation patterns increases. Postfire forest recovery is slower, and reburning risk is higher, on nutrient-poor floodplains of black-water rivers, compared to the nutrient-richer floodplains of white- and clear-water rivers. Moreover, forest recovery is significantly slower in regions flooded for prolonged periods, regardless of river type. Our results call for urgent prevention and monitoring of floodplain forest fires across the Amazon basin, with particular attention to black-water floodplains, to prevent large-scale vegetation shifts and cascading ecosystem changes on biodiversity and ecosystem services provided by floodplain forests. PubDate: 2025-02-25
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