Wetlands最新文献

Understanding the dynamic patterns of wetlands in the Yellow River basin and promoting connectivity among them are important for the protection and restoration of wetlands in this basin. Although many existing studies effectively optimize the structural characteristics of ecological networks, they often overlook the spatial distribution of the actual landscape to be optimized and the associated ecological risks. This study centers on Maduo County in Qinghai Province, employing the MSPA model and connectivity indices to meticulously analyze the spatial dynamics of wetland alterations and hydrological connectivity over the past two decades. The introduced concept of optimizing the importance index involves the stratification of low-connectivity wetland patches, identified as nodes for optimization. A theoretical assessment of the complexity and connectivity robustness of the river network before and after optimization was performed. Findings reveal: (1) The core area and connectivity of wetlands in Maduo County have exhibited persistent growth. The centroid of wetlands shifted southeastward in both periods, albeit at differing angles. (2) Hydrological connectivity of wetland patches in Maduo County experienced rapid enhancement from 2000 to 2010, maintaining stability from 2010 to 2020. (3) There are 44 nodes to be optimized, with 6, 13, and 25 nodes in levels 1, 2, and 3, respectively. As the number of levels increases, the nodes slated for optimization are more likely to be interconnected within the river network. Post-optimization, both the complexity and connectivity of the river network show improvement. The study will offer fundamental theoretical support for wetland research in the Yellow River Basin.

Wetlands, widely distributed and hotspots of biodiversity, play a crucial role in global biogeochemical cycles and human well-being. However, despite their ecological importance, wetlands worldwide are under threat due to widespread conversion into agricultural fields, leading to changes in hydrology, increased salinity, and more frequent eutrophication. In response to these challenges, constructed wetlands are created to treat agricultural wastewater and mitigate eutrophication. This study aims to assess the effect of natural vs. constructed wetlands on ecosystem functioning (organic matter decomposition of the dominant vegetation: Phragmites australis and Typha angustifolia). We conducted this study in the Ebro River Delta (NE Spain), which represents a deltaic wetland affected by agricultural land-use changes, examining two constructed and two natural wetlands. Our findings indicate that the influence of agricultural runoff on the decomposition process was similar in both types of wetlands, suggesting that freshwater agricultural runoff has a consistent effect on ecosystem functioning, regardless of its origin, natural vs. constructed. Differences in macroinvertebrate communities associated with leaf litter were likely due to specific conductivity but did not impact decomposition rates. The estimated time required to decompose 95% of the T. angustifolia litter produced annually in the studied wetlands ranged from 288 to 856 days. In constructed wetland, this decomposition time exceeded one year, contributing to soil formation and carbon sequestration in wetland ecosystems. Our study suggests that the utilization of constructed wetlands for treating agricultural runoff can aid in mitigating the impacts of agricultural land use in these areas.

Vernal pools—small seasonal wetlands—provide critical breeding habitat for many species but are under-protected in environmental regulation. Because vernal pools are not rare in the northeastern United States, regulatory emphasis is typically placed on protecting “significant” vernal pools yet scientific criteria for determining thresholds for conservation significance remain poorly developed. We used an evidence-based approach to identify thresholds of pool significance based on populations of breeding amphibians in five ecoregions and across urbanization gradients of New York State, where a recent revision to wetland law allows regulation based on amphibian productivity. We combined existing population survey data with new surveys to yield a dataset of 587 pools for estimating statistical distributions of productivity of two indicator species: spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus). Spotted salamander egg mass counts were significantly lower in highly developed landscapes. Larger pools were generally more productive for both species yet no single habitat feature reliably predicted high egg mass counts. Pool incidence and productivity also varied regionally: the Hudson-Mohawk region hosted the most known vernal pools and highest egg mass counts and the Lake Plain region the fewest known pools. Our dataset yielded threshold options for guiding pool protection that varied by the proportion of pools targeted. We suggest a lower standard for protecting pools in high-development areas and that presence of other pool-breeding indicator species could also qualify pools for significance. These recommendations can guide regulators in affording protection critical to small wetland habitats specific to regional and landscape contexts.

The Drift Prairie, in central North America, has been largely converted from grasslands to croplands, but still contains thousands of wetlands used by shorebirds and waterfowl during breeding and migration periods. Consequently, many of the remaining wetlands are situated within cropland where disturbance regimes (i.e., fire, grazing, and water-level dynamics), which occurred naturally prior to agricultural development, have been highly altered by landscape fragmentation from agriculture practices. Currently, smaller wetlands within crop fields are subject to disturbances stemming from agricultural practices (i.e., manipulations), such as burning, disking, harvesting, and mowing. We evaluated vegetation structure of idled (i.e., not recently manipulated by farming practices) and manipulated agricultural wetlands to investigate whether management method or resulting vegetation structure had greater influence on occurrence probabilities and densities of dabbling ducks and shorebirds during spring. All manipulation methods reduced vegetation heights compared to idled wetlands and most manipulations reduced the proportion of vegetation cover in inundated areas. Wetland manipulations generally increased shorebird occurrence compared to idled wetlands, whereas vegetation variables better explained duck occurrence probabilities. Duck occurrence peaked in wetlands with lower vegetation coverage (32%), and duck densities decreased as vegetation coverage increased beyond 10%. While more studies are needed to understand underlying mechanisms driving these outcomes, our results indicate that including periodic disturbances that reduce dense vegetation within wetlands in agricultural fields would increase their use by migrating and breeding shorebirds and dabbling ducks.

The temporal changes in the effect of damming on the hydrological and ecological condition of a river and associated riparian wetland were examined in the present study. Does the degree of hydrologic and ecological alteration decline over time? Hydrological alteration was assessed in reference to the wetland water richness (WWR) modelling in three phases: pre-dam phase (up to 1992), post-dam phase 1 (1993–2012), and phase 2 (2013–2020). Periodicity of river flow at season scale was assessed usingthe wavelet transform model. The degree of ecological alteration was measured using a range of variability approach (RVA) and flow duration curve (FDC). From the analysis, it was revealed that after damming, the monthly flow failure rate increased (70–96%). The eco-deficit in the river was further exacerbated as the temporal distance increased. As a consequence of this, wetland water richness (WWR) maps of different phases exhibited continuous loss in the poor WWR parts. Eco-deficit condition of the wetland became severe in post-dam phase 1 and it was continued but with a lesser rate of increase in the next phase. The findings of this study would have significant implications for ecological flow management in rivers even after damming in order to continue eco-flow in downstream river reach and support riparian wetlands of immense ecosystem values. The study suggests conducting comparable studies with longer post-dam lengths in order to better determine how the effects of damming change over time.

This study was prepared to investigate the ecogeomorphological aspects of the Kızılırmak mouth and its immediate environs, which have been seriously subjected to anthropogenic pressures in recent years. Situated in the center of Turkey's most significant wetland, the Kızılırmak delta, is the research area. In this study, remote sensing methods and field observations were used together, and the collected data were interpreted with an interdisciplinary approach by experts in geomorphology, ornithology, ichthyology, botany, physical geography, and environmental engineering. The Altınkaya and Derbent dams built on the Kızılırmak river negatively affected the sediment budget of the delta. Significant part of the dried floodplains was turned into agricultural field. Later, the stream was taken into an artificial canal. The former bed parts outside the canal turned into lakes and swamps. For this reason, between 1990 and 2021, the coastline was retreated by 500 m, 75.1 ha of wetland were converted into agricultural land and 18.1 ha of new lake area was created. The biological and hydrological features of the study region changed as a result of these changes; habitats were fragmented, animal breeding and nesting grounds were damaged, and some animal populations tended to decline. Despite this, many artificial lakes still have wetland characteristics and can be preserved as a suitable habitat for many different plants and animals. In light of this study, it is advised that the current wetland management plan be carefully revised and implemented.

The U.S. Army Corps of Engineers, under Sect. 404 of the Clean Water Act, requires that development projects that discharge fill to Waters of the United States, including wetlands, must provide compensation through the wetland mitigation process. The Army Corps prefers that compensation is provided through purchase of credits from wetland mitigation banks, which are large wetland restoration projects constructed by third-party bank sponsors for the purpose of selling wetland mitigation credits for a profit. We assessed the regulatory outcomes of banks in the Chicago, USA, region, which possesses one of the country’s most well-developed banking markets. We used data from 22 wetland mitigation banks in the Chicago District of the Army Corps to determine how successful banks were at meeting mandatory ecological performance standards by the end of a required monitoring period. We found that banks typically struggled to meet performance standards limiting dominance by non-native species, although they often met standards related to native species richness and dominance. Perennial plant species richness and floristic quality metrics generally increased during the banks’ five-year monitoring period. The results of this study can serve as a useful resource for the continued adaptation and improvement of performance standards and mitigation assessment.

Sorption processes at the soil-water interface are observed to be rapid and dominant pathways of dissolved organic carbon (DOC) exchange. However, kinetics data for sorption in any ecosystem are sparse, and specifically non-existent for temperate tidal marshes. In this study, sorption rate kinetics experiments were designed to constrain new formulations of a sediment flux model coded to include explicit sorption between soil organic carbon and DOC pools. Batch incubations for marsh soil samples from Taskinas Creek (VA, USA) and Jug Bay Wetlands Sanctuary (MD, USA) were performed anaerobically under four sets of initial conditions: permutations of two salinities (0, 35) and two DOC concentrations (0 mg L^-1, 275 mg L^-1). Rates were measured at seven time points over 24 h. These results are the first DOC sorption kinetics data for tidal marsh soils, revealing that 76% of total sorption occurred within 15 min. The results also revealed higher capacity for adsorption under high DOC concentrations and salinity, with differences in magnitude between soil types. Numerical models simulating processes from these experiments provided a range of rates by fitting linear first order and non-linear ordinary differential equations to the kinetic change in DOC concentration curves over time. The outputs suggested that introducing soil adsorption capacity improved model fits across all cases. These results provide a deeper understanding of the biogeochemical controls on sorption kinetics and suggest that it is crucial to incorporate sorption processes into sediment flux models to accurately represent DOC fluxes from tidal marshes.

The cultivation of flooding-tolerant grasses on wet or rewetted peatlands is a priority in climate change mitigation, balancing the trade-off between atmospheric decarbonisation and biomass production. However, effects of management intensities on greenhouse gas (GHG) emissions and the global warming potential (GWP) are widely unknown. This study assessed whether intensities of two and five annual harvest occurrences at fertilisation rates of 200 kg nitrogen ha^− 1 yr^− 1 affects GHG exchange dynamics compared to a ‘nature scenario’ with neither harvest nor fertilisation. Fluxes of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), using opaque and transparent chambers, were measured on a wet fen peatland with a mean water table depth of -10 cm below soil surface. Overall, no treatment effect was found on biomass yields and GHG emissions. Annual cumulative CH₄ emissions were low, ranging between 0.3 and 0.5 t CO₂-C eq ha^− 1 yr^− 1. Contrary to this, emissions of N₂O were high, ranging between 1.1 and 1.5 t CO₂-C eq ha^− 1 yr^− 1. For magnitudes of CH₄ and N₂O, soil moisture conditions and electrical peat properties were critical proxies. Atmospheric uptake of CO₂ by net ecosystem exchange was higher for the treatments with management. However, this benefit was offset by the export of carbon in biomass compared to the treatment without management. In conclusion, the results highlighted a near-equal GWP in the range of 10.5–11.5 t CO₂-C eq t ha^− 1 yr^− 1 for all treatments irrespectively of management. In a climate context, a restoration scenario but also intensive paludiculture practices were equal land-use options.

Optimizing the level of groundwater presents a viable strategy for mitigating the greenhouse gas (GHG) emissions associated with the cultivation of peatlands. This study investigated the impact of soil hydrological conditions on carbon dioxide (CO₂) and methane (CH₄) emissions. The CO₂ and CH₄ emissions from bare soil were continuously measured using an automated chamber system throughout the growing seasons from 2021 to 2023 at a boreal cultivated peat soil site. Annual CO₂ emissions from soil respiration averaged to 21,600 kg ha^-1 (April-November) corresponding to carbon (C) loss of 5890 kg ha^-1. The CO₂ emissions were highly temperature dependent. Lowering the groundwater level (GWL) was found to increase the CO₂ emissions nearly linearly. The soil functioned as a CH₄ sink for the majority of the growing season, and the total sink corresponded to 27 and 20 kg ha^-1 yr^-1 CO₂ equivalent in 2022 and 2023, respectively. The CH₄ emissions occurred generally when soil water content (SWC) exceeded 0.6 m³ m^-3 and when GWL was at the depth of less than 30 cm from soil surface. For optimal climate efficiency the mitigation measures must be implemented during the mid-growing season, and the water table should be brought close to the soil surface. Potentially, this can hamper the operation of machinery on the field and reduce the harvested yield. Thus, comprehensive cost-benefit analysis is necessary before adopting a raised water table level in large-scale crop production.