Seasonal Wetlands Research Articles

Net carbon dioxide exchange in a hyperseasonal cattle pasture in the northern Pantanal wetland of Brazil

The Pantanal is the largest seasonal wetland in the world with a landscape that consists of a mosaic of permanent aquatic habitats, and floodable and non-floodable savannas, pastures and forests. Drought events are expected to occur more frequently in the Pantanal biome under future climate conditions, but the effects of land management and hydrological extremes on pastures have been poorly studied at spatial scales relevant to local livestock. In this study, we measured CO2C fluxes using eddy covariance over a hydrological year on pastures within a cattle farm in the Brazilian Pantanal that experienced seasonal flooding. Our measurements show that seasonally flooded pastures were large emitters of CO2C, contributing 337 g CO2C m−2 year−1 to the atmosphere. During flooding, when the soils were anaerobic, and soil O2 was close to zero, the flooded pasture was a net sink of -18 g CO2C m−2, while during the aerobic phase (soil O2 > 15%) the pasture was a significant CO2 source to the atmosphere (301 g CO2C m−2). Transitions to and from anaerobic conditions corresponded to 54 g CO2C m−2. Our results indicate that the seasonally flooded cattle pastures in the Brazilian Pantanal may be an important regional source of CO2C for the atmosphere. Better management, and use of drought resistant grasses, may be a way to improve soil C stocks and limit emissions, especially as global climate change is anticipated to increase heating and drying for the Pantanal biome.

Creating a Detailed Wetland Inventory with Sentinel-2 Time-Series Data and Google Earth Engine in the Prairie Pothole Region of Canada

Wetlands in the Prairie Pothole Region (PPR) of Canada and the United States represent a unique mapping challenge. They are dynamic both seasonally and year-to-year, are very small, and frequently altered by human activity. Many efforts have been made to estimate the loss of these important habitats but a high-quality inventory of pothole wetlands is needed for data-driven conservation and management of these resources. Typical landcover classifications using one or two image dates from optical or Synthetic Aperture Radar (SAR) Earth Observation (EO) systems often produce reasonable wetland inventories for less dynamic, forested landscapes, but will miss many of the temporary and seasonal wetlands in the PPR. Past studies have attempted to capture PPR wetland dynamics by using dense image stacks of optical or SAR data. We build upon previous work, using 2017–2020 Sentinel-2 imagery processed through the Google Earth Engine (GEE) cloud computing platform to capture seasonal flooding dynamics of wetlands in a prairie pothole wetland landscape in Alberta, Canada. Using 36 different image dates, wetland flood frequency (hydroperiod) was calculated by classifying water/flooding in each image date. This product along with the Global Ecosystem Dynamics Investigation (GEDI) Canopy Height Model (CHM) was then used to generate a seven-class wetland inventory with wetlands classified as areas with seasonal but not permanent water/flooding. Overall accuracies of the resulting inventory were between 95% and 96% based on comparisons with local photo-interpreted inventories at the Canadian Wetland Classification System class level, while wetlands themselves were classified with approximately 70% accuracy. The high overall accuracy is due, in part, to a dominance of uplands in the PPR. This relatively simple method of classifying water through time generates reliable wetland maps but is only applicable to ecosystems with open/non-complex wetland types and may be highly sensitive to the timing of cloud-free optical imagery that captures peak wetland flooding (usually post snow melt). Based on this work, we suggest that expensive field or photo-interpretation training data may not be needed to map wetlands in the PPR as self-labeling of flooded and non-flooded areas in a few Sentinel-2 images is sufficient to classify water through time. Our approach demonstrates a framework for the operational mapping of small, dynamic PPR wetlands that relies on open-access EO data and does not require costly, independent training data. It is an important step towards the effective conservation and management of PPR wetlands, providing an efficient method for baseline and ongoing mapping in these dynamic environments.

Patterns of variation in plant diversity vary over different spatial levels in seasonal coastal wetlands

AbstractAimTo quantify the responses of alpha and beta diversity to multivariate gradients, incorporating variation in environmental and management variability in coastal dune slacks.LocationUnited Kingdom dune slacks.MethodsPlant community composition, plant nutrient status and soil characteristics were measured for 164 quadrats in 41 dune slacks across 12 coastal sand dune systems. Data were collated on climate and atmospheric deposition. Hydrological regimes at daily resolution were modelled and calibrated using daily‐to‐monthly site measurements, from which we calculated quadrat‐level hydrological metrics. Alpha diversity (richness, Shannon diversity and Pielou's evenness) metrics and beta diversity (turnover and nestedness) for species and genera were calculated across three spatial levels from sand dune system (highest) to dune slack to quadrat (lowest).ResultsDiversity patterns depended on the spatial and taxonomic level considered. At smaller spatial levels (between dune slacks and between quadrats), alpha and beta diversity varied along gradients driven by soil characteristics, water table depth and atmospheric deposition. At larger spatial levels (between sand dune systems), patterns of beta diversity were a consequence of plant nutrient status. There was little variability in alpha diversity along this same gradient, with only small changes in Pielou's species evenness. Patterns at a coarser taxonomic level (genus) mirrored those at the species level.Main conclusionWe show that patterns of variation in plant diversity are dependent on the spatial level considered, but taxonomic level made little difference in understanding these patterns. Therefore, if we do not consider patterns across different spatial levels, important environmental and management drivers could be missed. The high biodiversity value and degree of threat to these European protected habitats makes such understanding invaluable for their conservation.

Patterns and drivers of Nothobranchius killifish diversity in lowland Tanzania.

Temporary pools are seasonal wetland habitats with specifically adapted biota, including annual Nothobranchius killifishes that survive habitat desiccation as diapausing eggs encased in dry sediment. To understand the patterns in the structure of Nothobranchius assemblages and their potential in wetland conservation, we compared biodiversity components (alpha, beta, and gamma) between regions and estimated the role and sources of nestedness and turnover on their diversity. We sampled Nothobranchius assemblages from 127 pools across seven local regions in lowland Eastern Tanzania over 2 years, using dip net and seine nets. We estimated species composition and richness for each pool, and beta and gamma diversity for each region. We decomposed beta diversity into nestedness and turnover components. We tested nestedness in three main regions (Ruvu, Rufiji, and Mbezi) using the number of decreasing fills metric and compared the roles of pool area, isolation, and altitude on nestedness. A total of 15 species formed assemblages containing 1–6 species. Most Nothobranchius species were endemic to one or two adjacent regions. Regional diversity was highest in the Ruvu, Rufiji, and Mbezi regions. Nestedness was significant in Ruvu and Rufiji, with shared core (N. melanospilus, N. eggersi, and N. janpapi) and common (N. ocellatus and N. annectens) species, and distinctive rare species. Nestedness apparently resulted from selective colonization rather than selective extinction, and local species richness was negatively associated with altitude. The Nothobranchius assemblages in the Mbezi region were not nested, and had many endemic species and the highest beta diversity driven by species turnover. Overall, we found unexpected local variation in the sources of beta diversity (nestedness and turnover) within the study area. The Mbezi region contained the highest diversity and many endemic species, apparently due to repeated colonizations of the region rather than local diversification. We suggest that annual killifish can serve as a flagship taxon for small wetland conservation.

Assessing the effects of different urban landscapes and built environment patterns on thermal comfort and air pollution in Erzurum city, Turkey

Urban environmental issues have a negative impact on urban quality of life in cities. Erzurum city is a very special place in the world because it has a very high altitude, harsh, long winter period, and high air pollution that affects the human thermal comfort sensation and the quality of life negatively. The purpose of this research is to assess the effects of different landscapes and built environmental patterns on thermal comfort and air pollution. The urban microclimate factors were recorded by field measurement weather stations and the air pollution data was collected from Turkish government monitoring stations. The thermal comfort was evaluated by the Physiologically Equivalent Temperature (PET°C) index. The results show that there is an extreme variation in the city's climate during the year. In August, the maximum temperature is 33.0 °C and the maximum average temperature is 23.0 °C, while in December the lowest temperature is −35.0 °C and the maximum average temperature is −11.4 °C. At the Ata Botanical Garden (wooded area) and in rural open areas, the temperature is 13.0 °C lower in the summer and 10.0 °C–15.0 °C lower in the winter than in urban areas. The highest average values (PET°C) were found in the city center (11.2 °C) and wooded areas (10.0 °C), while the lowest average values of PET were found in the open rural area (4.7 °C) in both seasons. Seasonal wetland (7.1 °C) and industrial (9.6 °C) areas experienced moderate thermal comfort. The Taşhan area, located near the city center and surrounded by an industrial zone, is the most polluted in the city. The statistical analysis shows that there is a significant correlation between the Ozone (O3) and the PET °C values, with R2 = 0.47 in this area. The wooded areas were found to be advantageous in raising thermal comfort and lowering air pollution.

Remote sensing assessment of available green water to increase crop production in seasonal floodplain wetlands of sub-Saharan Africa

Producing more food for a growing population requires sustainable crop intensification and diversification, particularly in high-potential areas such as the seasonal floodplain wetlands of sub-Saharan Africa (SSA). With emerging water shortages and concerns for conserving these multi-functional wetlands, a further expansion of the cropland area must be avoided as it would entail increased use of blue water for irrigation and infringe on valuable protected areas. We advocate an efficient use of the prevailing green water on the existing cropland areas, where small-scale farmers grow a single crop of rainfed lowland rice during the wet season. However, soil moisture at the onset of the rains (pre-rice niche) and residual soil moisture after rice harvest (post-rice niche) may suffice to cultivate short-cycled crops. We developed a methodological approach to analyze the potential for green water cultivation in the pre- and post-rice niches in the Kilombero Valley Floodplain in Tanzania, as a representative case for seasonal floodplain wetlands in SSA. The three-step approach used open-access remote sensing datasets to: (i) extract cropland areas; (ii) analyze soil moisture conditions using evaporative stress indices to identify the pre- and post-rice niches; and (iii) quantify the green water availability in the identified niches through actual evapotranspiration (AET).We identified distinct patterns of green water being available both before and after the rice-growing period. Based on the analyses of evaporative stress indices, the pre-rice niche tends to be longer (~70 days with average AET of 20–40 mm/10-day) but also more variable (inter-annual variability >30%) than the post-rice niche (~65 days with average AET of 10–30 mm/10-day, inter-annual variability <15%). These findings show the large potential for cultivating short-cycled crops beyond the rice-growing period, such as green manure, vegetables, maize, and forage legumes, by shifting a portion of the nonproductive AET flows (i.e., soil evaporation) to productive flows in form of crop transpiration. A cropland area of 1452 to 1637 km2 (53–60% of the total cropland area identified of 2730 km2) could be cultivated using available green water in the dry season, which shows the significance of such change for food security, livelihoods, and resilience of the agricultural community in Kilombero. A wider application of the developed approach in this study can help identifying opportunities and guiding interventions and investments towards establishing sustainable intensification and diversification practices in floodplain wetlands in SSA.

Impacts of Climate Change on a Coastal Wetland from Model Simulation Combining Satellite and Gauge Observations: A Case Study of Jiangsu, China

Coastal wetlands are affected by both natural processes and human activities. In the present study, the impacts of natural processes on wetland area variations along the Jiangsu coast in the East China Sea were investigated using a long-term high-resolution numerical model (55 years from 1955 to 2010) validated by satellite and gauge observations. In our 55-year simulation, a 1.33 km2 yr−1 decreasing trend of wetland area as a result of global warming was identified. It was found that the wetland area varied depending on the following temporal scales: intra-seasonal, seasonal, interannual, and decadal. Tides and steric sea level changes are responsible for the intra-seasonal and seasonal wetland variations, respectively. The long-term variations are attributable to the El Niño-Southern Oscillation and Pacific Decadal Oscillation. These basin-scale phenomena cause changes in the local wind patterns along the Jiangsu coast and impact the wetland variation on long-term scales.

Assessing Wetland ecosystem health in Sundarban Biosphere Reserve using pressure-state-response model and geospatial techniques

Coastal wetlands as the potential ecosystems, provide a wide range of benefits counting from ecosystem services to livelihood opportunities. Wetlands are continuously being degraded throughout the world especially in coastal ecosystems due to intensifying pressure on these resources and changing global climatic patterns. The wetlands in Sundarban Biosphere Reserve (SBR) are unique in character as these are surrounded by numerous rivers, creaks and mangrove forest. The present work is a concerted attempt to assess the health conditions of coastal wetland ecosystem in the SBR, India. Coastal wetlands of SBR were delineated during 1989–2017. Geospatial layers of site-specific indicators were prepared and were applied to the PSR model to examine the health of the wetland ecosystem. The model was also utilized to examine the impact of anthropogenic activities on wetland ecosystem and to ascertain the relationship among ecological pressure-state-response of ecosystem. The findings revealed that area under agriculture has been transformed into aquaculture. The shortage of fresh water supply for agriculture and increased salinity transformed many croplands to seasonal wetlands throughout the SBR. The overall ecosystem health of Sundarban has been decreased during the last two decades due to anthropogenic pressure and climate change issues. The result also indicated that the ecosystem fragmentation and human interference rate are two main dominating factors for declining wetland health in SBR. The findings of the study may help in formulating policy for the management of coastal wetland ecosystem.

Seasonal flooding wetland expansion would strongly affect soil and sediment organic carbon storage and carbon-nutrient stoichiometry

In the past few decades, many non-flooding uplands (NF) and permanent flooding waters (PF) have been turned into seasonal flooding wetlands (SF) at the global scale. This trend could severely threaten global climate system by changing carbon cycling in terrestrial and aquatic ecosystems. However, the effects of SF expansion on soil and sediment organic carbon (SOC) storage and carbon-nutrient stoichiometry are far from clearly understood. Therefore, we explored SOC storage and carbon-nutrient stoichiometry among adjacent NF, SF and PF using 817 samples at 0–100 cm depth increment at Poyang Lake and Shengjin Lake in the middle-lower Yangtze River floodplain, China. The SFs of the two lakes were both Carex lakeshore wetlands. The NF of Shengjin Lake was a near-natural forest, while the NF of Poyang Lake was a disturbed grassland. The results showed that SOC storage at SFs of Poyang Lake and Shengjin Lake was 75.61 and 98.01 Mg C/ha at 0–100 cm depth increment. The difference in SOC storage among nearby NF, SF and PF depended on depth and disturbance. SOC storage at SF was equivalent to that at near-natural NF, but was much higher than that at disturbed NF. SOC storage at SF was 12.62%–24.50% higher than that at PF at 0–30 cm depth increment, but was 15.16%–25.87% lower than that at PF at 0–100 cm depth increment. Edaphic carbon and nutrients followed allometric relationships at most sites and C increased faster than N and P along the depth gradients. Carbon-nutrient stoichiometric relationships at SF and PF were similar, and were more coupled than those at near-natural NF. This research illustrates the strong effects of seasonal flooding on SOC sequestration in terrestrial and aquatic ecosystems, and expands our understanding of carbon cycling in these two ecosystems.

Functional Wetland Loss Drives Emerging Risks to Waterbird Migration Networks

Migratory waterbirds (i.e., shorebirds, wading birds, and waterfowl) rely on a diffuse continental network of wetland habitats to support annual life cycle needs. Emerging threats of climate and land-use change raise new concerns over the sustainability of these habitat networks as water scarcity triggers cascading ecological effects impacting wetland habitat availability. Here we use important waterbird regions in Oregon and California, United States, as a model system to examine patterns of landscape change impacting wetland habitat networks in western North America. Wetland hydrology and flooded agricultural habitats were monitored monthly from 1988 to 2020 using satellite imagery to quantify the timing and duration of inundation—a key delimiter of habitat niche values associated with waterbird use. Trends were binned by management practice and wetland hydroperiods (semi-permanent, seasonal, and temporary) to identify differences in their climate and land-use change sensitivity. Wetland results were assessed using 33 waterbird species to detect non-linear effects of network change across a diversity of life cycle and habitat needs. Pervasive loss of semi-permanent wetlands was an indicator of systemic functional decline. Shortened hydroperiods caused by excessive drying transitioned semi-permanent wetlands to seasonal and temporary hydrologies—a process that in part counterbalanced concurrent seasonal and temporary wetland losses. Expansion of seasonal and temporary wetlands associated with closed-basin lakes offset wetland declines on other public and private lands, including wildlife refuges. Diving ducks, black terns, and grebes exhibited the most significant risk of habitat decline due to semi-permanent wetland loss that overlapped important migration, breeding, molting, and wintering periods. Shorebirds and dabbling ducks were beneficiaries of stable agricultural practices and top-down processes of functional wetland declines that operated collectively to maintain habitat needs. Outcomes from this work provide a novel perspective of wetland ecosystem change affecting waterbirds and their migration networks. Understanding the complexity of these relationships will become increasingly important as water scarcity continues to restructure the timing and availability of wetland resources.

Seasonal agricultural wetlands act as potential source of N2O and CH4 emissions

Seasonal wetlands and depressions in agricultural fields that accumulate nutrients from runoff water might act as hotspots of nitrous oxide (N2O) and methane (CH4) emissions. However, the spatiotemporal pattern of these gases from different parts of agricultural fields had not been compared. A two-year field experiment was conducted in Ontario, Canada, to test whether field locations with higher wetness act as N2O and CH4 hotspots. The objectives included, i) to classify agricultural field using topographical wetness index (TWI), ii) to determine the spatiotemporal patterns of N2O, CH4, and soil properties from TWI classes; and iii) to determine the impact of soil variables on N2O and CH4 emission prediction. The field was divided into four classes based on TWI, i) low TWI (C1; steep slopes), ii) medium TWI and slopes (C2), iii) Higher TWI (C3; low slopes), and iv) very high TWI (C4; seasonal wetlands and depressions). Each TWI class had six sampling points as replicates to collect soil and gas samples during corn (2019) and soybean (2020) seasons. TWI classes had a significant impact on N2O and CH4 emissions. Mean maximum and minimum N2O emissions were observed during corn season from C4 (153 ± 34) and C1 (69 ± 35 µg N2O-N m-2h−1), respectively. However, during soybean season, C1 had higher (70 ± 1), and C4 had lower average (26.5 ± 8 µg N2O-N m-2h−1) emissions. Higher mean CH4 emissions were observed from C4 and C1, respectively, during corn (1264 ± 778) and soybean (60 ± 44 µg CH4-C m-2h−1) seasons. Regression analysis revealed that N2O emissions were mainly controlled by nitrate, electrical conductivity, and moisture during corn and ammonium, pH, and nitrate during soybean season. Similarly, CH4 emissions were regulated by moisture and clay during corn season and ammonium and pH during soybean season. These relationships could help upscale greenhouse gas emissions at regional levels and formulate mitigation strategies.

A Novel Workflow for Seasonal Wetland Identification Using Bi-Weekly Multiple Remote Sensing Data

Accurate wetland mapping is essential for their protection and management; however, it is difficult to accurately identify seasonal wetlands because of irregular rainfall and the potential lack of water inundation. In this study, we propose a novel method to generate reliable seasonal wetland maps with a spatial resolution of 20 m using a seasonal-rule-based method in the Zhalong and Momoge National Nature Reserves. This study used Sentinel-1 and Sentinel-2 data, along with a bi-weekly composition method to generate a 15-day image time series. The random forest algorithm was used to classify the images into vegetation, waterbodies, bare land, and wet bare land during each time period. Several rules were incorporated based on the intra-annual changes in the seasonal wetlands and annual wetland maps of the study regions were generated. Validation processes showed that the overall accuracy and kappa coefficient were above 89.8% and 0.87, respectively. The seasonal-rule-based method was able to identify seasonal marshes, flooded wetlands, and artificial wetlands (e.g., paddy fields). Zonal analysis indicated that seasonal wetland types, including flooded wetlands and seasonal marshes, accounted for over 50% of the total wetland area in both Zhalong and Momoge National Nature Reserves; and permanent wetlands, including permanent water and permanent marsh, only accounted for 11% and 12% in the two reserves, respectively. This study proposes a new method to generate reliable annual wetland maps that include seasonal wetlands, providing an accurate dataset for interannual change analyses and wetland protection decision-making.

Carbon Isotopic Evidence for Gas Hydrate Release and Its Significance on Seasonal Wetland Methane Emission in the Muli Permafrost of the Qinghai-Tibet Plateau.

In order to determine the significant role of gas hydrate in seasonal wetland methane emission at the drilling-affected permafrost, the carbon isotopic monthly field monitoring of methane (CH4), as well as carbon dioxide (CO2), emitted from near-surface soil and a gas hydrate drilling well (DK-8) was conducted in the Muli permafrost of the Qinghai-Tibet Plateau. The methane source effused from the well DK-8 was calculated as −25.9 ± 1.4‰ and −26.5 ± 0.5‰, respectively, by the Keeling and Miller Tans plots, with the carbon isotope fractionation (εC) between CO2 and CH4 from −25.3‰ to −32.1‰. The carbon isotopic signatures are indicative of thermogenic origin associated with gas hydrate dissociation. The near-surface soil-emitted methane has δ13CCH4 values between −52.0 ± 1.2‰ and −43.2 ± 1.8‰ with the heaviest in December and the lightest in July. Further, the εC values of near-surface soil-emitted gases were between 28.6‰ and 47.9‰, significantly correlated with the δ13CCH4 values. The linear correlation between εC and δ13CCH4 values indicated binary end-member of microbial and thermogenic sources control the seasonal variation of wetland methane emission. The thermogenically derived methane was identified as the dominant methane source in autumn and winter, compared with the increasing contribution of microbially derived methane in spring and summer. The finding provides reliable evidence for gas hydrate release on the seasonal wetland methane emission in the Muli permafrost affected by drilling activities. The combined application of εC and δ13CCH4 to distinguish thermogenic from biogenic methane is well established and powerful in complex environments, which can provide an improved constraint on source apportionment for wetland emitted methane in the permafrost of the Qinghai-Tibet Plateau.

Estuarine Fish Feeding Changes as Indicator to Mangrove Restoration Success in Seasonal Karstic Wetlands

The loss of mangrove areas due to anthropogenic activities has triggered efforts to recover or restore these ecosystems, their functions, and associated diversity. Such functions include nursery areas and energy flow through trophic relationships for a large variety of inhabitant species (e.g., fish). The food webs and trophic dynamics of estuarine fish provide important information on the food resources in mangrove ecosystems and their response to restoration processes. Nonetheless, few studies focus on using fish feeding characteristics as an approximation to assess the conservation or recovery status of these aquatic ecosystems. Thus, the aim of the present study was to compare the trophic dynamics of an ichthyic community in a mangrove ecosystem related to karstic wetlands in the Mexican–Caribbean using freshwater, estuarine, and marine fish species as bioindicators of the restoration process in mangroves. Stomach contents were analyzed for eight species of fish inhabiting specific mangrove zones (1—conserved zone, and 2—restored zone; a zone exposed to ecological restoration processes due to impacts of anthropic activities) related to karstic wetlands in the Mexican–Caribbean. Four feeding characteristics were considered: trophic guild, trophic level, feeding strategy, and prey abundance. Results showed differences and changes in the use of food sources at the trophic level mainly for Floridichthys polyommus, changing from a secondary consumer in the conserved zones to a primary consumer in the restored zones. This suggests that the feeding characteristics of the inhabiting fish are related to the mangrove’s conservation/restoration status and the trophic dynamics in the community. The results of this study are relevant as a tool for mangrove restoration plans regarding the analysis of fish and their food prey, in order to perform an easy and rapid assessment to determine the conservation/restoration status of these aquatic ecosystems from a functional perspective.

Interception and Redistribution of Precipitation by Parkinsonia aculeata L.: Implications for Palo Verde National Park Wetlands, Costa Rica

Seasonal wetlands in the tropics are important habitats for local and migratory bird species. In the northwestern Pacific of Costa Rica, Palo Verde National Park has one of the most important seasonal wetlands of Central America. The management history of this wetland has shown the impact of invasive plant species such as Parkinsonia aculeata L. whose cover extension and canopy structure impact not only the ecological niches of bird species, but also the wetland hydrology. A 300 m2 plot was established in a P. aculeata stand to evaluate the role of P. aculeata on the partitioning and redistribution of precipitation. Gross precipitation (PGr), throughfall (PTF) and stemflow (PSF) were measured on a daily basis to determine the interception of precipitation (PI) and net precipitation (PNet). A total of 43 precipitation events were sampled during the wet season of 2003. We measured 530.5 mm of PGr and 458 mm of PTF, with an average sampling error of 0.7 mm or 6.1%. Canopy storage capacity was estimated at 1.47 mm, throughfall 88.73%, stem flow 2.63% and a total interception of 8.64%, with a PNet coefficient of 0.9475. The relationships between gross precipitation (PGr) with throughfall (PTF), stemflow (PSF) and net precipitation (PNet) were evaluated using linear regression models. P. aculeata showed to have one of the highest net precipitation and lowest precipitation interception among small trees.

Iso-Wetlands: unlocking wetland ecologies and agriculture in prehistory through sulfur isotopes

Iso-Wetlands is a new, NERC-funded collaborative research project involving researchers at UCL Institute of Archaeology, the University of Leeds and the UK Centre for Ecology and Hydrology. The project is developing sulfur isotope analysis of archaeological plants and animals as a new tool for exploring hydrological conditions under which agricultural production was taking place. This development has the potential to improve understanding of water management strategies in the past, particularly in relation to seasonal floodwater agriculture and wetland agriculture (for example, rice paddy systems). The project will open wider possibilities for the use of sulfur isotopes in archaeology and ecology to examine wetland habitat use by both people and animals.

Wintering waterbirds diversity and their impact factors in coastal lake wetlands of the Yangtze River in Jiangsu Province

长江及其中下游湖泊湿地组成了独特的江-河复合型生态系统，孕育了极高的生物多样性，是全球生物多样性研究的热点区域之一.该区域是东亚-澳大利西亚迁徙通道上最重要的水鸟越冬地之一，每年冬季有超过百万只水鸟在此越冬，因此，分析相关因素对越冬水鸟多样性的影响对维持其越冬安全具有重要意义.然而，目前相关研究多集中在如鄱阳湖、洞庭湖、升金湖等部分国家级保护区内，对经济较发达的江苏省沿江区域湖泊湿地水鸟多样性的研究仍不多见.本研究选择江苏长江沿江10处代表性湖泊湿地，于2018—2020年冬开展越冬水鸟调查，同时结合环境和人为因素，分析其对区域越冬水鸟多样性的影响.3次调查共记录到越冬水鸟42种109998只，隶属于6目9科.按地理区系划分，古北界16种，广布种15种，古北界-东洋界9种，东洋界2种；按生态类群划分，有游禽22种，涉禽20种.在10处湖泊湿地中，石臼湖水鸟物种数和数量均最多，金牛湖水鸟物种数和数量均为最低；Shannon-Wiener和Inverse-Simpson多样性指数最高的为石臼湖，最低分别为长荡湖和昆承湖.β多样性结果表明石臼湖水鸟群落与其它湿地相似性最低，长荡湖次之.β多样性分解分析结果显示，区域β多样性主要形成机制为物种替换.石臼湖对区域β多样性的相对贡献显著高于其它湖泊湿地，其次是长荡湖，相对贡献最低的是尚湖.线性模型结果表明：越冬水鸟丰富度与湿地总面积呈正相关，与缓冲区植被和水体面积呈负相关.人均GDP与越冬水鸟丰富度呈显著负相关.越冬水鸟物种数与湖泊湿地面积呈正相关，与人均GDP呈负相关.水鸟多样性指数受面积和人均GDP影响均不显著.江苏沿江地区是我国经济最发达的区域之一，对其越冬水鸟多样性及其影响因素开展研究进而提出相关保护建议，如持续开展越冬水鸟监测，及时发现保护空缺，提高对湿地周边区域土地利用状况的关注度等.本研究结果不仅为本地区越冬水鸟保护工作提供依据，同时也为上游经济相对薄弱但发展较快的地区开展相关保护工作提供参照.;The Yangtze River and its floodplain are unique for the extensive wetlands, recharged by summer monsoonal precipitation, laden with nutrients and sediment. It's the largest amount of shallow and seasonal flooded wetlands in the world, providing ecosystem services to tens of millions of people. The wetlands also support globally significant numbers of wintering waterbirds. Every year, more than 1 million waterbirds spend winter here. It is critical to understand the effects of different variables on wintering waterbirds diversity. So far, most of the research were focused on some National Nature Reserves, e.g. Lake Poyang, Lake Dongting and Lake Shengjin. The researches concerning wintering waterbirds diversity on lake wetlands located in the Lower Yangtze River floodplain in Jiangsu Province are still limited, where the economic is relatively developed. In this study, we systematically surveyed 10 representative wetlands along the Yangtze River in Jiangsu Province from 2018 to 2020 and then analyzed the effect of ecological and anthropogenic factors on waterbird abundance, species richness and diversities. In total, 109998 waterbird of 42 species were recorded, belonging to 6 orders and 9 families. Of them, 22 species are Natatores and the others are all Waders. In terms of the biogeographic distribution, 16 species belong to Paleartics, 15 species are wide distributive species, 9 species belong to Paleartics-Oriental, and 2 species belong to Oriental. Among the 10 lake wetlands, Lake Shijiu has the highest Shannon-Wiener and Inverse-Simpson diversity index, and the lowest are Lake Changdang and Lake Kuncheng respectively. In addition, the community composition dissimilarity (β diversity) between Lake Shijiu and the other lakes are the highest, following by Lake Changdang. Results of the decomposition of β diversity suggested that species replacement was the main process influencing regional β diversity. Lake Shijiu had a significant higher relative contribution to regional β diversity, followed by Lake Changdang, while Lake Shanghu had the lowest relative contribution. Wintering waterbird abundance positively correlated with total area of wetlands but negatively affected by vegetation area and water area in the buffer area, as well as the effect of per capita GDP. Number of wintering bird species positively correlated with total area of lake wetlands but negatively affected by per capita GDP. Area had no effects on both Shannon-Wiener and Inverse-Simpson indices. As one of the most developed areas in China, unveiling the effects of different variables on wintering waterbirds diversity may not only offer practical conservation measures for this area, for example, carrying out continuous waterbird monitoring projects, detecting conservation gaps and playing close attention on landscape changes of surrounding area, but also provide a good sample for the conservation work in up-stream areas of the Yangtze River where the economic is ongoing developing.

Immature stages of the limnephilid caddisfly Verger lutzi (Navás 1918) (Trichoptera: Limnephilidae ): description and larval life-history traits in seasonal forested wetlands of Northwestern Patagonia

The genus Verger Navás 1918 (Trichoptera: Limnephilidae), is a Neotropical genus exclusive to the Andean region, with most of its species distributed from Tierra del Fuego to north central Chile and Argentina. Currently, 20 species of the genus have been described from adults and only six larvae have been associated and diagnosed. The ecology of the species is completely unknown. In this work, we describe and illustrate the immature stages of Verger lutzi (Navás 1918) and study its breeding phenology, larval growth and adult emergence. The main characters that enable the separation of this species are the coloration the body, shape of the anterior ventral apotome, shape and distribution of metanotal setal areas, distribution of tracheal gills and number of accessory teeth in the anal prolegs. Reproduction occurs during the summer and females lay their eggs on the wetland basin formed by humid leaf litter and organic debris, covered by herbaceous vegetation. Larvae hatch after flooding and overwinter in the wetland. Larvae develop fast during spring and emergence begins in December before the wetland dries up. Description of the immature stages is helpful for use of macroinvertebrates biomonitoring, ecological studies and understanding their ecosystem services in seasonal-lentic habitats.

Systematic method for mapping fine-resolution water cover types in China based on time series Sentinel-1 and 2 images

Humans have been transforming natural surface water bodies into various types of artificial water cover to meet the growing demand for food, energy, and flood protection in recent decades. These changes have exerted cumulative impacts on the water cycle, environment, and ecology. Although the geographical distribution of and changes in water cover types is essential to understanding these changes, timely and accurate acquisition and updating are difficult to accomplish, mainly because of the lack of a practical and effective classification method, especially at the global and national scales. From the perspective of water cover, first we suggest a comprehensive water cover classification system in terms of water sources, water body shapes, and water usage, including rivers, reservoirs, lakes, agricultural ponds, seasonal wetlands, and rice fields. An automatic and operational classification method based on shape features and flooding frequency (AuCoSaFF) is developed accordingly. Then, we employ this method to produce an unprecedented 10-meter spatial resolution China Water Cover Map (CWaC) using time series Sentinel-1 and Sentinel-2 images acquired in 2020 and obtained from the Google Earth Engine. The validation shows that this dataset has an overall accuracy of 86% and a kappa coefficient of 0.83. The CWaC is the first thematic mapping on water cover types over all of China, and it provides information on the complete water cover types. It indicates that China’s water cover area is 240,383 km2, of which natural water accounts for 56.3%. China’s water bodies are mainly distributed in Heilongjiang, Tibet, and Qinghai provinces. A comparison with seven other water-related data products highlights the advantages of the AuCoSaFF in acquiring high spatial and temporal resolution information about the complete water cover types at large scales. The shape-based and inundation frequency-based automatic method underlines the potentials of fast water cover type mapping at large scales using existing water datasets. We also anticipate that this freely available dataset will provide evidence of the states of and changes in wetlands, help to improve our understanding of human influences on the hydrologic cycle, and inform water-management decision-making.

Effects and mechanisms of land-types conversion on greenhouse gas emissions in the Yellow River floodplain wetland

The mechanism and extent of changes in greenhouse gas (GHG) emissions from seasonal river-floodplain wetlands subjected to land-type conversion are unknown. We monitored GHG fluxes and characterized soil microbial communities in four types of wetland (Riverside lower-beach wetland (RLW), Riverside higher-beach wetland (RHW), Cultivated wetland (CW), Mesophytic wetland (MW)) in the Yellow River flood land. Results revealed that land reclamation activities altered the distribution patterns of carbon (C) and nitrogen (N) in soil, as well as the structure and activities of microbial communities, leading to changes in the GHG emissions. Cumulative CO2 and N2O emissions were highest in CW, which were 2.10–10.71 times and 3.19–8.61 times greater than the other three wetlands, respectively, whereas cumulative CH4 emissions were highest in RLW (1850.192 mg·m−2). CW exhibited the highest 100-years-scale Global Warming Potential (GWP100-CO2-eq) (81.175 t CO2-eq·ha−1), which was 9.93, 3.12, and 2.11 times greater than RLW, RHW, and MW. Moreover, reclaiming riverside wetland as farmland will increase CO2 and N2O emission fluxes by 54.546–72.684 t·ha−1 and 2.615–2.988 kg·ha−1, respectively. 16S rRNA high throughput sequencing revealed that bacterial community composition changed significantly overtime and seasons. GHG fluxes showed a significant positive linear correlation with bacterial OTUs (y = 0.71x–319.4, R2 = 0.304) and Shannon index (y = 228.62x–796.6, R2 = 0.336). Structure equation models indicated that soil C, N and moisture content were the primary factors influencing bacterial community evolution, which had an impact on GHG fluxes. Actinomycetes were significantly affected by total carbon (TC) content, dissolved organic carbon (DOC), and C/N, while ammonia oxidizing and nitrifying bacteria were greatly influenced by NO3−-N rather than TN and NH4+-N content. Opportunities exist to reduce GHG emissions and mitigate climate change by maintaining the original state of riverside wetland or restoring cultivated land to wetland in the Yellow River floodplain wetland.