Flooded Wetlands Research Articles

Impact of litter quality on the stability and storage of soil carbon in flooded wetlands

Context High inputs of plant litters and slow decomposition of soil organic carbon (SOC) influence the biogeochemical cycling of soil carbon in flooded wetlands. Aims To investigate the effects of different quality litter inputs on SOC stability and storage in flooded wetlands. Methods A 180-day microcosmic experiment to investigated the decomposition of litters of two dominant plants (Carex cinerascens Kukenth., CC; Cyperaceae family) and Triarrhena lutarioriparia L. Liu, TL; Poaceae family), in Poyang Lake Wetlands. Key results CC litters (high-quality, low lignin/N mass ratio) reduced gross content of SOC, but increased labile carbon and labile index (LI) of soils. In contrast, inputs of TL litters (low-quality, high lignin/N mass ratio) increased SOC gross content and recalcitrant carbon fractions of soils, but reduced soil labile carbons and LI. Significant effects of litters on SOC were not observed until ∼30 days indicating that the effects of litter inputs on soil carbon pools in flooded wetlands need time to be activated. CC and TL litters both increased the soil microbial biomass carbon (MBC) content. Soil MBC in CC treatments was significantly affected by the litter ash-free dry mass, while that in TL treatments was significantly affected by mass loss. Conclusions Litter quality may regulate the growth of soil MBC via different microbial growth strategies. Implications Our results suggest that inputs of high-quality litters can yield a high amount of labile carbon through stimulated microbial decomposition, leading to an overall loss of carbon. In contrast, inputs of low-quality litters can promote the microbial production of more recalcitrant carbons and increase soil carbon stability and carbon sequestration.

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.

Changes in biomass burning, wetland extent, or agriculture drive atmospheric NH<sub>3</sub> trends in select African regions

Abstract. Atmospheric ammonia (NH3) is a precursor to fine particulate matter and a source of nitrogen (N) deposition that can adversely affect ecosystem health. The main sources of NH3 – agriculture and biomass burning – are undergoing are or expected to undergo substantial changes in Africa. Although evidence of increasing NH3 over parts of Africa has been observed, the mechanisms behind these trends are not well understood. Here we use observations of atmospheric NH3 vertical column densities (VCDs) from the Infrared Atmospheric Sounding Interferometer (IASI) along with other satellite observations of the land surface and atmosphere to evaluate how NH3 concentrations have changed over Africa from 2008 through 2018, and what has caused those changes. In West Africa NH3 VCDs are observed to increase during the late dry season, with increases of over 6 % yr−1 in Nigeria during February and March (p<0.01). These positive trends are associated with increasing burned area and CO trends during these months, likely related to agricultural preparation. Increases are also observed in the Lake Victoria basin region, where they are associated with expanding agricultural area. In contrast, NH3 VCDs declined over the Sudd wetlands in South Sudan by over 1.5 % yr−1, though not significantly (p=0.28). Annual maxima in NH3 VCDs in South Sudan occur during February through May and are associated with the drying of temporarily flooded wetland soils, which favor emissions of NH3. The change in mean NH3 VCDs over the Sudd is strongly correlated with variation in wetland extent in the Sudd: in years when more area remained flooded during the dry season, NH3 VCDs were lower (r=0.64, p<0.05). Relationships between biomass burning and NH3 may be observed when evaluating national-scale statistics: countries with the highest rates of increasing NH3 VCDs also had high rates of growth in CO VCDs; burned area displayed a similar pattern, though not significantly. Livestock numbers were also higher in countries with intermediate or high rates of NH3 VCD growth. Fertilizer use in Africa is currently low but growing; implementing practices that can limit NH3 losses from fertilizer as agriculture is intensified may help mitigate impacts on health and ecosystems.

Impact assessment of solid runoff on heavy metals migration during high floods on the Amur river

Inhomogeneity of the concentrations of chemical elements in the cross-section of the Amur River is considered as a function of the state of their soluble and suspended forms. Flooding of wetlands and urbanized areas contributes to the removal of pollutants into the river channel. The wide spread of fens on the left bank contributes to the concentration of organic matter along the left bank of the river. Terrigenous material mostly comes from the right bank, where agricultural fields are concentrated. The ratio of their concentrations is maintained by the duration of the flood. The mechanisms of redistribution of elements between their suspended and soluble forms have been studied. The mechanisms of sorption of chemical compounds on mineral and organic colloids are described. It was found that mineral colloids with a negative charge due to electrostatic attraction sorb electrically neutral compounds (hydroxoaqua complexes [Mn(OH)2(OH2]0, ammonia [Cu(NH3)4(OH)2]0. The role of organic material in the redistribution of chemical compounds between soluble and suspended forms is shown. Organic colloids with molecular mass > 5.0 kDa precipitate complex cations – [FeHSO4]+, [FeHSO4]2+, [CuHSO4]+. An organic substance with a molecular mass of <2.0 kDa has a greater complexing ability for Fe(2)3+, Cu2+, Zn2+, Mn2+ ions. They bind metals to organo-mineral complexes by chemical interaction and form mobile organo-mineral complexes and heteropolar salts.

Leveraging Google Earth Engine platform to characterize and map small seasonal wetlands in the semi-arid environments of South Africa

Although significant scientific research strides have been made in mapping the spatial extents and ecohydrological dynamics of wetlands in semi-arid environments, the focus on small wetlands remains a challenge. This is due to the sensing characteristics of remote sensing platforms and lack of robust data processing techniques. Advancements in data analytic tools, such as the introduction of Google Earth Engine (GEE) platform provides unique opportunities for improved assessment of small and scattered wetlands. This study thus assessed the capabilities of GEE cloud-computing platform in characterising small seasonal flooded wetlands, using the new generation Sentinel 2 data from 2016 to 2020. Specifically, the study assessed the spectral separability of different land cover classes for two different wetlands detected, using Sentinel-2 multi-year composite water and vegetation indices and to identify the most suitable GEE machine learning algorithm for accurately detecting and mapping semi-arid seasonal wetlands. This was achieved using the object based Random Forest (RF), Support Vector Machine (SVM), Classification and Regression Tree (CART) and Naïve Bayes (NB) advanced algorithms in GEE. The results demonstrated the capabilities of using the GEE platform to characterize wetlands with acceptable accuracy. All algorithms showed superiority, in mapping the two wetlands except for the NB method, which had lowest overall classification accuracy. These findings underscore the relevance of the GEE platform, Sentinel-2 data and advanced algorithms in characterizing small and seasonal semi-arid wetlands.

Alpine soil microbial community structure and diversity are largely influenced by moisture content in the Zoige wetland

The Zoige alpine wetland is one of the most sensitive ecosystems to global climate change. It is the largest alpine wetland in the world and currently suffers from serious drought and degradation. In this study, soil microbial communities of five soils with different moisture content were investigated by Illumina MiSeq high-throughput sequencing of 16S rRNA. The results showed that soil acidity and the content of soil nutrients decreased with the decrease in soil moisture. The microbial richness indices (Chao1 and ACE) and diversity index (Shannon) were highest in the flooded wetland (FW) and lowest in the unflooded mound near the flooded wetland (UW). The relative abundance showed four dominated phyla among all the soil microbes in five soils: Proteobacteria (36.5%), Acidobacteria (26.1%), Actinobacteria (9.4%) and Bacteroidetes (5.8%). Moreover, Proteobacteria (51.4%) of UW was significantly (P < 0.05) higher than that of other soils, while Actinobacteria (1.6%), Gemmatimonadetes (0.9%) and Nitrospirae (0.03%) of UW were significantly (P < 0.05) lower than those of other soils. Principal component analysis (PCA) and redundancy analysis (RDA) revealed that soil samples of UW differed most from samples of other soils. Proteobacteria was positively correlated with water-soluble phosphorus, while Actinobacteria and Bacteroidetes were negatively correlated with total organic carbon and total nitrogen. Our findings revealed that soils in transitional unstable state from flooded to aridification had the lowest microbial diversity, and drought led to long-term changes in the microbial community in the Zoige wetland, which may cause further degradation of alpine wetland ecosystem functions.

Irruptive White Ibis breeding is associated with use of freshwater crayfish in the coastal Everglades

AbstractAs avian reproductive success is generally prey limited, identifying important prey types or sizes and understanding mechanisms governing prey availability are important objectives for avian conservation ecology. Irruptive White Ibis (Eudocimus albus) nesting at coastal colonies in the southern Everglades numbered over 100,000 nests in the 1930s. A century of drainage and altered hydrologic patterns reduced aquatic prey availability and eliminated large nesting events; nesting activity in recent decades has been typically less than 5% of historical peaks. Hydrologic restoration is expected to increase ibis nesting activity, but which prey types will support high nesting effort is less clear. In 2017 and 2018, we collected food boluses from White Ibis chicks at coastal colonies in Everglades National Park. We also monitored regional nesting activity from 1999 to 2018. In 2017, the region had 1,075 nests, typical of the past several decades; but in 2018, there were 30,420 nests, representing the highest recorded nesting activity in 87 yr. Prey composition varied between years; estuarine crabs dominated nestling boluses in 2017, while crayfish and fish were dominant prey in 2018. Crayfish, especially Procambarus alleni, were heavily exploited by ibis early in the 2018 breeding season, while fish were used more at the end. Crayfish abundances in wetlands near the colonies were higher prior to 2018, and more crayfish-producing short-hydroperiod wetlands remained available for ibis foraging in 2018. Our results support previous studies indicating that crayfish are important prey for breeding ibises and suggest that unprecedented, extensive flooding of seasonal wetlands promoted crayfish production and initiated the irruptive breeding in 2018. Our observations indicate that rehydration of the southern Everglades could restore ibis nesting activity at coastal colonies, but further investigations of hydrologic variation, crayfish production, and ibis foraging and nesting activity will be helpful to understand these dynamics and the importance of short-hydroperiod wetlands.

Soil physicochemical properties drive the variation in soil microbial communities along a forest successional series in a degraded wetland in northeastern China.

The Sanjiang Plain is the biggest freshwater wetland locating in northeastern China. Due to climate change and human activities, that wetland has degraded to a successional gradient from the original flooded wetland to dry shrub vegetation and a forest area with lower ground water level, which may result in changes in soil microbiologic structure and functions. The present study investigated the microbial diversity and community structure in relation to soil properties along that successional gradient. The soil physico‐chemical properties changed significantly with degradation stage. The Shannon diversity index of both soil bacteria (5.90–6.42) and fungi (1.7–4.19) varied significantly with successional stage (both p < .05). The community structures of soil bacteria and fungi in the early successional stages (i.e., the wetland) were significantly determined by water content, total nitrogen, and available nitrogen concentrations in soils, while those in the later successional stages (i.e., forests) were significantly structured by soil organic carbon, soil pH, and available phosphorus concentrations. These results suggest that the soil microbial structure is mainly determined by soil properties rather than by plant community such as plant species composition along successional stages.

Contrasting climate controls on the hydrology of the mountainous Cauca River and its associated sedimentary basin: Implications for interpreting the sedimentary record

In coupled “source-to-sink” systems, spatial differences in hydrology and geomorphology influence how processes in the source are recorded in the sink. The catchment of the tropical Cauca River (source) in the northern (Colombian) Andes, and its associated Mojana lowland sedimentary basin (sink), are a model system in which to explore the relationship between climate processes that control runoff and erosion in the upper catchment, and sediment deposition in the lower basin that occurs through avulsion events and seasonal wetland flooding. This study employed historical climate and hydrologic data from the Cauca River watershed and its associated sedimentary basin, along with topographic data and satellite imagery. We discovered that the Cauca River catchment and its associated Mojana Basin are governed by different patterns of intra- and inter-annual climate variability. Biannual passage of the Intertropical Convergence Zone (ITCZ) over the watershed, annual incursion of the Choco Jet, and sub-decadal variability of the El Niño Southern Oscillation (ENSO) all modulate runoff and sediment fluxes that ultimately become fluvial deposits (e.g., crevasse splays, channel and floodplain sediments). Fluctuations in wetland water levels and area, preserved as lacustrine and marsh deposits, are influenced primarily by annual variations in rainfall that are controlled by the yearly northernmost extent of the ITCZ. Long-term erosion in the Cauca River catchment is controlled largely by active tectonism in the northern Central Cordillera. Avulsion events on the Cauca River in 2010 and 2011 occurred as a consequence of levee failure during a period of high runoff associated with the negative phase of the El Niño Southern Oscillation (ENSO) along with higher cross-floodplain than down-valley slopes in the basin.

Avanço antrópico na bacia hidrográfica do Rio Barigui entre 1999 e 2019 e seu impacto sobre o escoamento superficial avaliado pela alteração da sua curva-número (CN)

The monitoring of anthropic expansion in river basins from the assessment of land cover is very useful for water resources management, as in the case of the CN-SCS rainfall-runoff model, which uses the concept of curve number (CN) to estimate which the rainfall potential to become runoff based on the watershed’s soil and land cover. This research evaluated the evolution of land cover in the Barigui River basin between 1999 and 2019 and its impact on hydrological characteristics based on the variation of their CN. Therefore, Landsat images were classified for the study years and the hydrological types of soil in the basin were defined. The results indicated that there was a significant anthropic advance in the region, with an increase in urbanization (~21 km2) and a reduction in forested areas (~22 km2). However, this advance did not affect significantly the total CN value of the basin, due to the predominant, more impermeable type of soil, and how the changes in land cover occurred, with flooding of wetlands and the consequent increase in permeability in some regions.

Taxonomy, palaeoecology and stratigraphy of the middle Miocene mollusk fauna from the Gračanica coal pit near Bugojno in Bosnia and Herzegovina

During the early and middle Miocene, the Dinarides Lake System (DLS) was a major hotspot of freshwater mollusk diversity in southeastern Europe. The numerous intramontane lake basins, originating by combined effects of tectonic subsidence and humid climate, accumulated thick lacustrine successions. Diagenetic overprint and leaching of these carbonate-rich deposits have facilitated insights to faunal contents for only a few basins up to the present. We contribute to filling this gap by documenting for the first time a mollusk fauna from the Bugojno Basin in Bosnia and Herzegovina. The fauna originates from a coal-bearing succession representing a gradual flooding of the coastal wetlands followed upwards by the establishment of perennial lacustrine settings in the basin. Our taxonomic analyses documents 17 gastropod and two bivalve species. New to science are IIllyricocongeria forcakovici nov. sp., Prososthenia krijgsmani nov. sp. and Bania goehlichae nov. sp. The palaeoecological analysis based on quantified samples shows distinct shifts in mollusk composition and abundance. The terrestrial taxa are restricted to the coal-bearing interval of the section; melanopsids, neritids and hydrobiids are abundant in deltaic and littoral settings, whereas bivalves are frequent in littoral and sublittoral environments. In line with previous results, which have evidenced a high degree of intralacustrine radiation in the DLS, the Lake Bugojno fauna shows a low to moderate level of similarity to other DLS faunas. The dissimilarity may partly also result from its younger age as suggested by the presence or absence of regional biostratigraphic marker species.

The use of fatty acids to identify food sources of secondary consumers in wetland mesocosms

Increasing demand for freshwater during the last century has so severely degraded many wetland ecosystems that they are some of the most seriously impacted environments in the world. Environmental flows are used as a management tool to restore parts of the hydrological regime altered by human water use, to rehabilitate these wetlands. Research and monitoring to date has focused on understanding ‘flow-ecology’ relationships, without investigating the mechanisms underlying them. We sought to understand how different basal food sources are incorporated into fish tissue in temporary wetland systems. This study provides a necessary first step toward the development of mechanistic research that investigates the effects of variation in fatty acids (FA) within the food and prey base on top predators. We added different sources of fatty acids to wetland mesocosms by adding extra food sources including redgum leachate to increase planktonic bacteria populations, cyanobacteria, green algae and biofilm matrix to observe how they were incorporated into secondary consumers. Wetland soil and water was added to replicate mesocosms, left for 28 days to produce zooplankton and then Western carp gudgeons added. There was a clear shift in the invertebrate assemblage structure following the introduction of the gudgeons. There was also a clear difference in assemblage structure and nutritional value between benthic and planktonic invertebrates. However, the addition of extra food sources did not generate differing FA profiles between treatments in the substratum fractions, invertebrates or fish after 14 days. We suggest that food sources generated within the mesocosms themselves may have outweighed any treatment effects. Using flooded wetland mesocosms potentially would have provided more realistic knowledge of the food web mechanisms of wetland inundation rather than feeding zooplankton fed specific primary food sources to fish. However, future experiments attempting to identify the mechanisms of the transfer of basal food sources in wetlands to secondary consumers may wish to directly feed fish primary consumers raised on specific basal food sources.

DNA metabarcoding reveals metacommunity dynamics in a threatened boreal wetland wilderness

The complexity and natural variability of ecosystems present a challenge for reliable detection of change due to anthropogenic influences. This issue is exacerbated by necessary trade-offs that reduce the quality and resolution of survey data for assessments at large scales. The Peace-Athabasca Delta (PAD) is a large inland wetland complex in northern Alberta, Canada. Despite its geographic isolation, the PAD is threatened by encroachment of oil sands mining in the Athabasca watershed and hydroelectric dams in the Peace watershed. Methods capable of reliably detecting changes in ecosystem health are needed to evaluate and manage risks. Between 2011 and 2016, aquatic macroinvertebrates were sampled across a gradient of wetland flood frequency, applying both microscope-based morphological identification and DNA metabarcoding. By using multispecies occupancy models, we demonstrate that DNA metabarcoding detected a much broader range of taxa and more taxa per sample compared to traditional morphological identification and was essential to identifying significant responses to flood and thermal regimes. We show that family-level occupancy masks high variation among genera and quantify the bias of barcoding primers on the probability of detection in a natural community. Interestingly, patterns of community assembly were nearly random, suggesting a strong role of stochasticity in the dynamics of the metacommunity. This variability seriously compromises effective monitoring at local scales but also reflects resilience to hydrological and thermal variability. Nevertheless, simulations showed the greater efficiency of metabarcoding, particularly at a finer taxonomic resolution, provided the statistical power needed to detect change at the landscape scale.

Differences of soil enzyme activities and its influencing factors under different flooding conditions in Ili Valley, Xinjiang.

BackgroundA wetland is a special ecosystem formed by the interaction of land and water. The moisture content variation will greatly affect the function and structure of the wetland internal system.MethodIn this paper, three kinds of wetlands with different flooding levels (Phragmites australis wetland (long-term flooding), Calamagrostis epigeios wetland(seasonal flooding) and Ditch millet wetland (rarely flooded)) in Ili Valley of Xinjiang China were selected as research areas. The changes of microbial biomass carbon, soil physical and chemical properties in wetlands were compared, and redundancy analysis was used to analyze the correlation between soil physical and chemical properties, microbial biomass carbon and enzyme activities (soil sucrase, catalase, amylase and urease). The differences of soil enzyme activities and its influencing factors under different flooding conditions in Ili Valley were studied and discussed.ResultThe results of this study were the following: (1) The activities of sucrase and amylase in rarely flooded wetlands and seasonally flooded wetlands were significantly higher than those in long-term flooded wetlands; the difference of catalase activity in seasonal flooded wetland was significant and the highest. (2) Redundancy analysis showed that soil organic carbon, dissolved organic carbon, total phosphorus and soil microbial biomass carbon had significant effects on soil enzyme activity (p < 0.05). (3) The correlation between soil organic carbon and the sucrase activity, total phosphorus and the catalase activity was the strongest; while soil organic carbon has a significant positive correlation with invertase, urease and amylase activity, with a slight influence on catalase activity. The results of this study showed that the content of organic carbon, total phosphorus and other soil fertility factors in the soil would be increased and the enzyme activity would be enhanced if the flooding degree was changed properly.

Hydrological connectivity: One of the driving factors of plant communities in the Yellow River Delta

Abstract Coastal wetlands play an important role in regional and even continental sustainable development because of their valuable ecosystem services. The coupling mechanism among hydrology, edaphic factors, and vegetation is the key to coastal wetland management. The current study conducted in the Yellow River Delta used an improved-comprehensive hydrological connectivity structure index, Topographic Over Field Capacity Index (TOFCI), based on both soil water conditions (SWC) and topography to highlight the role of hydrological connectivity on intertidal flat (IF), tidal marsh (TM), semi-artificial pond (AP) and riverside intermittent flooded (RS) wetland classes among other environmental variables. The results showed plant community distributions and structures among wetland classes differed from each other significantly, and hydrological connectivity structure is one of the driving factors. The results provided three pieces of evidence for this inference: 1) according to PCA results, the contribution of TOFCI is the highest among all environmental variables; 2) TOFCI values show significant difference among different plant communities; 3) TOFCI is also significantly correlated to species composition and distribution according to the CCA and RDA results. TOFCI values are positively linearly correlated to the plant coverage and biomass in intertidal flat wetlands according to linear regression analysis. Furthermore, salinity, soil total nitrogen and soil total phosphorus also influence plant community distribution and species composition. Finally, simple parameters for soil water conditions or topographic characteristics do not show significant explanatory power to hydrology-vegetation interaction. The results of the current study provide a new perspective for coastal wetland conservation and restoration.

Patterns of invertebrate emergence and succession in flooded wetland mesocosms

Floodplain wetlands are some of the most productive ecosystems available to aquatic and terrestrial organisms. However, regulation of lowland rivers can disrupt ecological processes occurring in the river–floodplain ecosystems, and environmental water can be delivered to affected wetlands to maintain productivity. It is not well understood at what stage following inundation there would be sufficient invertebrate biomass and large-sized individuals to support production and reproduction of secondary consumers. In this study we follow changes in the abundances of invertebrates after wetting in three mesocosm trials using soil from two wetlands from the north of the Murray–Darling Basin over 6-week periods. Peak abundances generally occurred in either the fifth or sixth weeks, but abundances were high after 2–3 weeks. Our results suggest that inundation of wetlands using environmental watering can achieve high productivity within a short time frame, within weeks. However, how quickly the high productivity is passed on to second-order consumers remains unclear and should be an area of future research.

The basal food sources for Murray cod (Maccullochella peelii) in wetland mesocosms

The use of freshwater for human consumption and agriculture has resulted in many wetland ecosystems being some of the most seriously impacted ecosystems in the world. In attempts to rehabilitate wetland ecosystems environmental flows are used to restore parts of the hydrological regime altered by human water use. The use of environmental water intends to improve ecosystem health, but frequently aims to have specific outcomes for populations of higher-order consumers such as iconic fish and bird species. To date, research and monitoring has mainly focused on understanding ‘flow-ecology’ relationships, without investigating the mechanisms underlying them. We sought to understand the importance of different basal food sources to the growth of the endangered Murray cod in temporary wetland systems using fatty acid biomarkers. We flooded replicate mesocosms with two different wetland soils to produce sufficient zooplankton prey to sustain and grow Murray cod larvae for approximately 2 weeks. The fatty acid profiles of Murray cod and percentages of different biomarkers were compared at the start and finish of the experiment and our results suggest that the most important basal food source is green algae. However, the biomarkers of diatoms, cyanobacteria and bacteria also increased and differed between wetlands with different hydrological regimes. It is unclear if our results can be extended to other wetland systems and we encourage further research both into the relationship between length of wetland flooding and invertebrate densities in other systems. We also encourage research into the mechanistic pathways in which green algae carbon is transferred through food webs to higher order consumers in wetland systems to help generalise our results to other wetlands and support the management of wetlands through the timing and duration of flooding from environmental water.

Breeding, dispersal, migration and conservation of the Black-winged Stilt (Himantopus himantopus) in Hungary

Abstract The Black-winged Stilt was the bird of the year in Hungary in 2019. The population of the species increased from 20–25 breeding pairs to 550–680 pairs from 1980s to the present. 75–85% of the Hungarian population bred on effluent pools for pigs and settling pools at sugar beet factories in the first half of 1990s. There were significantly more breeding pairs in Hungary in 1999 compared to previous years, and finally 871 breeding pairs of Black-winged Stilts were documented in 2000 and the Hungarian population was estimated at 940–960 pairs. There were 550–680 breeding pairs in Hungary between 2015 and 2017. Significantly more clutches had more than five eggs in the sampled colonies during the influx in 2000 than in the egg collections before 1971 or in the sampled colony in 2008 as well. First arrivals reached Hungary between 5 and 20 March (median: 15 March) between 2005 and 2019. These arrival dates fall approximately a month earlier than the former arrival dates in mid-April during the 1980s. 470 Black-winged Stilts were observed in a single flock during post-breeding dispersal, this flock was the largest ever documented in Hungary. Stilts left Hungary by the first half of September in the 1980s, and in contrast, they left Hungary between 27 August and 4 January (median: 19 October) between 2005 and 2019. Recently, the most departure dates fall one and a half to three months later compared to the departure dates in the 1980s. Black-winged Stilts marked in Hungary disperse in the Carpathian Basin during their post-fledging/post-breeding dispersal. Based on ring readings of two individuals, they start to migrate southwest with stopover sites in Italy, but their wintering areas are unknown. Stilts hatched in Portugal (one individual) and France (two individuals) bred in Hungary during the large influxes in 1999 and 2000. Five Black-winged Stilts hatched in Italy were observed later in Hungary and are supposed to be breeders in Hungary in most cases. Furthermore, one individual captured as an adult in Spain and two trapped in Italy were observed in Hungary. The Hungarian population of Black-winged Stilt is threatened by predation on eggs and chicks, drainage of wetlands, and also by human-induced flooding of artificial wetlands (e.g. fishponds). Stilts regularly occupy artificial breeding islands the first years after habitat restoration. The Hungarian population of Black-winged Stilts is increasing due to habitat management with grazing animals, especially with Mangalica ‘Woolly’ Pigs and Water Buffalos.

Land-use change increases climatic vulnerability of migratory birds: Insights from integrated population modelling.

Knowledge of land-use patterns that could affect animal population resiliency or vulnerability to environmental threats such as climate change is essential, yet the interactive effects of land use and climate on demography across space and time can be difficult to study. This is particularly true for migratory species, which rely on different landscapes throughout the year. Unlike most North American migratory waterfowl, populations of northern pintails (Anas acuta; hereafter pintails) have not recovered since the 1980s despite extended periods of abundant flooded wetlands (i.e. ponds). The mechanisms and drivers involved in this discrepancy remain poorly understood. While pintails are similar to other ducks in their dependence on ponds throughout their annual cycle, their extensive use of croplands for nesting differentiates them and makes them particularly vulnerable to changes in agricultural land use on prairie breeding grounds. Our intent was to quantify how changes in land use and ponds on breeding grounds have influenced pintail population dynamics by developing an integrated population model to analyse over five decades (1961-2014) of band-recovery, breeding population survey, land-use and pond count data. We focused especially on the interactive effects of pond counts and land use on pintail productivity, while accounting for density-dependent processes. Pintail populations responded more strongly to annual variation in productivity than survival. Productivity was positively correlated with pond count and negatively correlated with agricultural intensification. Further, a positive interaction between pond count and agricultural intensification was insufficient to overcome the strong negative effect of agricultural intensification on pintail productivity across nearly all pond counts. The interaction also indicated that pintail populations were more negatively impacted by the decrease in ponds associated with climate change under higher agricultural intensification. Our results indicate that pintail populations have become more vulnerable to climate change under intensified land use, which suggests that future conservation strategies must adapt to these altered relationships. The interactive effects of land use and climate on demography should be considered more frequently in animal ecology, and integrated population models provide an adaptable framework to understand vital rates and their drivers simultaneously.

Synchronizing conservation to seasonal wetland hydrology and waterbird migration in semi‐arid landscapes

AbstractIn semi‐arid ecosystems, timing and availability of water is a key uncertainty associated with conservation planning for wetland‐dependent wildlife. Wetlands compose only 1–3% of these landscapes; however, large populations of migratory waterbirds rely on these wetlands to support energetically demanding life history events such as breeding and migration. Migration is considered a crucial period for birds associated with individual survival and reproductive success, yet our understanding of migration ecology remains limited. To better inform conservation planning supportive of these demands, we quantified synchrony of wetland flooding and waterbird migration by reconstructing bi‐monthly surface water patterns from 1984 to 2015 across 11.4 million ha of the semi‐arid Great Basin, USA. Results were then linked to seasonal migration chronologies for seven dabbling ducks species. Seasonal patterns were used in landscape planning simulations to assess efficiency in conservation strategies that aligned temporally sensitive wetland flooding and species migration. Wetland data were combined with land tenure to evaluate periodicity in waterfowl reliance on public and private lands. We found migration chronologies misaligned with wetland flooding. In spring, half (43–59%) to three‐quarters (68–74%) of seasonal wetlands were flooded and available to early‐ and late‐migrating species while seasonal drying restricted wetland flooding to 13–20% of sites during fall migration. Simulations showed wetland conservation inconsiderate of temporal availability was only 67–75% efficient in meeting waterfowl habitat goals on private lands that made up ~70% of flooded wetland area in spring. Private–public wetland flooding was equivalent during fall migration. Accounting for spatiotemporal patterns of wetland flooding is imperative to improving efficiencies linked to migratory bird conservation. Timing of public–private wetland flooding, demonstrated by our models, provides landscape context that emphasized a joint role in supporting migratory waterbird habitat. Integrated management scenarios may capitalize on public lands’ flexibility to expand fall flooding to offset seasonal drying on private lands while targeted incentive‐based conservation assures private wetland flooding in spring. Such scenarios illustrate benefits of holistic public–private wetlands management representing a forward‐looking alternative that aligns conservation with forecasts of increasing water scarcity.