Natural Wetlands Research Articles

Application of artificial wetland technology in Miyun Reservoir water management

In recent years, with the increasing attention to environmental pollution, water quality management has become an important part of protecting water resources and maintaining ecological balance. And as an important means of water pollution remediation, artificial wetlands have gradually received widespread attention. Miyun Reservoir, as an important drinking water source in Beijing, is particularly important for water quality management. As an ecological restoration technology, artificial wetland has significant water quality improvement effect by simulating and improving the function of natural wetland. Therefore, artificial wetland has important scientific research and practical significance in the water management of Miyun Reservoir. In this paper, we will discuss the application of artificial wetland in water management of Miyun Reservoir, and summarise the results and conclusions of the study, highlight the impact and significance of the study, and look forward to the future research direction. By exploring the application of artificial wetlands in reservoir water management, it is expected to provide scientific basis and technical support for water resource management departments and decision makers, and contribute to the improvement of water quality and ecological restoration of Miyun Reservoir.

A global meta-analysis on the drivers of salt marsh planting success and implications for ecosystem services

Planting has been widely adopted to battle the loss of salt marshes and to establish living shorelines. However, the drivers of success in salt marsh planting and their ecological effects are poorly understood at the global scale. Here, we assemble a global database, encompassing 22,074 observations reported in 210 studies, to examine the drivers and impacts of salt marsh planting. We show that, on average, 53% of plantings survived globally, and plant survival and growth can be enhanced by careful design of sites, species selection, and novel planted technologies. Planting enhances shoreline protection, primary productivity, soil carbon storage, biodiversity conservation and fishery production (effect sizes = 0.61, 1.55, 0.21, 0.10 and 1.01, respectively), compared with degraded wetlands. However, the ecosystem services of planted marshes, except for shoreline protection, have not yet fully recovered compared with natural wetlands (effect size = −0.25, 95% CI −0.29, −0.22). Fortunately, the levels of most ecological functions related to climate change mitigation and biodiversity increase with plantation age when compared with natural wetlands, and achieve equivalence to natural wetlands after 5–25 years. Overall, our results suggest that salt marsh planting could be used as a strategy to enhance shoreline protection, biodiversity conservation and carbon sequestration.

Simulation of wetland carbon storage in coastal cities under the coupled framework of socio-economic and ecological sustainability: A case study of Dongying city

Wetlands are an important part of the global carbon cycle, and wetland protection is an important way to achieve carbon neutrality and synergistic benefits between humans and ecosystems in China. However, most of the previous studies lack the influencing factors and driving paths of wetland carbon storage (WCS) from the perspective of coupled systems. Based on the SD-PLUS-InVEST coupling model and the socio-economic and ecological sustainability (SEES) coupling framework, this paper reveals the driving-feedback mechanism of wetland areas (WAs) from 2005 to 2060, and realizes the dynamic monitoring of WAs and a detailed assessment of WCS in Dongying city. The results show the following: WAs have a positive feedback relationship with the water resources and ecosystem service (ES) subsystems but a negative feedback relationship with the population and economic subsystems. The business as usual (BAU) scenario led to a malignant transformation of natural wetlands (NWs)-artificial wetlands (AWs)-production land (PL), increasing WCS by expanding AWs. The coordinated sustainable development (CSD) scenario created a virtuous PL-AW-NW transformation, increasing 421,700 tons of WCS compared with BAU. This study holds great significance for the protection, restoration, and sustainable development of wetland resources in coastal cities.

Flexible migration and habitat use strategies of an endangered waterbird during hydrological drought

AbstractWildlife species confront threats from climate and land use change, exacerbating the influence of extreme climatic events on populations and biodiversity. Migratory waterbirds are especially vulnerable to hydrological drought via reduced availability of surface water habitats. We assessed how whooping cranes (Grus americana) modified habitat use and migration strategies during drought to evaluate their resilience to changing conditions and adaptive capacity. We categorized >8000 night‐roost sites used by 146 cranes from 2010 to 2022 and examined relative use during non‐drought, moderate drought, and extreme drought conditions. We found cultivated and uncultivated palustrine and lacustrine wetlands were generally used less during droughts than non‐drought conditions. Conversely, impounded palustrine and lacustrine systems and rivers served more frequently as drought refugia (i.e., used more during drought than non‐drought conditions). Night roosts occurred primarily on private lands (86% overall); public land use decreased with latitude and increased with drought severity, with greatest use (56%) occurring during severe autumn drought in the southern Great Plains. Quantifying use of identified critical habitats in the United States indicated that Cheyenne Bottoms State Waterfowl Management Area and Quivira National Wildlife Refuge were used less during drought, and the Central Platte River and Salt Plains National Wildlife Refuge received similar use during drought compared to non‐drought conditions. Our findings provide insights into compensatory use of habitats, where impounded surface water may function in a complementary fashion with natural wetlands. Collectively, these and other types of wetlands distributed across the migration corridor provided a reliable network of habitat available across the Great Plains. A diversity of wetlands available during variable environmental conditions would be useful in supporting continued recovery of whooping cranes and likely have benefits for a wide array of migratory birds.

Ecological characteristics and seasonal changes of macrozoobenthos in the waters of Miaodao Archipelago, China

To understand the macrozoobenthic community composition and spatial-temporal distribution characteristics of macrobenthos in the waters of Miaodao Archipelago, Yantai, Shandong and its response to habitat changes, we conducted surveys of macrobenthos and environmental elements in the waters of Miaodao Islands in May (spring), August (summer), and October (autumn) in 2022. Results showed that a total of 127 macrozoobenthic species were recorded, with Mollusca and Annelida (Polychaeta) as the dominant taxa, consisting of 47 and 45 species, respectively. The key dominant species included Sternaspis chinensis, Glycinde bonhourei, Moerella hilaris, and Amphioplus (Lymanella) japonicus. The average annual density and biomass of macrozoobenthos were 190 ind·m-2 and 28.69 g·m-2, respectively. There was no significant seasonal differences in density and biomass. The Shannon diversity index (H), evenness index (J), and richness index (D) averaged 3.10, 0.90, and 2.40, respectively. Cluster analysis results showed low similarity coefficients of community among the three seasons, suggesting a distinct distribution pattern. Factors such as bottom seawater temperature, chlorophyll a, nutrient, sediment grain size, and organic matter content could significantly influence the structure and diversity of macrozoobenthic community. Compared with historical research data, the Changdao National Wetland Nature Reserve and the implementation of enclosure aquaculture have led to notable changes in the dominant species of macrobenthos. Specifically, there was a noticeable decline in both density and H, and an increase in biomass and J. Additionally, body size of benthic fauna was transitioning from small to big.

Identification and scoring of conservation gaps in wetlands of China's coastal provinces: Implications for extending protected areas

Wetlands in China's coastal provinces are strategically positioned along migratory flyways for waterbirds, serving as essential habitats and stopover sites due to the expansive land area and abundant wetland resources they offer. This study aimed to introduce a simplified index system to enable rapid assessment and prioritization of unprotected areas for wetlands in China's coastal provinces. A spatial analysis was conducted, combining wetland distribution and existing protected areas data and spatial extent of wetlands extracted by remote sensing data. Results indicate substantial gaps in coverage, covering an area of 108.33 × 104 ha, with 76% being natural wetlands. Over half of these gaps are identified as high-value wetlands with significant ecological functions. The uneven distribution of unprotected wetlands reflects a tension between economic development and wetland conservation. Our findings support the expansion of the existing coastal wetland protected areas' coverage, as well as protecting critical habitats in conservation gaps, and establishing of a network-based waterbird protection system. This research contributes to informed decision-making and policy in wetlands' conservation planning.

Deteriorating habitat suitability and connectivity of waterbirds in the Bohai Sea Rim: Consequences of land use transformation

Wetlands in the Bohai Sea Rim play an indispensable role in maintaining the stability of waterbird populations on the East Asian-Australian flyway. However, motivated by economic development and urban expansion, coastal wetlands in this region have been extensively reclaimed, leading to a decline in the area and degradation of natural wetlands over the past two decades. We analyzed the temporal and spatial changes of suitable habitats of different groups of waterbirds and quantified habitat connectivity changes and the importance of different patches by using the Probability of Connectivity. The results show that the suitable habitat area of all the different groups of waterbirds decreased sharply from 2000 to 2020. In addition, the utilization ratio by waterbirds of artificial habitats increased. Land use is the primary environmental variable determining the distribution of suitable habitats. Meanwhile, the connectivity of habitats of different groups of waterbirds has also been declining. However, the patches of Tianjin and Hebei in Bohai Bay still have high importance for waterbirds, particularly shorebirds. Expanding existing protection areas to cover the above-mentioned patches is recommended. We also advocate stricter protection measures and necessary ecological restoration activities on both the natural and artificial wetlands.

Metal and nutrient uptake by natural wetland plants in a tropical man-made wetland of Sri Lanka

Phytoremediation of contaminated soil is an environmentally-friendly approach to minimize the impacts of nutrients and heavy metals on an ecosystem. Hence, selecting appropriate plants with phytoextraction potential is paramount to remediatie contaminated soils. This study aimed to investigate the nutrient and metal contents of four natural aquatic plants, including Cyperus rotundus, Eleocharis dulcis, Typha angustifolia, and Schoenoplectus grossus. They were grown in the meadow of a small reservoir in Sri Lanka to assess their phytoextraction ability using plant and soil samples collected at 32 sampling points in the meadow. Their biological concentration (roots/soil), accumulation (shoots/soil), and translocation (shoots/roots) factors were determined to assess element mobility and phytoextraction ability. Total K, Na, Mg, Ca, Zn, Cu, Fe, Mn, As, Pb, and Cd contents of plants and soil samples were measured using an Inductivity Couple Plasma Optical Emission Spectrophotometer. ANCOVA was used as a statistical test to assess the best plant type in terms of nutrient and metal absorption. Plant shoots exhibited significantly greater values for P, Na, Mg, Zn, Cd, and Fe than their roots. Their biological concentration, accumulation and translocation factors were not different among the four plant species. However, these values were >1 for all the species, indicating their potential to be used as hyperaccumulators. T. angustifolia, with its high potential for nutrient and metal accumulation and the highest aesthetic appeal, was selected as the best overall wetland species for phytoremediation purposes.

Changes in wetland landscape and inundation patterns in the middle and lower reaches of the Yangtze River Basin from 1990 to 2020

Wetlands are crucial to diverse societies and ecosystems but are threatened globally. Natural wetlands in the middle and lower reaches of the Yangtze River Basin (MLRYRB) have long been exploited to meet the increasing food and energy demands, especially in recent decades. However, how their landscapes and hydrological patterns changed over time was poorly qualified, which was crucial to conserving biodiversity and ecosystems. In this study, we proposed a new wetland classification procedure taking advantage of the shape, topography, landscape patterns, and phenology to map the distribution of six wetland types in the MLRYRB in 1990 and 2020 with Landsat images. The transitions among different wetland types and associated driving factors were examined. Artificial wetlands expanded by 3907.6 km2 while natural wetlands decreased by 423.2 km2, resulting in a net area increase of 3484.4 km2. Farmland reclamations, aquacultural activities, urban expansion, and dam constructions induced 70 % of the area's loss of natural wetlands. Meanwhile, spatiotemporal patterns in wetland inundation dynamics were determined with agglomerative hierarchical cluster analysis. Widespread transitions from perennial water to seasonal wetlands were detected. Notably, 47.8 % of the natural wetlands experienced significant drying trends, and as a result, the mean yearly inundated periods for natural wetlands decreased from 303 days in 1990 to 272 days in 2020. Given the substantial structural alterations, wetland destruction was more severe than the area reflected. Our results suggested that category-based changes in wetland areas, inundation patterns, associated driving forces, and underlying ecological consequences should be comprehensively assessed to conduct scientific conservation and prevent “paper offsets.”

Carbon fluxes of China's coastal wetlands and impacts of reclamation and restoration.

Coastal wetlands play an important role in regulating atmospheric carbon dioxide (CO2) concentrations and contribute significantly to climate change mitigation. However, climate change, reclamation, and restoration have been causing substantial changes in coastal wetland areas and carbon exchange in China during recent decades. Here we compiled a carbon flux database consisting of 15 coastal wetland sites to assess the magnitude, patterns, and drivers of carbon fluxes and to compare fluxes among contrasting natural, disturbed, and restored wetlands. The natural coastal wetlands have the average net ecosystem exchange of CO2 (NEE) of -577 g C m-2 year-1, with -821 g C m-2 year-1 for mangrove forests and -430 g C m-2 year-1 for salt marshes. There are pronounced latitudinal patterns for carbon dioxide exchange of natural coastal wetlands: NEE increased whereas gross primary production (GPP) and respiration of ecosystem decreased with increasing latitude. Distinct environmental factors drive annual variations of GPP between mangroves and salt marshes; temperature was the dominant controlling factor in salt marshes, while temperature, precipitation, and solar radiation were co-dominant in mangroves. Meanwhile, both anthropogenic reclamation and restoration had substantial effects on coastal wetland carbon fluxes, and the effect of the anthropogenic perturbation in mangroves was more extensive than that in salt marshes. Furthermore, from 1980 to 2020, anthropogenic reclamation of China's coastal wetlands caused a carbon loss of ~3720 Gg C, while the mangrove restoration project during the period of 2021-2025 may switch restored coastal wetlands from a carbon source to carbon sink with a net carbon gain of 73 Gg C. The comparison of carbon fluxes among these coastal wetlands can improve our understanding of how anthropogenic perturbation can affect the potentials of coastal blue carbon in China, which has implications for informing conservation and restoration strategies and efforts of coastal wetlands.

Response of plants and soils to inundation duration and construction of the plant‒soil association mode in the hydro‒fluctuation belt of the reservoir wetland

Hydro-Fluctuation Belt (HFB), a periodically exposed bank area formed by changes in water level fluctuations, is critical for damaging the reservoir wetland landscape and ecological balance. Thus, it is important to explore the mechanism of hydrological conditions on the plant-soil system of the HFB for protection of the reservoir wetland and landscape restoration. Here, we investigated the response of plant community characteristics and soil environment of the HFB of Tonghui River National Wetland Park (China), is a typical reservoir wetland, to the duration of inundation, as well as the correlation between the distribution of dominant plants and soil pH, nutrient contents, and enzyme activity by linear regression and canonical correlation analyses. The results show that as the duration of inundation decreases, the vegetation within the HFB is successional from annual or biennial herbs to perennial herbs and shrubs, with dominant plant species prominent and uneven distribution of species. Soil nutrient contents and enzyme activities of HFB decreased with increasing inundation duration. Dominant species of HFB plant community are related to soil environment, with water content, pH, urease, and available potassium being principle soil environmental factors affecting their distribution. When HFB was inundated for 0–30 days, soil pH was strongly acidic, with available potassium content above 150 mg kg−1 and higher urease activity, distributed with Arundo donax L., Polygonum perfoliatum L., Alternanthera philoxeroides (Mart.) Griseb., and Daucus carota L. communities. When inundated for 30–80 days, soil pH was acidic, with lower available potassium content (50–150 mg kg−1) and urease activity, distributed with Beckmannia syzigachne (Steud.) Fern.+ Polygonum lapathifolium L., Polygonum lapathifolium L., Medicago lupulina L. + Dysphania ambrosioides L. and Leptochloa panicea (Retz.) Ohwi communities. Using the constructed HFB plant-soil correlation model, changes in the wetland soil environment can be quickly judged by the succession of plant dominant species, which provides a simpler method for the monitoring of the soil environment in the reservoir wetland, and is of great significance for the scientific management and reasonable protection of the reservoir-type wetland ecosystem.

Effects of land-use on soil C, N, and P stocks and stoichiometry in coastal wetlands dependent on soil depth and latitude

Coastal land-use is increasingly affected by Spartina alterniflora invasion, coastal reclamation, and climate change, which have been suggested to exert vital controls on soil carbon (C), nitrogen (N), and phosphorus (P) cycles, however, the effects on the geographical distributions of these element stocks and stoichiometry remain unclear. We analyzed the depth (0–100 cm) and latitudinal (19–41°N) patterns of soil C, N, and P contents, stocks, and ratios in 120 Chinese coastal wetlands differing in land-use (reclaimed wetlands, natural wetlands, invasive wetlands, and bare mudflats) and climate (tropics, subtropics, and temperate). We observed stable depth patterns of soil contents, stocks, and ratios, owing to the stable depth patterns of soil conditions in each land-use. Top soils (0–30 cm) generally had higher C, N, and P contents and N:P ratio but lower C:N and C:P ratios than deep soils (30–100 cm). We found that soil C content and P stock remained constant, soil C stock, N and P contents and N:P ratio increased significantly, but soil N stock and C:N and C:P ratios decreased significantly with decreasing latitude; however, such correlations tended to be weaker in reclaimed wetlands and invasive wetlands. Land-use changes also significantly altered the magnitude of soil element stoichiometry. The effects of S. alterniflora invasion on soil C, N, and P storages can be shifted from negative in tropics to positive in temperate regions, whereas the negative effects of coastal reclamation in tropics disappeared in temperate regions. Overall, compared with natural wetlands, S. alterniflora invasion slightly decreased, whereas coastal reclamation largely decreased soil C, N, and P contents and stocks. Compared with bare mudflats, S. alterniflora invasion significantly increased C and N contents and N:P ratio but decreased C:N ratio, whereas coastal reclamation significantly decreased P content and stock and C:N ratio but increased N:P ratio, especially in top soils. Our findings will be helpful for understanding and assessing soil C sequestration and nutrient cycling in globally disturbed coastal wetlands.

Response of the Stability of Soil Aggregates and Erodibility to Land Use Patterns in Wetland Ecosystems of Karst Plateau

The world’s natural wetlands, which have important ecological functions, are being lost at an alarming rate. The erosion and deposition of soil on wetlands is a major cause of wetland conversion to agriculture. An urgent problem to be solved is how to slow down the erosion and deposition of wetlands resulting from land use. Land use patterns affect soil properties, thereby affecting soil aggregate stability and erodibility. Evaluating the effects of land use patterns on soil aggregate stability and erodibility in small watersheds of wetland ecosystems of karst plateau is of great importance. Thus, we compared the soil properties, aggregate stability indicators and soil erodibility of shrubland, grassland, artificial forest land and sloping farmland for evaluating the impact of various land use patterns on soil aggregate stability and erodibility in typical karst plateau wetland ecosystems. Our results showed that the mass fraction of soil aggregates > 0.25 mm was the main component in the four land uses, with greater variation in aggregates > 5 mm; overall, MWD, GMD and WSA0.25 were higher in grassland and shrubland than in sloping farmland and artificial forest land, while K values, PAD and SCAI showed the opposite trend. Correlation analysis showed that effective soil nutrients had a positive effect on soil aggregate stability. In conclusion, the stability of soil aggregates and resistance to soil erosion were strongest under the influence of shrubland. Our study showed that shrubland can better improve soil aggregate stability and erosion resistance, which may provide a guide for protecting and restoring karst plateau wetland ecosystems.

Wetland conservation legislations: global processes and China’s practices

Abstract Natural wetland areas in China have experienced a continuous decline over the past two decades, which is partly due to the lack of comprehensive wetland protection laws and regulations. Despite investing over 4.24 billion USD in wetland conservation and restoration since 2000, the deterioration of wetlands persists. This study reviews the development of global wetland protection laws and regulations, analyzes the progress of wetland legislation in China and explores the impact of economic development levels on wetland protection legislation, while also providing an in-depth interpretation of the core elements of the ‘Wetland Protection Law of the People’s Republic of China’. The results indicate that since the late 1940s, wetland protection laws and regulations have begun to emerge, with most developed countries gradually implementing related policies between the 1980s and 1990s; about 71% of wetland protection laws are concentrated in 29 countries, while 69 countries still lack specific wetland protection laws. An analysis of 962 global documents reveals that wetland protection legislation mainly focuses on the protection of water resources, species and ecosystems. China’s wetland legislation started late, with the ‘Wetland Protection Law of the People’s Republic of China’ being officially implemented only in June 2022. Furthermore, the study points out that economic development plays a crucial role in wetland legislation worldwide. Lastly, the article summarizes the key features of the ‘Wetland Protection Law of the People’s Republic of China’, including the improvement of the environmental protection legislative system, increased penalties for illegal occupation of wetlands, clearer protection goals and the assurance of the integrity and connectivity of wetland ecosystems through stringent policies.

Comparison of three machine learning algorithms for retrieving soil moisture information from Sentinel-1A SAR data in northwest Shandong plain, China

Soil moisture (SM) plays a critical role in the growth and management of grain in semi-humid regions. However, little is known about how to integrate satellite data with machine learning to accurately retrieve SM information in these areas. This study compares the capability of three machine learning algorithms, Random Forest (RF), Support Vector Machine (SVM), and Artificial Neural Network (ANN), to extract SM information over the Northwest Shandong Plain using multi-phase dual-polarized Sentinel-1A satellite data. The backscattering coefficients were obtained through standard intensity and phase processing to calculate the SAR indices, and several characteristic parameters were extracted as impact factors using the Cloude-Pottier decomposition. The importance of these factors was analyzed, while the performance of each machine learning algorithm was comprehensively evaluated using the K-fold cross-validation method. The best-performing model was utilized to retrieve the spatio-temporal changes in SM in the study area. The findings indicate the following: (1) The first eigenvalue has the greatest impact on retrieval accuracy, followed by entropy, where the intensity component of Shannon's entropy is more important than its polarization component; (2) The addition of more impact factors does not bring a continuous improvement in model performance, but the optimal factor combinations differ for different machine learning retrieval models; (3) The RF model trained using the IM12 combination demonstrates better performance than SVM and ANN in retrieving SM information, with a coefficient of determination (R2) of 0.55 and a root mean square error of 6.12 vol% on the validation set. The level of SM in the Yellow River National Wetland Park is higher than that of the surrounding areas, with substantial seasonal changes. Precipitation, temperature, and vegetation significantly influence the regional variations in SM at the macroscopic level.

Optimising CH4 simulations from the LPJ-GUESS model v4.1 using an adaptive Markov chain Monte Carlo algorithm

Abstract. The processes responsible for methane (CH4) emissions from boreal wetlands are complex; hence, their model representation is complicated by a large number of parameters and parameter uncertainties. The arctic-enabled dynamic global vegetation model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator) is one such model that allows quantification and understanding of the natural wetland CH4 fluxes at various scales, ranging from local to regional and global, but with several uncertainties. The model contains detailed descriptions of the CH4 production, oxidation, and transport controlled by several process parameters. Complexities in the underlying environmental processes, warming-driven alternative paths of meteorological phenomena, and changes in hydrological and vegetation conditions highlight the need for a calibrated and optimised version of LPJ-GUESS. In this study, we formulated the parameter calibration as a Bayesian problem, using knowledge of reasonable parameters values as priors. We then used an adaptive Metropolis–Hastings (MH)-based Markov chain Monte Carlo (MCMC) algorithm to improve predictions of CH4 emission by LPJ-GUESS and to quantify uncertainties. Application of this method on uncertain parameters allows for a greater search of their posterior distribution, leading to a more complete characterisation of the posterior distribution with a reduced risk of the sample impoverishment that can occur when using other optimisation methods. For assimilation, the analysis used flux measurement data gathered during the period from 2005 to 2014 from the Siikaneva wetlands in Southern Finland with an estimation of measurement uncertainties. The data are used to constrain the processes behind the CH4 dynamics, and the posterior covariance structures are used to explain how the parameters and the processes are related. To further support the conclusions, the CH4 flux and the other component fluxes associated with the flux are examined. The results demonstrate the robustness of MCMC methods to quantitatively assess the interrelationship between objective function choices, parameter identifiability, and data support. The experiment using real observations from Siikaneva resulted in a reduction in the root-mean-square error (RMSE), from 0.044 to 0.023 gC m−2 d−1, and a 93.89 % reduction in the cost function value. As a part of this work, knowledge about how CH4 data can constrain the parameters and processes is derived. Although the optimisation is performed based on a single site's flux data from Siikaneva, the algorithm is useful for larger-scale multi-site studies for a more robust calibration of LPJ-GUESS and similar models, and the results can highlight where model improvements are needed.

Response of underwater photosynthesis to light, CO2, temperature, and submergence time of Taxodium distichum, a flood-tolerant tree.

Partial or complete submergence of trees can occur in natural wetlands during times of high waters, but the submergence events have increased in severity and frequency over the past decades. Taxodium distichum is well-known for its waterlogging tolerance, but there are also numerous observations of this species becoming partially or complete submerged for longer periods of time. Consequently, the aims of the present study were to characterize underwater net photosynthesis (PN) and leaf anatomy of T. distichum with time of submergence. We completely submerged 6 months old seedling of T. distichum and diagnosed underwater (PN), hydrophobicity, gas film thickness, Chlorophyll concentration and needles anatomy at discrete time points during a 30-day submergence event. We also constructed response curves of underwater PN to CO2, light and temperature. During the 30-day submergence period, no growth or formation new leaves were observed, and therefore T. distichum shows a quiescence response to submergence. The hydrophobicity of the needles declined during the submergence event resulting in complete loss of gas films. However, the Chlorophyll concentration of the needles also declined significantly, and it was there not possible to identify the main cause of the corresponding significant decline in underwater PN. Nevertheless, even after 30 days of complete submergence, the needles still retained some capacity for underwater photosynthesis under optimal light and CO2 conditions. However, to fully understand the stunning submergence tolerance of T. distichum, we propose that future research concentrate on unravelling the finer details in needle anatomy and biochemistry as these changes occur during submergence.

The recovery of soil eukaryotic alpha and beta diversity after wetland restoration

Soil eukaryotes play an important role in regulating the ecological processes and ecosystem functioning. However, the recovery potential of soil eukaryotic diversity during wetland restoration is largely unknown. We compared the alpha and beta diversity of soil eukaryotes of farmlands and natural and restored wetlands to explore the underlying abiotic and biotic driving forces in the Sanjiang Plain, China. We found that there was no significant difference of the alpha diversity of soil eukaryotes, while the beta diversity of soil eukaryotes differed significantly between the three land use types, with the mean values in the restored wetlands in between those in the natural wetlands and farmlands. The composition of soil eukaryotic communities were less diverse in farmlands compared to restored and natural wetlands. Network property of soil eukaryotes community (positive: negative edges) increased from farmlands to restored wetlands to natural wetlands, indicating enhanced species positive: negative interactions during restoration. The structural equation modeling indicated that species positive: negative interactions and soil nutrients directly affected soil eukaryotic beta diversity. Soil pH and soil water content indirectly affected soil eukaryotic beta diversity by directly affecting species interactions. Our findings suggest that wetland restoration could change soil environment, strengthen microbial cooperation, and increase eukaryotic beta diversity. However, it may take a very long time to reach the original level of soil eukaryotic structure and diversity.

Effects of returning paddy field to wetland on composition and stability of soil aggregates in the Yellow River Delta.

The composition and stability of soil aggregates are important indicators for measuring soil quality, which would be affected by land use changes. Taking wetlands with different returning years (2 and 15 years) in the Yellow River Delta as the research object, paddy fields and natural wetlands as control, we analyzed the changes in soil physicochemical properties and soil aggregate composition. The results showed that soil water content, total organic carbon, dissolved organic carbon and total phosphorus of the returning soil (0-40 cm) showed an overall increasing trend with returning period, while soil pH and bulk density was in adverse. There was no significant change in clay content, electrical conductivity, and total nitrogen content. The contents of macro-aggregates and micro-aggregates showed overall increasing and decreasing trend with returning period, respectively. The stability of aggregates in the topsoil (0-10 cm) increased with returning years. Geometric mean diameter and mean weight diameter increased by 8.9% and 40.4% in the 15th year of returning, respectively, while the mass proportion of >2.5 mm fraction decreased by 10.5%. There was no effect of returning on aggregates in subsoil (10-40 cm). Our results indicated that returning paddy field to wetland in the Yellow River Delta would play a positive role in improving soil structure and aggregate stability.

Farm advisors’ perspectives on barriers and opportunities for wetland creation – the view from Sweden

Farm advisors are important knowledge transfer agents for improving rural sustainability. Most literature focuses on their role in improving farm economies, but they can also promote greater environmental sustainability. Across Europe, most natural wetlands have been drained, impacting multiple ecosystem services (ES) including biodiversity support and nutrient retention, highlighting the need for increased restoration and creation efforts. In Sweden, these efforts depend on voluntary landowner actions. We interviewed farm advisors to learn how they encourage landowners to create and manage wetlands and the institutional barriers they still encounter. Advisors highlighted trust and long-term relationships as key success factors and considering landowner motivations that often prioritize recreational and cultural ES. Advisors noted overly complex bureaucracy, breaks in funding, inadequate long-term support, and lack of holistic perspectives as barriers for wetland creation. These insights about successful advisor/landowner interactions for wetland creation can be applied when implementing other agri-environmental measures.