Wetland Degradation Research Articles

Potential distribution prediction of Deyeuxia angustifolia in the Tumen River Basin and analysis of major impact factors

Deyeuxia angustifolia acts as an indicator of the changes in wetland ecosystems and plays an important ecological role in their functions. Previous studies have shown that the Tumen River Basin is of wide global interest as a transboundary basin area with abundant wetland ecological resources. Despite the implementation of wetland conservation measures in recent years, the distribution area of D. angustifolia in this basin has been reduced due to climate change and anthropogenic activities. Therefore, we used MaxEnt and geographic information system to model a suitable habitat for this species, simulated changes in the habitat, and applied Jackknife to assess the influencing environmental variables. The Jackknife tests showed that slope orientation, solar radiation in September, and total nitrogen were the dominant environmental factors affecting the potential distribution of D. angustifolia. Compared to the current distribution, the total area of land highly and moderately suitable for this species will decrease in the 2050’s and 2070’s, respectively, under two representative concentration paths (RCPs), shifting the centroid of its suitable area and direction of wetland degradation to the northeast. Our study of the projected potential distribution of D. angustifolia in the basin under future climate change could provide important information for its conservation, management, sustainable use, and early warning to prevent its extinction.

Heterogeneity of wetland landscapes and their relationships with anthropogenic disturbances and precipitation in a semiarid region of China.

Wetlands in semiarid regions have important ecological functions and provide services that are partly dependent on the landscape pattern and structure; therefore, it is important to assess the heterogeneity of wetland landscape conditions for wetland conservation and management. Widespread wetland degradation resulting from main factors in semiarid regions highlights the need for exploring the heterogeneity of wetland landscapes and their relationships with anthropogenic disturbances and precipitation. Wetlands in our study referred to natural wetlands, including marshes, rivers, and lakes. We used overall landscape metrics to assess wetland landscape conditions and used grid landscape metrics at a scale of 30km using a moving window method to explore the heterogeneity of wetland landscapes during the period (1986-2019) for western Jilin Province. We performed Spearman correlation analyses of the landscape metrics with the Hemeroby index (HI) and mean annual precipitation (MAP). We suggested that wetland landscape composition metrics (e.g., NP and PD) and configuration metrics (e.g., ED and AI) had positive correlations with HI by 2019 (p < 0.01); in addition, wetland landscape composition metrics (e.g., NP and PD) and configuration metrics (e.g., ED) were negatively correlated with MAP during 1986-2019. In conclusion, wetland landscapes have become increasingly fragmented over the past few decades (1986-2019) in western Jilin Province and the reasons for this result mainly include the household contract responsibility system, along with rural productivity, severe overgrazing and reclamation, and climate change. Wetland landscape composition was positively correlated with human interference and negatively correlated with mean annual precipitation.

Engaging communities towards restoring hillslope seep wetlands in the Tsitsa River catchment of South Africa

Considering the increase of wetland degradation globally, a need exists for an integrated approach that involves communities to collectively protect and sustain wetlands. In the Tsitsa River catchment, South Africa, hillslope seep wetlands are among the vulnerable wetland ecosystems with potential to trigger erosion in the landscape. This study engaged with livestock owners in communities to elicit information regarding their knowledge of hillslope seep wetlands, and their understanding of the importance of these wetlands. Using purposive sampling, researchers interviewed 31 livestock owners and analysed the data using thematic analysis. Results revealed that communities largely perceived hillslope seep wetlands as important ecosystems for their livelihoods. They recognized that the importance stems from services provided by these wetlands. Although the communities viewed hillslope seep wetlands as important ecosystems for livelihoods, however, they also perceived them as highly eroded ecosystems. Community members indicated willingness to strengthen local natural resource governance systems, which could lead to better management or restoration of hillslope seep wetlands. Protective strategies for hillslope seep suggested included fencing, active herding and rotational grazing. This study provides one example from South Africa demonstrating the importance of active involvement of local communities toward successful management of natural resources.

Optimising stocking rates on livestock farms neighbouring wetlands for sustainable productivity and ecological stability

Uganda’s wetlands, especially in south-western Uganda are increasingly being invaded by cattle herders, particularly during droughts. Such uncontrolled grazing is accelerating wetland degradation. The objective of this study was to assess seasonal forage availability on farms neighbouring Ekigaaga wetland in south-western Uganda, and to determine their optimum stocking for sustainable productivity and ecological stability. The grazed area on each side of the virgin wetland was taken as a block, giving two blocks. In each block, three square metre sampling plots were demarcated along a transect line cutting across farms adjacent to the wetland. Some of these plots were fenced and others were left open to grazing by livestock. Two months after setting up the study, vegetation samples were collected from the fenced and unfenced plots in each block once every month, for a period of six months. Livestock classes and numbers grazing on each block were established and standardised into Tropical Livestock Units (TLU); where one TLU is equivalent to a cow weighing 250 kg. During wet and dry seasons, Cynodon dactylon was the most abundant forage species in the unfenced plots in both blocks. Fencing increased the prevalence of Chloris gayana and Themeda triandra in block 2. Sporobolus pyramidalis was the most abundant weed in both blocks. Fenced and unfenced plots in block 1 had higher grazeable forage yields (488.05 and 399.97 kg ha-1, respectively) than block 2 (432.08 and 371.97 kg ha-1, respectively). The TLU that could be safely grazed on blocks 1 and 2 were 121 and 107, respectively compared to the TLU being grazed on blocks 1 (279) and 2 (381). Therefore, to sustain the productivity and ecological stability of these grazing areas, there is need to control weeds/thickets, improve forage resources by oversowing with quality forages, and to adjust livestock numbers to match with forage quantities available for grazing.&#x0D;

Analysis of Spatial–Temporal Variations and Driving Factors of Typical Tail-Reach Wetlands in the Ili-Balkhash Basin, Central Asia

The Ili River Delta (IRD) is the largest delta in the arid zone of Central Asia. Since the 1970s, the entire delta system has undergone a series of changes due to climate change and the impoundment of the Kapchagay Reservoir upstream of the delta, triggering an ecological crisis. Wetlands play a crucial ecological role in biodiversity conservation. Most studies have mainly focused on the response of vegetation and soil microbial to ecological changes in the delta, ignoring the dynamic processes of wetlands changes. Hence, such changes in the IRD and the underlying mechanisms need to be investigated in depth. In this study, wetlands in the IRD from 1975 to 2020 were extracted based on Landsat images using the object-oriented method; changes in the wetland area, wetland landscape pattern, NDVI, and NPP were analyzed; and the contributions of natural and human factors to wetland evolution were quantified. The results indicated the following: (1) From 1975 to 2020, the wetland area of the IRD showed an increasing trend, and changes in the wetland area were mainly found in the middle part of the delta near the Saryesik Peninsula. (2) The wetland landscape pattern in the IRD changed markedly from 1975 to 2020. The dominant patches of the wetland in the middle of the delta continued to expand; the patch aggregation index (AI) increased, and the landscape fragmentation index (LFI) decreased. (3) From 2000 to 2020, the average annual normalized difference vegetation index (NDVI) and net primary productivity (NPP) in the IRD increased, which is consistent with the change in wetland expansion. (4) Inflow to the delta from the Ili River and the water level of Balkhash Lake are significantly correlated with the wetland area, which are the dominant factors driving wetland evolution; and water evaporation from the Kapchagay Reservoir and irrigation water diversion on the left bank of the reservoir obviously intensified the process of lake water level decline and wetland degradation during 1970 to 1985. These results can provide scientific background for making informed ecological protection decisions in the IRD under the impacts of climate change and human activities.

Alpine wetland degradation reduces carbon sequestration in the Zoige Plateau, China

Alpine wetland plays an important role in the global carbon balance but are experiencing severe degradation under climate change and human activities. With the aim to clarify the effect of alpine wetland degradation on carbon fluxes (including net ecosystem CO2 exchange, NEE; ecosystem respiration, ER; gross ecosystem productivity, GEP, and CH4 flux), we investigated 12 sites and measured carbon fluxes using the static chamber method in the Zoige alpine wetland during August 2018, including undegraded wetland (UD), lightly degraded wetland (LD), moderately degraded wetland (MD), and severely degraded wetland (SD). The results showed that carbon sink strengths differ among the Zoige wetlands with different degradation stages during the growing season. From UD to LD, the rate of carbon sequestration (mean value of NEE) increased by 25.70%; however, from LD to SD, it decreased by 81.67%. Wetland degradation significantly reduced soil water content (SWC), soil organic carbon (SOC), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN). NEE was significantly correlated with MBC and MBN, while ER was positively correlated with ST but negatively correlated with SOC (P &amp;lt; 0.01). Among all measured environmental factors, GEP was positively correlated with pH (P &amp;lt; 0.01), while CH4 flux was most closely correlated with SOC, SWC, MBC, MBN, and ST (P &amp;lt; 0.001), and was also affected by pH and NO3– content (P &amp;lt; 0.01). These results suggest that the capacity of carbon sequestration in the Zoige wetlands reduced with intensification of the degradation. This study provides a reference for sustainably managing and utilizing degraded wetlands under climate change.

Phylogenetic relationship and soil salinity shape intraspecific trait variability of Phragmites australis in the Yellow River Delta

Soil salinization has been one of the main causes of ecosystem degradation in many estuarine wetlands under global climate changes, but it remains unclear how salinization shifts the phenotypic variability and genetic diversity of the foundation plant species in estuarine wetlands. To reveal the effects of salinization on natural populations of foundation plant species, we investigated the intraspecific variation of Phragmites australis using five functional traits (shoot height, leaf length, panicle length, seed number per panicle, and mass per seed) and ten microsatellite markers in the five sites across the Yellow River Delta. The salinity was indicated by electrical conductivity, and the reproductive strategy was estimated by the ratio of panicle length to shoot height. The linear models showed that the shoot height, leaf length, and panicle length had significantly negative correlations to soil salinity, while the mass per seed had a significantly positive correlation to soil salinity. However, there were no significant relationships between the seed number per panicle or reproductive ratio and soil salinity. The genetic diversity within populations was high in all sites (He &amp;gt; 0.5), but the genetic differentiation between populations was very weak (FST from 0.0074 to 0.0212), which suggested that there was a strong genetic flow among populations. Genetic structure analyses showed two phylogenetic groups of P. australis distributed in four of five surveyed sites across the Yellow River Delta. Our study also found significant phylogenetic signals in the leaf length and mass per seed, suggesting a substantial role of phylogenetic relationship (technically, neutral genetic relatedness) in intraspecific variation and salt adaptation of P. australis. Our study provides novel insight into the adaptative responses of the foundation plant species to soil salinization from individual traits to population genetics and offers significant implications for ecological restoration and adaptive management of saline lands in estuarine wetlands.

Detecting Vegetation to Open Water Transitions in a Subtropical Wetland Landscape from Historical Panchromatic Aerial Photography and Multispectral Satellite Imagery

Over the last century, direct human modification has been a major driver of coastal wetland degradation, resulting in widespread losses of wetland vegetation and a transition to open water. High-resolution satellite imagery is widely available for monitoring changes in present-day wetlands; however, understanding the rates of wetland vegetation loss over the last century depends on the use of historical panchromatic aerial photographs. In this study, we compared manual image thresholding and an automated machine learning (ML) method in detecting wetland vegetation and open water from historical panchromatic photographs in the Florida Everglades, a subtropical wetland landscape. We compared the same classes delineated in the historical photographs to 2012 multispectral satellite imagery and assessed the accuracy of detecting vegetation loss over a 72 year timescale (1940 to 2012) for a range of minimum mapping units (MMUs). Overall, classification accuracies were &gt;95% across the historical photographs and satellite imagery, regardless of the classification method and MMUs. We detected a 2.3–2.7 ha increase in open water pixels across all change maps (overall accuracies &gt; 95%). Our analysis demonstrated that ML classification methods can be used to delineate wetland vegetation from open water in low-quality, panchromatic aerial photographs and that a combination of images with different resolutions is compatible with change detection. The study also highlights how evaluating a range of MMUs can identify the effect of scale on detection accuracy and change class estimates as well as in determining the most relevant scale of analysis for the process of interest.

Participatory Approach to Wetland Governance: The Case of The Memorandum of Understanding of the Sečovlje Salina Nature Park

Wetlands are defined as dynamic ecosystems that combine the characteristics of aquatic and terrestrial ecosystems and are important from ecological as well as social and economic perspectives. In response to the intense degradation and alteration of wetlands, communities have developed various management strategies. One of the ways to achieve more effective participatory wetland management is to introduce the concept of a Wetland Contract, a voluntary agreement that ensures sustainable management and development of wetlands. This study on the Sečovlje Salina Nature Park in Slovenia follows the methodology of the preparation (legal framework, scientific description and stakeholder analysis) and implementation (organization of Territorial Labs, scenario planning and development) stages of the Wetland Contract concept. Of approximately 200 potential stakeholders, 34 participated in the Territorial Labs, and 16 stakeholders signed the less binding type of Wetland Contract, called the Memorandum of Understanding. The Memorandum of Understanding and its implementation process, which included systematic cross-sectoral participation, successfully overcame conflicts between stakeholders with different interests. The methodology used has shown great potential for further applications in wetlands of common interest.

Forty Years of Wetland Status and Trends Analyses in the Great Lakes Using Landsat Archive Imagery and Google Earth Engine

Wetlands provide many benefits, such as water storage, flood control, transformation and retention of chemicals, and habitat for many species of plants and animals. The ongoing degradation of wetlands in the Great Lakes basin has been caused by a number of factors, including climate change, urbanization, and agriculture. Mapping and monitoring wetlands across such large spatial and temporal scales have proved challenging; however, recent advancements in the accessibility and processing efficiency of remotely sensed imagery have facilitated these applications. In this study, the historical Landsat archive was first employed in Google Earth Engine (GEE) to classify wetlands (i.e., Bog, Fen, Swamp, Marsh) and non-wetlands (i.e., Open Water, Barren, Forest, Grassland/Shrubland, Cropland) throughout the entire Great Lakes basin over the past four decades. To this end, an object-based supervised Random Forest (RF) model was developed. All of the produced wetland maps had overall accuracies exceeding 84%, indicating the high capability of the developed classification model for wetland mapping. Changes in wetlands were subsequently assessed for 17 time intervals. It was observed that approximately 16% of the study area has changed since 1984, with the highest increase occurring in the Cropland class and the highest decrease occurring in the Forest and Marsh classes. Forest mostly transitioned to Fen, but was also observed to transition to Cropland, Marsh, and Swamp. A considerable amount of the Marsh class was also converted into Cropland.

Integrating Agroecological Food Production, Ecological Restoration, Peasants’ Wellbeing, and Agri-Food Biocultural Heritage in Xochimilco, Mexico City

Chinampería, a jeopardized precolonial agricultural practice, persists in the Xochimilco wetland, Mexico City. Agroecological chinampa production is a recognized UNESCO World Heritage Site, and contributes to the sustainability of both the urban wetland and the city. The ‘chinampa-refuge’ model (CRM) is a transdisciplinary effort to strengthen traditional agroecological practices and ecological restoration. Through an inter/transdisciplinary research framework, we addressed the model’s role in the sustainability of this socio-ecosystem concerning four significant drivers of the wetland’s transformation. The CRM has improved water quality locally, increased the suitable habitat for native aquatic biodiversity, and supported traditional agroecological practices, thus improving the quality and safety of food products. However, there are clear challenges regarding production and commercialization, some of which may be addressed through the strengthening of the social organization and collective action. However, other challenges are beyond the reach of chinampa producers’ efforts and the CRM, but are decisive in changing the degradation trends. In order to address these challenges, urgent and participatory government actions are needed based on the recognition of the causes of wetland degradation and the role of traditional chinampa production in its sustainability.

Degradation reduces the diversity of nitrogen-fixing bacteria in the alpine wetland on the Qinghai-Tibet Plateau.

Biological nitrogen fixation is a key process in the nitrogen cycle and the main source of soil available nitrogen. The number and diversity of nitrogen-fixing bacteria directly reflect the efficiency of soil nitrogen fixation. The alpine wetland on the Qinghai-Tibet Plateau (QTP) is degrading increasingly, with a succession toward alpine meadows. Significant changes in soil physicochemical properties accompany this process. However, it is unclear how does the soil nitrogen-fixing bacteria change during the degradation processes, and what is the relationship between these changes and soil physicochemical properties. In this study, the nifH gene was used as a molecular marker to further investigate the diversity of nitrogen-fixing bacteria at different stages of degradation (none, light, and severe degeneration) in the alpine wetland. The results showed that wetland degradation significantly reduced the diversity, altered the community composition of nitrogen-fixing bacteria, decreased the relative abundance of Proteobacteria, and increased the relative abundance of Actinobacteria. In addition to the dominant phylum, the class, order, family, and genus of nitrogen-fixing bacteria had significant changes in relative abundance. Analysis of Mantel test showed that most soil factors (such as pH, soil water content (SWC), the organic carbon (TOC), total nitrogen (TN), and soil C:P ratio) and abundance had a significant positive correlation. TOC, TN, total phosphorus (TP), soil C:P ratio and Shannon had a significant positive correlation with each other. The RDA ranking further revealed that TOC, SWC, and TN were the main environmental factors influencing the community composition of nitrogen-fixing bacteria. It is found that the degradation of the alpine wetland inhibited the growth of nitrogen-fixing bacteria to a certain extent, leading to the decline of their nitrogen-fixing function.

Effects of morphology and sediment permeability on coastal lagoons’ hydrological patterns

Mediterranean coastal lagoons are influenced from a wide variety of external factors such as surface and groundwater flows and climate dynamics. They are also vulnerable to human activities, which have caused a significant loss of these types of habitats. As a result, the EU habitat management have now prioritized restoration of natural wetlands. However, there is a lack of systemic studies on the mechanisms of coastal wetland degradation and ecohydrological processes that determine restored ecological functioning as an end goal, as well as a lack of reference sites to make comparisons. Furthermore, while lagoon morphometry and underlying sediment permeability have been studied extensively, combining these disciplines to evaluate lagoon hydrology and salinity dynamics is yet to be fully explored. The aim of this study was to analyze the hydrological dynamics of 4 newly constructed lagoons and compare them with 2 natural lagoons in the La Pletera salt marshes and evaluate the restoration and conservation efforts. We use the General Lake Model (GLM) to assess water volume fluctuations, salinity variability and lagoon water circulation (groundwater and surface water inflows, outflows and evaporation). We also combine data of the underlying lithological characteristics and lagoon morphometry, to compare and better understand the interplay of these parameters on the hydrological behavior of each lagoon. Results indicated that the older and natural lagoons exhibited more consistent patterns of confinement; with deeper morphologies, lower evaporation effect, lower water circulation, and more annual patterns of salinity fluctuation. The presence of low-permeability layers also resulted in less fluctuation of higher salinity levels. Conversely, three of the four new lagoons had similar, shallower morphologies and higher evaporation fluxes, but exhibited different water circulation patterns due to the presence or absence of low permeability layers. Also, their salinity fluctuations were more influenced by seasonal mixing than by evaporation, indicating more susceptibility to climatic influence in their annual hydrological pattern than in the natural lagoons. This could prove important when constructing and restoring lagoons according to predetermined morphology and underlying sediment patterns, as it could ultimately limit or enhance the success of set objectives and overall ecological functioning in a flooding – confinement driven lagoon ecosystem conditioned by irregular and unpredictable climatic events.

Characterizing seasonal and long-term dynamics of a lacustrine wetland in Xinjiang, China, using dense time-series remote sensing imagery

ABSTRACT Wetland degradation and ecological restoration has become a topic of key research interest, particularly in the context of climate change and excessive water resource utilization. The Aiximan wetland, a major lacustrine wetland in Xinjiang, China, has shrunk in area by approximately 80% over the last 30 years. An ecological water transfer project (EWTP) was implemented in 2017 in an attempt to reverse this shrinking. The project involves seasonal flooding through three canals during the growing season of the wetland. In this paper, we explore the history of the Aiximan wetland over the last 30 years using a dense time series of remote sensing images to analyse the spatio-temporal changes of the wetland. We focus on intermittent flood inundation and wetland vegetation growth before and after the EWTP initiation, as well as the role of agricultural expansion in the decline of the wetland. The results indicate the following: (1) The annual maximum of open water area, which had fallen to 25.91 km2 by 2016, increased to 47.54 km2 in 2019 due to the water transfers. However, although the area of wetland vegetation also increased following the water transfers, it did not regain the maximum extent it had in 2013. (2) The percentage of the total wetland area with vegetation cover steadily declined from 54.2% in 1990 to 13.4% in 2019, and 72.84% of the loss of wetland was due to conversion to farmland. (3) The loss of wetland vegetation over the last 20 years corresponds to a period when the wetland water area fell below a threshold of 30 km2, and the wetland vegetation accounted for less than 60% of the wetland area. (4) The Aiximan wetland has recently shown signs of recovery due to the EWTP. However, the remote sensing time series suggests that wetland vegetation restoration will require the wetland water area to exceed 30 km2. Adjusting the timing of intermittent flood inundation to encourage vegetation growth may also be important for sustainable restoration of the Aiximan wetland ecology.

Transformation and risk assessment of the East Kolkata Wetlands (India) using fuzzy MCDM method and geospatial technology

The East Kolkata Wetlands (EKW) is located on the eastern periphery of the city of Kolkata and extends up to the Bidyadhari-Matla River confluence. It is a Ramsar Site and acts as an absorber basin for a large number of contaminants drained from Kolkata. Agricultural lands, sewage-fed fisheries, garbage dumping fields, horticulture, and built-up areas are included in this protected area, that covers approximately 125 km2. It reveals that climate change reduces the variety of wetland ecosystem services and increases socio-economic vulnerability and economic stress. The human encroachment, reclamation of land for agriculture, aquaculture, and urban expansion in and around Kolkata has recently adversely threatened the EKW. The remotely sensed data, socio-economic data, and responses of inhabitants have been used to analyse the EKW’s risk and vulnerability. We employed geospatial analysis by using the Multi-Criteria Decision Making (MCDM) method using nine risk factors. An in-depth analysis of the EKW using geospatial techniques and the Fuzzy Analytic Hierarchy Process (FAHP) helped to understand the EKW transformations through vulnerability and risk analysis. The results show that the transformation of the wetland to aquaculture, eutrophication and pollution, road proximity, waste dumping, population density, and growth are the main factors for the deteriorating health, quality, and environment of the EKW. It also reveals that quantitative and qualitative evaluations of ecosystem services, wetland degradation, transformation, and cause-effect rapport should be periodically assessed using scientific methods like FAHP, RS, GIS to formulate resilient, integrated plans and strategy for the sustainable management of the EKW.

Changes in soil free-living diazotrophic community and co-occurrence patterns along desert wetland degradation gradient in the Mu Us Desert, northern China

Climate change and human activities have led to the degradation of desert wetlands. Free-living diazotrophs are vital to soil nitrogen input. However, a comprehensive understanding of how soil free-living diazotrophic community and co-occurrence patterns respond to desert wetland degradation is lacking. Here, quantitative polymerase chain reaction (qPCR) and amplicon sequencing targeted on nitrogenase ( nifH ) genes and network analysis were used to investigate soil free-living diazotrophic abundance, diversity and composition and co-occurrence patterns along the wetland degradation gradient [non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD) wetlands] in the southeastern of Mu Us Desert, northern China. Results showed the abundance, Shannon, Simpson, Chao1 and Ace indexes decreased ( P < 0.05) by 14.6%, 20.7%, 2.1%, 46.5% and 45.0% at SD, respectively, whereas no significant difference ( P > 0.05) was observed between ND and LD. The relative abundance of Proteobacteria generally decreased across the degradation (53.5%–19.7%), while the variation was opposite for Cyanobacteria from ND to MD (6.2%–40.1%). Soil organic carbon had the strongest linkage with abundance, diversity and composition, followed by total nitrogen, moisture and pH. The lowest network nodes, edges and density were observed at MD and SD, indicating the complexity of free-living diazotrophic networks was reduced by continued degeneration. Overall, severe desert wetland degradation more negatively affects soil free-living diazotrophic abundance, diversity and network complexity than light degradation. The degradation promotes the growth of autotrophic diazotrophs, inhibiting heterotrophic diazotrophs. These changes are mostly related to the loss of soil organic carbon.

Monitoring vital signs: Wetland vegetation responses to hydrological resources in the Macquarie Marshes NSW, Australia

AbstractHuman intervention through damming, diversion and extraction of water resources has created regulated dryland river systems. As a result, connectivity between river channels and floodplain wetlands has diminished. Wetland function is fundamentally linked to water availability: flooding exchanges water, nutrients, sediments and biota with the floodplain. Water allocation for environmental flows may mitigate wetland degradation following river regulation by improving hydrological connectivity between rivers and floodplain wetlands. We report the results (2014–15 to 2018–19) of a vegetation monitoring program in the Macquarie Marshes in north western New South Wales. As part of the long‐term program, we monitored semi‐permanent wetland (Water Couch (Paspalum distichum) grassland or sedgeland dominated) and River Red Gum (Eucalyptus camaldulensis) forest/woodland communities along with environmental and water resource availability predictors. During the five‐year period, we found linear and nonlinear responses of functional group abundance and species richness to the water year and to time since last inundation. We also found differences in species assemblages in response to the flow and flooding regime, particularly water year and inundation duration. These results indicated that wetlands continued to express dry and wet phase responses. We also observed a depressed response to the large 2016–17 flood event by a subset of semi‐permanent wetland sites that had not been inundated in 3 years, compared with sites that were more recently inundated. This result indicated that environmental water management, along with protection of natural inundation events, may improve the resilience of floodplain wetlands: increased hydrological connectivity may promote a stronger wetland response when floods occur. Our results indicate that inundation, in part comprised of managed environmental flows, is a primary driver of species assemblage and functional group representation in semi‐arid floodplain wetlands.

The impacts of flood-mitigation structures on floodplain ecosystems: a review of three case studies from Australia and France

ABSTRACT This study is concerned with the physical impacts of flood-mitigation structures on ‘humanised’ and ‘natural’ floodplain ecosystems. The former constitute fertile, well drained and developed surfaces. The latter are mainly degraded wetland areas located in the backwater zones of wide, low-lying floodplains. Three rivers are investigated: the Hawkesbury–Nepean and the Macleay Rivers in New South Wales, Australia and the Durance River in southern France. Their floodplains, flood-mitigation works and floodplain ecosystems are analysed, together with site- and time-dependent differences in their floodplains, their exploitation and their degradation. Conservation of floodplains seeks to reverse wetland degradation, and to increase biodiversity and sustainability, as well as preserving developed floodplains. This study discusses gaps in our biophysical knowledge of ecosystems and the absence of ecological indicators of degradation. It also considers the lack of data on socio-economic values for what are unique, site- and time-specific, biophysical systems. Only when such inadequacies are addressed will the values of ecosystems be fully understood. Then cost-effective management might be possible. These knowledge gaps contribute to the many problems of floodplain management, which are likely to increase when the additional impacts of population increase and global warming become apparent.

Application of soil quality index to determine the effects of different vegetation types on soil quality in the Yellow River Delta wetland

Assessment of soil quality in different vegetation types of wetland ecosystems is essential for soil functioning, such as nutrient cycling and vegetation growth, particularly the maintenance of wetland ecosystem sustainability. Wetland degradation can extremely influence soil quality. However, prediction of soil quality in terms of soil quality index in wetland soils remains obscure. In this study with the fundamental goal to assess soil quality, we have intended to assemble a range of soil quality indicators to characterize the soil quality index (SQI). The minimum data set (MDS) from the Principal component analysis (PCA) was used to determine the SQI. With such objectives, three vegetation types: Robinia pseudoacacia community (tree), Tamarix chinensis community (bush), and Suaeda salsa community (grass) were selected in the Yellow River Delta wetland, eastern of China. A total of 108 soil samples [3 sites (tree, bush and grass)—3 field plots—3 replicates—4 soil depth layers: 0–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm] were collected for laboratory analyses. This study showed that there were high variations in soil physical and chemical properties among the three sites. Soil organic carbon (SOC), silt, clay, and pH at tree site, total soil porosity (TSP), soil organic carbon (SOC), pH, and soil bulk density (SBD) at bush site, and total soil porosity (TSP), silt, and soil electronic conductivity (SEC) at grass site were retained in the MDS. SOC and TSP were the key soil quality indicators. The values of the SQI at 0–10 cm soil depth at all three sites (2.236, 0.895, and 2.573 respectively) were the highest compared with other soil depths, indicating the best soil quality in the upper soil layers (0–10 cm). The values of the SQI at 0–10 cm soil depth at both tree site and grass site were similar, and they were higher than those at bush site. At tree site, the values of the SQI decreased with increasing soil depth, which indicated that soil quality became worse with depth. At bush site, the values of the SQI decreased with increasing soil depth (0–40 cm), while the values increased at 40–60 cm depth, indicating better soil quality in the deeper soil layers (40–60 cm). At grass site, the values of the SQI at 10–20 cm and 40–60 cm soil depth were lower than those at 20–40 cm soil depth, indicating better soil quality at 20–40 cm soil depth. It is concluded that the SQI can be compared more accurately in different vegetation types of wetland ecosystems based on its simplicity and quantitative flexibility. These findings are of importance because the assessment of the SQI allows to quantify different vegetation effects on soil quality.

Analysis of drought conditions and their impacts in a headwater stream in the Central European lower mountain ranges

Headwaters represent a significant fraction of the global stream length and are important for streamflow quality and quantity. Since climate change is predicted to affect runoff generation processes fundamentally, it is essential to understand potential consequences for the water availability in headwater catchments. The Lehstenbach catchment, located in the Fichtel Mountains (Germany), represents many headwater catchments in the lower mountain ranges in Central Europe. This study’s primary objective is to predict and analyze potential shifts in the catchment’s water balance, estimate periods of hydrological drought conditions, and their characteristics. For this purpose, we used an integrated process-based hydrological model to represent surface/groundwater interactions and runoff generation mechanisms for the Lehstenbach catchment until 2100, using a Regional Climate Model Ensemble. The simulations indicate decreased water availability in summer and autumn, mainly due to increased evapotranspiration rates. The Minimum Environmental Flow (MEF), a quantitative measure of aquatic species’ exposition to abnormally low streamflow conditions, implies an increase of low flow conditions towards 2100. A first estimate indicates a possible increase of hydrological drought duration and intensity in the future. These findings suggest severe impacts on ecosystem health and services, such as decreasing water availability, leading to consequences like forest and wetland degradation and declining biodiversity. These findings can be used to implement suitable mitigation strategies to reduce climate change effects on the headwater ecosystems, such as water shortage for irrigation and drinking water supply and loss of flora and fauna.