Wetland Condition Research Articles

Assessment of wetland dynamics in terms of status and temporal changes using RS &GIS in Aligarh District, UP, India

Wetland is an effective ecosystem but its resources are influenced in varying degrees by global economic development and expansion of potential survival of human life. The accurate mapping of wetland types and monitoring their dynamic changes provide the scientific foundation for wetland conservation and restoration. Aligarh district had many wetlands but due to legal and illegal encroachment, they are shrinking. No wetland mapping has been done before to compare the past and present situation of wetlands. Therefore under this study, an attempt has been made to understand the status of wetlands in Aligarh district in terms of their number and areal extent and also assess the temporal changes during 2002-2017 using the multi-temporal Landsat imageries. Supervised Classification with the Maximum Likelihood algorithm was used to classify the wetlands. There was a 1826.67 ha area covered through wetlands that is 0.5% of its total geographic area. The maximum number of wetlands was point wetlands (having less than 1 ha area. In the last 15 years, the area of wetlands decreased by 57%. The overall accuracy of the supervised image produced was 87.50% with a kappa value of 0.75.

Mapping African wetlands for 2020 using multiple spectral, geo-ecological features and Google Earth Engine

Wetlands provide numerous ecosystem services essential for biodiversity conservation, climate change mitigation, and human well-being. Nevertheless, there are still no complete and uniform wetland maps providing information on the location, distribution, size, and changing status of wetlands in Africa. In this study, we used 130,000 Landsat satellite images and 270,000 sampling points evenly distributed across Africa to classify wetlands with a random forest classifier based on the Google Earth Engine (GEE) cloud platform. This resulted in the first systematic and comprehensive map of existing wetlands in Africa that quantified the area and distribution of these wetlands at a spatial resolution of 30 m, with an overall wetland producer accuracy of 90.22 % and user accuracy of 95.74 %. To address the seasonal variation in African wetlands, we used a dynamic threshold segmentation method based on the Otsu method, which can extract the extent of wetlands under different periods more accurately based on Landsat time series and African phenology data. Our results show that the total African existing wetlands extent from 2019 to 2021 (here in 2020), was approximately 1,341,500 km2, excluding shallow marine waters, comprises 3.98 % of Africa's total land area. Of these wetlands, inland wetlands account for 81 %, and coastal wetlands account for 19 %. The wetlands in Africa were symmetrically distributed around the equator and decreased with increasing latitude, accounting for 97 % of the total wetland area being within the 20°N and 20°S latitudes. African marshes were highly dynamic, expanding by 92.22 % from the dry to wet season. Our study demonstrates the substantial potential of large data samples, multiple wetland classification features (spectral-temporal, topographic, and hydrological features), and random forest classification in GEE for large-scale wetland mapping. The resulting wetland maps provide new baseline data for large-scale monitoring of seasonal dynamics and long-term trends in African wetlands.

Ecological Conditions and Ecosystem Services of Artificial Wetlands in Semiarid Ethiopian Highlands

The main purpose of the study was to investigate the ecological status, ecosystem services (ESs) with their relative importance, and the local communities’ perception of the management of Washa and Borale artificial wetlands located in the Semiarid Ethiopian Highlands. The results revealed that many of the communities relied mainly on farming and livestock rearing with small land size (≤ 1 ha) and large family size. Grass harvesting, free grazing, farming, wetland conversion, and water extraction were the main anthropogenic factors causing the wetlands’ ecological disturbance. The ecological status of Washa and Borale wetlands were thus moderately (67) and highly degraded (80), respectively. Yet, the various ESs categorized as provisioning, regulating, cultural, and supporting services, were still delivered from both sites. Vegetables (carrots, potatoes, garlic), crops (barley, beans), grass, water, and crafting materials were the products obtained from the wetlands. Some educational, research, and recreational services were also delivered mainly from the Washa site. Still, erosion, flooding, carbon regulation, and biota (plants, birds, fish) supporting services were provided at both sites. Yet, many of the ESs provided had low and medium importance due to the wetlands’ impairedness. Yet, the water and food delivered from the wetlands had high and even higher importance than the other services due to their being designed for providing water mainly for irrigation and livestock watering. Still, Washa provided higher cultural, regulating, and supporting services than the Borale’s owing to its being moderately impaired and lesser buffer and catchment area disturbance. Overall, many of the ESs delivered had low and medium importance because of the wetlands’ biodiversity loss, ecological degradation, and water reduction chiefly in the dry season. Yet, the people had good perceptions of the wetlands’ management. Hence, for the wetlands’ restoration, urgent action is required via developing a management plan.

How do microplastics adsorb metals? A preliminary study under simulated wetland conditions

Microplastics (MPs) are widely detected in wetlands as emerging pollutants of global concern. Co-occurrence of MPs and trace metals in wetlands is common and the vector effects of MPs on other environmental pollutants have been increasingly reported. However, the interaction of different MPs and trace metals under environmentally realistic conditions is not well understood. Here, we investigated the adsorption capacity of MPs for metals under simulated conditions of Poyang Lake wetlands in Jiang Xi, China, a Ramsar site of international importance for conservation and sustainable use. ICP-MS was used to quantify the amount of adsorbed metals onto different types of MPs. SEM-EDS and micro-FTIR were used to examine the morphological and chemical characteristics of MPs before and after metal adsorption. The influence of internal (polymer types and particle sizes of MPs) and external factors (water pH values, organic matters, ion strength, and sediment) on metal adsorption was systematically investigated. Metal adsorption equilibrium was most achieved at 72 h. The adsorption capacity of MP types to metal ions tended to decrease as PP > PE > PS, and the amount of adsorbed metals decreased as Cu > Pb > Cd. The amount of adsorbed metals generally decreased with the increase of particle size of MPs. With the increase of water pH and K+ strength, the adsorption of metals by MPs showed an increasing and then decreasing trend; the adsorption capacity of MPs increased with the increase of fulvic acid. Under the simulated sedimentary conditions, the adsorption of different metals by MPs also tended to be Cu > Pb > Cd, which was mainly determined by metal concentrations in the sediments collected in situ. The results of this study improve our understanding of metal-MP interaction under simulated environmental conditions, shedding new light on the environmental behavior of MPs and metals in wetlands.

Knowledge Level of Farmers in Accessing Agricultural Information through Smartphone

The present study was conducted to assess the knowledge level of rice, millets, and cotton farmers on accessing agricultural information through smartphone. Ex Post Facto Research Design was followed in this study since it aimed to assess the knowledge level of farmers. The study was conducted during May and June 2022. It was decided to conduct the study on three types of crops representing wetland, dryland and commercial conditions, for comparison purposes. Based on maximum area under cultivation in the state, rice for wetland condition, millets for dryland condition and cotton for commercial farming were selected for the research. The study was conducted in three districts viz., Thanjavur, Salem and Virudhunagar, which were selected based on the highest area under rice, millets and cotton respectively. From each of the three districts, two blocks were selected and from the selected blocks, three villages from each block were selected for the study based on maximum area under the rice, millets, and cotton crop. Based on proportionate random sampling technique, 180 respondents were selected for the study. The responses of the respondents were subjected to frequency and percentage analysis. Most of the millet growers (90.00%), rice growers (86.67%), and cotton growers (85.00%) had low level of overall knowledge on accessing agricultural information through smartphone. Majority of the rice, millets, and cotton respondents had high level of knowledge on Uzhavan app, PM Kisan web portal, Google Pay, WhatsApp, and Google Play Store. The knowledge level could be enhanced by more promotional activities of extension workers by conducting awareness campaigns on important mobile apps and web portals related to agriculture, and by conducting trainings and demonstrations on utilizing smartphones for accessing agricultural information through browsing internet, mobile apps, and web portals.

The lunar nodal cycle controls mangrove canopy cover on the Australian continent.

Long-phase (interannual) tidal cycles have been shown to influence coastal flooding and sedimentation, but their role in shaping the extent and condition of tidal wetlands has received little attention. Here, we show that the 18.61-year lunar nodal cycle, popularly termed the “lunar wobble,” is a dominant control over the expansion and contraction of mangrove canopy cover over much of the Australian continent. Furthermore, the contrasting phasing of the 18.61-year lunar nodal cycle between diurnal and semidiurnal tidal settings has mediated the severity of drought impacts in northern bioregions. Long-phase tidal cycles regulate maximum tide heights, are an important control over mangrove canopy cover, and may influence mangrove ecosystem services including forest productivity and carbon sequestration at regional scales.

Using a vegetation index to assess wetland condition in the Prairie Pothole Region of North America.

Wetlands deliver a suite of ecosystem services to society. Anthropogenic activities, such as wetland drainage, have resulted in considerable wetland loss and degradation, diminishing the intrinsic value of wetland ecosystems worldwide. Protecting remaining wetlands and restoring degraded wetlands are common management practices to preserve and reclaim wetland benefits to society. Accordingly, methods for monitoring and assessing wetlands are required to evaluate their ecologic condition and outcomes of restoration activities. We used an established methodology for conducting vegetation-based assessments and describe a case study consisting of a wetland condition assessment in the Prairie Pothole Region of the North American Great Plains. We provide an overview of an existing method for selecting wetlands to sample across broad geographic distributions using a spatially balanced statistical design. We also describe site assessment protocols, including vegetation survey methods, and how field data were applied to a vegetation index that categorized wetlands according to ecologic condition. Results of the case study indicated that vegetation communities in nearly 50% of the surveyed wetlands were in very poor or poor condition, while only about 25% were considered good or very good. Approximately 70% of wetlands in native grasslands were categorized as good or very good compared to only 12% of those in reseeded grasslands (formerly cropland). In terms of informing restoration and management activities, results indicated that improved restoration practices could include a greater focus on establishing natural vegetation communities, and both restored and native prairie wetlands would benefit from enhanced management of invasive species.

Ecological health assessment of Ethiopian wetlands: Review and synthesis

Assessment and monitoring of wetlands' ecology is vital to evaluate their ecological conditions, and provide information to support management decisions. Cognizant of this fact, wetland ecological assessment has been an important research agenda. As elsewhere in the world, wetland ecological assessment has been conducted in Ethiopia. This review aims to assess the spatial coverage of wetland ecological studies, the types of assessment tools employed for ecological assessment, the existing status of wetlands' ecologies and the drivers of wetland ecological decline. The review shows that not more than 30 ecological assessment studies have been conducted and published in reputable scientific journals. These studies mainly focused on only three river and lake basins and not more than 40 wetlands. This suggested wetlands’ ecological assessment has gotten scant research attention in the country. Physicochemical indicators have widely been employed to assess the ecological status of wetlands. Even though biological organisms are better indicators, biological approaches have been less applied in Ethiopia to assess the ecological status of wetlands. Therefore, there is an urgent need to monitor and assess Ethiopian wetlands by developing and adopting wetland assessment tools mainly using biological indicators.

The Dammed and the Saved: a Conservation Triage Framework for Wetlands under Climate Change in the Murray–Darling Basin, Australia

As the impacts of climate change and water demands from irrigation continue to increase in the Murray–Darling Basin, water for the environment is becoming more scarce and the ecological conditions of many wetlands is poor. With water scarcity, conservation triage is becoming an increasingly relevant management option for environmental watering of wetlands. However, triage is controversial; being considered contrary to current conservation objectives and practices. We assessed environmental watering at two Ramsar wetlands, Macquarie Marshes and Gunbower Forest, based on international environmental treaty obligations and domestic policy settings, changes to flow regimes, wetland condition and current management. Triage decision making was found to be in tacit use at Macquarie Marshes, based on ‘rules of thumb’ and experiential ecohydrological knowledge, whereas formal environmental watering planning formed the basis for triage decision making at Gunbower Forest. We developed a framework for conservation triage of wetlands in the Murray–Darling Basin to stimulate change in the decision context for wetland conservation and adaptation under climate change. Conservation triage entails reframing of relationships between people and nature and values, rules and knowledge used by stakeholders. Because water is the medium by which wetland conservation outcomes eventuate, trade-offs between competing water uses can be realised with the triage framework.

Wise Management or Mismatch? Lessons from Japan

As a precious resource, wetlands support human life in various profound ways, either explicitly or implicitly. However, the values of wetlands have not been sufficiently recognized and greatly appreciated. Their management approaches are often sectoral, and wise use of wetlands is still more of a catchphrase than a well-used management practice. This paper presents a cross-sectoral case study for the evaluation of the primary management practices in a Ramsar-registered wetland in Japan. It employed a literature review, field and laboratory experiments, and a questionnaire survey as well for assessing the wetland conditions and identifying management problems. It revealed that the management of the wetland is still flood regulation–oriented, without sufficient consideration of bird habitats, and the water level drawdown operation for Lake Yanaka inside the wetland may lead to mass fish deaths. Furthermore, the reed burning practice is effective in maintaining the plant structure in the wetland but controversial from different perspectives. Moreover, the questionnaire survey results indicated that the public were not well informed of the wetland conditions and not convinced of the appropriateness of reed burning. Based on these findings, it was concluded that the registration under the Ramsar Convention did not lead to new strategies for the conservation and wise use of the wetland.

Depth-dependent patterns in the C:N:P stoichiometry of different soil components with reclamation time in coastal poplar plantations

Reclamation changes the ecological processes and environmental conditions in coastal wetlands, and greatly affects the biogeochemical cycling of the ecosystem. However, how afforestation influences C, N, and P stoichiometry in plant–soil systems with reclamation time remains unclear. We studied the variations in C, N, and P concentrations and stoichiometries in different poplar compartments (leaves, roots, and litter) and soil components (bulk soil, microbial biomass, and enzymes) in the soil profiles of one tideland (natural wetland) and three poplar plantations at different stages of reclamation (i.e., reclaimed 24, 44, and 64 years prior to data collection) in East China. The C:N:P stoichiometry of the poplar compartments did not vary with coastal reclamation stage despite there was a weak correlation in C:N:P stoichiometry between the poplar compartments and soil components. Afforestation greatly altered the C:N:P stoichiometry of the different soil components with soil depth and reclamation time, especially the microbial biomass (e.g., N:P ratio), which was mainly ascribed to a decrease in soil P availability. Moreover, the magnitude of variation in C:N:P stoichiometry reduced with soil depth. On the basis of a model of ecoenzymatic stoichiometry, we found that, compared with the tideland, microbial C limitation decreased in the 0–20 cm soil layer and increased in soil layers below 20 cm in the reclaimed lands, whereas the nutrient limitation shifted from P in the topsoil (0–40 cm depth) to N in the subsoil (40–100 cm depth). The microbial metabolism in the soil profile was mainly dominated by abiotic factors (e.g., soil C:N:P ratios and salinity). Additionally, reclamation time had a relatively small effect on the microbial resource use limitations in the soil profile. Overall, afforestation in coastal reclaimed lands reshaped the vertical pattern of the C:N:P stoichiometry of different soil components and aggravated microbial C, N, and P limitations. However, the variation in microbial nutrient requirements among the different investigated reclamation stages was less marked. Our results have practical implications for soil nutrient management in poplar plantations on coastal reclaimed land.

Wetland Hydroperiod Analysis in Alberta Using InSAR Coherence Data

Wetlands are dynamic environments, the water and vegetation of which can change considerably over time. Thus, it is important to investigate the hydroperiod status of wetlands using advanced techniques such as remote sensing technology. Wetland hydroperiod analysis has already been investigated using optical satellite and synthetic aperture radar (SAR) backscattering data. However, interferometric SAR (InSAR) coherence products have rarely been used for wetland hydroperiod mapping. Thus, this study utilized Sentinel-1 coherence maps produced between 2017 and 2020 (48 products) to map the wetland hydroperiod over the entire province of Alberta, Canada. It was observed that a coherence value of 0.45 was an optimum threshold value to discriminate flooded from non-flooded wetlands. Moreover, the results showed that most wetlands were inundated less than 50% of the time over these four years. Furthermore, most wetlands (~40%) were seasonally inundated, and there was a small percentage of wetlands (~5%) that were never flooded. Overall, the results of this study demonstrated the high capability of InSAR coherence products for wetland hydroperiod analysis. Several suggestions are provided to improve the results in future works.

Carbon storage in Mexican wetland soils

The present study focuses mainly on knowing the current status of wetlands in the context of carbon sequestration in Mexican soils, for a good attention, management and dissemination of these ecosystems, without neglecting the importance it represents at local, regional and national levels before this environmental crisis and the eco-systemic services that wetlands provide, both social and environmental, since most of the studies on C sequestration and GHG emission have been conducted in temperate zones. In this review study, emphasis is placed on coastal, lacustrine or riparian wetlands, which are currently in a state of conservation risk due to various anthropogenic activities, for example, cattle ranching and agriculture (Marín-Muñiz, 2013).

Status and Population Trends of Great Cormorant Phalacrocorax carbo sinensis Breeding in Greece

We analysed trends in the breeding population of Great Cormorants in Greece during the period 1988–2014 when at least 20 colonies were recorded. The number of colonies doubled over the study period reaching 14 in 2014 from seven in 1988. There was also a continuous increase in the number of nests: from 952 in 1988 to 9256 in 2014, presenting an annual change of +26.5% ± 0.05 (SD). Most of the colonies were situated in freshwater lakes, three in deltas and one on the seacoast. Nine colonies were mixed with other colonially nesting species (mostly from the Ardeidae family). Of the 14 colonies 11 were found in trees. Two colonies were situated on the ground, four in bushes, two on reed rhizome islets and one on cliff ledges. Five out of the 14 active colonies in 2014, comprising 87% of the total recorded nests, were in wetlands of low altitude (0–45 m a.s.l.). The rest were situated in mountainous wetlands at altitudes ranging from 235 to 853 m a.s.l. One colony, at Lake Kerkini, contained the majority of nests in Greece (6650, being 72% in 2014). The second largest colony, at Lake Volvi, had 900 nests, followed by the Greek part of Prespa with 625 nests (in three colonies) in 2014. The percentage of nests in newly established colonies increased after 2003, reaching its highest value (14%) in 2009. The reason for the growth in both colonies and nests over the years is attributed to the increasing availability of fish, the protection status of wetlands and the absence of disturbance. Particularly after 2002 the species increased in numbers and established colonies in new areas, which is probably related to the expanding breeding populations of the species in north-eastern European countries and a corresponding increase in wintering numbers in Greece. This needs further attention by monitoring and research.

Geomorphic and tectonic development of Swan Valley, southeast Idaho, since the eruption of the Basalt of Antelope Flat—new 40Ar/39Ar, geochemical, and paleomagnetic data

Swan Valley is a graben in eastern Idaho that formed by extension along the Grand Valley and Snake River faults and preserves a record of explosive rhyolitic volcanism sourced from the Yellowstone Plateau and Heise volcanic fields, as well as locally sourced basaltic lavas. The Pleistocene Basalt of Antelope Flat intersected the South Fork of the Snake River and generated a temporary hyaloclastite dam. Previous workers proposed that the lava dam allowed for the accumulation of water that led to the generation of paleo-Swan Lake. Although lacustrine deposits from paleo-Swan Lake have not been described or mapped, several-meters thick intercalated hyaloclastites and pillow lavas require the interaction between continued volcanism and standing water. In this work, we present new geochemical, geochronologic, and paleomagnetic data to reinterpret the eruptive history of the basalts within the valley, estimate the volume and duration to fill paleo-Swan Lake, and calculate incision rates of the Snake River through Quaternary basalts. Using geochemical and paleomagnetic data, we reinterpret deposits previously mapped as the Basalt of Antelope Flat as three temporally distinct units. The duration to fill paleo-Swan Lake is calculated as 12 to 20 years. An absence of lacustrine deposits, shorelines, or other indicators of a lake environment led us to propose that shallow, marshy, wetland conditions existed locally to produce hydrovolcanic deposits characteristic of the Basalt of Antelope Flat. We report a new 40Ar/39Ar age of 904 ± 11 ka (2σ) for the Basalt of Antelope Flat, which we use to determine an average incision rate of 0.014 cm/yr for the Snake River through Quaternary basalts. Our multi-method approach provides updated constraints to the eruptive and geomorphological history of southeastern Idaho.

The environmental quality and macroinvertebrate community structures of wetlands found in the Lake Tana Watershed, Ethiopia

The present study was conducted to assess the environmental quality status and macroinvertebrate community structures of wetlands using macroinvertebrates as bioindicators. A multimetric biotic index approach was used for the study. The findings revealed 3,367 macroinvertebrates belonging to 37 families. The percentages of Ephemeroptera, Odonata, and Tricoptera (%EOT), percent Diptera, percent filterercollectors, the ratio of Ephemeroptera, Plecoptera, and Trichoptera to Chironomid (EPT/C), the Biological Monitoring Working Party Score, and the Shannon–Wiener diversity index were all significantly related to human disturbance and could be used to assess water quality. Based on the macroinvertebrate index, human disturbance had a significant impact on Shesher wetland, a relatively lower impact on Avaji and Yitamot, and a moderate impact on Chimba, while Dena and Wonjeta had good habitat quality. Their water quality was very poor, poor, moderate, and very good, in that order. Farming, leather tanning, waste dumping, and effluent discharges were responsible for the poor habitat quality of impacted wetlands. Therefore, unless managed properly, human disturbance activities in the wetlands catchment were threatening macroinvertebrates and the wetlands ecosystem. Hence, implementation of catchment-based management together with continuous health status monitoring and a standalone wetland policy should be established.

Community Structure of Benthic Macrofauna and the Ecological Quality of Mangrove Wetlands in Hainan, China

Few studies have systematically assessed the ecological status of mangrove wetlands following the stress of anthropogenic activities in China. This study investigated the spatial and seasonal distribution of benthic macroinvertebrate communities and assessed the ecological quality of mangrove habitats on an island scale in Hainan, China (containing the third largest mangrove area of China and the highest mangrove species richness). For the benthic macrofauna community structure, a total of 102 macrobenthic taxa belonging to 50 families were identified, with Crustaceans, Molluscs, Polychaetes, and Oligochaeta having relative abundances of 52.3%, 36.1%, 10.8%, and 0.8%, respectively. Decapoda and Gastropoda dominated the benthic community abundance. Non-metric multidimensional scaling and an analysis of similarities revealed significantly different macroinvertebrate assemblages among the regions during the two seasons. The South mangroves had the lowest macrofauna species numbers, biodiversity, richness, and abundance. The macrofaunal species richness, Shannon index, Margalef index, abundance, and biomass markedly affected by region and season. As indicated by the biotic indices AMBI (AZTI’s Marine Biotic Index) and M-AMBI, more than half of the mangrove habitats on Hainan Island were slightly to heavily disturbed and had poor to moderate ecological quality. Our results recommend long-term monitoring for evaluating the quality status of mangrove wetlands and avoiding extensive land-use conversion of mangroves. Holistic approaches considering ecological characteristics and combining information on both floral and faunal functionality would contribute to the effective management and conservation of mangroves in disturbed areas.

Potential role of submerged macrophytes for oxic methane production in aquatic ecosystems

AbstractMethane (CH4) from aquatic ecosystems contributes to about half of total global CH4emissions to the atmosphere. Until recently, aquatic biogenic CH4production was exclusively attributed to methanogenic archaea living under anoxic or suboxic conditions in sediments, bottom waters, and wetlands. However, evidence for oxic CH4production (OMP) in freshwater, brackish, and marine habitats is increasing. Possible sources were found to be driven by various planktonic organisms supporting different OMP mechanisms. Surprisingly, submerged macrophytes have been fully ignored in studies on OMP, yet they are key components of littoral zones of ponds, lakes, and coastal systems. High CH4concentrations in these zones have been attributed to organic substrate production promoting classic methanogenesis in the absence of oxygen. Here, we review existing studies and argue that, similar to terrestrial plants and phytoplankton, macroalgae and submerged macrophytes may directly or indirectly contribute to CH4formation in oxic waters. We propose several potential direct and indirect mechanisms: (1) direct production of CH4; (2) production of CH4precursors and facilitation of their bacterial breakdown or chemical conversion; (3) facilitation of classic methanogenesis; and (4) facilitation of CH4ebullition. As submerged macrophytes occur in many freshwater and marine habitats, they are important in global carbon budgets and can strongly vary in their abundance due to seasonal and boom‐bust dynamics. Knowledge on their contribution to OMP is therefore essential to gain a better understanding of spatial and temporal dynamics of CH4emissions and thus to substantially reduce current uncertainties when estimating global CH4emissions from aquatic ecosystems.

Effects of aridity on carbon, nitrogen, and phosphorus contents in soils and plants of mountain swamps, Zhejiang, China

Mountain swamps in Zhejiang Province have been suffered from severe drouhgt threats because of climate change and artificial interruption. Sphagnum bogs and swamps were gradually degraded into arid swamps. However, the effects of arid processes on the C, N, P contents of soils and their stoichiometry in mountain swamps are still unclear. We measured C, N and P concentrations, pH values, and bulk density in the upper 0-60 cm soil layers in the stands of five mountain swamps with the different arid levels. Moreover, the aboveground biomass and the C, N, P concentrations in the crushed plant mixture were also measured. The results showed that the soils of mountain swamps in Zhejiang Province were rich in soil organic carbon (SOC), total nitrogen (TN), but infertile in phosphorus (TP). Aboveground biomass, soil pH, bulk density increased, while SOC, TN, TP, C:N, C:P, N:P decreased with aridity. Soil pH and bulk density had significant negative correlations with SOC, TN, and TP in soils, respectively. The differences in the C, N, P accumulation in the soils were probably associated with litterfall production, the oxygen condition of wetlands, and the degree of plant decomposition at the different types of mountain swamps. In all, arid trends were obvious at the mountain swamps in Zhejiang Province. Soil nutrients, such as C, N, P, deceased, while plant community succeeded from the wet swamp to the mesophyte vegetation with the arid processes. The contents of C, N and P in the plants varied across species, and were not coupled with those in the soils.

Assessing degradation of lake wetlands in Bashang Plateau, China based on long-term time series Landsat images using wetland degradation index

Continuous monitoring of wetland dynamics and regional-scale assessment of wetland degradation are important to understand wetland ecosystem processes and to formulate restoration measures. The lake wetlands in Bashang Plateau play vital roles in providing essential resources and maintaining biodiversity in North China, while they were not fully investigated in previous studies. In addition, previous studies on wetland degradation assessment mostly relied on wetland area change every five or ten years. Continuous dynamics of wetlands was rarely considered. In this study, we developed a new wetland degradation index (WDI) to assess lake wetland degradation in Bashang Plateau based on time series Landsat imagery from 1985 to 2020 on Google Earth Engine platform. WDI integrates three indicators, namely lake shrinkage index (LSI), vegetation degradation index (VDI) and soil degradation index (SDI), which represents hydrodynamics of wetland inundation, vegetation, and soil conditions of wetlands, respectively. Different from previous research that utilized remotely sensed image to extract wetland every five or ten years, the LSI considers time-series continuous dynamics of lake water inundations and the transitions between water and non-water on a pixel-by-pixel basis. Our results showed that small lake wetlands with area less than 8 ha are dominant in Bashang Plateau. Both the number and the area of lake wetlands showed large interannual variations. The number (area) of lake wetlands reached 1715 (31,419 ha) in 1995–1996 and were only 493 (7,717 ha) in 2009–2010. The total area of the lake wetlands in 2019–2020 was only around 1/3 of that in 1995–1996. The LSI, VDI, SDI, as well as WDI demonstrate large spatial variations among the lake wetlands and within the lake wetlands. Wetlands in the western and central subregions experienced more severe degradation than those in the eastern subregion, and the edge of the wetlands normally showed more severe degradation. The resulted degradation grades are consistent with our field investigations. Among the 11 counties in Bashang Plateau, Zhangbei (ZB) county in the western subregion has the largest area with severe and very severe degradation grades. Degradation of lake wetlands was mainly associated with groundwater level declination which was induced by anthropogenic activities and economic development. The proposed WDI in this study can be widely applicable for regional-scale wetland degradation assessment using remote sensing techniques and thus further help decision making in lake wetland conservation and restoration.