Search

Abstract: In recent years, wetland restoration measures have created extensive concerns globally. The theory and practice of restoring wetland vegetation diversity in wetlands through soil seed banks is discussed in this paper. A comparative study on soil seed bank and species composition in Yeyahu Wetland, Beijing, was conducted in 2007. Species and quantities of seeds from 12 sample sites were counted and measured by the seed-germinating method. After germination, 27 species belonging to 16 families and 23 genera were recorded, with an average of 11.75 species per sample site, and total average density of 24831.0individuals/m2. There were significant differences between the soil seed bank and vegetation in spring, summer and autumn, with similarity coefficients of 0.2620±0.0868, 0.2580±0.0778 and 0.1953±0.0452, respectively. Also in 2008, by using the seed bank technique, vegetation diversity was restored in a degraded wetland near Maying River of Yeyahu Wetland through the processes of spot selection, topographic surveying, water level monitoring, and vegetation management. The results showed that in the restored regions, both species and diversity coefficients of vegetation observably increased: 73.68% of the hydrophytic species we discovered were transplanted from provenance regions; germination of seeds in the soil lasted until late September; and many species completed their life history and produced new seeds to renew the seed bank. In addition, the results suggested that seed bank technique not only increased richness and multiplicity of vegetation, but also provided food chains with animal diversity in wetlands. [Copyright &y& Elsevier]

• Wetland Degradation Index (WDI) was constructed on a pixel-by-pixel basis. • WDI incorporates lake shrinkage index (LSI), vegetation/soil degradation index. • LSI considers long-term continuous variations of water extent with Landsat images. • First assessment on lake wetland degradation in Bashang Plateau, China. 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. [ABSTRACT FROM AUTHOR]

Abstract: An integrated wetland system (IWS) including constructed wetlands (CWs) and modified natural wetlands (NWs) for wastewater treatment to replenish water to wetlands located at the Beijing Wetland School (BWS) in Beijing, China, is presented in this paper. The synergistic effects of CWs and NWs on treated water quality are investigated. The IWS is proved to be an effective wastewater treatment technique and a better alternative to alleviate the water shortage for conservation of wetlands based on the monitoring data obtained from October 2007 to 2008. The results show that CWs and NWs play different roles in removing contaminants from wastewater. The COD removal efficiency in CWs is higher than that in modified NWs, whereas the modified NWs can compensate for the deficiency of CWs where a stable and sufficient rhizosphere is not fully formed in the start-up period. All removal rates of COD, TN, and TP in CWs and modified NWs vary from 50 to 70%, while the total removal rate of COD, TN, and TP in IWS is about 85–90%. The operational results show that the maximum area loading of organic pollutants in modified NWs (65kg/had) is slightly higher than the empirical one (60kg/had) recommended by for free water surface wetlands. [ABSTRACT FROM AUTHOR]

Abstract: The transport of dissolved inorganic nitrogen in wetlands was investigated in the Yeyahu National Preserve of Beijing, China, from July to December 2011. Stable isotope of nitrogen (15N) as NH4 + was added to experimental mesocosms vegetated by seven common wetland plants. The 15N abundance in soil and various plant parts were measured at prescribed time intervals during the 49-day experimental period. Rapid 15N enrichments were found in soil and aquatic plants during the first sampling event at day 3 and typically increased linearly during the experimental period. Highest 15N enrichment was found in submerged plants, followed by emergent plants and soil. No differences in δ 15N values were found among leaves and stems of all submerged plants (Potamogeton pusillus, Potamogeton perfoliatus, Najas marina, Ceratophyllum demersum), suggesting that these plant structures are equally effective in nitrogen assimilation. The roots of P. perfoliatus displayed the lowest enrichment compared to the stems and leaves. Such results indicate that submerged plant roots may have a relatively weak role in nitrogen assimilation. The two emergent plants (Phragmites australis and Typha orientalis) showed no differences in δ 15N values among all plant parts, suggesting rapid translocation of nitrogen from roots to other portions. This experiment demonstrates that wetland soil and plant stems and leaves are major sinks for dissolved nitrogen from the surface water and provides valuable insight into nitrogen retention and transport pathways in various wetland plants. [Copyright &y& Elsevier]