Modelling of soil organic carbon and bulk density in invaded coastal wetlands using Sentinel-1 imagery
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Soil carbon
River water quality is substantially influenced by adjacent wetlands. The water exchange estimate is a step in the process of developing a model capable of simulating management strategies for wetlands of the Lower River Murray and their effect on nutrient load in the river. An expanded wetland process model was used to find the water exchange between wetlands, where there is a lack of channel morphology data and no measured wetland water turnover. This paper describes the development of the wetland ecosystem model WETMOD to include spatial driving variables of the floodplain landscape. The added spatial driving variables for WETMOD are used to account for local variations and inflow into a wetland, particularly to reflect bi-directional water and nutrient exchange between the River Murray and the wetlands. The spatial driving variables are derived from a database containing site-specific flow and nutrient data from the river and wetlands. In order to simulate the water exchange between individual wetlands and the River Murray an ad hoc flux estimation technique was developed. This was based on a combination of the river flow volume and the wetland specific budget of phosphorus (PO4-P) simulated by WETMOD. We demonstrate that it is possible to obtain the turnover volume of water in a wetland using nutrient modelling output.
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Outflow
Inflow
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The wetlands in the Congo Basin play a significant role in dampening the flood waves in the fluvial system by storing water at flooding peaks and later releasing it. Quantifying the sources and sinks of the wetland waters is essential to understanding the routing of carbon, sedimentation, and other nutrients that are transported with the hydrological fluxes. In this study, we quantify the hydrological fluxes, including precipitation, upland runoff, evapotranspiration, and river-wetland exchanges supplying and draining the wetlands by integrating remote sensing measurements and modeling. Annually, river-wetland exchanges contribute less than 20% of the total inflows into the wetlands, whereas precipitation and runoff contribute to more than 80% of total inflows. However, river-wetland exchanges could contribute more than 20% and up to 90% of water storages in some wetlands at peak storage season. The river-wetland exchanges contribute 40% to 60% of the total outputs, while evaporation is responsible for the rest of the total outputs. Overall, our analysis results suggest that the Congo wetlands receive water from the river at peak storage season and supply water to the river most times of the year.
Wet season
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Global climate cycle and carbon balance are one of the cores of current research in climate change and regional sustainable development,also one of the topics in a series of large-scale international cooperation in scientific research.One of the highlights in global change and terrestrial ecosystem research is on carbon cycle in wetland ecosystem.Wetland soil is the source and sink of various green gas and important pool of organic carbon with high carbon density and long-term of storage.The distribution area of global coastal wetland is approximately 203×103 km2,and the accumulation rate of carbon in coastal wetland is 210±20 g C· m-2· a-1 which is much higher than peat wetlands.Methane's emission is also inhibited due to the large amount of SO2-4 ions in coastal wetland soil.Hence,it's more obvious of the inhibition effect on green gas emission in coastal wetland.Although Yancheng coastal wetland is induced in the list of world key wetlands of international importance,the characterization of organic cycle and distribution of soil organic carbon are still no reports.It's essential for us to study on the changes of organic carbon storage in wetland soil and it's distribution in soil profiles,it's also important for us to understand the relationship between carbon storage and carbon cycle in terrestrial ecosystem,and to provide scientific basis for evaluation and protection coastal wetland ecosystem.
Soil carbon
Carbon sink
Terrestrial ecosystem
Global Change
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There is increasing interest in the use of wetlands to intercept nutrients in diffuse run-off from rural catchments. However, the scientific basis for this strategy is far from secure. While research in several countries provides support for this approach, there is a general lack of rigorous data sets of nutrient balances showing the real effect of such wetlands on the quality of run-off emanating from rural catchments. Research being conducted on two natural and one constructed wetlands in south-eastern Australia will contribute to filling this gap. In each of these three wetlands, volume of inflow and outflow is being measured at 15 minute intervals. Automatic water samplers connected to the flow measurement device are measured and are triggered to take samples at appropriate intervals during run-off events. All these water samples are analysed chemically and the total loads of selected chemicals entering and leaving a wetland are calculated for several storm events over the winter and spring period during 1993. Results for Total Nitrogen and Total Phosphorus show that during winter there is a net release of these nutrients from the linear wetlands with greater flows resulting in greater flushing. However, in spring and early summer there was a net retention of nutrients in the wetlands despite similar hydrological loadings. These results were affected by the size of the wetland relative to the catchment (and therefore retention time), land use of the catchment, any intrusion of ground water and the nature of the wetland in terms of its shape and vegetation.
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Clean Water Act
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Impacts of land use, specifically soil disturbance, are linked to reductions of soil organic carbon (SOC) stocks. Correspondingly, ecosystem restoration is promoted to sequester SOC to mitigate anthropogenic greenhouse gas emissions, which are exacerbating global climate change. Restored wetlands have relatively high potential to sequester carbon compared to other ecosystems, but SOC accumulation rates are variable, which leads to high uncertainty in sequestration rates. To assess soil properties and carbon sequestration rates of freshwater mineral soil wetlands, we analyzed an extensive database of SOC concentrations from the Prairie Pothole Region (549 wetlands over 160,000 km2), which is considered one of the largest wetland ecosystems in North America. We demonstrate that SOC of wetland catchments varies among inner, transition, toe slope, and upland landscape positions (LSPs), as well as among land uses and soil depth segments. Soil organic carbon concentrations were greatest in the inner portion of the catchment (66 Mg ha−1) and progressively decrease towards the upland LSP (43 Mg ha−1). We also conducted a regional extrapolation based on LSP- and land-use-specific SOC stocks, and estimated that wetland and upland areas of PPR wetland catchments contain 141 and 178 Tg of SOC in the upper 15 cm of the soil profile, respectively. Regressing SOC by restoration age (years restored) showed that sequestration rates, which differ by LSP and depth, ranged from 0.35 to 1.10 Mg ha−1 year−1. Using these SOC sequestration rates, along with data from natural and cropland reference sites, we estimated that it takes 20 to 64 years for SOC levels of restored wetlands to return to natural reference conditions, depending on LSP and depth segment. Accounting for LSP reduces uncertainty and should refine future assessments of the greenhouse gas mitigation potential from wetland restoration.
Soil carbon
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Since most wetlands in the Sacramento Valley of California are dependent on artificial water delivery, supplying water for wetland management is the greatest challenge to wetland managers, especially during drought years. Efforts are needed to improve the security of water supplies for optimal habitat management and water quality improvement. This study contributes to these efforts by developing an eco-hydrologic model (Agricultural Policy/Environmental Extender [APEX]) of this wetland system, which has key components evaluated in the wetland simulation, including wetting and drying of wetland soils, competition and response of wetland species to wetland hydrology, settling of sediment, and nitrogen (N) removal. APEX model calibration (April of 2017 to May of 2018) and validation (June of 2018 to August of 2018) resulted in a percentage bias (PB) of 9.8% and –8.5%, respectively, for total volume of water holding in four serially connected wetlands. The N contents in the wetland waterbody were calibrated and validated using the monitored values collected during 2017 to 2018 and 2015 to 2016, respectively. All PB values for calibration and validation were over 35%. The calibrated model was used to evaluate the effects of wetland management and increasing temperature on N removal. Moreover, an additive regression model (ARM) was developed based on bird survey data and used to analyze bird dropping seasonal patterns and access their impacts on water quality in the studied wetlands. Based on the results of the model, the wetland water quality was influenced by waterfowl populations and eventually governed by water availability in each wetland cell. The N removal by wetlands was negatively affected by the volume of irrigation water. Moreover, increasing temperature caused a decrease in waterfowl population, which led to decreased N concentration by up to 42%. Overall, the results indicate that the developed model can be effectively used to quantify the effects of wetland management on water balance, water quality, and vegetation and to describe the nexus of wetland management, water use, and ecosystem service functions of managed wetlands.
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Wildlife refuge
Water storage
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A two-dimensional model MIKE21 coupled with a modified EcoLab module was applied to model the water quality of surface flow wetlands. In the model, vegetation effects, oxygen production, nutrient consumption by microorganisms and vegetation were set in the solutions of hydrodynamic, chemical, and biological processes. Based on the field investigation and measurements in the Guishui River wetland, the model was established for the downstream reaches of the Guishui River and the Sanli River. The model calculated the hydrodynamics and water quality changes by vegetation type and distribution. The model parameters were calibrated and results were validated using the measurements. The concentrations of ammonia nitrogen, phosphate, and total nitrogen at outflow decreased by 14.29%, 33.33%, and 20.00% in the presence of wetland vegetation compared to no wetland vegetation. During water circulation, the flow rate increased by 0.4 m3 ·s-1 at the inlet of Guishui and Sanli rivers, increasing the water level and velocity in some parts of the rivers. The water areas with vegetation in Sanli and Guishui rivers increased by 144.44% and 13.16%, respectively. The concentrations of ammonia nitrogen, phosphate, and total nitrogen at outflow decreased by 35.71%, 50.00%, and 46.67% compared to no wetlands and no circulation. The circulation strengthened the wetland purification function. The wetland vegetation distribution was organically integrated into the model for water quality calculation, which provides the technical support for the water quality response research under comprehensive measures such as river and lake wetland ecological restoration and water conservancy regulation.
Constructed wetland
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