Evaluating perturbations and developing restoration strategies for inland wetlands in the Great Lakes basin

Wetlands serve as atmospheric carbon dioxide (CO2) sinks, as well as atmospheric methane (CH4) source due to the anaerobic soil environment. Although some studies report that the CH4 emission from wetlands partially offset their net CO2 uptake, there is no global data analysis on the offset of net ecosystem exchange of CO2 (NEE) by CH4 emission in wetland ecosystems. In this study, we collected the data sets of NEE and CH4 flux which were simultaneously measured in the inland wetlands (peatland and non-peatland wetland) and coastal wetlands (seagrass beds, salt marshes and mangroves) around the world. The results showed that all types of wetlands were atmospheric CO2 sink, with the NEE values ranking as follows: mangrove (-2011.0 g CO2·m-2·a-1) < salt marsh (-1636.6 g CO2·m-2·a-1) < non-peatland wetland (-870.8 g CO2·m-2·a-1) < peatland (-510.7 g CO2·m-2·a-1) < seagrass bed (-61.6 g CO2·m-2·a-1). When CH4 flux being converted into CO2-equivalent flux (CO2-eq flux) based on the 100-year scale global warming potentials, we found that the CH4 emissions partially offset 19.4%, 14.0%, 36.1%, 64.9% and 60.1% of the net CO2 uptake in seagrass beds, salt marshes, mangroves, non-peatland wetland and peatland, respectively. Over the 20-year scale, CH4 emissions partially offset 57.3%, 41.4%, 107.0%, 192.0% and 177.3% of the net CO2 uptake, respectively. Some mangroves, peatlands, and non-peatland wetlands acted as net CO2 equivalent source. Over the 100-year scale, the net greenhouse gas balance of each wetland ecosystem was negative value, which indicated that even accounting CH4 emission, wetland ecosystem was still an atmospheric carbon sink. Our results indicated that clarifying the main regulation mechanism of CH4 emission from wetland ecosystems and proposing reasonable CH4 reduction measures are crucial to maintain the carbon sink function in wetland ecosystems, and to mitigate the trend of climate warming.

Inland wetlands are well represented ecosystems in Chile that are subjected to various pressures affecting conservation. Protection means legal and administrative initiatives which promote the protection and/or preservation of a wetland, either in its entirety, considering their areas of influence or its components. The aim of this work is to develop a methodology for estimating the value of protection of different types of inland wetlands in Chile. For this purpose: a) the Chilean regulations in relation to the issues of biodiversity, wetlands and water resources were compiled; (b) such legislation and its application were analyzed, (c) protection and restriction values of each legal standard was estimated, and then total protection value of standards applied to six types of wetlands in study. 47 legal rules related to protection of inland wetlands and eight directly or indirectly affecting conservation and wise use of wetlands were identified. In Chile there is no specific statutory rules or regulations on wetlands. Current legal standards do not protect equally the different types of inland wetlands, being swamp forests, peatlands and brackish Andean lakes less protected. To improve wetlands conservation, incentives promoting wetlands destruction must be eliminated and promulgate specific regulations for proper management and conservation.

Microbes are key drivers on wetland ecological processes, such as nutrient cycling, pollutants degradation and greenhouse gas emission. Despite the increasing studies of microbial community in driving wetland ecosystem processes, the mechanism of the relationship between microbial communities and key ecosystem functions remains poorly understood; in addition, the relationship between microbial diversity and wetland functions in different types of wetlands has not been analyzed in sufficient details. The diversity of microbial communities can be affected by abiotic (including biological matter, hydrological conditions, and temperature) and biological factors (such as typical plants). Understanding the relationships between microbial diversity and wetland functions in different types of wetlands is crucial for studying wetland ecological processes.The aim of this Research Topic is to clarify the characteristics and functions of microorganisms in different types of wetlands, and underlying mechanisms of the relationships between microbial communities and ecological functions. Within this topic, 6 articles have been published, fostering new ideas for the exploration of complex wetland ecosystems through microbial research.After accounting for the host selection effect of halophyte, Wang et al. investigated the distribution of bacterial communities in the rhizosphere (30-40cm) of typical coastal halophyte species (Phragmites australis and Suaeda salsa) in temperate and subtropical salt marshes, spanning 1100 km in eastern China. It's a study on a broad spatial scale. Their research revealed that the α-diversity of bacterial communities in the sediment of temperate salt marsh was higher than that of subtropical salt marsh. The stronger connections and more complex network structures were observed in the temperate salt marsh, while more cohesive modular structure of bacterial network was shown in subtropical salt marsh. Soil properties, geographic factors, and plant functional traits collectively shape bacterial communities in salt marsh, and soil chemical properties as well as root exudates regarded as most important predictors. Zhang et al. studied the broader regional-scale effects of salinity on the diversity and composition of methanotrophic communities in natural lake sediments. They filled the knowledge gap by investigating sediment samples collected from 13 lakes in Inner Mongolia, China. Their study showed that difference in the community structure of methanotrophs between the hypersaline sediment samples (salinity >0.69%) and the hyposaline samples (salinity <0.69%). Notably, salinity was significantly negatively correlated with methanotrophic diversity, indicating the higher of the salinity with the lower diversity of methanotrophic community, and the methanotroph network was more closely connected at low salinity.Functional diversity is a link between biodiversity and ecosystem functioning. In summary, although this research topic helps us to better understand the effects of particular environmental factor on microorganisms, few studies conduct long-term monitoring, which might lead to limited understanding of wetland microbes on temporal scales. What's more, studies are still needed on the coupling between the shifts of wetland microbial communities with the changes of ecosystem functions, understanding how the succession of microbial community could drive wetland ecosystem functions.

Description of the material HARC analyzed the response of ecological integrity of wetland functionality to energy exploration and production operations on the Upper Texas Gulf Coast. A decision support tool that will aid the oil and gas industry in minimizing loss of wetland function during energy exploration and production operations is the end result of this project. Application/Development We analyzed impacts of oil and gas exploration and production (e.g. transportation infrastructure, pipelines, and exploration and drilling site impacts) on wetlands, specifically Upper Texas Gulf Coast Wetlands; prioritizing these impacts specific to wetland function (such as coastal flooding mitigation or density of wintering waterfowl). The decision support tool contains land use/land cover classifications, wetland type and function, and prioritization of functions depending on wetland type and production stressors. Results, Observations, and Conclusions Our objectives are to prioritize wetland functions dependent on wetland type, wetland location and availability of function; cross-reference these functions with possible energy exploration and production operation impacts on the wetlands and then using this information in a decision support tool that will aid managers in determining best management practices in determining where to drill, technical alternatives to mitigate certain impacts, and choosing the options that will have most mitigation effect given limited financial resources. Significance of Subject Matter Wetlands provide many positive benefits to surrounding coastal ecosystems, both terrestrial and aquatic. These environmentally sensitive areas are often found in drilling and exploration territories in the Upper Texas Gulf Coast; providing options to decisions makers in terms of technical alternatives or BMPs will enable resources to be developed in a more environmentally sound manner.

Divergent response of blue carbon components to wetland types and hydrological effects in typical estuarine wetlands of Jiaozhou Bay, China

Summary1. Invasive zebra (Dreissena polymorpha) and quagga mussels (Dreissena bugensis) have become widespread throughout the Great Lakes basin. However, some types of Great Lakes coastal wetlands may be unsuitable for Dreissena invasion.2. To test this observation, artificial substrata were placed in wetlands (with emergent vegetation) and in adjacent open water (without emergent vegetation) habitats in two types of Great Lakes coastal ecosystems: drowned river mouth (DRM) and coastal fringing systems. Wetlands in DRM systems generally have deep organic sediment and limited water movement, whereas coastal fringing wetlands generally have low to moderate amounts of organic sediment and intense wind and wave action.3. We did not find a significant difference in Dreissena colonisation between wetlands and adjacent open water habitat in fringing systems. However, Dreissena colonisation was significantly lower in DRM wetlands than in the adjacent open water. We also found significantly lower survival in DRM wetlands than adjacent open water habitats, whereas survival did not differ significantly in coastal fringing wetlands and the adjacent open water.4. Our results suggest that vulnerability to Dreissena invasion varied among wetland types with DRM wetlands being less suitable than fringing wetlands. We suggest that colonisation and survival of Dreissena is lower in wetlands with deep organic sediment and less turbulent water.

A new approach for hydrologic performance standards in wetland mitigation

The purpose of this study is to investigate the land use intensity and land use change type at the basin scale in the middle and lower reaches of the Hanjiang River Basin (in Hubei Province, China) by combining the Landsat TM images in 1995 and 2000 with the land use database (in scale 1:10,000) and relative data. In this study, the basic data is acquired from the interpretation of remote sensing (RS) images. The intensity of land use and the rate of change in double-directions of land use dynamics are calculated with the support of software ARC/INFO. The intensity of land use is indicated by the intensity coefficient of land use, and the transition of land use types is quantified as the rate of change in double-direction of land use types and also expressed as the transition matrix of land use types. The results are expressed in space by Geographic Information System (GIS) software. Results of this study show that (1) the intensity of land use is high in the study region, the intensity coefficients of land use in 1995 and 2000 are 260.025 and 290.526, respectively, and the intensity of development and utilization of land is trend to increscent; and (2) the rate of land use change in double directions in the whole study region is 0.52 with great spatial variation and the differentiation of land use types. In the differentiation of land use types, the unutilized land (with the rate to 4.391) is developed fast, the grassland (with 2.836) and water area (with 1.664) are disturbed severely, and these changes will influence the eco-environment in the Hanjiang River Basin and all the Yangtze Basin. The rates of the farmland and the woodland are 0.424 and 0.344, respectively, meaning that the fundamentals of regional human-environmental system are relative stable. With this study, we can conclude that (1) the patterns of land use are increasingly changing in the study region, the environmental impacts are escalated on this stage, and the further outcomes are destined to change the stability of the regional human-environmental system; and (2) the most useful method to study the present land use and its change is through the use of the RS/GIS with the land use database (in scale 1:10,000).

White Oak Bayou watershed in the Arkansas River Valley is losing wetlands rapidly that could alter regional carbon cycles. Leaf decomposition of ash and oak were used to assess carbon cycling in five flat and five backwater wetlands within forested (54 %), urban (30 %), and pasture (7 %) catchment. Wetlands were dry in summer and wet the remaining year. Backwaters were expected to have faster decomposition rates from longer wet periods and more nutrients that would increase microbial and macroinvertebrate consumption. Backwaters held more water than flats and decomposition of both tree species was faster in backwaters (k:0.0032 ± 0.0007 day−1) compared to flats (k:0.0026 ± 0.0008 d−1, p = 0.018). Ash (0.0035 ± 0.0006 day−1) decomposed faster than oak (0.0023 ± 0.0005 day−1, p < 0.0001). Variation in ash decomposition rates was explained by inundation time and ammonium concentration. Variation in oak decomposition rates was explained by surrounding forest and nitrite + nitrate concentrations. Minor variations in hydrology affected decomposition rates of fast-breakdown leaf species, while differences in surrounding land use and nutrient concentrations affected rates of slow-breakdown species. Environmental factors altered by changing land use have important consequences for leaf decomposition. This study helps us to understand the influence that anthropogenic changes have on wetland function as urbanization continues to encroach upon wetlands in Arkansas.

Assessing urban wetlands dynamics in Wuhan and Nanchang, China

Spatial distribution data set of wetlands in Baiyangdian Basin

Wetlands play a critical role in modulating the global carbon cycle and significantly contribute to climate change mitigation. China’s wetlands are characterized by high diversity, a large total area, wide distribution, and strong regional variability. However, the carbon exchange dynamics across different wetland types and their controlling mechanisms remain poorly understood. Here, we quantified and compared CO2 fluxes (gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem productivity (NEP)) among China’s wetland types using eddy covariance measurements, analyzing spatial patterns and controlling mechanisms. Coastal wetlands exhibited higher annual GPP, ER, and NEP compared with inland wetlands. Among all wetland types, mangrove ecosystems had the highest carbon uptake capacity. The carbon conversion efficiency (CCE) of inland wetlands (0.89 ± 0.24) was higher than that of coastal wetlands (0.66 ± 0.12), suggesting that inland wetlands are less efficient at carbon fixation than coastal wetlands. However, due to their larger total area than that of coastal wetlands, inland wetlands in China likely constitute a greater overall CO2 sink. Spatially, GPP and NEP showed significant differences between the tropical/subtropical zones and the temperate/plateau zones (p &lt; 0.05), indicating the influence of climatic conditions. Climate factors influenced carbon fluxes primarily through their regulation of vegetation and soil features. The cascading relationships among climate, vegetation, and soil, as revealed by structural equation modeling (SEM), explained 61–71% of the spatial variation in GPP and ER, and 68% in NEP. Our findings provide valuable theoretical insights into the role of China’s wetland ecosystem in the global carbon cycle.

Exploring the dynamic relationship and coupling coordination between urban industrial co-agglomeration and intensive land use is vital to ensure high-quality urban development. Based on an industrial co-agglomeration model, a revised intensive land use model, and a coupling coordination model, this paper comprehensively measured the urban industrial co-agglomeration and intensive land use coupling coordination in eight cities in the Chengdu metropolitan area from 2004 to 2018. It was found that despite the structural adjustment of the secondary and tertiary industries during the study period, the industrial co-agglomeration in the Chengdu metropolitan area fluctuated, the intensive urban land use had spatial characteristics that were decreasing from the center to the periphery, and while the general coupling coordination level was increasing, the increase rate in each city was different. The coupling coordination between the urban industry co-agglomeration and the intensive land use was found to have “low-high-low” spatial characteristics from the southwest to the northeast of the Chengdu metropolitan area, which revealed the core position of Chengdu. Suggestions are provided to improve the industrial co-agglomeration and intensive urban land use coupling coordination.

Wetlands are increasingly considered as nature based solution as they provide valuable services and functions to the society and environment, such as water quality improvement and biodiversity support. However, while land use and climate change have been affecting the functions and service of these ecosystems, it has become important to study the large-scale behaviour of wetlands in the landscape. Consequently, previous studies have suggested studying wetlands within wetlandscapes, defined as catchments containing networks of several wetlands, in order to understand large-scale functions of wetlands and their response to land-use and climate changes. This emphasizes the ecohydrological interactions of wetlands rather than having focus of individual wetlands. As the concept of wetlandscape is new, we have been working on systematically quantifying its governing properties in two different studies.In the first study, we systematically quantified ecohydrological properties of individual wetlands (e.g. wetland area, wetland catchment area and wetland type) in multiple wetlandscapes that may impact biodiversity and modulate nutrient flows as well as characteristics of the whole wetlandscape in terms of their large-scale processes and functions. Results from this work showed that large wetlandscapes generally contained features to support different ecosystem services compare to smaller wetlandscapes. More specifically, results indicated that small wetlandscapes have a poor ability to route water through their wetlands which was in contrast to large wetlandscapes. This implies that large wetlandscapes have a higher potential for large-scale retention of nutrients and contaminants.The second study consisted of investigating spatial and temporal wetland storage dynamics for multiple wetlands in the landscape in order to address considerable knowledge gaps regarding hydrological functions of wetlands and wetlandscapes. More specifically, we use high-resolution monitoring of wetland water levels to assess storage patterns and inundation conditions. A key finding of this work is that the position of wetlands is important for storage dynamics and flood buffering. Notably we find that wetlands located in headwater regions showed larger water level variability during the growing season (spring, summer and autumn) and hence were more active in temporal water storage than wetlands located downstream in the wetlandscape. This variability in water level for headwater wetlands was also associated with complex and patchy inundation conditions, while downstream wetlands essentially showed dry-state conditions during the entire summer.Results from both studies show that ecohydrological properties of wetlandscapes can have implications for ecosystem service delivery (e.g., biodiversity support and water quality) at regional level as well as for using wetlands as nature-based solution. Present results also support the importance of wetlandscape studies and the priority of a wetlandscape focus in future management programs to various regional environmental challenges.

Attempts to replace wetlands or define hydrologic equivalence for wetland mitigation must be based on an understanding of the complexity of wetland hydrology and of the relationship of individual wetlands to the landscape. Because mitigation has the potential to re‐configure the kinds and spatial distribution of wetland ecosystems over large geographic areas, I advocate a landscape approach to defining hydrologic equivalence. This approach does not depend on specification of hydroperiod or other hydrologic variables for individual wetlands. It relies instead on knowledge of landscape properties that control wetland hydrology and water chemistry. In this paper I develop the conceptual framework for defining hydrologic equivalence for wetland mitigation viewed as a de facto landscape management policy with the potential to reduce the diversity of wetland types within regions. I review modern hydrogeological understanding of where wetlands form in the landscape and identify key hydrologic variables responsible for the formation of specific wetland types. I also review existing evaluations of mitigation projects in several states. On the basis of these reviews, I argue that, in setting regulatory criteria for judging hydrologic equivalence, the scale must be enlarged from the individual wetland project to include the broader landscape. Only this broader view can provide the context within which decision‐makers can evaluate the potential cumulative effects of individual mitigation decisions on broad‐scale patterns of wetland diversity. The landscape approach to defining hydrologic equivalence that I advocate is based on the concept of templates for wetland development. These templates are the diversity of settings created in specific landscapes by the complex interactions of hydrogeologic factors and climate. These interactions, in turn, control key hydrologic variables and hydrologically influenced chemical variables that cause specific wetland types to form. Hydrologic equivalence then can be defined at the scale of landscapes in terms of the kinds, numbers, relative abundances, and spatial distribution of wetland templates. The approach can be implemented through the identification of landscape goals and profiles based on knowledge of these templates. The profiles would catalog and map the diversity of wetland templates and the diversity of existing wetland types within a given landscape, focusing the attention of decision‐makers on broad‐scale patterns of loss in wetland types and providing a context within which individual mitigation projects could be evaluated. Landscape goals for maintaining a diversity of wetland templates are suggested.