Wetland Landscape Research Articles

基于加权Ripley's K-function的多尺度景观格局分析——以江苏盐城滨海湿地为例

PDF HTML阅读 XML下载 导出引用 引用提醒 基于加权Ripley's K-function的多尺度景观格局分析——以江苏盐城滨海湿地为例 DOI: 10.5846/stxb201307191915 作者: 作者单位: 南京大学地理与海洋科学学院,南京大学地理与海洋科学学院,南京大学 作者简介: 通讯作者: 中图分类号: 基金项目: 科技部重点支撑项目(2013CB956503);国家海洋局2010年海洋公益性行业科研专项(201005006)资助 Multi-scale analysis of landscape characteristics in coastal wetlands in Yancheng, Jiangsu, based on the weighted Ripley's K-function method Author: Affiliation: The School of Geographic and Oceanographic Sciences,Nanjing University,The School of Geographic and Oceanographic Sciences,Nanjing University,The School of Geographic and Oceanographic Sciences,Nanjing University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以1987,1992,1997,2002,2007年的遥感影像为例,首次尝试使用加权Ripley's K-function的多尺度格局分析方法,计算了20年来景观异质性在江苏盐城滨海湿地的时间变化和空间分布趋势。通过对研究区的样带划分以及景观类型的点状化处理,建立滨海湿地样带图层和1987-2007年间各类型景观的点格局数据库,从而分析滨海湿地不同类型景观的空间聚集特征变化。基于加权Ripley's K-function的计算表明,在各级空间尺度和时间变化上,各类型湿地的斑块都呈现出空间聚集分布状态,且1987年以来,不同湿地类型的聚集空间特征尺度和空间分布强度均出现了大幅的增减变化,除互花米草滩之外的自然湿地的聚集空间特征尺度和强度都有明显下降甚至少到无法被检测到,而人工湿地却呈现聚集特征尺度和强度的双增长,且该聚集程度有逐渐增强的趋势。分析表明,既考虑样点的空间位置信息又考虑样点分布范围的加权Ripley's K-function方法能很好地表征湿地景观在多尺度上的变异,且与传统空间景观指数等分析方法的结论在一定程度上保持一致。 Abstract:Based on remote sensing images from 1987, 1992, 1997, 2002, and 2007, the present study used the weighted Ripley's K-function multi-scale analysis method to calculate temporal changes and trends in the spatial distribution (i.e., heterogeneity) of coastal wetland landscape patterns over 20 years in Yancheng, Jiangsu. To analyze changes in the spatial clustering characteristics of different wetland landscape types, we divided the area into small belt transects and created a point pattern database for changing wetland landscapes from 1987 to 2007. The results obtained based on weighted Ripley's K-function analyses demonstrate that, over different spatial and temporal scales, all wetland landscapes presented an aggregated distribution. Moreover, for different wetland types, most patch radius and crowding indices indicate an obvious increase or decrease since 1987. Except for Spartina alterniflora, the aggregated patch radius and crowding of all other natural wetlands dropped sharply or even became undetectable, whereas both the aggregated patch radius and crowding indices in the constructed wetland increased rapidly, at higher rates over time. Our analyses revealed that the weighted Ripley's K-function method, which considers both the location and attributes of point samples, can clearly reveal spatial variations of landscapes at multiple scales. These novel results also agree with those obtained using other conventional analysis methods, such as landscape metrics. Additionally, in future, a deeper analysis of the mechanisms controlling such landscapes at various spatial scales will be conducted to provide quantitative implications for wetland management planning. Specifically, after the wetland polygon data were processed in ArcGIS, we transferred and calculated the spatial indices (patch radius and crowding) in the Matlab R2011a. It was found that, to some extent, the weighted Ripley's K-function could mitigate the occurrence of two false results that were caused by the traditional Ripley's K-function. First, in conventional analysis, large wetland areas are more likely to produce limited numbers of point samples when they are exported directly into a dimensionless point from a polygon; this has resulted in the spatial distribution of some wetlands being interpreted as random or dispersed, even when they exhibit obvious aggregations in the GIS layers. Conversely, the weighted Ripley's K-function takes the dimensions of such points into consideration; accordingly, it is able to reflect changes in the area of study objects in continuous space, thus allowing characterization of changes in the spatial clustering of wetlands at multiple scales. In this study, the extraction and spatial distribution of wetlands distributed in a large area proved the validity of the improved method. Second, traditional methods have tended to produce "false" conclusions or overestimate aggregation when applied to the most seriously fragmented wetlands, which typically generate numerous point samples. In contrast, sample areas in the improved method are weighted, allowing spatial distributions to be represented more accurately. For example, in the present study, we were able to avoid the "over-aggregation" of the spatial distribution of Aeluropus littoralis that may have been produced by traditional methods. Thus, we were able to reveal actual changes in the distribution of Aeluropus littoralis, demonstrating that it shrunk gradually (and almost disappeared) at various scales owing to crowding. 参考文献 相似文献 引证文献

基于围垦特征的海滨地区景观格局变化研究——以盐城海岸为例

基于围垦特征的海滨地区景观格局变化研究——以盐城海岸为例

Impacts of the creation, expansion and management of English wetlands on mosquito presence and abundance - developing strategies for future disease mitigation.

The incidence of mosquito-borne diseases is increasing in Europe, partly due to the incursion of a number of invasive species known to be vectors of dengue and chikungunya viruses, but also due to the involvement of native species in the transmission of West Nile virus and malaria. For some of these pathogens, there is a risk of the re-emergence of vector-borne diseases that were once widespread in Europe, but declined partly due to large-scale land-drainage projects. Some mosquito species exploit container habitats as breeding sites in urban areas; an adaptation to human-made micro-habitats resulting from increased urbanisation. However, many species thrive in natural wetland ecosystems. Owing to the impacts of climate change there is an urgent need for environmental adaptation, such as the creation of new wetlands to mitigate coastal and inland flooding. In some cases, these initiatives can be coupled with environmental change strategies to protect a range of endangered flora and fauna species by enhancing and extending wetland landscapes, which may by driven by European legislation, particularly in urban areas. This paper reviews field studies conducted in England to assess the impact of newly created wetlands on mosquito colonisation in a) coastal, b) urban and c) arable reversion habitats. It also considers the impact of wetland management on mosquito populations and explores the implications of various water and vegetation management options on the range of British mosquito species. Understanding the impact of wetland creation and management strategies on mosquito prevalence and the potential risk of increasing the levels of nuisance or disease vector species will be crucial in informing health and well-being risk assessments, guiding targeted control, and anticipating the social effects of extreme weather and climate change. Although new wetlands will certainly extend aquatic habitats for mosquitoes, not all species will become a major nuisance or a vector concern as a result. Understanding how the design and management of wetlands might exacerbate mosquito densities is crucial if we are to manage nuisance mosquitoes and control vector species in the event of a disease outbreak. This entomological evidence-base will ensure that control strategies achieve optimal efficacy at minimal cost.

Assessing Landscape Ecological Risk for a World Natural Heritage Site: a Case Study of Bayanbulak in China

Wetland protection, floral and faunal resource management, and habitat migration are all concerns for the ecological risk of wetland landscapes. Indices of landscape-scale ecological risks have the potential to influence changes in landscape patterns, the conditions of endangered plants and animals, and influences from nature and humans. Semi-variation function and gravity center models were used to quantify risk area changes. The changes of landscape ecological risk were analyzed for Bayanbulak Wetland from 2000 to 2010. In addition to landscape and species distribution data, GIS technology and remote sensing were used in this study. Results show that landscape structure changed over the 10-year period, with high-cover grassland area decreasing the most. Landscape pattern index types also changed for the study area. The number of landscapetype patches to low-cover grassland decreased, the landscape fragmentation index of dry land and high-cover grassland was reduced, and the interference degree of middle-cover grassland increased over the study period. The index of landscape ecological risk decreased from 2000 to 2010, with the spatial structure changing from a single center concentration to a multi-center distribution. All varying ecological risk regions of gravity centers moved from the northeast to the southwest. The gravity migration of the Level 2 region moved the furthest. Additionally, evidence suggests that various threatening factors reduce the ecological function and systems of wetlands. These include climate change, biological invasion, human activities, and water pollution. This paper assesses the heritage site landscape ecological risk and calculates the gravity center change of the region, which can be formulated to enrich and develop the research of small- and medium-sized wetlands in cold, semi-arid climates.

Assessment of wetland fragmentation in the middle reaches of the Heihe River by the type change tracker model

The quantitative research of wetland landscape fragmentation in the middle reaches of the Heihe River is important for the wetland and oasis sustainable development in the Hexi Corridor. Based on the data of remote sensing and GIS, we constructed the type change tracker model with sliding window technique and spatially morphological rule. The suitable scale and optimum scale of the fragmentation model of wetland landscape in the middle reaches of the Heihe River were determined by the area frequency statistics method, Chi-square distribution normalized scale variance, fractal dimension and diversity index. By integrating type change tracker model and the optimum scale with GIS spatial analysis, the spatial distribution characteristics of wetland landscape fragmentation in different periods and the related spatial-temporal change process were clarified. The results showed that (1) the type change tracker model, which analyzes the spatial pattern of wetland fragmentation on the pixel level, is better than the traditional wetland fragmentation analysis on the landscape and patch levels; (2) The suitable scale for the wetland fragmentation ranged from 150 m×150 m to 450 m×450 m and the optimum scale was 250 m×250 m in the middle reaches of the Heihe River; and (3) In the past 35 years, the total wetland area decreased by 23.2% and the fragmentation of wetland markedly increased in the middle reaches of the Heihe River. The areas of core wetlands reduced by 12.8% and the areas of perforated, edge and patch wetlands increased by 0.8%, 3.1% and 8.9%, respectively. The process of wetland fragmentation in the research region showed the order of core wetland, perforated or edge wetland, patch wetland or non-wetland. The results of this study would provide a reference for the protection, utilization and restoration of limited wetland resources and for the sustainable development of the regional eco-environment in the Heihe River Basin.

Carbon sequestration in different wetland plant communities in the Big Cypress Swamp region of southwest Florida

Wetlands offer many ecosystem services, including the long-term sequestering of carbon (C) in soil. Here we present a study of C sequestration rates in a relatively undisturbed wetland landscape of southwest Florida. Accordingly, carbon sequestration was determined in four wetland plant communities and an adjacent hydric pine flatwood community that represent a gradient of inundation extent. Going from the wettest to the driest, communities were designated as: deep slough, bald cypress (Taxodium distichum), wet prairie and pond cypress (Taxodium distichum var. imbricarium). An adjacent hydric pine flatwood community was also included in the study as a reference upland site. Three soil cores were collected from each of these communities and were analyzed for total C content. Core samples were also analyzed for 137Cs and 210Pb activity to estimate accretion rates. C sequestration rates (g-C m−2 yr−1) were the highest in the deep slough (98 ± 9) and bald cypress (98 ± 5) followed by the pond cypress (64 ± 7), wet prairie (39 ± 1) and pine flatwood (22 ± 5). These results suggest that impediment of decomposition by anaerobic conditions caused by prolonged wet cycles, may not account for all the variability in C sequestration rates observed in this subtropical setting. Instead, this variability could also be attributed to other factors like the quantity and chemical composition of the organic material reaching the soil. When methane emissions are taken into account, cypress-dominated (bald and pond cypress) and the deep slough communities act as net carbon sinks.

Seasonality of the Urban Heat Island Effect in Madison, Wisconsin

AbstractSpatial and temporal variation in the urban heat island (UHI) effect from March 2012 through October 2013 was characterized using continuous temperature measurements from an array of up to 151 fixed sensors in and around Madison, Wisconsin, an urban area of population 407 000 surrounded by lakes and a rural landscape of agriculture, forests, wetlands, and grasslands. Spatially, the density of the built environment was the primary driver of temperature patterns, with local modifying effects of lake proximity and topographic relief. Temporally, wind speed, cloud cover, relative humidity, soil moisture, and snow all influenced UHI intensity, although the magnitude and significance of their effects varied by season and time of day. Seasonally, UHI intensities tended to be higher during the warmer summer months and lower during the colder months. Seasonal trends in monthly average wind speed and cloud cover tracked annual trends in UHI intensity, with clearer, calmer conditions that are conducive to the stronger UHIs being more common during the summer. However, clear, calm summer nights still had higher UHI intensities than clear, calm winter nights, indicating that some background factor, such as vegetation, shifted baseline UHI intensities throughout the year. The authors propose that regional vegetation and snow-cover conditions set seasonal baselines for UHI intensity and that factors like wind and clouds modified daily UHI intensity around that baseline.

Research on Ecological Restoration of Wetland Landscape in Reclamation Land Environment

This paper first analyses the advantage of coastal reclamation and its impact on the environment, finally proposed reclamation development mode of benign development which can provide the reasonable reference for the further research of reclamation. The article puts forward that exploitation should follow the principles of both protection and development. Through the full investigation of biological resources, wetland environmental carrying capacity of natural attributes, and huge demand and utilization situation of wetland and other social attributes of the reclamation, to analyze of wetland ecosystem service function, so as to accurately judge the reclamation suitability. Therefore, the reclamation is not only to meet the requirements of economic development, more attention should be paid to the protection of coastal wetland region.

Advances in research on wetlands of the Tibetan Plateau

About 80% of the global wetlands are being degraded or lost, and wetland ecosystem has become one of the most endangered ecosystems in the world. As a sensitive area to global change and protective barrier for the security of ecosystems in Asia, the Tibetan Plateau has a wetland area of about 13.19×104km2, which is an important part of the wetland ecosystem in China. With increasingly more remote sensing technology applied, Tibetan Plateau wetland research entered a new period of rapid development. This article summarizes remote sensing research literature of the Tibetan Plateau from 1992 to 2013, aiming to provide a reference for Tibetan Plateau wetland research in the future. The following aspects of research are reviewed: monitoring methods, research topics, and existing problems. The analysis shows that:(1) In the past 30 years, the research on Tibetan Plateau wetlands was focused on dynamic change monitoring of wetland area, landscape patterns, and ecological environment based on remote sensing technology. Attention was paid to building models to analyze the trend of change of the wetlands in three dimensions, taking an ecological system perspective.(2) Such research concludes that: 1) From 1990 to 2006, the wetland area generally decrease at an annual rate of 0.13%, and the landscape diversity decline at an annual rate of 0.17%. 2) In contrast, from 2003 to 2009, the depth of the lakes on the Tibetan Plateau had increased at an annual rate of 0.20 m; from 1970 to 2011, water storage of the lakes increased at an annual rate of 2.2 km3; from 1976 to 2009, lake area of the interior drainage area of the plateau increased at an annual rate of 0.83%. 3) From 1965 to 2002, change of the Tibetan Plateau wetlands was controlled by the climate. Wetland degradation and change around areas of human activity are a result of increased human activities. The existing problems of remote sensing research of the Tibetan Plateau wetlands are that: accuracy of digital analysis of remote sensing images and cloud removal need to be improved; a comprehensive perspective is needed for the research of the Tibetan Plateau wetland system. Based on the review, this article identifies the following key areas of future research:(1) Taking full advantage of remote sensing monitoring of wetlands characterized by multidate, multispectral, real- time, dynamic, and repeated coverage. Strengthening comprehensive research and remote sensing research of areas lacking conventional data;(2) Establishing a regional specific wetland remote sensing classification system that is technically operable, and conducting basic research on improving the Tibetan Plateau wetland remote sensing classification system and applications;(3) Focusing more on quantitative study on ecosystem functions of wetlands and decision support system for wetland ecosystem management;(4) Discussing responses and adaptation mechanisms of the Tibetan Plateau wetland ecosystem under the background of global change, especially the differences in responses and adaptation mechanisms under the impacts of different temporal and spatial scales. Coupling the models of hydrology, ecology, meteorology, soil, and environment to predict the trend of wetland degradation and revealing regional differences of response between different areas of the plateau in the face of global change;(5) Advancing remote sensing methods for Tibetan Plateau wetland research, strengthening the integration of RS, GIS, and GPS methods, and promoting the construction of a Tibetan Plateau wetland information platform.

The avifauna of Western Siberia taiga zone wetlands (Tomsk oblast)

Wetland landscapes are widely spread in the Western Siberia taiga zone. Wetlands serve climatic and hydrological global functions, as well as many others. They also form the habitats for many species of animals. Dynamic development of Western Siberia wetlands and human influence on them demand the investigation of the wetlands’ bird population. This study aims to determine the wetland avifauna species diversity and to evaluate bird abundance and current state of rare species listed in Red Data Book. The study was carried out in the southern and middle taiga zones and in subtaiga. The study is based on the surveys that authors made in 2007–2013 in Tomsk oblast and also on the data gathered by the scientists in the Western Siberia forest zone. Counts were made according to Y.S. Ravkin’s methods. Counts of bird density are based on mean discovery distance on the routes. A total of 600 km walking and 150 water counting routes (by boats) were covered. It was found that 225 bird species inhabit Western Siberia wetland landscapes (196 – Tomsk oblast). Near 80% of birds inhabiting wetlands nest here.

Origins of functional connectivity in a human-modified wetland landscape

Spatial heterogeneity in habitat conditions within a landscape should influence degree of movement of species between natural and artificial environments. For wetland landscapes, this functional connectivity was predicted to emerge from the influence of spatiotemporal patterns of depth on permeability of habitat edges and distance and directedness of cross-habitat dispersal. We quantified how connectivity between canals and marshes of the Florida Everglades varies with species and landscape patterns bordering canals by using radio telemetry to measure movement of a native (Florida largemouth bass, Micropterus salmoides floridanus) and a nonnative species (Mayan cichlid, Cichlasoma urophthalmus) common to canals. Both species moved similar distances inside canal networks, but Mayan cichlids dispersed outside of canals more frequently, at shallower conditions, and over greater distances than Florida largemouth bass. As topographic relief increased in marshes bordering canals, dispersal between these habitats decreased in distance and became more directed, with Florida largemouth bass sensitive to depth variability at a smaller spatial scale than Mayan cichlids. The way fish traits interact with submerged landscape structure to influence connectivity can serve as a basis for predicting potential impacts of artificial habitats that arise from dispersal outside their borders.

Caville Manor and the Enterprise of the Twelfth-Century Bishops of Durham

Historical notes discovered on a fifteenth-century Yorkshire rental allow us to reconstruct the astonishing level of investment made by Bishop Hugh du Puiset of Durham (1153–95) in organising the drainage of the carrs in southern Howdenshire, and the way the process was managed. These notes and other evidence reveal that the bishop financed the cutting of at least three major drains in the 1160s or 1170s, and then made preferential grants and sales of parcels of land to clerics and laymen, who undertook the completion of the scheme. In doing this he transformed the wetland landscape of the north bank of the Ouse, built up his manor of Howden’s rent roll by fee-farms, and created a new group of minor gentry within his lordship. The notes also have something to say about the maintenance of episcopal rentals in Howden in the twelfth century, parallel to the famous Boldon Book which Bishop Hugh compiled for his diocese.

Analysis of landscape fragmentation processes and driving forces in wetlands in arid areas: A case study of the middle reaches of the Heihe River, China

Landscape fragmentation in wetlands usually implies degradation of its ecological functions. Landscape fragmentation divides wetlands into isolated islands, which disturbs the energy flow and nutrient cycling within the wetland. Research into the development and causes of landscape fragmentation in wetlands is urgently needed for effective monitoring and protection of wetlands. We use a combination of techniques including remote sensing, a landscape index model, and redundancy analysis to analyze landscape fragmentation and its driving forces in the middle reaches of the Heihe River from both temporal and spatial perspectives. A new mathematic morphological method that enhances the credibility of landscape fragmentation analysis without changing the original pixel size of the interpreted data is proposed for the calculation of landscape indices. The combination of this new mathematic morphological method and traditional landscape pattern indices enhances the evaluation strategy for landscape fragmentation. Our results demonstrate that the fragmentation processes that affect the wetland landscape of the study area are primarily represented as the shrinking of core wetland area and decrease in mean size of wetland patches. Our results also show an increase in the fragmentation index (FS) of the landscape in recent decades. The impacts of natural factors on wetland landscape fragmentation processes are typically reflected in changes in climate and hydrology. In the study area, temperature, which is more important than precipitation in driving wetland landscape fragmentation processes, cannot be omitted. In addition, our analysis proves that unnecessary human activity is a major threat for sustainable development and maintenance of wetlands.

Architecture Planning of Wetland Landscape

Wetland Park to establish a reasonable use of wetland resources, to meet the needs of visitors to leisure and entertainment life, while being overexploited to the wetland ecosystem restoration and the chance to rest, to protect the wetland environment provides an effective use patterns. Papers presented wetland landscape planning and construction methods and content, providing a distinctive local urban wetland park.

Dynamics of landscape patterns in an inland river delta of Central Asia based on a cellular automata-Markov model

The analysis of landscape pattern changes is of significant importance for understanding spatial ecological dynamics and maintaining sustainable development, especially in wetland ecosystems, which are experiencing indirect human disturbances in arid Central Asia. This study attempted to examine the temporal and spatial dynamics of landscape patterns and to simulate their trends in the Ili River delta of Kazakhstan through quantitative analysis and a cellular automata (CA)-Markov model. This study also sought to examine the effectiveness of using the CA-Markov model for investigating the dynamics of the wetland landscape pattern. The total wetland area, including the river, lake, marsh, and floodplain areas, and the area of sandy land have remained steady, while that of desert grassland has decreased slightly, and shrublands have increased slightly from approximately 1978 to 2007. However, the wetland and shrubland areas exhibited a trend of increasing by 18.6 and 10.3 %, respectively, from 1990 to 2007, while the desert grassland and sandy land areas presented the opposite trend, decreasing by 30.3 and 24.3 %, respectively. The landscape patterns predicted for the year 2020 using probabilistic transfer matrixes for 1990–2007 (Scenario A) and 1990–1998 (Scenario B), respectively, indicated that the predicted landscape for 2020 tends to improve based on Scenario A, but tends to degrade based on Scenario B. However, the overall Kappa coefficient of 0.754 for the 2020 predicted landscapes based on Scenarios A and B indicates that the differences in the predicted landscapes are not distinct. This research indicates that the applied CA-Markov model is effective for the simulation and prediction of spatial patterns in natural or less disturbed landscapes and is valuable for developing land management strategies and reasonably exploiting the wetland resources of the Ili River delta.

Spatio–Temporal Dynamics of Wetland Landscape Patterns Based on Remote Sensing in Yellow River Delta, China

The wetland landscape patterns of the Yellow River Delta have undergone an extremely significant change due to rapid economic development since 2000. The aim of this paper is to quantitatively analyze spatial and temporal changes of these wetlands in the recent decade. Three sets of wetland maps were acquired using object–oriented classification method based on remotely sensed imageries in 2000, 2005 and 2010. Then landscape indices from class and landscape level using FRAGSTATS 3.3 software were used to quantify the spatial and temporal dynamics of wetlands. The results showed that wetlands coverage decreased by approximately 2.27%. Natural wetlands decreased while constructed wetlands increased, especially prawn pools, which increased by 268.33%. Wetland landscape patches gradually became more complex and decentralized. Wetlands distribution analysis indicated that wetlands were mainly located in the area 45 km from the coastline. The study indicated a relatively high diversity at the estuary of the river and the north of the study area. However, wetlands were highly fragmented in the south of the study area and urban area. Dynamic of wetlands was mainly caused by human–induced factors, especially GDP and urban built–up area.

Change of Landscape Pattern in Yalu-River Estuary Wetland

Three phases of remote sensing image data of Yalu-river estuary wetland taken respectively in 1983、1995 and 2007 were interpreted though ARCGIS software and the change of landscape pattern was analyzed with three categories of indices from the landscape pattern and landscape levels by means of using FRAGSTATS software. Results show that the 1983-2007, the research area of wetland landscape changes drastically, wetland landscape made of natural wetlands to artificial wetland, wetland fragmentation degree deepening, artificial wetland distribution area expanded. During the study period, the influence of human activities on the wetland increase and increase in area of sea aquaculture is the main cause of the yalu estuary wetland area reducing, is also one of the main reasons for the region function of wetland degradation.

Study on Spatio-Temporal Changes of Wetland Landscape Patterns in the Modern Yellow River Delta

The wetland distribution in the modern Yellow River Delta is extracted by using a combination method of supervised classification based on the Landsat TM images in 1991, 2001 and 2011. The changes of wetland were analyzed from landscape index in the paper. The result shows that the area of natural wetland degrades, while the area of artificial wetland increases from 1991 to 2011. The transfer trajectory of spatial centroids of the wetland shows that it shifts towards southeast. Man-made driving forces are the main factors that cause natural wetlands degrades.

Сучасний стан перезволожених ландшафтних систем Львівської обл.

Reviewed the current state of wetland landscape systems (PLC) Lviv region. Highlighted areas PLC of good ecological status, with a satisfactory ecological condition and unsatisfactory environmental conditions. Key words: overmoistened landscape systems (OLS)peat, peat, drainage improvement, environmental stabilizing factors, environmental destabilizing factors.

Ebullitive methane emissions from oxygenated wetland streams.

Stream and river carbon dioxide emissions are an important component of the global carbon cycle. Methane emissions from streams could also contribute to regional or global greenhouse gas cycling, but there are relatively few data regarding stream and river methane emissions. Furthermore, the available data do not typically include the ebullitive (bubble-mediated) pathway, instead focusing on emission of dissolved methane by diffusion or convection. Here, we show the importance of ebullitive methane emissions from small streams in the regional greenhouse gas balance of a lake and wetland-dominated landscape in temperate North America and identify the origin of the methane emitted from these well-oxygenated streams. Stream methane flux densities from this landscape tended to exceed those of nearby wetland diffusive fluxes as well as average global wetland ebullitive fluxes. Total stream ebullitive methane flux at the regional scale (103MgCyr(-1) ; over 6400km(2) ) was of the same magnitude as diffusive methane flux previously documented at the same scale. Organic-rich stream sediments had the highest rates of bubble release and higher enrichment of methane in bubbles, but glacial sand sediments also exhibited high bubble emissions relative to other studied environments. Our results from a database of groundwater chemistry support the hypothesis that methane in bubbles is produced in anoxic near-stream sediment porewaters, and not in deeper, oxygenated groundwaters. Methane interacts with other key elemental cycles such as nitrogen, oxygen, and sulfur, which has implications for ecosystem changes such as drought and increased nutrient loading. Our results support the contention that streams, particularly those draining wetland landscapes of the northern hemisphere, are an important component of the global methane cycle.