Influence of Different Plant Species on Methane Emissions from Soil in a Restored Swiss Wetland

Plants are a major factor influencing methane emissions from wetlands, along with environmental parameters such as water table, temperature, pH, nutrients and soil carbon substrate. We conducted a field experiment to study how different plant species influence methane emissions from a wetland in Switzerland. The top 0.5 m of soil at this site had been removed five years earlier, leaving a substrate with very low methanogenic activity. We found a sixfold difference among plant species in their effect on methane emission rates: Molinia caerulea and Lysimachia vulgaris caused low emission rates, whereas Senecio paludosus, Carex flava, Juncus effusus and Typha latifolia caused relatively high rates. Centaurea jacea, Iris sibirica, and Carex davalliana caused intermediate rates. However, we found no effect of either plant biomass or plant functional groups – based on life form or productivity of the habitat – upon methane emission. Emissions were much lower than those usually reported in temperate wetlands, which we attribute to reduced concentrations of labile carbon following topsoil removal. Thus, unlike most wetland sites, methane production in this site was probably fuelled chiefly by root exudation from living plants and from root decay. We conclude that in most wetlands, where concentrations of labile carbon are much higher, these sources account for only a small proportion of the methane emitted. Our study confirms that plant species composition does influence methane emission from wetlands, and should be considered when developing measures to mitigate the greenhouse gas emissions

Vegetation Type Dominates the Spatial Variability in CH<inf>4</inf> Emissions Across Multiple Arctic Tundra Landscapes

Methane (CH4) emissions from Arctic tundra are an important feedback to global climate. Currently, modelling and predicting CH4 fluxes at broader scales are limited by the challenge of upscaling plot-scale measurements in spatially heterogeneous landscapes, and by uncertainties regarding key controls of CH4 emissions. In this study, CH4 and CO2 fluxes were measured together with a range of environmental variables and detailed vegetation analysis at four sites spanning 300 km latitude from Barrow to Ivotuk (Alaska). We used multiple regression modelling to identify drivers of CH4 flux, and to examine relationships between gross primary productivity (GPP), dissolved organic carbon (DOC) and CH4 fluxes. We found that a highly simplified vegetation classification consisting of just three vegetation types (wet sedge, tussock sedge and other) explained 54% of the variation in CH4 fluxes across the entire transect, performing almost as well as a more complex model including water table, sedge height and soil moisture (explaining 58% of the variation in CH4 fluxes). Substantial CH4 emissions were recorded from tussock sedges in locations even when the water table was lower than 40 cm below the surface, demonstrating the importance of plant-mediated transport. We also found no relationship between instantaneous GPP and CH4 fluxes, suggesting that models should be cautious in assuming a direct relationship between primary production and CH4 emissions. Our findings demonstrate the importance of vegetation as an integrator of processes controlling CH4 emissions in Arctic ecosystems, and provide a simplified framework for upscaling plot scale CH4 flux measurements from Arctic ecosystems

Methane and Carbon Dioxide Fluxes from a European Alpine Fen Over the Snow-Free Period

ISSN:0277-5212ISSN:1943-624

Successes and limitations of phytotechnologies at field scale : Outcomes, assessment and outlook from COST Action 859

Purpose : Many agricultural and brownfield soils are polluted and more have become marginalised due to the introduction of new, risk-based legislation. The European Environment Agency estimates that there are at least 250,000 polluted sites in the member states that require urgent remedial action. There is also significant volumes of wastewaters and dredged polluted sediments. Phytotechnologies potentially offer a cost-effective in situ alternative to conventional technologies for remediation of low to medium-contaminated matrices, e.g. soils, sediments, tailings, solid wastes and waters. For further development, social and commercial acceptance, there is a clear requirement for up-to-date information on successes and failures of these technologies based on evidence from the field. This review reports the outcomes from several integrated experimental attempts to address this at both field and market level in the 29 countries participating in COST Action 859. Results and discussion : This review offers insight into the deployment of promising and emergent in situ phytotechnologies, for sustainable remediation and management of contaminated soils and water, that integrative research findings produced between 2004 and 2009 by members of COST Action 859. Many phytotechnologies are at the demonstration level, but relatively few have been applied in practice on large sites. They are not capable of solving all problems. Those options that may prove successful at market level are (a) phytoextraction of metals, As and Se from marginally contaminated agricultural soils, (b) phytoexclusion and phytostabilisation of metal- and As-contaminated soils, (c) rhizodegradation of organic pollutants and (d) rhizofiltration/rhizodegradation and phytodegradation of organics in constructed wetlands. Each incidence of pollution in an environmental compartment is different and successful sustainable management requires the careful integration of all relevant factors, within the limits set by policy, social acceptance and available finances. Many plant stress factors that are not evident in short-term laboratory experiments can limit the effective deployment of phytotechnologies at field level. The current lack of knowledge on physicochemical and biological mechanisms that underpin phytoremediation, the transfer of contaminants to bioavailable fractions within the matrices, the long-term sustainability and decision support mechanisms are highlighted to identify future R&D priorities that will enable potential end-users to identify particular technologies to meet both statutory and financial requirements. Conclusions : Multidisciplinary research teams and a meaningful partnership between stakeholders are primary requirements that determine long-term ecological, ecotoxicological, social and financial sustainability of phytotechnologies and to demonstrate their efficiency for the solution of large-scale pollution problems. The gap between research and development for the use of phytoremediation options at field level is partly due to a lack of awareness by regulators and problem owners, a lack of expertise and knowledge by service providers and contractors, uncertainties in long-term effectiveness and difficulties in the transfer of particular metabolic pathways to productive and widely available plants. Networks such as COST Action 859 are highly relevant to the integration of research activity, maintenance of projects that demonstrate phytoremediation at a practical field scale and to inform potential end-users on the most suitable techniques. Biomass for energy and other financial returns, biodiversity and ecological consequences, genetic isolation and transfer of plant traits, management of plant-microorganism consortia in terrestrial systems and constructed wetlands, carbon sequestration and soil and water multi-functionality are identified as key areas that need to be incorporated into existing phytotechnologies