Land–atmosphere exchange of carbon dioxide (CO2) in peatlands exhibits marked seasonal and inter-annual variability, which subsequently affects the carbon (C) sink strength of catchments across multiple temporal scales. Long-term studies are needed to fully capture the natural variability and therefore identify the key hydrometeorological drivers in the net ecosystem exchange (NEE) of CO2. Since 2002, NEE has been measured continuously by eddy-covariance at Auchencorth Moss, a temperate lowland peatland in central Scotland. Hence this is one of the longest peatland NEE studies to date. For 11 years, the site was a consistent, yet variable, atmospheric CO2 sink ranging from −5.2 to −135.9 g CO2-C m−2 yr−1 (mean of −64.1 ± 33.6 g CO2-C m−2 yr−1). Inter-annual variability in NEE was positively correlated to the length of the growing season. Mean winter air temperature explained 87% of the inter-annual variability in the sink strength of the following summer, indicating an effect of winter climate on local phenology. Ecosystem respiration (Reco) was enhanced by drought, which also depressed gross primary productivity (GPP). The CO2 uptake rate during the growing season was comparable to three other sites with long-term NEE records; however, the emission rate during the dormant season was significantly higher. To summarise, the NEE of the peatland studied is modulated by two dominant factors: - phenology of the plant community, which is driven by winter air temperature and impacts photosynthetic potential and net CO2 uptake during the growing season (colder winters are linked to lower summer NEE), - water table level, which enhanced soil respiration and decreased GPP during dry spells. Although summer dry spells were sporadic during the study period, the positive effects of the current climatic trend towards milder winters on the site's CO2 sink strength could be offset by changes in precipitation patterns especially during the growing season.

Northern peatlands are one of the most important global sinks of atmospheric carbon dioxide (CO 2 ) ; their ability to sequester C is a natural feedback mechanism controlled by climatic variables such as precipitation, temperature, length of growing season and period of snow cover. In the UK it has been predicted that peatlands could become a net source of carbon in response to climate change with climate models predicting a rise in global temperature of ca. 3 o C between 1961-1990 and 2100. Land-atmosphere exchange of CO 2 in peatlands exhibits marked seasonal and inter-annual variations, which have significant short- and long-term effects on carbon sink strength. Net ecosystem exchange (NEE) of CO 2 has been measured continuously by eddy-covariance (EC) at Auchencorth Moss (55˚47’32 N, 3˚14’35 W, 267 m a.s.l.), a temperate peatland in central Scotland, since 2002. Auchencorth Moss is a low-lying, ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from < 0.5 m to > 5 m and the site has a mean annual precipitation of 1155 mm. The vegetation present within the flux measurement footprint comprises mixed grass species, heather and substantial areas of moss species ( Sphagnum spp. and Polytrichum spp.). The EC system consists of a LiCOR 7000 closed-path infrared gas

Eddy-covariance measurements of carbon dioxide (CO2) fluxes have been running continuously at the Auchencorth Moss peatland site in Scotland (55o47’32N, 3o14’35W, 267 m a.s.l.) since the spring of 2002 which makes this study one of the longest ones to date on a peatland system. Auchencorth Moss is a low-lying, ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from 0.5 m and the site has a mean annual precipitation of 1155 mm. The open moorland site has an extensive uniform fetch of blanket bog to the south, west and north. The vegetation present within the flux measurement footprint comprises mixed grass species, heather and substantial areas of moss species (Sphagnum spp. and Polytrichum spp.).

Abstract. Improved data on biosphere-atmosphere exchange are fundamental to understanding the production and fate of ammonia (NH3) in the atmosphere. The GRAMINAE Integrated Experiment combined novel measurement and modelling approaches to provide the most comprehensive analysis of the interactions to date. Major inter-comparisons of micrometeorological parameters and NH3 flux measurements using the aerodynamic gradient method and relaxed eddy accumulation (REA) were conducted. These showed close agreement, though the REA systems proved insufficiently precise to investigate vertical flux divergence. Grassland management had a large effect on fluxes: emissions increased after grass cutting (−50 to 700 ng m−2 s−1 NH3) and after N-fertilization (0 to 3800 ng m−2 s−1) compared with before the cut (−60 to 40 ng m−2 s−1). Effects of advection and air chemistry were investigated using horizontal NH3 profiles, acid gas and particle flux measurements. Inverse modelling of NH3 emission from an experimental farm agreed closely with inventory estimates, while advection errors were used to correct measured grassland fluxes. Advection effects were caused both by the farm and by emissions from the field, with an inverse dispersion-deposition model providing a reliable new approach to estimate net NH3 fluxes. Effects of aerosol chemistry on net NH3 fluxes were small, while the measurements allowed NH3-induced particle growth rates to be calculated and aerosol fluxes to be corrected. Bioassays estimated the emission potential Γ = [NH4+]/[H+] for different plant pools, with the apoplast having the smallest values (30–1000). The main within-canopy sources of NH3 emission appeared to be leaf litter and the soil surface, with Γ up to 3 million and 300 000, respectively. Cuvette and within-canopy analyses confirmed the role of leaf litter NH3 emission, which, prior to cutting, was mostly recaptured within the canopy. Measured ammonia fluxes were compared with three models: an ecosystem model (PaSim), a soil vegetation atmosphere transfer model (SURFATM-NH3) and a dynamic leaf chemistry model (DCC model). The different models each reproduced the main temporal dynamics in the flux, highlighting the importance of canopy temperature dynamics (Surfatm-NH3), interactions with ecosystem nitrogen cycling (PaSim) and the role of leaf surface chemistry (DCC model). Overall, net above-canopy fluxes were mostly determined by stomatal and cuticular uptake (before the cut), leaf litter emissions (after the cut) and fertilizer and litter emissions (after fertilization). The dynamics of ammonia emission from leaf litter are identified as a priority for future research.

A mechanistic model of grassland dynamics is used to simulate fluxes of carbon dioxide (CO2) and nitrous oxide (N2O) in European grasslands. The simulations refer to five sites belonging to a monitoring network setup within the framework of the European Union project GREENGRASS. Simulated gross primary productivity ranges from 0.4 to 1.9kgCm−2year−1 depending on environmental conditions and management. Ecosystem respiration is calculated in the order of 0.7–1.5kgCm−2year−1, resulting in a net CO2 uptake of about 0.3kgCm−2year−1, in reasonable agreement with observations. Linear relationships between ecosystem respiration and gross primary productivity, as well as between net primary productivity and annual precipitation are indicated by the simulations. Annual emissions of N2O are predicted in the range of 1–5kgNha−1year−1, a factor of 2–10 higher than observed. This is caused by an overestimation of the background fluxes. On the other hand, the model fails to faithfully reproduce timing, duration and magnitude of peak emissions triggered by the application of mineral and organic fertilizers and by rain events.

The full greenhouse gas balance of nine contrasted grassland sites covering a major climatic gradient over Europe was measured during two complete years. The sites include a wide range of management regimes (rotational grazing, continuous grazing and mowing), the three main types of managed grasslands across Europe (sown, intensive permanent and semi-natural grassland) and contrasted nitrogen fertilizer supplies. At all sites, the net ecosystem exchange (NEE) of CO2 was assessed using the eddy covariance technique. N2O emissions were monitored using various techniques (GC-cuvette systems, automated chambers and tunable diode laser) and CH4 emissions resulting from enteric fermentation of the grazing cattle were measured in situ at four sites using the SF6 tracer method. Averaged over the two measurement years, net ecosystem exchange (NEE) results show that the nine grassland plots displayed a net sink for atmospheric CO2 of -240 +/- 70 g C m(-2) year(-1) (mean confidence interval at p > 0.95). Because of organic C exports (from cut and removed herbage) being usually greater than C imports (from manure spreading), the average C storage (net biome productivity, NBP) in the grassland plots was estimated at -104 +/- 73 g cm(-2) year(-1) that is 43% of the atmospheric CO2 sink. On average of the 2 years, the grassland plots displayed annual N2O and CH4 (from enteric fermentation by grazing cattle) emissions, in CO2-C equivalents, of 14 +/- 4.7 and 32 +/- 6.8 g CO2-C equiv. m(-2) year(-1), respectively. Hence, when expressed in CO2-C equivalents, emissions of N2O and CH4 resulted in a 19% offset of the NEE sink activity. An attributed GHG balance has been calculated by subtracting from the NBP: (i) N2O and CH4 emissions occurring within the grassland plot and (ii) off-site emissions of CO2 and CH4 as a result of the digestion and enteric fermentation by cattle of the cut herbage. On average of the nine sites, the attributed GHG balance was not significantly different from zero (-85 +/- 77 g CO2-C equiv. m(-2) year(-1)).

Soil/atmosphere exchange fluxes of nitrous oxide were monitored for a 3-year period at 10 grassland sites in eight European countries (Denmark, France, Hungary, Ireland, Italy, The Netherlands, Switzerland and United Kingdom), spanning a wide range of climatic, environmental and soil conditions. Most study sites investigated the influence of one or several management practices on N2O exchange, such as nitrogen fertilization and grazing intensity. Fluxes were measured using non-steady state chambers at most sites, and alternative measurement techniques such as eddy covariance and fast-box using tunable diode laser spectroscopy were implemented at some sites. The overall uncertainty in annual flux estimates derived from chamber measurements may be as high as 50% due to the temporal and spatial variability in fluxes, which warrants the future use of continuous measurements, if possible at the field scale. Annual emission rates were higher from intensive than from extensive grasslands, by a factor 4 if grazed (1.77 versus 0.48 kg N2O-N ha−1 year−1) and by a factor 3 if ungrazed (0.95 versus 0.32 kg N2O-N ha−1 year−1). Annual emission factors for fertilized systems were highly variable, ranging from 0.01% to 3.56%, but the mean emission factor across all sites (0.75%) was substantially lower than the IPCC default value of 1.25%. Emission factors for individual fertilization events increased with soil temperature and were generally higher for water-filled pore space values in the range 60–90%, though precipitation onto dry soils was also shown to lead to high losses of N2O-N from applied fertilizer. An empirical, multiple regression model to predict N2O emission factors on the basis of soil temperature, moisture and rainfall is developed, explaining half of the variability in observed emission factors.

Agricultural management of grasslands results in sequestration and emission of greenhouse gases (GHGs, particularly CO2, N2O and CH4). Here, we used a process-based model (DNDC) to estimate the fluxes of the major GHGs from grasslands at 0.5° resolution across Europe, and combined these to produce a spatially explicit estimate of the total global warming potential (GWP, expressed in CO2 equivalents). The DNDC model [Li, C., Frolking, S., Crocker, G.J., Grace, P.R., Klir, J., Korchens, M., Poulton, P.R., 1997. Simulating trends in soil organic carbon in long-term experiments using the DNDC model. Geoderma 81, 45–60] simulates carbon and nitrogen cycling in agro-ecosystems at a sub-daily time step and consists of four interacting submodels: soil and climate (including water flow and leaching), plant growth, decomposition, and denitrification. Input data sets for grassland area, climate, nitrogen deposition, and soil properties were collated. The typical current grassland management regime was established for ten biogeographical regions on the basis of questionnaires sent to national experts, and used to derive model input data. A 20-year simulation was carried out using DNDC for each site. Simple estimates of methane emissions from grazing livestock were made according to the IPCC Tier 1 method. Most grassland areas are net sources for GHGs in terms of total global warming potential—the beneficial effect of sequestering carbon in soil is outweighed by the emissions of N2O from soil and (predominantly) CH4 emissions from livestock. The net effect of European grasslands on GWP (emission of 23TgCyear−1) corresponds to a 2.5% increase on the EU-15 fossil fuel CO2 emissions (907TgCyear−1).

Ecosystem models are used to explore scientific questions and as a means of decision support. It is therefore essential to assess the quality of the outputs from these. One important measure of quality of model outputs is their uncertainty that arise from uncertainties in measurements. In this study, uncertainty associated with simulation of NEE (net ecosystem exchange) by the PaSim (pasture simulation model) model was tested at four grassland sites. The effect of measurement uncertainties in the main input factors for climate (temperature, precipitation, global radiation), atmospheric CO2 concentration, soil characteristics (bulk density, clay fraction, pH, carbon content of different pools), and management (N input) on output uncertainty of NEE prediction was explored. Monte Carlo runs were performed for 2 years, 2002 and 2003, using Latin Hypercube sampling from probability density functions (PDF) for each input factor. Global uncertainty, represented by the standard deviation of the NEE estimates, was generally higher in 2003 than in 2002 per site with full data records for both years. There was considerable variation in global uncertainty from site to site and between years. These results indicate that output uncertainty does not depend solely on absolute input uncertainties. The mean NEE of the global uncertainty distribution was also different from the NEE result of the single model run using the default set of input factors. The results clearly indicate the dependency of factor importance and uncertainty in model simulations on the environmental conditions of the system under study. One indication is that more environmentally constrained systems produce higher uncertainties in model results. We conclude that any application of the model within decision support should be accompanied by a case specific uncertainty analysis presenting the mean of the output distribution as model results. The consequences of these findings for the application of PaSim at the continental scale are discussed.

We report two cases of occupational asthma caused by sensitisation to powdered fungicides fluazinam and chlorothalonil, from the same fungicide formulation plant. Both developed work related lower respiratory symptoms after a latent interval of asymptomatic exposure. The diagnosis in each case was confirmed with a serial peak flow record in the workplace followed by specific inhalation tests. These fungicides are known to cause dermatitis; this report indicates that these compounds can induce specific immunological reactions in the airways as well as skin.