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In Finland, there are almost 500,000 second homes and in some areas the number of second home owners exceeds that of permanent residents. Currently, second home owners are also spending more time in their second homes. If second home owners are not permanent residents, administration may exclude them from local institutions, and treat second home owners as only partial members of the community. It has been stated that municipal decision making and the role of the municipality as an actor in the local community should be broadened in order to strengthen democracy and the participation of its residents as a core of municipal self-administration. Hence, participating in communal decision making is mainly possible only for permanent residents. The issue is whether it is possible to change this situation via the municipalities' own reforms and state regulations. New municipal administration experiments have recently emerged in Finland. Here we study how the new local administrative model, the Communal District Committee, has affected local participation and local governance in a rural areas by exploring second home owners' opportunities to participate in local decision making and development processes. The data consists of documents, focus group discussions and a questionnaire. We used qualitative and quantitative methods in the data analysis. We found, on one hand, that permanent residents of villages recognise second home owners' hesitation to participate in local issues requiring planning and decision making. On the other hand, local-level communal decision making does not promote the participation of second home residents. On the basis of the findings of the study, we suggest that the municipal authorities should recognise the existence and importance of second home owners in the area, acknowledge them better in municipal plans and strategies, and offer them more resources and means to participate. [ABSTRACT FROM AUTHOR]

Governing urban green infrastructure is challenging due to the various institutions, interests and values involved in municipal planning, decision-making and management processes. Indicators of urban ecosystem services and green infrastructure may support the development of mutual understanding among municipal authorities and the creation of usable information. In this study, the application of ecosystem services (ES) indicators is approached through knowledge-brokering and boundary work theories. We apply a set of GIS-based ES indicators in a medium-sized Finnish city in a collaborative process with local civil servants in order to provide overarching information on the green infrastructure and to enhance dialogue among civil servants. We present the three phases of the indicator application process (conceptual, instrumental and reflection phases) describe the indicator-based boundary work, and identify factors affecting the process. The results highlight the importance of collaboration and active knowledge brokering in indicator applications, involving a combination of conceptual and methodological expertise on the ES approach with knowledge on local environment and relevant policy and planning issues, as well as iterative reflection throughout the indicator application process. Finally, some critical characteristics of boundary work in applying the ES indicators are proposed. [ABSTRACT FROM AUTHOR]

Abstract: Indicators describing sustainability and, more recently, well-being have raised considerable interest throughout the world. Much conceptual and empirical research exists focusing on the criteria for sustainability and development of indicators, while relatively few studies examine the actual use and influence of indicators. Employing document analysis and interviews of key actors, we explore the use of sustainable development indicators at national and EU level and draw forth lessons relevant for topical discussion of the measurement of human well-being. We apply a conceptual model of three main types of indicator use: instrumental, conceptual, and political. The results indicate that the use of sustainability indicators is mainly confined to the ‘indicator circuit’ formed by indicator-developers themselves and actors obliged to use the indicators. The results suggest that direct instrumental use of indicators shows limited potential, whereas conceptual use is the key for enhanced indicator influence in the long term. Political use of indicators cannot be controlled by the indicator-developers. [Copyright &y& Elsevier]

Light pollution is increasingly affecting ecosystems and human health. We present results from an online survey aimed to chart what aspects of lighting are considered harmful and how light pollution is perceived by the public. We focus on affluent societies by using Finland as an example of a northern industrialised country. The survey generated 2053 responses, particularly from well-educated urban persons living in residential areas and interested in astronomy or environmental issues. The results show that the lighting of residential areas and lighting serving traffic are considered the most common sources of light pollution while commercial lighting is perceived as the most annoying form of light use. Respondents commonly considered light pollution as a disturbance for outdoor recreation and relaxation. The results suggest that the ecological and health effects of light pollution emphasised by the research are poorly known by the people emphasising the aesthetic aspects. The results indicate relatively wide but passive acceptance for policy measures aimed at reducing light pollution. [ABSTRACT FROM PUBLISHER]

The timing of the disappearance of the snow cover in spring, or snow melt day (SMD), is a key parameter controlling the carbon dioxide balance between the northern mire and heath ecosystems and the atmosphere. We present a simple method for the determination of the SMD using a satellite-based surface albedo product (SAL). The method is based on the local change of albedo from higher wintertime values towards the lower summertime values. The satellite SMD timing correlates well with the SMD determined from snow depth measurements at Finnish weather stations (r = 0.86, slope 1.05). In 50% of the cases the error was 3.4 days or less and bias less than half a day. This would lead to a moderate uncertainty in the annual CO2 balance of mire and heath ecosystems, if the published SMD-CO2 balance relations are valid. However, due to the limited data sets available a systematic validation is left for the future. [ABSTRACT FROM AUTHOR]

The northern wetlands are one of the major sources of methane into the atmosphere. We measured annual methane emission from a boreal minerotrophic fen, Siikaneva, by the eddy covariance method. The average wintertime emissions were below 1 mg m−2 h−1, and the summertime emissions about 3.5 mg m−2 h−1. The water table depth did have any clear effect on methane emissions. During most of the year the emission depended on the temperature of peat below the water table. However, during the high and late summer the emission was independent on peat temperature as well. No diurnal cycle of methane flux was found. The total annual emission from the Siikaneva site was 12.6 g m−2. The emissions of the snow free period contributed 91% to the annual emission. The emission pulse during the snow melting period was clearly detectable but of minor importance adding only less than 3% to the annual emission. Over 20% of the carbon assimilated during the year as carbon dioxide was emitted as methane. Thus methane emission is an important component of the carbon balance of the Siikaneva fen. This indicates need of taking methane into account when studying carbon balances of northern fen ecosystems. [ABSTRACT FROM AUTHOR]

The first measurements of nitrous oxide (N2O) emissions from a landfill by the eddy covariance method are reported. These measurements were compared to enclosure emission measurements conducted at the same site. The average emissions from the municipal landfill of the Helsinki Metropolitan Area were 2.7 mg N m-2 h-1 and 6.0 mg N m-2 h-1 measured by the eddy covariance and the enclosure methods, respectively. The N2O emissions from the landfill are about 1 order of magnitude higher than the highest emissions reported from Northern European agricultural soils, and 2 orders of magnitude higher than the highest emissions reported from boreal forest soils. Due to the small area of landfills as compared to other land-use classes, the total N2O emissions from landfills are estimated to be of minor importance for the total emissions from Finland. Expressed as a greenhouse warming potential (GWP100), the N2O emissions make up about 3% of the total GWP100 emission of the landfill. The emissions measured by the two systems were generally of similar magnitude, with enclosure measurements showing a high small-scale spatial variation. [ABSTRACT FROM AUTHOR]

The processes responsible for methane (CH4) emissions from boreal wetlands are complex; hence, their model representation is complicated by a large number of parameters and parameter uncertainties. The arctic-enabled dynamic global vegetation model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator) is one such model that allows quantification and understanding of the natural wetland CH4 fluxes at various scales, ranging from local to regional and global, but with several uncertainties. The model contains detailed descriptions of the CH4 production, oxidation, and transport controlled by several process parameters. Complexities in the underlying environmental processes, warming-driven alternative paths of meteorological phenomena, and changes in hydrological and vegetation conditions highlight the need for a calibrated and optimised version of LPJ-GUESS. In this study, we formulated the parameter calibration as a Bayesian problem, using knowledge of reasonable parameters values as priors. We then used an adaptive Metropolis–Hastings (MH)-based Markov chain Monte Carlo (MCMC) algorithm to improve predictions of CH4 emission by LPJ-GUESS and to quantify uncertainties. Application of this method on uncertain parameters allows for a greater search of their posterior distribution, leading to a more complete characterisation of the posterior distribution with a reduced risk of the sample impoverishment that can occur when using other optimisation methods. For assimilation, the analysis used flux measurement data gathered during the period from 2005 to 2014 from the Siikaneva wetlands in Southern Finland with an estimation of measurement uncertainties. The data are used to constrain the processes behind the CH4 dynamics, and the posterior covariance structures are used to explain how the parameters and the processes are related. To further support the conclusions, the CH4 flux and the other component fluxes associated with the flux are examined. The results demonstrate the robustness of MCMC methods to quantitatively assess the interrelationship between objective function choices, parameter identifiability, and data support. The experiment using real observations from Siikaneva resulted in a reduction in the root-mean-square error (RMSE), from 0.044 to 0.023 gC m -2 d -1 , and a 93.89 % reduction in the cost function value. As a part of this work, knowledge about how CH4 data can constrain the parameters and processes is derived. Although the optimisation is performed based on a single site's flux data from Siikaneva, the algorithm is useful for larger-scale multi-site studies for a more robust calibration of LPJ-GUESS and similar models, and the results can highlight where model improvements are needed. [ABSTRACT FROM AUTHOR]

The processes responsible for methane (CH4) emissions from boreal wetlands are complex, and hence their model representation is complicated by a large number of parameters and parameter uncertainties. The arctic-enabled dynamic global vegetation model LPJ-GUESS is one such model that allows quantification and understanding of the natural wetland CH4 fluxes at various scales ranging from local to regional and global, but with several uncertainties. The model contains detailed descriptions of CH4 production, oxidation, and transport controlled by several process parameters. Complexities in the underlying environmental processes, warming-driven alternative paths of meteorological phenomena, and changes in hydrological and vegetation conditions are highlight the need for a calibrated and optimised version of LPJGUESS. In this study we formulated the parameter calibration as a Bayesian problem, using knowledge of reasonable parameters values as priors. We then used an adaptive Metropolis Hastings (MH) based Markov Chain Monte Carlo (MCMC) algorithm to improve predictions of CH4 emission by LPJ-GUESS and to quantify uncertainties. Application of this method on uncertain parameters allows greater search of their posterior distribution, leading to a more complete characterisation of the posterior distribution with reduced risk of sample impoverishment that can occur when using other optimisation methods. For assimilation, the analysis used flux measurement data gathered during the period 2005 to 2014 from the Siikaneva wetlands in southern Finland with an estimation of measurement uncertainties. The data are used to constrain the processes behind the CH4 dynamics, and the posterior covariance structures are used to explain how the parameters and the processes are related. To further support the conclusions, the CH4 flux and the other component fluxes associated with the flux are examined. The results demonstrate the robustness of MCMC methods to quantitatively assess the interrelationship between objective function choices, parameter identifiability, and data support. As a part of this work, knowledge about how the CH4 data can constrain the parameters and processes is derived. Though the optimisation is performed based on a single site's flux data from Siikaneva, the algorithm is useful for larger-scale multi-site studies for more robust calibration of LPJ-GUESS and similar models, and the results can highlight where model improvements are needed. [ABSTRACT FROM AUTHOR]

Arctic‐boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic‐boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003–2015) vegetation gross primary productivity (GPP), ecosystem respiration (Reco), net ecosystem CO2 exchange (NEE; Reco − GPP), and terrestrial methane (CH4) emissions for the Arctic‐boreal zone using a satellite data‐driven process‐model for northern ecosystems (TCFM‐Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM‐Arctic to obtain daily 1‐km2 flux estimates and annual carbon budgets for the pan‐Arctic‐boreal region. Across the domain, the model indicated an overall average NEE sink of −850 Tg CO2‐C year−1. Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH4 emissions from tundra and boreal wetlands (not accounting for aquatic CH4) were estimated at 35 Tg CH4‐C year−1. Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high‐latitude carbon status and also indicates a continued need for integrated site‐to‐regional assessments to monitor the vulnerability of these ecosystems to climate change. [ABSTRACT FROM AUTHOR]

Emissions of biogenic volatile organic compounds (BVOCs) are a crucial component of biosphere-atmosphere interactions. In northern latitudes, climate change is amplified by feedback processes in which BVOCs have a recognized, yet poorly quantified role, mainly due to a lack of measurements and concomitant modeling gaps. Hence, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, rendering their predictions highly uncertain. Here, we show how tundra isoprene emissions respond vigorously to temperature increases, compared to model results. Our unique dataset of direct eddy covariance ecosystem-level isoprene measurements in two contrasting ecosystems exhibited Q10 (the factor by which the emission rate increases with a 10 °C rise in temperature) temperature coefficients of up to 20.8, that is, 3.5 times the Q10 of 5.9 derived from the equivalent model calculations. Crude estimates using the observed temperature responses indicate that tundra vegetation could enhance their isoprene emissions by up to 41% (87%)--that is, 46% (55%) more than estimated by models--with a 2 °C (4 °C) warming. Our results demonstrate that tundra vegetation possesses the potential to substantially boost its isoprene emissions in response to future rising temperatures, at rates that exceed the current Earth system model predictions. [ABSTRACT FROM AUTHOR]

Recent climate change mitigation strategies rely on the reduction of methane (CH 4) emissions. Carbon and hydrogen isotope ratio (δ13 C CH4 and δ2 H CH4) measurements can be used to distinguish sources and thus to understand the CH 4 budget better. The CH 4 emission estimates by models are sensitive to the isotopic signatures assigned to each source category, so it is important to provide representative estimates of the different CH 4 source isotopic signatures worldwide. We present new measurements of isotope signatures of various, mainly anthropogenic, CH 4 sources in Europe, which represent a substantial contribution to the global dataset of source isotopic measurements from the literature, especially for δ2 H CH4. They improve the definition of δ13 C CH4 from waste sources, and demonstrate the use of δ2 H CH4 for fossil fuel source attribution. We combined our new measurements with the last published database of CH 4 isotopic signatures and with additional literature, and present a new global database. We found that microbial sources are generally well characterised. The large variability in fossil fuel isotopic compositions requires particular care in the choice of weighting criteria for the calculation of a representative global value. The global dataset could be further improved by measurements from African, South American, and Asian countries, and more measurements from pyrogenic sources. We improved the source characterisation of CH 4 emissions using stable isotopes and associated uncertainty, to be used in top-down studies. We emphasise that an appropriate use of the database requires the analysis of specific parameters in relation to source type and the region of interest. The final version of the European CH 4 isotope database coupled with a global inventory of fossil and non-fossil δ13 C CH4 and δ2 H CH4 source signature measurements is available at 10.24416/UU01-YP43IN. [ABSTRACT FROM AUTHOR]

Although grazing is the primary land use in the savanna lowland of southern Kenya, the effects of grazing on soil carbon dioxide flux (R S) remain unclear. A 12-month study was conducted from January to December 2020 on the effects of six grazing intensities sites (overgrazed (OG), heavily grazed (HG), moderately grazed (MG), moderately to lightly grazed (M-LG), lightly grazed (LG) and no grazing (NG)) on R S on. A camera trap was used to monitor the total number of animals at each site, indicating the grazing intensity. Weekly measurements of R S were taken using static greenhouse gas chambers along with simultaneous measurements of soil temperature (T S) and volumetric soil water content (W S) (depth of 5 cm). Mean R S at HG, MG, M-LG and LG sites was approximately 15–25% higher than at NG and OG sites (p < 0.001). Mean W S increased with decrease in grazing especially in the dry season, while T S increased with increase in grazing. We observed bimodal temporal variation in R S and W S due to two wet seasons in the year. Thus, variation in R S across the study period followed the changes in W S rather than those in T S. Mean values of R S in the wet seasons were significantly higher (> 45%) than those in the dry seasons, and W S accounted for 71% of the temporal variability in R S (p < 0.05). In addition, the enhanced vegetation index (EVI, interpreted as a proxy for vegetation cover) explained 60% of the variance of R S , and W S and EVI together explained 75%. EVI showed a negative relationship (p < 0.05) with animal intensity, indicating that more grazing reduced vegetation cover and, consequently, soil organic carbon and biomass. Soil bulk density was lower at less grazed sites. While R S variability was unaffected by total nitrogen content, pH, and texture, correspondence analysis demonstrated that the main factors influencing R S dynamics across the year under different grazing intensities were W S and vegetation cover. Our results contribute to closing the existing knowledge gap regarding the effects of grazing intensity on R S in East Africa savannas. Therefore, this information is of great importance in understanding carbon cycling in savanna grassland, as well as the identification of the potential consequences of increasing land pressure caused by rising livestock numbers, and will assist in the development of climate-smart livestock management in East Africa. • Soil CO 2 fluxes decreased with an increase in grazing. • Grazing reduced the vegetation cover, herbaceous aboveground biomass, and increased bulk density. • Enclosure no grazing had lower soil CO 2 fluxes due to lower soil temperturestemperatures and understorey. • Volumetric soil water content and vegetation cover explained the temporal variation in soil CO 2 fluxes. • Results are important in developing climate-smart pastoralism transformation in East Africa. [ABSTRACT FROM AUTHOR]

Recent climate change mitigation strategies rely on the reduction of methane (CH4) emissions. δ13CCH4 and δ²HCH4 measurements can be used to distinguish sources and thus to understand the CH4 budget better. The CH4 emission estimates by models are sensitive to the isotopic signatures assigned to each source category, so it is important to provide representative estimates of the different CH4 source isotopic signatures worldwide. We present new measurements of isotope signatures of various, mainly anthropogenic, CH4 sources in Europe, which represent a substantial contribution to the global dataset of source isotopic measurements from the literature, especially for δ²HCH4. They improve the definition of δ13CCH4 from waste sources, and demonstrate the use of δ²HCH4 for fossil fuel source attribution. Results from previous studies were combined in a common database that we updated with our new measurements, as well as with additional literature. We found that microbial sources are generally well characterised. The large variability in fossil fuels isotopic compositions requires particular care in the choice of weighting criteria for the calculation of a representative global value. The global dataset could be further improved by measurements from African, South American and Asian countries, as well as more measurements from pyrogenic sources. The final version of the European methane isotope database coupled with a global inventory of fossil and non-fossil δ13CCH4 and δ²HCH4 source signature measurements, is available at: https://doi.org/10.24416/UU01-4PO56T (Menoud et al., 2021a). [ABSTRACT FROM AUTHOR]

• Nitrous oxide (N2O) emission estimates from forest ecosystems are based currently on emission measurements using soil enclosures. Such enclosures exclude emissions via tall plants and trees and may therefore underestimate the whole-ecosystem N2O emissions. • Here, we measured plant-mediated N2O emissions from the leaves of potted beech ( Fagus sylvatica) seedlings after fertilizing the soil with 15N-labelled ammonium nitrate (15NH415NO3), and after exposing the roots to elevated concentrations of N2O. • Ammonium nitrate fertilization induced N2O + 15N2O emissions from beech leaves. Likewise, the foliage emitted N2O after beech roots were exposed to elevated concentrations of N2O. The average N2O emissions from the fertilization and the root exposure experiments were 0.4 and 2.0 µg N m−2 leaf area h−1, respectively. Higher than ambient atmospheric concentrations of N2O in the leaves of the forest trees indicate a potential for canopy N2O emissions in the forest. • Our experiments demonstrate the existence of a previously overlooked pathway of N2O to the atmosphere in forest ecosystems, and bring about a need to investigate the magnitude of this phenomenon at larger scales. [ABSTRACT FROM AUTHOR]

The Arctic tundra plays an important role in the carbon cycle as it stores 50% of global soil organic carbon reservoirs. The processes (fluxes) regulating these stocks are predicted to change due to direct and indirect effects of climate change. Understanding the current and future carbon balance calls for a summary of the level of knowledge regarding chamber-derived carbon dioxide (CO2) flux studies. Here, we describe progress from recently (2000–2016) published studies of growing-season CO2 flux chamber measurements, namely GPP (gross primary production), ER (ecosystem respiration), and NEE (net ecosystem exchange), in the tundra region. We review the study areas and designs along with the explanatory environmental drivers used. Most of the studies were conducted in Alaska and Fennoscandia, and we stress the need for measuring fluxes in other tundra regions, particularly in more extreme climatic, productivity, and soil conditions. Soil respiration and other greenhouse gas measurements were seldom included in the studies. Although most of the environmental drivers of CO2 fluxes have been relatively well investigated (such as the effect of vegetation type and soil microclimate on fluxes), soil nutrients, other greenhouse gases and disturbance regimes require more research as they might define the future carbon balance. Particular attention should be paid to the effects of shrubification, geomorphology, and other disturbance effects such as fire events, and disease and herbivore outbreaks. An improved conceptual framework and understanding of underlying processes of biosphere–atmosphere CO2 exchange will provide more information on carbon cycling in the tundra. [ABSTRACT FROM AUTHOR]

Wetlands are one of the most significant natural sources of methane (CH4/to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2/. Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2, and oxygen (O2/in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O2 concentrations that affect the CH4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH4 emissions in this model version. [ABSTRACT FROM AUTHOR]

Boreal/arctic wetlands are dominated by diverse plant species, which vary in their contribution to CH 4 production, oxidation and transport processes. Earlier studies have often lumped the processes all together, which may induce large uncertainties into the results. We present a novel model, which includes three vegetation classes and can be used to simulate CH 4 emissions from boreal and arctic treeless wetlands. The model is based on an earlier biogeophysical model, CH4MOD wetland . We grouped the vegetation as graminoids, shrubs and Sphagnum and recalibrated the vegetation parameters according to their different CH 4 production, oxidation and transport capacities. Then, we used eddy-covariance-based CH 4 flux observations from a boreal (Siikaneva) and a subarctic fen (Lompolojänkkä) in Finland to validate the model. The results showed that the recalibrated model could generally simulate the seasonal patterns of the Finnish wetlands with different plant communities. The comparison between the simulated and measured daily CH 4 fluxes resulted in a correlation coefficient ( R 2 ) of 0.82 with a slope of 1.0 and an intercept of − 0.1 mg m − 2 h − 1 for the Siikaneva site (n = 2249, p < 0.001) and an R 2 of 0.82 with a slope of 1.0 and an intercept of 0.0 mg m − 2 h − 1 for the Lompolojänkkä site (n = 1826, p < 0.001). Compared with the original model, the recalibrated model in this study significantly improved the model efficiency (EF), from − 5.5 to 0.8 at the Siikaneva site and from − 0.4 to 0.8 at the Lompolojänkkä site. The simulated annual CH 4 emissions ranged from 7 to 24 g m − 2 yr − 1 , which was consistent with the observations (7–22 g m − 2 yr − 1 ). However, there are some discrepancies between the simulated and observed daily CH 4 fluxes for the Siikaneva site ( RMSE = 50.0%) and the Lompolojänkkä site ( RMSE = 47.9%). Model sensitivity analysis showed that increasing the proportion of the graminoids would significantly increase the CH 4 emission levels. Our study demonstrated that the parameterization of the different vegetation processes was important in estimating long-term wetland CH 4 emissions. [ABSTRACT FROM AUTHOR]

Holocene peatland development and associated carbon (C) dynamics were reconstructed for a southern boreal Finnish peatland complex with fen and bog areas. In order to assess the role of local factors and long-term allogenic climate forcing in peatland development patterns, we studied a total of 18 peat cores and reconstructed vertical peat growth and lateral peat area expansion rates, the C accumulation rate (CAR), past vegetation composition and past methane (CH 4 ) fluxes. We combined fossil plant data with measured contemporary CH 4 flux – vegetation relationship data to reconstruct CH 4 fluxes over time. When these reconstructions were added to the CAR estimations, a more complete picture of Holocene-scale C dynamics was achieved. Basal peat ages showed that expansion of the peat area was rapid between 11,000 and 8000 cal. BP, but decreased during the dry mid-Holocene and is probably currently limited by basal topography. A similar pattern was observed for peat growth and CAR in the fen core, whereas in the bog core CAR increased after ombrotrophication, i.e. after 4400 cal. BP. The effect of fire on vegetation and CAR was more conspicuous at the bog site than at the fen site. The CH 4 flux reconstructions showed that during the Holocene CH 4 emissions at the fen site decreased from 19 ± 15 to 16 ± 8 g CH 4 m −2 yr −1 and at the bog site from 20 ± 15 to 14 ± 8 g CH 4 m −2 yr −1 . Our results suggest that a combination of changing climate, fire events and local conditions have modified the autogenic peatland development and C dynamics. [ABSTRACT FROM AUTHOR]

Significant climate risks are associated with a positive carbon-temperature feedback in northern latitude carbon-rich ecosystems,making an accurate analysis of human impacts on the net greenhouse gas balance of wetlands a priority. Here, we provide a coherent assessment of the climate footprint of a network of wetland sites based on simultaneous and quasi-continuous ecosystem observations of CO2 and CH4 fluxes. Experimental areas are located both in natural and in managed wetlands and cover a wide range of climatic regions, ecosystem types, and management practices. Based on direct observations we predict that sustained CH4 emissions in natural ecosystems are in the long term (i.e., several centuries) typically offset by CO2 uptake, although with large spatiotemporal variability. Using a space-for-time analogy across ecological and climatic gradients, we represent the chronosequence from natural to managed conditions to quantify the "cost" of CH4 emissions for the benefit of net carbon sequestration. With a sustained pulse- response radiative forcing model, we found a significant increase in atmospheric forcing due to land management, in particular for wetland converted to cropland. Our results quantify the role of human activities on the climate footprint of northern wetlands and call for development of active mitigation strategies for managed wetlands and new guidelines of the Intergovernmental Panel on Climate Change (IPCC) accounting for both sustained CH4 emissions and cumulative CO2 exchange. [ABSTRACT FROM AUTHOR]

In this study latent heat flux ( λE) measurements made at 65 boreal and arctic eddy-covariance ( EC) sites were analyses by using the Penman-Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas-fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman-Monteith equation was calibrated with variable surface resistances against half-hourly eddy-covariance data and clear differences between ecosystem types were observed. Based on the modeled behavior of surface and aerodynamic resistances, surface resistance tightly control λE in most mature forests, while it had less importance in ecosystems having shorter vegetation like young or recently harvested forests, grasslands, wetlands and tundra. The parameters of the Penman-Monteith equation were clearly different for winter and summer conditions, indicating that phenological effects on surface resistance are important. We also compared the simulated λE of different ecosystem types under meteorological conditions at one site. Values of λE varied between 15% and 38% of the net radiation in the simulations with mean ecosystem parameters. In general, the simulations suggest that λE is higher from forested ecosystems than from grasslands, wetlands or tundra-type ecosystems. Forests showed usually a tighter stomatal control of λE as indicated by a pronounced sensitivity of surface resistance to atmospheric vapor pressure deficit. Nevertheless, the surface resistance of forests was lower than for open vegetation types including wetlands. Tundra and wetlands had higher surface resistances, which were less sensitive to vapor pressure deficits. The results indicate that the variation in surface resistance within and between different vegetation types might play a significant role in energy exchange between terrestrial ecosystems and atmosphere. These results suggest the need to take into account vegetation type and phenology in energy exchange modeling. [ABSTRACT FROM AUTHOR]

Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release. [ABSTRACT FROM AUTHOR]

Abstract: We determined the accuracy of the dynamic chamber system for measuring VOC emissions of trees and soil in the field at SMEAR II station, Hyytiälä, Southern Finland. The study was based on creating a known source of different VOCs inside the chamber and measuring the concentration dynamics in the chamber by a proton transfer reaction mass spectrometer (PTR-MS) connected to the chamber. The chamber system underestimated the artificially generated VOC emission rates at varying degree. In isoprene, monoterpene and many oxygenated VOCs the underestimation was 5–30% but in some compounds with protonated mass >100 amu the signal was almost completely lost. The underestimation mainly originated in the chamber but the length of the sample tubing also affected the observed magnitude of the standard gas emission. The systematic error was higher at high relative humidity than in drier conditions, which suggests that the thickness of the water film adsorbed on the chamber inner surfaces contributes to the VOC loss rate in the chamber. Increasing the length of the chamber closure time slightly reduced the systematic underestimation of emission in most of the studied compounds although the underestimation persisted for at least 10 min. A dynamic chamber setup enables measurement of VOC emissions with good accuracy and precision while minimising the disturbance of the chamber to the object being measured. [Copyright &y& Elsevier]

Many wetland ecosystems such as peatlands and wet tundra hold large amounts of organic carbon (C) in their soils, and are thus important in the terrestrial C cycle. We have synthesized data on the carbon dioxide (CO2) exchange obtained from eddy covariance measurements from 12 wetland sites, covering 1–7 years at each site, across Europe and North America, ranging from ombrotrophic and minerotrophic peatlands to wet tundra ecosystems, spanning temperate to arctic climate zones. The average summertime net ecosystem exchange of CO2 (NEE) was highly variable between sites. However, all sites with complete annual datasets, seven in total, acted as annual net sinks for atmospheric CO2. To evaluate the influence of gross primary production (GPP) and ecosystem respiration ( Reco) on NEE, we first removed the artificial correlation emanating from the method of partitioning NEE into GPP and Reco. After this correction neither Reco ( P= 0.162) nor GPP ( P= 0.110) correlated significantly with NEE on an annual basis. Spatial variation in annual and summertime Reco was associated with growing season period, air temperature, growing degree days, normalized difference vegetation index and vapour pressure deficit. GPP showed weaker correlations with environmental variables as compared with Reco, the exception being leaf area index (LAI), which correlated with both GPP and NEE, but not with Reco. Length of growing season period was found to be the most important variable describing the spatial variation in summertime GPP and Reco; global warming will thus cause these components to increase. Annual GPP and NEE correlated significantly with LAI and pH, thus, in order to predict wetland C exchange, differences in ecosystem structure such as leaf area and biomass as well as nutritional status must be taken into account. [ABSTRACT FROM AUTHOR]

Boreal forests emit a large amount of monoterpenes into the atmosphere. Traditionally these emissions are assumed to originate as evaporation from large storage pools. Thus, their diurnal cycle would depend mostly on temperature. However, there is indication that a significant part of the monoterpene emission would originate directly from de novo synthesis. By applying 13CO2 fumigation and analyzing the isotope fractions with proton transfer reaction mass spectrometry (PTR-MS) and classical GC-MS, we determined the fractions of monoterpene emissions originating from de novo biosynthesis in Pinus sylvestris (58%), Picea abies (33.5%), Larix decidua (9.8%) and Betula pendula (100%). Application of the observed split between de novo and pool emissions from P. sylvestris in a hybrid emission algorithm resulted in a better description of ecosystem scale monoterpene emissions from a boreal Scots pine forest stand. [ABSTRACT FROM AUTHOR]

• Soil CO 2 fluxes varied with stand age with older stands emitting more CO 2 fluxes than the young stands. • Soil moisture and vegetation status are important drivers of CO 2 fluxes in the tropics. • Contribution of soil N 2 O and CH 4 to GHG emissions at site scale are negligible. • Sisal plantations are a minor contributor of agricultural GHG emissions in Kenya. Sisal (Agave sisalana) is a climate-resilient crop grown on large-scale farms in semi-arid areas. However, no studies have investigated soil greenhouse gas (GHGs: CO 2 , N 2 O and CH 4) fluxes from these plantations and how they relate to other land cover types. We examined GHG fluxes (Fs) in a sisal chronosequence at Teita Sisal Estate in southern Kenya. The effects of stand age on Fs were examined using static GHG chambers and gas chromatography for a period of one year in seven stands: young stands aged 1–3 years, mature stands aged 7–8 years, and old stands aged 13–14 years. Adjacent bushland served as a control site representing the surrounding land use type. Mean CO₂ fluxes were highest in the oldest stand (56 ± 3 mg C m-2 h-1) and lowest in the 8-year old stand (38 ± 3 mg C m-2 h-1), which we attribute to difference in root respiration between the stand. All stands had 13–28% higher CO₂ fluxes than bushland (32 ± 3 mg C m-2 h-1). CO 2 fluxes in the wet season were about 70% higher than dry season across all sites. They were influenced by soil water content (W S) and vegetation phenology. Mean N 2 O fluxes were very low (<5 µg N m-2 h-1) in all sites due to low soil nitrogen (N) content. About 89% of CH 4 fluxes were below the detection limit (LOD ± 0.02 mg C m-2 h-1). Our results imply that sisal plantations have higher soil CO 2 emissions than the surrounding land use type, and the seasonal emissions were largely driven by W S and the vegetation status. Methane and nitrous oxide are of minor importance. Thus, soil GHG fluxes from sisal plantations are a minor contributor to agricultural GHG emissions in Kenya. [ABSTRACT FROM AUTHOR]

Long-term measurements of fluxes of sensible heat ( H), latent heat ( LE) and carbon dioxide ( Fc) were made from December 2005 to August 2006 over an urban landscape in Helsinki, Finland using the direct micrometeorological eddy covariance technique. Three distinguished sectors of land-use cover (vegetation, roads and buildings) allowed comparisons of fluxes over different urban surfaces. The normalized standard deviation of wind and scalars as a function of atmospheric stability were typical for rough surfaces, as were turbulence spectra and cospectra. Footprint analysis was performed by a boundary-layer one and half-order closure model allowing for discrimination of surface and canopy sinks/sources and complex topography. Fluxes were analysed as average diurnal courses over winter, spring and summer periods. H exceeded LE reaching 300 W m–2 over urban and road surfaces in the summer and it was close to 100 W m–2 in the winter. LE was highest in the summer over vegetation cover attaining 150 W m–2. The emission rate of CO2 was high over road sector [20 μmol (m2s)–1][Correction added after online publication 16 Oct 2007: 30 μmol changed to 20 μmol] while in the vegetation sector it remained below 5 μmol (m2s)–1 and at summertime reached even −10 μmol(m2 s)−1[Correction added after online publication 16 Oct 2007: wording of sentence altered]. Effluxes from soil measured by chambers were 1–3 μmol (m2s)−1. Fc correlated with traffic density and a background non-vehicle flux was 1 μmol (m2s)−1[Correction added after online publication 16 Oct 2007: 2 μmol changed to 1 μmol]. [ABSTRACT FROM AUTHOR]

Eddy covariance (EC) measurements of net ecosystem CO2 exchange (NEE) were conducted on a boreal sedge fen in southern Finland (61°50′N, 24°12′E) during a 1.5-yr period covering two summers in 2004–2005. The EC data were complemented by chamber measurements, which enabled the partition of the daytime NEE into respiration and photosynthesis. A special emphasis was put on the hydrometeorological responses of CO2 exchange during a drought period in July 2005. A mean CO2 efflux of 0.009 mgCO2 m−2 s−1 was observed during mid-winter (January–February), while the night-time respiration during the two Julys averaged 0.09 mgCO2 m−2 s−1. During both years the mean mid-day uptake in late July was about −0.16 mgCO2 m−2 s−1. An annual CO2 balance of −188 gCO2 m−2 was observed in 2005. A slightly higher net sink of −219 gCO2 m−2 was estimated for 2004. The drought period experienced in July 2005 caused a clear depression in the daily NEE values. From the combined analysis of EC and chamber measurements it was concluded that this was mainly due to increased respiration, but evidence was also found of suppressed photosynthesis due to a high VPD. [ABSTRACT FROM AUTHOR]

Net CO2 exchange measured under well-mixed atmospheric conditions in four different mires in Sweden and Finland were used to analyse which factors were controlling photosynthesis and respiration. The parameters of a light response function showed strong seasonal variations with similar behaviour for all mires. The half-monthly nighttime respiration rates in the central part of the growing season were about two times higher in the southernmost, warmest site, Fäje, as compared to the northernmost, coldest site, Kaamanen. However, Kaamanen had high photosynthesis rates, and this in combination with the long daylight periods in the middle of the summer caused Kaamanen to have the largest net ecosystem exchange (NEE) during the summer period. Fäje that showed the highest productivity had also the highest respiration and therefore, the lowest NEE during summer. Correlation between half-monthly components and different environmental variables showed the highest correlation between the components themselves. Thereafter came temperature except for Fäje where water table depth (WTD) explained most of the variance both for detrended and temperature-normalized components. All sites showed dependencies between WTD and the respective components during drying up periods. Temperature sensitivity was higher for productivity than for respiration indicating that CO2 uptake would increase during global warming. [ABSTRACT FROM AUTHOR]

On the afternoon of 3 July 2004 in Hyytiälä (Juupajoki, Finland), convective cells produced a strong downburst causing forest damage. The SMEAR II field station, situated near the damage site, enabled a unique micrometeorological analysis of a microburst with differences above and inside the canopy. At the time of the event, a squall line associated with a cold front was crossing Hyytiälä with a reflectivity maximum in the middle of the squall line. A bow echo, rear-inflow notch, and probable mesovortex were observed in radar data. The bow echo moved west-north-west, and its apex travelled just north of Hyytiälä. The turbulence data were analysed at two locations above the forest canopy and at one location at sub-canopy. At 1412 EET (Eastern European Time, UTC+2), the horizontal and vertical wind speed increased and the wind veered, reflecting the arrival of a gust front. At the same time, the carbon dioxide concentration increased due to turbulent mixing, the temperature decreased due to cold air flow from aloft and aerosol particle concentration decreased due to rain scavenging. An increase in the number concentration of ultra-fine particles (< 10 nm) was detected, supporting the new particle formation either from cloud outflow or due to rain. Five minutes after the gust front (1417 EET), strong horizontal and downward vertical wind speed gusts occurred with maxima of 22 and 15 m s−1, respectively, reflecting the microburst. The turbulence spectra before, during and after the event were consistent with traditional turbulence spectral theory. [ABSTRACT FROM AUTHOR]

The continuous measurements of aerosol particle deposition velocity have been performed from January 2004 to January 2005 using a REA technique with dynamic deadband. We measured aerosol particle deposition velocity in the size range of 10–150 nanometer with 5–10 nanometer steps using differential mobility analyser for sizing. We were able to measure two size classes simultaneously. One size class was changed at one month intervals, another we kept constant at 30 nm to investigate the effect of seasonal and meteorological variation on deposition velocity. We found that the 80–100 nanometer size particles had the lowest deposition velocity, about 0.4 cm s−1. Deposition velocity increased with decreasing or increasing particle diameter from 80–100 nanometer size. We also found that deposition velocity increases as a function of friction velocity. [ABSTRACT FROM AUTHOR]

Continuous and area-integrating monitoring of methane (CH4) and carbon dioxide (CO2) emissions was performed for 6 and 9 months, respectively, at a municipal landfill in Finland with the micrometeorological eddy covariance (EC) method. The mean CH, emission from June to December was 0.53 mg m-2 s-1, while the CO2 emission between February and December averaged 1.78 mg m-2 s-1. The CH4 emissions from the summit area of the landfill, where active waste deposition was going on, were 1.7 times as high as from the slope area with a better surface cover. The variation in emissions over the source area of the measurement was high. Significant seasonal variation, linked to air and soil temperature, was only seen in the CO2 release rates. Results obtained with the EC method were comparable to those measured with closed static chambers. According to the EC measurements, the gas recovery system decreased CH4 fluxes by 69–79%. The ratio of the measured CH4 and CO2 emissions roughly indicated the route of the landfill gas emission, resembling the ratio of the gases measured in the gas wells (1.24) when the emission originated from the area with no oxidizing cover layer and being smaller when CH4 oxidation had taken place. [ABSTRACT FROM AUTHOR]

Peatlands play an important role in the global carbon cycle as they contain a large soil carbon stock. However, current climate change could potentially shift peatlands from being carbon sinks to carbon sources. Remote sensing methods provide an opportunity to monitor carbon dioxide (CO2) exchange in peatland ecosystems at large scales under these changing conditions. In this study, we developed empirical models of the CO2 balance (net ecosystem exchange, NEE), gross primary production (GPP), and ecosystem respiration (ER) that could be used for upscaling CO2 fluxes with remotely sensed data. Two to three years of eddy covariance (EC) data from five peatlands in Sweden and Finland were compared to modelled NEE, GPP and ER based on vegetation indices from 10 m resolution Sentinel-2 MSI and land surface temperature from 1 km resolution MODIS data. To ensure a precise match between the EC data and the Sentinel-2 observations, a footprint model was applied to derive footprint-weighted daily means of the vegetation indices. Average model parameters for all sites were acquired with a leave-one-out-cross-validation procedure. Both the GPP and the ER models gave high agreement with the EC-derived fluxes (R2 = 0.70 and 0.56, NRMSE = 14% and 15%, respectively). The performance of the NEE model was weaker (average R2 = 0.36 and NRMSE = 13%). Our findings demonstrate that using optical and thermal satellite sensor data is a feasible method for upscaling the GPP and ER of northern boreal peatlands, although further studies are needed to investigate the sources of the unexplained spatial and temporal variation of the CO2 fluxes. [ABSTRACT FROM AUTHOR]

The high-resolution Sentinel-2 data potentially enable the estimation of gross primary productivity (GPP) at finer spatial resolution by better capturing the spatial variation in a heterogeneous landscapes. This study investigates the potential of 10 m resolution reflectance from the Sentinel-2 Multispectral Instrument to improve the accuracy of GPP estimation across Nordic vegetation types, compared with the 250 m and 500 m resolution reflectance from the Moderate Resolution Imaging Spectroradiometer (MODIS). We applied linear regression models with inputs of two-band enhanced vegetation index (EVI2) derived from Sentinel-2 and MODIS reflectance, respectively, together with various environmental drivers to estimate daily GPP at eight Nordic eddy covariance (EC) flux tower sites. Compared with the GPP from EC measurements, the accuracies of modelled GPP were generally high (R2 = 0.84 for Sentinel-2; R2 = 0.83 for MODIS), and the differences between Sentinel-2 and MODIS were minimal. This demonstrates the general consistency in GPP estimates based on the two satellite sensor systems at the Nordic regional scale. On the other hand, the model accuracy did not improve by using the higher spatial-resolution Sentinel-2 data. More analyses of different model formulations, more tests of remotely sensed indices and biophysical parameters, and analyses across a wider range of geographical locations and times will be required to achieve improved GPP estimations from Sentinel-2 satellite data. [ABSTRACT FROM AUTHOR]

AbstractFor effective adaptation and mitigation strategies of climate change, adequate data on greenhouse gases (GHGs) emissions from a wide range of land use and land cover types is a prerequisite. Such data is limited in Africa and especially in areas that face diverse land use changes because of human activities. In this study, we measured carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes in the lowland part of South-Eastern Kenya, using the static chamber method and gas chromatography. Gas samples were collected from four dominant land uses: farmland, bushland, conservation area, and grazing land. Eight individual gas sampling campaigns were conducted targeting wet and dry season and transition periods in between covering a total of 12 months. Data on soil moisture and soil temperature were also collected to better understand the flux patterns. Conservation area recorded the highest average CO2 fluxes (74.2mg CO2 m-2 h-1) followed by bushland (46.2mg CO2 m-2 h-1), grazing land (45.6mg CO2 m-2 h-1) and lastly farmland (39.5mg CO2 m-2 h-1). CO2 fluxes across land use were found to vary significantly (p-value<0.001). Those in the conservation area were higher than the other land use by about 37%-47% on average. CO2 fluxes also varied significantly across seasons with highest fluxes recorded during the transition period from wet to dry season. N2O, on the other hand, was highest in the grazing land (1.2ug N2O m-2 h-1), followed by farmland (1.14 ug N2O m-2 h-1), conservation area (1.13ug N2O m-2 h-1) and lastly bushland (0.91ug N2O m-2 h-1). The differences between the land uses were not found to be significant. Most CH4 fluxes across all land use were below the detection limit ranging on average from -0.011mg CH4 m-2 h-1, -0.018mg CH4 m-2 h-1, -0.024mg CH4 m-2 h-1, -0.025mg CH4 m-2 h-1 for in the grazing area, bushland, conservation area, and farmland respectively. For N2O and CH4, there were no significant differences in fluxes across seasons. Our results showed a non-linear relationship of CO2, N2O and CH4 fluxes with increasing temperature. For soil moisture, the rate of CO2 emission increased with increasing soil moisture contents especially after a period of dry season. In the conservation area and grazing area, higher CO2 and N2O fluxes can be attributed to high carbon (C) and nitrogen (N) contents, a dense root network and high C input from grass decay.KEYWORDS: Static Chamber, Seasonal Variability, Climate Change, Bushland, Conservation, Grazing land, Farmland. [ABSTRACT FROM AUTHOR]