Browsing by Subject "Treibhausgas"

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Agriculture as emission source and carbon sink : economic-ecological modelling for the EU-15
(2010) Blank, Daniel; Zeddies, Jürgen
The thesis develops and applies analytical tools to describe economic and ecological impacts of greenhouse gas mitigation strategies in European agriculture. Agriculture is widely perceived as emission source, but actually it can also act as emission sink by sequestration of atmospheric carbon to agricultural soils. Thereby, soil carbon pools potentially store twice as much carbon as contained in the atmosphere. In view of this circumstance, the study analysed agricultural emission sources and mitigation scenarios in the area of conservation tillage and bio-energy production. The analysis was within a mixed-integer programming model optimizing total gross margins of typical farms of NUTS-II-regions in the EU-15. For this micro-economic analysis high quality region specific cost estimates for main agricultural products were indispensible. Thereby a new approach was developed that draws European accountancy data and German engineering cost data. The first dataset comprises of up-to-date crop-unspecific cost data as indicated by European bookkeeping farms. The second comprises of crop specific cost data from German farms. Through a combination of both datasets crop specific estimates of production costs on regional level for the EU-15 evolved. Another study that starts from accountancy data to deduct product cost estimates is currently funded by the European Commission (Farm Accountancy Cost Estimation and Policy Analysis of European Agriculture). By monetarizing greenhouse gas emissions, the Kyoto-Protocol has increased the demand for economic-ecological models to analyse emission scenarios. The study model, EU-EFEM, integrates biophysical data to site-specifically simulate soil carbon dynamics in terms of the mitigation scenario ?conservational tillage?. This approach provides a level of detail that is significantly superior to the one achieved by soil emission factors specified only to global climate zones, a few soil types, and soil management alternatives like provided by the global standard work for the calculation of greenhouse gas emissions, the guidelines of the Intergovernmental Panel on Climate Change (IPCC). The biophysical data was integrated from the EPIC-model to which an interface was established. In the analysis of the agricultural sink function increased input of organic matter, crop rotational modifications, and conservational tillage were assessed. A first scenario that could be monitored relatively easily forces minimum shares of conservational tillage per farm. It was shown that all farms in the EU-15 could comply even with a forced share of 100%. But on average, shares exceeding 80% entail economic losses, basically because of the incompatibility of certain current crop rotations with conservational tillage. Against the average loss of 20 ?/ha in case of 100% of forced conservational tillage, stand single farms facing a loss of 350 ?/ha. Simultaneously soil carbon accumulation remained at marginal levels. In another scenario that directly forces soil carbon accumulation while leaving the choice of the appropriate means to farmers, an accumulation of 181 million tCO2e was achieved. This value corresponds to a forced accumulation of 1.0 t C/ha, a rate out of reach for 25 out of all analysed NUTS-II-regions. Mitigation costs are at 70 ?/tCO2e in this case, but at 10 ?/tCO2e only if only those regions are considered in which the minimum accumulation rates can be achieved. The latter is a competitive value compared to current values of EU traded emission rights. Policy, however, should withdraw from a regulation forcing minimum SOC-accumulation. Main reasons are the difficult monitoring, which would be required on site level, and the absence of a success guarantee on side of farmers for taken measures. Designing effective political instruments, the humus balance as stipulated in the Cross-Compliance regulation of the reformed AGENDA 2000 represents a prefect starting point. The study also analyzed agricultural biogas production with electricity recovery in a combined heat and power (CHP) unit and different (waste) heat utilization rates. European agriculture could increase annual profits by 1.6 to 9.2 billion ? depending mainly on waste heat utilization rate. In the best case, the contribution to climate change mitigation is 263 Mill tCO2e while realising a mitigation gain of 5 ?/tCO2e when excluding subsidies comprised in the feed-in tariff. Being an issue in any discussion about agricultural bio-energy production, the study also analyses the competition for agricultural land with food and feed production. Tapping the full agricultural biogas production potential, 28.7% of grassland and 18.5% of arable land would be bound, although the study constrains biogas production to co-fermentation with manure. The impacts of this competition on agricultural prices could not be analysed in this study, since the applied model is a farm model and not a market equilibrium model. By means of literature research, however, it was concluded that subsidies of biogas production should focus on promoting the fermentation of manure and the utilization of waste heat in order to limit area competition and not to promote the utilization of cultivated biomass.
Biochar amendment for C sequestration in a temperate agroecosystem : implications for microbial C- and N-cycling
(2018) Bamminger, Chris; Kandeler, Ellen
Climate warming will have great impact on terrestrial ecosystems. Different soil properties such as temperature and moisture will be altered, thereby influencing C- and N-cycles, microbial activity as well as plant growth. This may contribute to the observed increase in soil greenhouse gas (GHG) emissions under climate change. Therefore, new options are needed to mitigate theses projected consequences. Biochar is primarily suggested to be effective in long-term C sequestration in agricultural soils due to its long-term stability. In addition, it could be applied to improve various soil properties, plant growth and to reduce soil GHG emissions. To date, knowledge about such beneficial biochar effects in soil under predicted warming climate is extremely scarce. In the first study, a slow-pyrolysis biochar from Miscanthus x giganteus feedstock (600 °C, 30 Min.) was incubated for short time (37d) under controlled laboratory conditions in agricultural soil in the presence of earthworms and N-rich litter (Phacelia tanacetifolia Benth.). Biochar increased microbial abundances and the fungal-to-bacterial PLFA ratio after 37 days in arable soil applied with litter suggesting improved living conditions for microorganisms with biochar. Fungi may benefit most from newly created habitats due to colonizable biochar pores and surfaces. Additionally, fungi could have also mineralized small amounts of recalcitrant biochar-C during plant litter decomposition. Without litter, biochar led to interactions between earthworms and soil microorganisms resulting in enhanced bacterial and fungal abundances. This indicates better growth habitats for soil microbes in earthworm casts containing biochar. Soil respiration and metabolic quotients (qCO2) and N2O emissions (in litter treatments) were decreased after biochar application suggesting a more efficient microbial community and underscoring the GHG mitigation potential of the used biochar. The field experiment, investigated in the second and third study, focused on the stability and long-term soil C sequestration potential of comparable Miscanthus biochar (850 °C, 30 Min.). Related effects on soil GHG emissions, physical, chemical and microbiological soil properties as well as plant growth were determined in an agroecosystem at year-round elevated soil temperature (+2.5 °C, since 2008). The second study investigated the short-term effects of biochar on microbial abundances and growth of winter rapeseed during the first year after field application to a warmed temperate arable soil. It was found that fungal biomass and the fungal-to-bacterial ratio were increased in the warmed biochar plots only after three months in the presence of spring barley litter from the previous growing season. The disappearance of this effect points to an overall high stability of the investigated biochar. Moreover, biochar proved to be effective in mitigating negative effects of seasonal dryness on microbial abundances and early plant growth in the dry spring period in 2014. However, biochar had no effect on final aboveground biomass of winter rapeseed at harvest in the first growing season. As shown in the third study, after two vegetation periods of winter rapeseed and spring wheat, the assumption that plant productivity in already fertile temperate arable soils is unlikely to be further enhanced with biochar amendment, was confirmed. Total CO2 emissions after two years were not reduced by biochar and remained unchanged even under warming suggesting a high degradation stability of the used biochar. N2O emissions were increased in biochar-amended soil at elevated soil temperature, presumably due to enhanced water and fertilizer retention with biochar. By using the global warming potential (GWP100) of total soil GHG emissions, the storage of biochar-C in soil was estimated to compensate warming-induced elevated soil GHG emissions for 20 years. To conclude, this thesis revealed that biochar may have only minor influence on soil microorganisms and crop growth in temperate, fertile arable field soils. However, it was shown that biochar could be a valuable tool for C sequestration in temperate arable soils, thus potentially offsetting a warming-induced increase in GHG emissions. In order to face climate change impacts, more long-term studies on microbiological effects and the C sequestration potential of biochar in cultivated soil under warming are urgently needed.
Biogenic Greenhouse Gas Emissions from Agriculture in Europe - Quantification and Mitigation
(2002) Freibauer, Annette; Zeddies, Jürgen
This dissertation analyses relevant potential mitigation strategies of biogenic greenhouse gases (GHGs) in the agriculture of the European Union (EU) in light of the Kyoto Protocol. It identifies where important sources and mitigation potentials are located and what uncertainty, environmental ancillary effects and costs are associated with them. Literature reviews are performed and methodologies for environmental assessment and GHG accounting are further developed. On this basis, GHG emissions are quantified and reduction potentials are assessed at European level. In 1995, European agriculture emitted 0.84 ± 0.29 Tg N2O, 8.1 ± 1.9 Tg methane (CH4) and 39 Tg ± 25 carbon dioxide (CO2), which adds up to 470 ± 80 Tg CO2-equivalents or 11% of the overall anthropogenic greenhouse gas emissions of the EU. The detailed methodology developed here adequately resolves regional specifics of agricultural conditions and reduces the methodological uncertainty in the estimates to half of the one in the official national inventories. European agricultural soils will at maximum sequester carbon in the order of 100 Tg a-1 CO2 over the coming years, which may also provide other environmental benefits. The biological potential of bioenergy in the EU allows to substitute for 400 to 800 Tg a-1 CO2-equivalents. From an environmental perspective, the use of perennials, especially of residues and woody biomass, is preferable to intensively grown annual crops. The biological potential for technical GHG reduction measures in EU agriculture is between 100 and 200 Tg a-1 CO2-equivalents. Promising measures promote the extensivation of arable cropping by reducing nitrogen inputs, technological innovation in animal husbandry, which is best accompanied by a further decline in animal numbers, as well as rewetting drained organic soils. Most measures will provide ancillary environmental benefits. Changing the socio-economic and political frame conditions may enhance the GHG mitigation potential.
Contribution of smallholder ruminant livestock farming to enteric methane emissions in Lower Nyando, Western Kenya
(2018) Onyango, Alice Anyango; Dickhöfer, Uta
The present study proposed some area-specific solutions and/or recommendations to common challenges hindering accurate estimation of enteric methane (CH4) emissions from sub-Saharan smallholder cattle systems. The results show that enteric CH4 from cattle systems in Kenya are an important contributor to agricultural greenhouse gases (GHG) and hence, needs close attention in the on-going process of developing Nationally Appropriate Mitigation Actions in the Kenyan livestock sector. However, the multi-functionality of animals in these systems should be considered in future in the assessment of emission factors (EF) and (emission intensities) EI. There appears to be great potential for reducing emissions, for example by improving animal husbandry, animal feeding and performance.
Gaseous N emissions from a loamy soil as affected by N fertilization strategies, and by the use of nitrification and urease inhibitors - Results from field and incubation experiments
(2023) Guzman Bustamante, Ivan; Müller, Torsten
Agricultural activities are responsible for a substantial share of anthropogenic greenhouse gases. At the same time, agricultural production must feed a growing world population under a changing climate. In the case of wheat, the use of nitrogen (N) fertilizers is needed in order to insure grain yield and quality. Nevertheless, its use is associated with reactive N losses, which are detrimental for the environment and human health. Among the gaseous N species emitted after N fertilization we find nitrous oxide (N2O), a potent greenhouse gas, and ammonia (NH3) that after its deposition can be oxidized to N2O. Chemical compounds such as nitrification and urease inhibitors (NIs and UIs, respectively) are a useful tool, able to raise the fertilizer nitrogen use efficiency, by retarding the nitrification of ammonium based fertilizer in the case of NIs and by retarding the hydrolysis of urea in the case of UIs. A side benefit of the use of NIs is the reduction of N2O emissions. The use of UIs reduces the NH3 volatilization. One of the most used NIs in Europe is 3,4-dimethylpyrazol phosphate (DMPP) which can be applied with ammonium sulfate nitrate (ASN). The relatively new NI, 3,4-dimethylpyrazol succinic acid (DMPSA), acts similarly to DMPP but has a different time of action and can be applied to several fertilizers, unlike DMPP. N-(n-butyl) thiophosphoric triamide (NBPT) is an effective UI that provenly reduces NH3 volatilization by inhibiting the urease enzyme. In a two-year field experiment with winter wheat several fertilizer strategies were tested, including splitting strategies, use of NIs and reduction of N amount. Reducing N amount reduces the amount of soil mineral N, which is the substrate for N2O producing microbiological processes, nitrification and denitrification. Splitting of N fertilizer might reduce soil mineral N as well because N fertilizer applications are better suited to the physiological needs of the wheat plants. Applying NIs in splitting schemes may further mitigate emissions. The relationship between N amount and N2O losses in a wheat production system was investigated by applying lower and higher N amounts than the recommended N application rate. Use of DMPP was able to reduce N2O emissions in both years, not only on an annual basis (by 21 %: 3.1 vs 2.5 kg N2O-N ha-1 a-1 average for both years) but also during winter, when up to 18 % of total annual emissions occurred. A change of the soil microbial community due to DMPP could be the reason for the reduction of winter emissions 8 to 12 months after DMPP application. An economic assessment of N fertilizer amount showed that DMPP applied with suboptimal N fertilizer amounts can maintain yield and at the same time decrease yield scaled N2O emissions compared to an optimal N fertilizer rate without NI. Using CAN together with the NI DMPSA reduced N2O emissions only during the vegetation period. On an annual basis, DMPSA did not significantly reduce N2O emissions. Because DMPSA and DMPP were applied with different N fertilizers with different ammonium and nitrate shares, a direct comparison between these two NIs cannot be made. A traditional threefold split fertilization did not reduce annual emissions compared to a single application of ASN or CAN. Nevertheless, the use of DMPP in twofold split applications reduced annual emissions significantly by 33 % and increased protein content by 1.6 %. Because N2O flux peaks were not as high as expected after N fertilization during the first year, a short experiment investigating the effect of soil moisture, N and C application on N2O fluxes was conducted. A C limitation of the field was found, which explained high N2O emission events when C was available, e.g. after rewetting of dry soil and incorporation of straw after harvest. In this context we tested the removal of wheat straw – which should reduce the organic substrate supply for denitrifiers – as a possible mitigation strategy. Nevertheless, the removal of straw had no effect on N2O emissions. Furthermore, the effect of DMPP on microorganisms was studied in an incubation experiment: the copy number of bacterial amoA genes (nitrifiers) was lowered by the use of DMPP, while the number of archaeal amoA genes was increased by DMPP. Gene copy number of denitrifiers was unaffected by DMPP, nevertheless, soil respiration was reduced when DMPP was applied. It seems as DMPP has an inhibiting effect on heterotrophic organisms, nevertheless, the investigated variables did not support this hypothesis, so that further investigation is needed. The effect of NBPT and straw residues on NH3 and N2O emissions was studied in a two-week incubation experiment with a slightly alkaline soil. NBPT reduced NH3 volatilization and N2O fluxes from urea fertilization almost completely. Incorporation of straw residues significantly increased N2O emissions. In a further four-week incubation experiment, the effect of NBPT in two concentrations and DMPP was studied. A higher NBPT concentration as the recommended rate, reduced NH3 emissions by 53 %; DMPP on the other hand increased NH3 volatilization by 70 %. Regarding N2O, DMPP reduced emissions to the same level as the unfertilized control; NBPT only shifted the emission peak so that by the end of the experiment no difference in the cumulative N2O emission was found between urea and NBPT treatments. These results show that UI can lead to a reduction of N2O emissions, but the ammonium formed by the urea hydrolysis should be used by crops, otherwise it serves as a substrate for N2O production in soils. In the final incubation experiment, the combined application of a NI (DMPSA) and a UI (NBPT) was studied. Lower concentrations than the recommended doses were applied in order to assess synergistic effects. The combined application of DMPSA and NBPT did not lead to synergistic effects in the analyzed variables (soil urea amount, soil mineral N, ammonia volatilization, soil respiration and N2O emission). The higher the NBPT concentration, the slower urea was hydrolyzed and the higher the reduction in NH3 volatilization. A third of DMPSA application rate was enough to reduce N2O emissions; however, the use of NI increased NH3 losses. Our results highlight the importance of annual datasets when assessing mitigation strategies for N2O. For wheat production, a reduction of the N fertilizer amount when a NI is used should be taken into consideration. When elite wheat cultivars are grown split application with NI fertilizers could ensure high protein content and simultaneously reduce N2O emission. Urea fertilizer should be applied with NI and UI so that NH3 volatilization and N2O emission is reduced. Nevertheless, long-term effects of these compounds on soil microbiology must be monitored to avoid unseen ecotoxicological effects. Since some of these compounds or their metabolites might be absorbed by plants and end up in food and feed more research is needed to protect consumers.
Impact of land use change on soil respiration and methane sink in tropical uplands, Southwestern China
(2020) Lang, Rong; Cadisch, Georg
Land use conversion could modulate soil CO2 emissions and the balance between CH4 oxidation and production via changing soil physical, chemical and biological properties. Large areas of natural forests have been converted to rubber plantations in Southeast Asia, but its impact on soil CO2 and CH4 fluxes has not been sufficiently understood. This study was conducted in Xishuangbanna, Southwestern China, aiming to quantify the impact of this land use change on soil CO2 and CH4 fluxes and to clarify mechanisms responsible for the differences between natural forests and rubber plantations. Dynamics of soil respiration rates in two land uses were compared, and a mixed effect model was used in studying the interference of soil moisture on estimating temperature sensitivity (Q10) of soil respiration (Chapter 2). The land use change impact on the ability of soils to function as CH4 sink was firstly assessed with surface CH4 fluxes measured by static chambers, and then assessed with gas concentration profiles determined from soil probes. Confounded controlling factors and land use effects were disentangled, and the pathway of interactions between CH4 processes and mineral nitrogen was identified (Chapter 3). The concentration gradient method and one-dimensional diffusion-oxidation model were applied to quantify the vertical distribution of CH4 uptake in soil profiles, and to separate the relative control by gas diffusivity and by methanotrophic oxidation on CH4 uptake (Chapter 4). Distinct different temporal patterns of soil respiration were observed on sites during most of the rainy season: forest maintained a high soil respiration rate, while soil respiration in rubber plantations became suppressed (by up to 69%). Forest soils thus emitted the highest amount of CO2 with an annual cumulative flux of 8.48 ± 0.71 Mg C ha-1 yr-1, compared to 6.75 ± 0.79, 5.98 ± 0.42 and 5.09 ± 0.47 Mg C ha-1 yr-1 for 22-year-old rubber, rubber-tea intercropping, and 9-year-old rubber, respectively. Adding a quadratic soil moisture term into the regression model accounted for interference of moisture effect on the effect by soil temperature, therefore, improved temperature sensitivity assessments when high soil moisture suppressed soil respiration under rubber plantations. The static chamber method showed that soils under natural forest were stronger CH4 sinks than soils under rubber plantations, with annual CH4 fluxes of -2.41 ± 0.28 kg C ha-1 yr-1 and -1.01 ± 0.23 kg C ha-1 yr-1, respectively. Water-filled pore space was the main factor explaining the differences between natural forests and rubber plantations. Although soils under rubber plantations were more clayey than soils under natural forest, this was proved not to be the decisive factor driving higher soil moisture and lower CH4 uptake in the former soils. Concentration gradients method showed that CH4 consumption in 0-5 cm soil was significantly higher in natural forests than in rubber plantations, with a mean CH4 flux of -23.8 ± 1.0 and -14.4 ± 1.0 ug C m-2 h-1 for forest and rubber plantations, respectively. The atmospheric CH4 oxidized by top 10 cm soil accounted for 93% and 99% of total consumption for forest and rubber plantations, respectively. CH4 diffusivity at four sampled depths were significantly lower in rubber plantation than in forest. This reduced CH4 diffusivity, caused by altered soil water regime, predominately explained the weakened CH4 sink in converted rubber plantations. Estimated isotopic fractionation factor for carbon due to CH4 oxidation was 1.0292 ± 0.0015 (n=12). Modeling 13CH4 distribution in soil profiles using a diffusion-oxidation model explained the observations in the dry season, but suggested CH4 production in subsoil in the rainy season. In summary, converting natural forests into rubber plantations tended to reduce soil CO2 emissions, but this conversion substantially weakened CH4 uptake by tropical upland soils. The altered soil water regime and conditions of soil aeration under converted rubber plantations appear to have a pronounced impact on processes of gaseous carbon fluxes from soils. The clarified mechanisms in this study could improve the regional budget of greenhouse gases emissions in response to land use change and climate change.
Nachhaltige Biogasproduktion unter besonderer Berücksichtigung des Einsatzes von Zuckerrüben und Grünlandaufwuchs sowie der Gärrestverwertung
(2017) Auburger, Sebastian; Bahrs, Enno
The present cumulative dissertation assesses the sustainability of biogas production in Germany from different points of view. A special focus is brought to sugar beets and grassland as a biogas feedstock as well as to biogas residue utilization. Chapter 2 presents an approach of manure distribution within regions based on municipality biogas and livestock production data. The developed algorithm distributes nutrients of nutrient surplus municipalities to municipalities with nutrient adsorption capacity within a study area (Lower Saxonia and North Rhine-Westphalia). It was shown that farmers and biogas producers will be confronted with higher manure and biogas digestate disposal costs. Chapter 3 enlarges the view by taking pig producers and experts interviews into consideration. Chapter 4 presents an approach to determine the regional biogas feedstock input based on regional agricultural production cost data and almost 8,000 biogas plants in Germany. By using a linear optimization approach regional feedstock inputs are calculated. Furthermore greenhouse gas emissions of power production based on biogas are estimated. Chapter 5 enlarges the modeling approach by an energy balancing tool and assesses sugar beets as an energy crop for biogas production in detail. Therefore different scenarios are taken into account. Silage corn was the most competitive feedstock over almost every region in Germany. Round about 160 kg CO2eq per kWh from biogas production were calculated, which is a significant lower value in comparison to greenhouse gas emissions from current power mix in Germany. Chapter 6 focuses on grassland as a biogas feedstock. Based on data availability calculation had to be restricted to Federal States of Schleswig-Holstein, Lower Saxonia and Bavaria. Results show that grassland is a competitive biogas feedstock in regions, which are characterized by unfavorable production circumstances of silage corn and only if for grassland favorable scenario assumptions are chosen.
The role of Phragmites australis in carbon, water and energy fluxes from a fen in southwest Germany
(2019) van den Berg, Merit; Streck, Thilo
The global carbon emission from peat soils adds up to 0.1 Gt-C per year. Under anaerobic conditions, organic material is decomposed to methane (CH4). Over a 100-year cycle, methane is a 28 times stronger greenhouse gas than carbon dioxide and is an important factor for climate change. Therefore, there is a great interest to get a better understanding of the carbon flows in peatlands. Phragmites peatlands are particularly interesting due to the global abundance of this wetland plant (Phragmites australis, common reed) and the highly efficient internal gas transport mechanism. This is a humidity-induced convective flow (HIC) to transport oxygen (O2) to the roots and rhizomes, with the effect that simultaneously soil gases (CH4 and CO2) can be transported to the atmosphere via the plant. Thereby, Phragmites is expected to have a high evapotranspiration (ET) rate due to the large leaf area, open water habitat and high aerodynamic roughness. This ET could highly influence the hydrology of the system. Because he accumulation of organic material occurs because of limiting oxygen levels, hydrological processes are fundamental in the development of peatlands. The research aims were: 1) to clarify the effect of plant-mediated gas transport on CH4 emission, 2) to find out whether Phragmites peatlands are a net source or sink of greenhouse gases, and 3) to evaluate ET in perspective of surface energy partitioning and compare results with FAO’s Penman-Monteith equation. CO2, CH4 and latent and sensible energy fluxes were measured with the eddy covariance (EC) technique within a Phragmites-dominated fen in southwest Germany in 2013, 2014 and 2016. In 2016, a field experiment was set up to quantify the contribution of plant-mediated CH4 transport to the overall CH4 flux and how it influences ebullition. One year of EC flux data (March 2013–February 2014) shows very clear diurnal and seasonal patterns for both CO2 and CH4. The diurnal pattern of CH4 fluxes was only visible when living green reed was present. This diurnal cycle had the highest correlation with global radiation, which suggests a high influence of HIC on CH4 emission. But if the cause were HIC, relative humidity should correlate stronger with CH4 flux. Therefore, we conclude that in addition to HIC at least one other mechanism must have been involved in the creation of the convective flow within the Phragmites plants. We quantified the influence of pressurized flow within Phragmites on total CH4 emission in a field experiment (see chapter 3) and found between 23% and 45% lower total CH4 flux when pressurized flow was excluded (by cutting or cutting and sealing the reed). The gas transport pathways from the soil to the atmosphere changed as well. Relative contribution of ebullition to the total flux increased from 2% in intact Phragmites to 24-37% in cut vegetation. This increase in ebullition in cut vegetation, obviously, did not compensate the excluded pathway via the pressurized air flow at our site. It also means that the effect of CH4 bypassing the oxic water layer by plant transport on CH4 emission is much larger than the effect of O2 transport through the plants on CH4 oxidation and production in the rhizosphere. Overall, the fen was a sink for carbon and greenhouse gases in the measured year, with a total carbon uptake of 221 g C m-2 yr-1 (26% of the total assimilated carbon). The net uptake of greenhouse gases was 52 g CO2 eq.m-2 yr-1, which is obtained from an uptake of CO2 of 894 g CO2 m-2 yr-1 and a release of CH4 of 842 g CO2 eq.m-2 yr-1. Compared to the long term uptake of carbon by northern peatlands (20–50 g C m-2 yr-1) 212 g C yr-1 is therefore very high. One year of measurements is not enough to draw hard conclusions about the climate change impact of this peatland. The measured ET at our site was lower than other Phragmites wetlands in temperate regions. ET was half the amount of precipitation (see chapter 4). Therefore, the risk of the wetland to dry out is not realistic. ET was especially low when there was little plant activity (May and October). Then, the dominant turbulent energy flux was sensible heat not latent heat. This can be explained by the high density of dead reed in these months. the reed heats up causing a high sensible heat flux. Evaporation was low due to the shading of the water layer below the canopy and low wind velocities near the surface. FAO’s Penman-Monteith equation was a good estimator of measured ET with crop factors from the regression model of Zhou and Zhou (2009) (see chapter 4). Especially the day-to-day variation was modeled very well. Their model had air temperature, relative humidity and net radiation as input variables. This is likely related to stomatal resistance, which depends on the same variables. Therefore, the model of Zhou and Zhou (2009) is an interesting tool for calculating daily crop factors and it is probably robust enough to be used also in different regions.