Matthias Drösler

Characteristics of dissolved organic matter following 20 years of peatland restoration

The changes in the amounts and composition of dissolved organic matter (DOM) following long-term peat restoration are unknown, although this fraction of soil organic matter affects many processes in such ecosystems. We addressed this lack of knowledge by investigating a peatland in south-west Germany that was partly rewetted 20 years ago. A successfully restored site and a moderately drained site were compared, where the mean groundwater levels were close to the soil surface and around 30 cm below surface, respectively. The concentrations of dissolved organic carbon (DOC) at 4 depths were measured over one year. The specific absorbance was measured at 280 nm and the fluorescence spectra were used to describe the aromaticity and complexity of DOM. The investigations showed that 20 years of peatland restoration was able to create typical peatland conditions. The rewetted site had significantly lower DOC concentrations at different depths compared to the drained site. The specific UV absorbance showed that the rewetted site had a lower level of aromatic DOM structures. The decreasing specific UV absorbance might indicate an increasing contribution of small organic molecules to DOM. It was hypothesized that the decreasing DOC concentrations and the relative enrichment of small, readily degradable organic molecules, reflect the slower decomposition of organic matter after the re-establishment of the water table. Seasonal trends provided substantial evidence for our hypothesis that reduced DOC concentrations were caused by reduced peat decomposition. During summer, the elevated DOC values were accompanied by an increase in DOM aromaticity and complexity. Our results demonstrated a close link between C mineralization and DOC production. We concluded that long-term peatland restoration in the form of the successful re-establishment of the water table might result in reduced peat decomposition and lower DOC concentrations. The restoration of peatlands seems to have a positive impact on C sequestration.

Observations and Status of Peatland Greenhouse Gas Emissions in Europe

A peatland is a type of ecosystem where carbon (C) along with nitrogen and several other elements has been accumulated as peat originating from the plant litter deposited on the site. A logical consequence of the above definition of peatlands is that they are ecosystems, which by way of nature are a sink for atmospheric carbon dioxide (CO 2 ). This is the case because more C is accumulated through photosynthesis than is released through respiration. As a consequence of this, organic matter accumulates as peat. The C accumulated in peatlands is equivalent to almost half the total atmospheric content, and a hypothetical sudden release would result in an instantaneous 50% increase in atmospheric CO 2 . While this scenario is unrealistic, it nevertheless highlights the central role of peatlands where huge amounts of CO 2 have almost entirely been “consumed” since the last glacial maximum, but could respond differently as a result of future changes in climatic conditions. Peatlands have, hence, over the last 10,000 years helped to remove significant amounts of CO 2 from the atmosphere. A complicating factor in this respect is that in terms of the major greenhouse gases (GHGs), peatlands are not just acting as a sink for CO 2 . The wet conditions that lead to the slow decomposition of organic material and enable peat accumulation to occur, also cause significant amounts of the powerful GHG methane (CH 4 ) to be formed. Indeed global wetlands (predominantly peatlands) are considered to be the largest single source of atmospheric CH 4 also when considering all anthropogenic emissions. Peatlands are, therefore, also a key player in the atmospheric CH 4 budget and as a result also influence the global climate.

DenNit – Experimental analysis and modelling of soil N2O efflux in response on changes of soil water content, soil temperature, soil pH, nutrient availability and the time after rain event

To quantify the effects of soil temperature (Tsoil), and relative soil water content (RSWC) on soil N2O emission we measured N2O soil efflux with a closed dynamic chamber in situ in the field and from soil cores in a controlled climate chamber experiment. Additionally we analysed the effect of soil acidity, ammonium, and nitrate concentration in the field. The analysis was performed on three meadows, two bare soils and in one forest. We identified soil water content, soil temperature, soil nitrogen content, and pH as the main parameters influencing soil N2O emission. The response of N2O emission to soil temperature and relative soil water content was analysed for the field and climate chamber measurements. A non-linear regression model (DenNit) was developed for the field data to describe soil N2O efflux as a function of soil temperature, soil moisture, pH value, and ammonium and nitrate concentration. The model could explain 81% of the variability in soil N2O emission of all individual field measurements, except for data with short-term soil water changes, namely during and up to 2 h after rain stopped. We validated the model with an independent dataset. For this additional meadow site 73% of the flux variation could be explained with the model.

Stakeholder perceptions of the impacts of rural funding scenarios on mountain landscapes across Europe

This article examines how alternative rural funding scenarios might influence the pattern of functional land types in mountain areas. The study aims were to explore the use of stakeholders to predict landscape change and to provide a future policy context for other papers in the Carbomont program. EU rural funding policies could have a strong influence on land use and landscapes in mountain areas. At eight sites across Europe, groups of local stakeholders were asked to compare the possible effects of three contrasting funding scenarios over an imagined period of 20 years on (1) the importance of the main land-use sectors; (2) the areas of the main land functional land types; and (3) the management of individual land types. Stakeholders also listed their interests in the area to help define the perspective of the group. The protocols used were ranking and scoring procedures that permitted quantification of changes and of the degree of consensus within the group. The scenarios were (1) continuation of current rural funding (status quo), (2) rapid reduction of farm income support (reduce support), and (3) increasing rural diversification funding (diversification). The eight countries sampled included five established EU members (UK, Germany, Austria, Italy, Spain), two new accession members (Czeck Republic and Slovakia), and Switzerland. There were predicted to be widespread reductions in the importance of the agricultural sector across Europe and increases in the transport, built environment, and tourism sectors. In general, the status quo scenario was perceived to be unsatisfactory in various respects, reduce support was worse, but diversification offered opportunities for conservation and development of mountain communities and land use. Changes in the areas of land types would mainly involve loss of arable and grazing land and increases in scrub, and settlements. Some elements of the landscape such as most forests, mountain tops, and wetlands would, however, be little affected by any of the scenarios.

Cultivating the climate: socio-economic prospects and consequences of climate-friendly peat land management in Germany

About 30% of the world’s soil carbon is stored in peat soils. Peat land’s functional principle of carbon storage greatly depends on management strategies. Therefore, agricultural peat land use becomes a focal point of interest in the current debate on climate protection. Agricultural management demands a drawdown of the water-level that causes degradation of the soils, as well as trace-gas emissions which have a negative impact on greenhouse-gas balance. Climate-friendly peat land management strategies, however, demand enhanced groundwater tables and decreased land-use intensity. Against this background, we analyse ways of re-organising agricultural peat land use within a case study located in Germany, where intensive peat land use accounts for 2.3–5.1% of the country’s overall greenhouse-gas emission. The study takes place in six regions which represent all possible socio-economic and natural conditions with regard to the range of existing peat land types, range of management and cultivation types, as well as the range of land-use intensity. To analyse potentials and effects of re-organising peat land use, stakeholder workshops and extensive farm surveys were carried out. The results indicate that reservations exist as regards a re-organisation of peat land management. Financial compensation for farmers appears necessary. The results also show that the potential of rearrangement throughout the regions varies significantly, mainly according to the existing level of interconnection and cooperation between local stakeholders, the technical feasibility of restoration and water logging and the level of agricultural profitability of peat land cultivation with regard to income, capital commitment and the share of affected peat land area.

Influence of Soil Organic Carbon on Greenhouse Gas Emission Potential After Application of Biogas Residues or Cattle Slurry: Results from a Pot Experiment

Abstract A change in the European Union energy policy has markedly promoted the expansion of biogas production. Consequently, large amounts of nutrient-rich residues are being used as organic fertilizers. In this study, a pot experiment was conducted to simulate the high-risk situation of enhanced greenhouse gas (GHG) emissions following organic fertilizer application in energy maize cultivation. We hypothesized that cattle slurry application enhanced CO 2 and N 2 O fluxes compared to biogas digestate because of the overall higher carbon (C) and nitrogen (N) input, and that higher levels of CO 2 and N 2 O emissions could be expected by increasing soil organic C (SOC) and N contents. Biogas digestate and cattle slurry, at a rate of 150 kg NH 4 + - N ha −1 , were incorporated into 3 soil types with low, medium, and high SOC contents (Cambisol, Mollic Gleysol, and Sapric Histosol, termed C low , C medium , and Chigh, respectively). The GHG exchange (CO 2 , CH 4 , and N 2 O) was measured on 5 replicates over a period of 22 d using the closed chamber technique. The application of cattle slurry resulted in significantly higher CO 2 and N 2 O fluxes compared to the application of biogas digestate. No differences were observed in CH 4 exchange, which was close to zero for all treatments. Significantly higher CO 2 emissions were observed in Chigh compared to the other two soil types, whereas the highest N 2 O emissions were observed in C medium . Thus, the results demonstrate the importance of soil type-adapted fertilization with respect to changing soil physical and environmental conditions.