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The cultivation of Sphagnum mosses on re-wetted peat bogs for use in horticulture is a new land use strategy. We provide the first greenhouse gas balances for a field-scale Sphagnum farming experiment on former bog grassland, in its establishment phase. Over two years we used closed chambers to make measurements of GHG exchange on production strips of Sphagnum palustre L. and Sphagnum papillosum Lindb. and on irrigation ditches. Methane fluxes of both Sphagnum species showed a significant decrease over the study period. This trend was stronger for S. papillosum. In contrast, the estimated CO2 fluxes did not show a significant temporal trend over the study period. The production strips of both Sphagnum species were net GHG sinks of 5- 9 t haC-1 aC-1 (in CO2-equivalents) during the establishment phase of the moss carpets. In comparison, the ditches were a CO2 source instead of a CO2 sink and emitted larger amounts of CH4, resulting in net GHG release of ~11 t haC-1 aC-1 CO2-equivalents. We conclude that Sphagnum farming fields should be designed to minimise the area covered by irrigation ditches. Overall, Sphagnum farming on bogs has lower on-field GHG emissions than low-intensity agriculture. [ABSTRACT FROM AUTHOR]

Organic soils in peatlands store a great proportion of the global soil carbon pool and can lose carbon via the atmosphere due to degradation. In Germany, most of the greenhouse gas (GHG) emissions from organic soils are attributed to sites managed as grassland. Here, we investigated a land use gradient from near-natural wetland (NW) to an extensively managed (GE) to an intensively managed grassland site (GI), all formed in the same bog complex in northern Germany. Vertical depth profiles of δ13C, δ15N, ash content, C=N ratio and bulk density as well as radiocarbon ages were studied to identify peat degradation and to calculate carbon loss. At all sites, including the near-natural site, δ13C depth profiles indicate aerobic decomposition in the upper horizons. Depth profiles of δ15N differed significantly between sites with increasing δ15N values in the top soil layers paralleling an increase in land use intensity owing to differences in peat decomposition and fertilizer application. At both grassland sites, the ash content peaked within the first centimetres. In the near-natural site, ash contents were highest in 10-60 cm depth. The ash profiles, not only at the managed grassland sites, but also at the near-natural site indicate that all sites were influenced by anthropogenic activities either currently or in the past, most likely due to drainage. Based on the enrichment of ash content and changes in bulk density, we calculated the total carbon loss from the sites since the peatland was influenced by anthropogenic activities. Carbon loss at the sites increased in the following order: NW< GE< GI. Radiocarbon ages of peat in the topsoil of GE and GI were hundreds of years, indicating the loss of younger peat material. In contrast, peat in the first centimetres of the NW was only a few decades old, indicating recent peat growth. It is likely that the NW site accumulates carbon today but was perturbed by anthropogenic activities in the past. Together, all biogeochemical parameters indicate a degradation of peat due to (i) conversion to grassland with historical drainage and (ii) land use intensification. [ABSTRACT FROM AUTHOR]

Peatlands store a great proportion of the global soil carbon pool and can loose carbon via the atmosphere due to degradation. In Germany, most of the greenhouse gas emis¬sions from organic soils are attributed to sites managed as grassland. Here we investi¬gated a land-use gradient from near-natural wetland (NW) to an extensively managed (GE) to an intensively managed grassland site (GI), all formed in the same bog com¬plex in northern Germany. Vertical depth profiles of δ13C, δ15N, ash content, C/N ratio, bulk density, as well as radiocarbon ages were studied to identify peat degradation and to calculate carbon loss. At all sites, including the near-natural site, δ13C depth profiles indicate aerobic decomposition in the upper horizons. Depth profiles of δ15N differed significantly between sites with increasing δ15N values in the top layers with increasing intensity of use, indicating that the peat is more decomposed. At both grassland sites, the ash content peaked within the first centimeter. In the near-natural site, ash contents were highest in 10-60 cm depth. This indicates that not only the managed grasslands, but also the near-natural site, is influenced by anthropogenic activities, most likely due to the drainage of the surrounding area. However, we found very young peat material in the first centimeter of the NW, indicating recent peat growth. The NW site accumulates carbon today even though it is and probably was influenced by anthropogenic activities in the past indicated by δ13C and ash content depth profiles. Based on the enrichment of ash content and changes in bulk density, we calculated carbon loss from these sites in retrograde. As expected land use intensification leads to a higher carbon loss which is supported by the higher peat ages at the intensive managed grassland site. All in¬vestigated biogeochemical parameters together indicate degradation of peat due to (i) conversion to grassland, (ii) historical drainage as well as recent development and (iii) land use intensification. [ABSTRACT FROM AUTHOR]

Re-wetting minerotrophic fens has become an important strategy to mitigate climate change in Germany. However, recent studies report raised methane (CH4) effluxes during the first years after flooding. A minerotrophic fen in north-east Germany that was re-wetted 15 years ago was exposed to exceptionally heavy rainfall and freshwater flooding in August 2011. We measured CH4 effluxes from wetland vegetation stands dominated by Phragmites australis (Cav.) Trin. ex Steud., Typha latifolia L. and Carex acutiformis Ehrh., using the closed-chamber method, fortnightly from March 2011 to March 2012 with extra sampling during the flooding. The respective annual effluxes of CH4 (mean ± 1 standard error) from the three vegetation types were 18.5 ± 1.3, 21.1 ± 1.2 and 47.5 ± 5.0 g m-2 a-1, with the August effluxes contributing 40 %, 50 % and 10 % of the annual effluxes. Despite the freshwater flooding in August, annual CH4 effluxes from the 15-year re-wetted fen are similar to those reported from pristine fens. These results are promising because they indicate that, although CH4 effluxes are elevated after re-wetting, they may return to values typical for pristine fens after 15 years. Hence, re-wetting can achieve the purpose of reducing greenhouse gas effluxes from drained minerotrophic fens. [ABSTRACT FROM AUTHOR]

Wetlands can either be net sinks or net sources of greenhouse gases (GHGs), depending on the mean annual water level and other factors like average annual temperature, vegetation development, and land use. Whereas drained and agriculturally used peatlands tend to be carbon dioxide (CO2) and nitrous oxide (N2O) sources but methane (CH4) sinks, restored (i.e. rewetted) peatlands rather incorporate CO2, tend to be N2O neutral and release CH4. One of the aims of peatland restoration is to decrease their global warming potential (GWP) by reducing GHG emissions. We estimated the greenhouse gas exchange of a peat bog restoration sequence over a period of 2 yr (1 July 2007-30 June 2009) in an Atlantic raised bog in northwest Germany. We set up three study sites representing different land use intensities: intensive grassland (deeply drained, mineral fertilizer, cattle manure and 4-5 cuts per year); extensive grassland (rewetted, no fertilizer or manure, up to 1 cutting per year); near-natural peat bog (almost no anthropogenic influence). Daily and annual greenhouse gas exchange was estimated based on closed-chamber measurements. CH4 and N2O fluxes were recorded bi-weekly, and net ecosystem exchange (NEE) measurements were carried out every 3-4 weeks. Annual sums of CH4 and N2O fluxes were estimated by linear interpolation while NEE was modelled. Regarding GWP, the intensive grassland site emitted 564±255 g CO2-C equivalents m-2 yr-1 and 850±238 g CO2-C equivalents m-2 yr-1 in the first (2007/2008) and the second (2008/2009) measuring year, respectively. The GWP of the extensive grassland amounted to -129±231 g CO2-C equivalents m-2 yr-1 and 94±200 g CO2-C equivalents m-2 yr-1, while it added up to 45±117 g CO2-C equivalents m-2 yr-1 and -101±93 g CO2-C equivalents m-2 yr-1 in 2007/08 and 2008/09 for the near-natural site. In contrast, in calendar year 2008 GWP aggregated to 441±201 g CO2-C equivalents m-2 yr-1, 14±162 g CO2-C equivalents m-2 yr-1 and 31±75 g CO2-C equivalents m-2 yr-1 for the intensive grassland, extensive grassland, and near-natural site, respectively. Despite inter-annual variability, rewetting contributes considerably to mitigating GHG emission from formerly drained peatlands. Extensively used grassland on moderately drained peat approaches the carbon sequestration potential of near-natural sites, although it may oscillate between being a small sink and being a small source depending on inter-annual climatic variability. [ABSTRACT FROM AUTHOR]

The assessment of emission factors for many peatlands is difficult, and reliable data on the exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) between soil and atmosphere of these areas is particularly scarce. Reasons for this are the multitude of soil and land use combinations that control greenhouse gas exchange and the high effort associated with data acquisition. We investigated the greenhouse gas exchange of a peat bog restoration sequence over a period of 2 yr (July 2007-June 2009) in an Atlantic raised bog in Northwest Germany. We set up three sites representing different land use intensities: intensive grassland (mineral fertilizer, cattle manure and 4-5 cuts per year); extensive grassland (no fertilizer or manure, maximal 1 cutting per year); near-natural peat bog (almost no anthropogenic influence). We obtained seasonal and annual estimates of greenhouse gas exchange based on closed chamber measurements. CH4 and N2O fluxes were recorded bi-weekly, CO2 NEE determinations were carried out 3-4 weekly. To get annual sums the CH4 and N2O fluxes were interpolated linearly while NEE was modelled. The intensive grassland site emitted 548±169gCO2-Cm-2 in the first and 817±140gCO2-Cm-2 in the second year. The extensive grassland site showed a slight uptake in the first year (-148 ± 143gCO2-Cm-2), and a small emission of 88±146gCO2-Cm-2 in the second year. In contrast to these agriculturally used sites, the near-natural site took up CO2-C in both years(-8±68gCO2-Cm-2 and -127±53gCO2-Cm-2). Under consideration of N2O and CH4 exchange, the total average greenhouse warming potential (GWP) for 2008 amounts to 441 ±157gm-2,14±152gm-2 and 31 ±68gm-2 CO2-C-equivalent for the intensive grassland, the extensive grassland and the near-natural site, respectively. Despite inter-annual variability, rewetting contributes considerably to mitigating GHG emission from formerly drained peatlands. Already extensively used grassland on moderately drained peat approaches the carbon sequestration potential of near-natural sites, albeit it may oscillate between being a small sink and being a small source depending on interannual climatic variability. [ABSTRACT FROM AUTHOR]

Drained peatlands are known to be important sources of carbon dioxide (CO2) and nitrous oxide (N2O). While CO2 emissions occur mainly during the growing season, large N2O emissions may occur during the non-growing season as well. Peatland re-wetting may be an effective measure to prevent those emissions. However, recent research shows that re-wetted peatlands may release large amounts of methane (CH4) during the years immediately after re-wetting whereas abandonment of intensive grassland on drained peat soils possibly leads to low nutrient supply and thus to small greenhouse gas (GHG) emissions. Here we examine the role of extensification practices (such as abandonment of mineral fertilisation, reduced cutting frequency and a cattle-free winter period) on GHG emissions from a temperate peatland during winter. From November 2009 to March 2010 GHG measurements were made on a minerotrophic fen five years after intensive grassland use was abandoned. During the measurement period CO2 and N2O emissions amounted to 4.4 t ha-1 and 2.6 t ha-1 CO2-equivalent, whilst CH4 emissions were negligible. Altogether the site emitted 7 t ha-1 CO2-equivalent, of which 37 % was N2O, even though the winter 2009/2010 was extraordinarily cold. Thus, extensification of grassland use alone may not be sufficient to reduce GHG emissions from temperate peatlands. [ABSTRACT FROM AUTHOR]

The large scale spatial heterogeneity of soil respiration caused by differences in site conditions is quite well understood. However, comparably little is known about the micro scale heterogeneity within forest ecosystems on homogeneous soils. Forest age, 5 soil texture, topographic position, micro topography and stand structure may influence soil respiration considerably within short distance. In the present study within site spatial heterogeneity of soil respiration has been evaluated. To do so, an improvement of available techniques for interpolating soil respiration data via kriging was undertaken. Soil respiration was measured with closed chambers biweekly from April 2005 to 10 April 2006 using a nested design (a set of stratified random plots, supplemented by 2 small and 2 large nested groupings) in an unmanaged, beech dominated old growth forest in Central Germany (Hainich, Thuringia). A second exclusive randomized design was established in August 2005 and continually sampled biweekly until July 2007. The average soil respiration values from the random plots were standardized by 15 modeling soil respiration data at defined soil temperature and soil moisture values. By comparing sampling points as well as by comparing kriging results based on various sampling point densities, we found that the exclusion of local outliers was of great importance for the reliability of the estimated fluxes. Most of this information would have been missed without the nested groupings. The extrapolation results slightly improved when additional parameters like soil temperature and soil moisture were included in the extrapolation procedure. Semivariograms solely calculated from soil respiration data show a broad variety of autocorrelation distances (ranges) from a few centimeters up to a few tens of meters. The combination of randomly distributed plots with nested groupings plus the in clusion of additional relevant parameters like soil temperature and soil moisture data permits an improved estimation of the range of soil respiration, which is a prerequisite for reliable interpolated maps of soil respiration. [ABSTRACT FROM AUTHOR]

The article examines the impact of restoration techniques on soil microbial biomass carbon and nitrogen and enzyme activity on an abandoned military training site in the Lüneburger Heaths in Germany. Restoration actions include spreading of heath plaggen, spreading of Festuca filiformis and succession. The pH, bulk density, abundance of roots, soil organic carbon (SOC) and nitrogen were measured after ten years of restoration. Bulk density and pH proved to be higher than on the reference site at all disturbed sites. SOC storage reached from 37 to 91 percent and the regeneration of nitrogen was slightly lower.

In Central Europe, most bogs have a history of drainage and many of them are currently being restored. Success of restoration as well as greenhouse gas exchange of these bogs is influenced by environmental stress factors as drought and atmospheric nitrogen deposition. We determined the methane and nitrous oxide exchange of sites in the strongly decomposed center and less decomposed edge of the Pietzmoor bog in NW Germany in 2004. Also, we examined the methane and nitrous oxide exchange of mesocosms from the center and edge before, during, and following a drainage experiment as well as carbon dioxide release from disturbed unfertilized and nitrogen fertilized surface peat. In the field, methane fluxes ranged from 0 to 3.8 mgm-2 h-1 and were highest from hollows. Field nitrous oxide fluxes ranged from 0 to 574μgm-2 h-1 and were elevated at the edge. A large Eriophorum vaginatum tussock showed decreasing nitrous oxide release as the season progressed. Drainage of mesocosms decreased methane release to 0, even during rewetting. There was a tendency for a decrease of nitrous oxide release during drainage and for an increase in nitrous oxide release during rewetting. Nitrogen fertilization did not increase decomposition of surface peat. Our examinations suggest a competition between vascular vegetation and denitrifiers for excess nitrogen. We also provide evidence that the von Post humification index can be used to explain nitrous oxide release from bogs, if the role of vascular vegetation is also considered. An assessment of the greenhouse gas release from nitrogen saturated restoring bogs needs to take into account elevated release from fresh Sphagnum peat as well as from sedges growing on decomposed peat. Given the high atmospheric nitrogen deposition, restoration will not be able to achieve an oligotrophic ecosystem in the short term. [ABSTRACT FROM AUTHOR]

In Central Europe, most bogs have a history of drainage and many of them are currently being restored. Success of restoration as well as greenhouse gas exchange of these bogs is influenced by environmental stress factors as drought and atmospheric nitrogen deposition. We determined the methane and nitrous oxide exchange of sites in the strongly decomposed center and less decomposed edge of the Pietzmoor bog in NW Germany in 2004. Also, we examined the methane and nitrous oxide exchange of mesocosms from the center and edge before, during, and following a drainage experiment as well as carbon dioxide release from disturbed unfertilized and nitrogen fertilized surface peat. In the field, methane fluxes ranged from 0 to 3.8mgm-2 h-1 and were highest from hollows. Field nitrous oxide fluxes ranged from 0 to 574 μgm-2 h-1 and were elevated at the edge. A large Eriophorum vaginatum tussock showed decreasing nitrous oxide release as the season progressed. Drainage of mesocosms decreased methane release to 0, even during rewetting. There was a tendency for a decrease of nitrous oxide release during drainage and for an increase in nitrous oxide release during rewetting. Nitrogen fertilization did not increase decomposition of surface peat. Our examinations suggest a competition between vascular vegetation and denitrifiers for excess nitrogen. We also provide evidence that the von Post humification index can be used to explain greenhouse gas release from bogs, if the role of vascular vegetation is also considered. An assessment of the greenhouse gas release from nitrogen saturated restoring bogs needs to take into account elevated release from fresh Sphagnum peat as well as from sedges growing on decomposed peat. Given the high atmospheric nitrogen deposition, restoration will not be able to achieve an oligotrophic ecosystem in the short term. [ABSTRACT FROM AUTHOR]

Abstract: The restoration of drained peat bogs in Northwest (NW) Europe is an important task of soil protection, but needs to cope with warmer and drier summers. Our examination took place in the Pietzmoor bog (Schneverdingen, NW Germany) that had been drained for fuel peat extraction until the 1970s and rewetted since then. We determined carbon dioxide (CO2) efflux in situ and in laboratory incubations. Also, we analyzed pore water for dissolved organic carbon (DOC), total and dissolved organic N (DON), nitrate (NO3 –) and ammonium (NH4 +) concentration. In Schneverdingen, the summer 2003 was record-breaking hot (mean temperature June to August elevated>3 K compared to long-term average) and dry (precipitation during the same period<59% of long-term average). In July 2003, the water table in the Pietzmoor subsided to>42 cm below the surface in July 2003, when in situ soil CO2 efflux was up to 23.4 g m–2 d–1 compared to 15.7 g m–2 d–1 in September. Prior to March 2003, DOC concentrations in pore water were < 180 mg l–1 and NH4 + was the dominant fraction of mineral N. In July 2003, DOC concentration rose to 249 g l–1, DON concentrations more than doubled, and NO3 – became the dominant fraction of mineral N. Due to the increased future likelihood of hot and dry summers in NW Germany, peat bog restoration efforts need take care that a water table close to the surface is maintained. [Copyright &y& Elsevier]

The article discusses nitrous oxide (N2O) has a powerful greenhouse gas atmospheric growth rate has accelerated over the past decade. Topics include anthropogenic N2O emissions result from soil N fertilization, has converted to N2O via oxic nitrification and anoxic denitrification pathways; and the primary global source of N2O has production for N cycling by microbiota in soils.