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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]

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]