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Global and climate change have many interlinkages with condi tions and processes at regional scales. The collaborated research topic Land Use Options - Strategies and Adaptation to Global Change focusses on the regional consequences of recent and expected patterns of Global Change.

The Arctic plays a key role in the Earths climate system, because global warming is predicted to be most pronounced at high latitudes, and one third of the global carbon pool is stored in ecosystems of the northern latitudes. The degradation of permafrost and the associated release of climate-relevant trace gases from intensified microbial turnover of organic carbon and from destabilized gas hydrates represent a potential environmental hazard.The microorganisms, which are the drivers of methane production and oxidation in Arctic wetlands, have remained obscure. Their function, population structure and reaction to environmental change is largely unknown, which means that also an important part of the process knowledge on methane fluxes in permafrost ecosystems is far from completely understood. This hampers prediction of the effects of climate warming on arctic methane fluxes. Understanding these microbial populations is therefore highly important for understanding the global climatic effects of a warming Arctic. This talk will examine the activity and diversity of methane-cycling microorganisms in Siberian permafrost ecosystems.

Ongoing global warming will increase the frequency of soil freeze-thaw cycles (FTCs) in cool-temperate and other high-latitude regions. The spatial relevance of seasonally frozen ground amounts to c. 55% of the total land area of the northern hemisphere. Evidence suggests that FTCs contribute to nutrient dynamics. Knowledge of their effects on plant communities is scarce, although plants may be the decisive factor in controlling ecosystem functions such as nutrient retention.Here, the effects are analysed of five additional FTCs in winter for the above- and below-ground productivity of experimental grassland communities and soil enzymatic activity over the following growing season.Freeze-thaw cycles increased the above-ground productivity but reduced root length over the whole subsequent growing season. In summer, no changes in soil enzymatic activities representing the carbon, nitrogen and phosphorus cycles were observed in the FTC-manipulated plots, except for an increased cellobiohydrolase activity.Changes in productivity resulting in an increased shoot-to-root ratio and shifts in timing are capable of altering ecosystem stability and ecosystem services, such as productivity and nutrient retention.

Climate change will increase the recurrence of extreme weather events such as drought and heavy rainfall. Evidence suggests that extreme weather events pose threats to ecosystem functioning, particularly to nutrient cycling and biomass production. These ecosystem functions depend strongly on below-ground biotic processes, including the activity and interactions among plants, soil fauna, and micro-organisms. Here, experimental grassland and heath communities of three phytodiversity levels were exposed either to a simulated single drought or to a heavy rainfall event. Both weather manipulations were repeated for two consecutive years. The magnitude of manipulations imitated the local 100-year extreme weather event. Heavy rainfall events increased below-ground plant biomass and stimulated soil enzyme activities as well as decomposition rates for both plant communities. In contrast, extreme drought did not reduce below-ground plant biomass and root length, soil enzyme activities, and cellulose decomposition rate. The low responsiveness of the measured ecosystem properties in face of the applied weather manipulations rendered the detection of significant interactions between weather events and phytodiversity impossible. Our data indicate on the one hand the close interaction between below ground plant parameters and microbial turnover processes in soil; on the other hand it shows that the plant-soil system can buffer against extreme drought events, at last for the period of investigation.

Based on lipid analyses, 16S rRNA/rRNA gene single-strand conformation polymorphism fingerprints and methane flux measurements, influences of the fertilization regime on abundance and diversity of archaeal communities were investigated in soil samples from the long-term (103 years) field trial in Bad Lauchstädt, Germany. The investigated plots followed a gradient of increasing fertilization beginning at no fertilization and ending at the 'cattle manure' itself. The archaeal phospholipid etherlipid (PLEL) concentration was used as an indicator for archaeal biomass and increased with the gradient of increasing fertilization, whereby the concentrations determined for organically fertilized soils were well above previously reported values. Methane emission, although at a low level, were occasionally only observed in organically fertilized soils, whereas the other treatments showed significant methane uptake. Euryarchaeotal organisms were abundant in all investigated samples but 16S rRNA analysis also demonstrated the presence of Crenarchaeota in fertilized soils. Lowest molecular archaeal diversity was found in highest fertilized treatments. Archaea phylogenetically most closely related to cultured methanogens were abundant in these fertilized soils, whereas Archaea with low relatedness to cultured microorganisms dominated in non-fertilized soils. Relatives of Methanoculleus spp. were found almost exclusively in organically fertilized soils or cattle manure. Methanosarcina-related microorganisms were detected in all soils as well as in the cattle manure, but soils with highest organic application rate were specifically dominated by a close phylogenetic relative of Methanosarcina thermophila. Our findings suggest that regular application of cattle manure increased archaeal biomass, but reduced archaeal diversity and selected for methanogenic Methanoculleus and Methanosarcina strains, leading to the circumstance that high organic fertilized soils did not function as a met

Wet tundra environments of the Arctic are natural sources of the climate relevant trace gas methane. The underlying microbial and geochemical processes are not yet well understood. The field investigations were carried out on the island Samoylov (N 72°, E 126°) located in the Lena Delta, Siberia. The study site represented an area of typical polygonal patterned grounds with ice-wedges. For the understanding and assessment of recent and future carbon dynamics of permafrost soils the processes of CH4 production and oxidation, the microbial community structure and the quality of DOM were studied in two soils of a polygonal tundra.The mean flux rate of the depression was 53.2 ± 8.7 mg CH4 m-2 d-1, whereas the mean flux rate of the dryer rim part of the polygon was 4.7 ± 2.5 CH4 m-2 d-1. Activities of methanogens and methanotrophs differed significantly in their rates and distribution patterns among the two investigated profiles. Community structure analysis showed similarities between both soils for esterlinked PLFAs and differences in the fraction of unsaponifiable PLFAs and PLELs. Furthermore, a shift of the overall composition of the microbiota with depth at both sites was indicated by an increasing portion of iso- and anteiso-branched fatty acids related to the amount of straight chain fatty acids. The quantity of dissolved organic matter (DOM), which represents an important C pool for microbial communities, correlated significant with the total concentrations of phospholipid fatty acids and ether lipids (PLFA and PLEL) a measure for microbial biomass. Although permafrost soils represent a large carbon pool, it was shown, that the reduced quality of organic matter leads to a substrate limitation of the microbial metabolism. This is an important finding for modelling and calculating trace gas fluxes from permafrost environments, because the known models are consider only the total carbon amount.It can be concluded by the presented results firstly that microbi

The turnover of N derived from rhizodeposition of faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) and the effects of the rhizodeposition on the subsequent C and N turnover of its crop residues were investigated in an incubation experiment (168 days, 15 degreesC). A sandy loam soil for the experiment was either stored at 6 degreesC or planted with the respective grain legume in pots. Legumes were in situ N-15 stem labelled during growth and visible roots were removed at maturity. The remaining plant-derived N in soil was defined as N rhizodeposition. In the experiment the turnover of C and N was compared in soils with and without previous growth of three legumes and with and without incorporation of crop residues. After 168 days, 21% (lupin), 26% (faba bean) and 27% (pea) of rhizodeposition N was mineralised in the treatments without crop residues. A smaller amount of 15-17% was present as microbial biomass and between 30 and 55% of mineralised rhizodeposition N was present as microbial residue pool, which consists of microbial exoenzymes, mucous substances and dead microbial biomass. The effect of rhizodeposition on the C and N turnover of crop residues was inconsistent. Rhizodeposition increased the crop residue C mineralisation only in the lupin treatment; a similar pattern was found for microbial C, whereas the microbial N was increased by rhizodeposition in all treatments. The recovery of residual N-15 in the microbial and mineral N pool was similar between the treatments containing only labelled crop residues and labelled crop residues + labelled rhizodeposits. This indicates a similar decomposability of both rhizodeposition N and crop residue N and may be attributable to an immobilisation of both N sources (rhizodeposits and crop residues) as microbial residues and a subsequent remineralisation mainly from this pool.

Peatlands are ecosystems of exceptional conservation value because of their beauty, biodiversity, importance in global geochemical cycles, and the paleoenvironmental records they preserve. Commercial extraction and drainage for forestry or agriculture have caused the destruction of many peatlands, especially in or close to urban areas of the northern temperate zone. Are these commercial and environmental interests irreconcilable? A close analysis suggests that limited peat extraction may actually increase biodiversity in some cases, and may be sustainable over the long term. As we learn more about how peatlands spontaneously regenerate following disturbance, and what conditions govern the re-establishment of a diverse community and the ability to sequester carbon, we increase our chances of being able to restore damaged peatlands. Preserving the chronological records hidden in the peat profile, the natural heritage value of peatlands, and the bulk of sequestered carbon, however, will remain incompatible with any form of exploitation.