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As a key component of the carbon cycle, soil CO2 efflux (SCE) is being increasingly studied to improve our mechanistic understanding of this important carbon flux. Predicting ecosystem responses to climate change often depends on extrapolation of current relationships between ecosystem processes and their climatic drivers to conditions not yet experienced by the ecosystem. This raises the question of to what extent these relationships remain unaltered beyond the current climatic window for which observations are avail-able to constrain the relationships. Here, we evaluate whether current responses of SCE to fluctuations in soil temperature and soil water content can be used to predict SCE under altered rainfall patterns. Of the 58 experiments for which we gathered SCE data, 20 were discarded because either too few data were available or inconsistencies precluded their incorporation in the analyses. The 38 remaining experiments were used to test the hypothesis that a model parameterized with data from the control plots (using soil temperature and water content as predictor variables) could adequately predict SCE measured in the manipulated treatment. Only for 7 of these 38 experiments was this hypothesis rejected. Importantly, these were the experiments with the most reliable datasets, i.e., those providing high-frequency measurements of SCE. Regression tree analysis demonstrated that our hypothesis could be rejected only for experiments with measurement intervals of less than 11 days, and was not rejected for any of the 24 experiments with larger measurement intervals. This highlights the importance of high-frequency measurements when studying effects of altered precipitation on SCE, probably because infrequent measurement schemes have insufficient capacity to detect shifts in the climate dependencies of SCE. Hence, the most justified answer to the question of whether current moisture responses of SCE can be extrapolated to predict SCE under altered precipitation regimes is “no” – as based on the most reliable data sets available. We strongly recommend that future experiments focus more strongly on establishing response functions across a broader range of precipitation regimes and soil moisture conditions. Such experiments should make accurate measurements of water availability, should conduct high-frequency SCE measurements, and should consider both instantaneous responses and the potential legacy effects of climate extremes. This is important, because with the novel approach presented here, we demonstrated that, at least for some ecosystems, current moisture responses could not be extrapolated to predict SCE under altered rainfall conditions., Biogeosciences, 11 (11), ISSN:1726-4170

The global climate is changing. This has been studied during the last 10 years in large scale field experiments with non-intrusive manipulations of temperature and precipitation and at one site also combined with enhanced atmospheric CO2 concentrations. The experiments are placed in vulnerable scrubland ecosystems across Europe and has been part of the EU-projects CLIMOOR and VULCAN and the coming infrastructure INCREASE. Shrubland ecosystems were chosen because they represent an important natural resource, which are known to be sensitive to observed changes in environmental pressures, and they provide a range of services for the society. The poster will present the experimental approach and a summary of climate change effects on ecosystem processes and functions. The experiments combine 2 different approaches to study climate effects on ecosystems. The first approach is known as "space for time" substitution, where the long term effect of a pressure on the ecosystem, e.g. temperature, at any particular site is studied by moving to another site, which is already exposed to the change in focus. This was done by carrying out the same studies in comparable ecosystems in UK, Denmark, the Netherlands, Hungary, Spain and Italy - 6 sites which are naturally exposed to large differences in the climatic conditions we wanted to study. The other approach applied is "ecosystem manipulations", which means that the ecosystem is exposed to the changes in the field by realistic manipulations of temperature and water and in one experiment in combination with CO2. In summary one could say that we superimposed manipulations with water and temperature on existing gradients with respect to the same factors. This combination of gradients and experimental manipulation of temperature and precipitation increases the potential for evaluating the generality of the observed responses to the changes in the climatic drivers.

13 páginas, 7 figuras, 4 tablas., Shrublands constitute significant and important parts of European landscapes providing a large number of important ecosystem services. Biogeochemical cycles in these ecosystems have gained little attention relative to forests and grassland systems, but data on such cycles are required for developing and testing ecosystem models. As climate change progresses, the potential feedback from terrestrial ecosystems to the atmosphere through changes in carbon stocks, carbon sequestration, and general knowledge on biogeochemical cycles becomes increasingly important. Here we present carbon and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m 2 to 18,546 g C m 2 , and the systems ranged from being net sinks (126 g C m 2 a 1 ) to being net sources ( 536 g C m 2 a 1 ) of carbon with the largest storage and sink of carbon at wet and cold climatic conditions. The soil carbon store dominates the carbon budget at all sites and in particular at the site with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation was more than 5 times aboveground litterfall carbon which is significantly greater than the factor of 2 reported in a global analysis of forest data. Nitrogen storage was also dominated by the soil pools generally showing small losses except when atmospheric N input was high. The study shows that in the future a climate-driven land cover change between grasslands and shrublands in Europe will likely lead to increased ecosystem C where shrublands are promoted and less where grasses are promoted. However, it also emphasizes that if feedbacks on the global carbon cycle are to be predicted it is critically important to quantify and understand belowground carbon allocation and processes as well as soil carbon pools, particularly on wet organic soils, rather than plant functional change as the soil stores dominate the overall budget and fluxes of carbon., The present study was carried out and funded by EU as part of two research projects CLIMOOR (contract ENV4-CT97-0694) and VULCAN (contract EVK2-CT-2000-00094), the participating research institutes, the CLIMAITE project, the Spanish (grant CGL2006-04025/BOS) and the Catalan (grant SGR2005-00312) governments, and the EU FP6 project NitroEurope (contract 017841).

The field site network (FSN) plays a central role in conducting joint research within all Assessing Large-scale Risks for biodiversity with tested Methods (ALARM) modules and provides a mechanism for integrating research on different topics in ALARM on the same site for measuring multiple impacts on biodiversity. The network covers most European climates and biogeographic regions, from Mediterranean through central European and boreal to subarctic. The project links databases with the European-wide field site network FSN, including geographic information system (GIS)-based information to characterise the test location for ALARM researchers for joint on-site research. Maps are provided in a standardised way and merged with other site-specific information. The application of GIS for these field sites and the information management promotes the use of the FSN for research and to disseminate the results. We conclude that ALARM FSN sites together with other research sites in Europe jointly could be used as a future backbone for research proposals. EC [GOCE-CT-2003-506675]