Mountain soils under a changing climate and land-use

Mountain ecosystems are currently experiencing the strongest climatic warming and the largest changes in land-use during the last millennia. The impacts of these changes on soils and their roles in the cycling of carbon and nutrients are, however, largely unknown. Here, we define mountain soils as soils from mountainous areas with cool summers and cold winters and thus, soils from ecosystems that are influenced by snow and ice and where biogeochemical processes are limited by temperature. Because climatic conditions, soil properties, plant species and productivity vary at a small scale in mountains, they provide a unique natural but a seldom used laboratory to study soil processes. In this special issue, we compile different studies on soils from European mountains, reaching from the functioning of mountain soils along natural climatic gradients to responses of greenhouse gas fluxes from mountain soils to experimental warming, soil frost and changes in precipitatio

Forest Soil Respiration under Climate Changing

The respiration of forest soils and the major factors controlling its rate are fairly well understood. The process is of utmost significance because its balance with the fixation of CO2 in the biomass defines whether a particular site is a source or sink of atmospheric CO2. Currently, the measurement of soil respiration in the field requires rather expensive experimental installations. Nevertheless, there are still some caveats in our understanding, such as the separation of autotrophic and heterotrophic soil respiration, the relevance of different groups of soil organisms, the effect of ecosystem disturbances in different types of forests on soil respiration with respect to magnitude and duration, the adaptation of soil respiration to changing site conditions, and the regional prediction of soil respiration, based on proxy data. Technical progress and additional contributions on process understanding will put us in the position of better predictions of the forest soil respiration. We encourage studies from all fields, including experimental studies, monitoring approaches and models, to contribute to this Special Issue in order to promote knowledge and adaptation strategies for the preservation, management, and future development of forest ecosystems

Review of existing information on the interrelations between soil and climate change. (ClimSoil). Final report

Carbon stock in EU soils – The soil carbon stocks in the EU27 are around 75 billion tonnes of carbon (C); of this stock around 50% is located in Sweden, Finland and the United Kingdom (because of the vast area of peatlands in these countries) and approximately 20% is in peatlands, mainly in countries in the northern part of Europe. The rest is in mineral soils, again the higher amount being in northern Europe. 2. Soils sink or source for CO2 in the EU – Both uptake of carbon dioxide (CO2) through photosynthesis and plant growth and loss of CO2 through decomposition of organic matter from terrestrial ecosystems are significant fluxes in Europe. Yet, the net terrestrial carbon fluxes are typically 5-10 times smaller relative to the emissions from use of fossil fuel of 4000 Mt CO2 per year. 3. Peat and organic soils - The largest emissions of CO2 from soils are resulting from land use change and especially drainage of organic soils and amount to 20-40 tonnes of CO2 per hectare per year. The most effective option to manage soil carbon in order to mitigate climate change is to preserve existing stocks in soils, and especially the large stocks in peat and other soils with a high content of organic matter. 4. Land use and soil carbon – Land use and land use change significantly affects soil carbon stocks. On average, soils in Europe are most likely to be accumulating carbon on a net basis with a sink for carbon in soils under grassland and forest (from 0 - 100 billion tonnes of carbon per year) and a smaller source for carbon from soils under arable land (from 10 - 40 billion tonnes of carbon per year). Soil carbon losses occur when grasslands, managed forest lands or native ecosystems are converted to croplands and vice versa carbon stocks increase, albeit it slower, following conversion of cropland. 5. Soil management and soil carbon – Soil management has a large impact on soil carbon. Measures directed towards effective management of soil carbon are available and identified, and many of these are feasible and relatively inexpensive to implement. Management for lower nitrogen (N) emissions and lower C emissions is a useful approach to prevent trade off and swapping of emissions between the greenhouse gases CO2, methane (CH4) and nitrous oxide (N2O). 6. Carbon sequestration – Even though effective in reducing or slowing the build up of CO2 in the atmosphere, soil carbon sequestration is surely no ‘golden bullet’ alone to fight climate change due to the limited magnitude of its effect and its potential reversibility; it could, nevertheless, play an important role in climate mitigation alongside other measures, especially because of its immediate availability and relative low cost for 'buying' us time. 7. Effects of climate change on soil carbon pools – Climate change is expected to have an impact on soil carbon in the longer term, but far less an impact than does land use change, land use and land management. We have not found strong and clear evidence for either overall and combined positive of negative impact of climate change (atmospheric CO2, temperature, precipitation) on soil carbon stocks. Due to the relatively large gross exchange of CO2 between atmosphere and soils and the significant stocks of carbon in soils, relatively small changes in these large and opposing fluxes of CO2, i.e. as result of land use (change), land management and climate change, may have significant impact on our climate and on soil quality. 8. Monitoring systems for changes in soil carbon – Currently, monitoring and knowledge on land use and land use change in EU27 is inadequate for accurate calculation of changes in soil carbon contents. Systematic and harmonized monitoring across EU27 and across relevant land uses would allow for adequate representation of changes in soil carbon in reporting emissions from soils and sequestration in soils to the UNFCCC. 9. EU policies and soil carbon – Environmental requirements under the Cross Compliance requirement of CAP is an instrument that may be used to maintain SOC. Neither measures under UNFCCC nor those mentioned in the proposed Soil Framework Directive are expected to adversely impact soil C. EU policy on renewable energy is not necessarily a guarantee for appropriate (soil) carbon management

Abiotic and Biotic Soil Characteristics in Old Growth Forests and Thinned or Unthinned Mature Stands in Three Regions of Oregon

We compared forest floor depth, soil organic matter, soil moisture, anaerobic mineralizable nitrogen (a measure of microbial biomass), denitrification potential, and soil/litter arthropod communities among old growth, unthinned mature stands, and thinned mature stands at nine sites (each with all three stand types) distributed among three regions of Oregon. Mineral soil measurements were restricted to the top 10 cm. Data were analyzed with both multivariate and univariate analyses of variance. Multivariate analyses were conducted with and without soil mesofauna or forest floor mesofauna, as data for those taxa were not collected on some sites. In multivariate analysis with soil mesofauna, the model giving the strongest separation among stand types (P = 0.019) included abundance and richness of soil mesofauna and anaerobic mineralizable nitrogen. The best model with forest floor mesofauna (P = 0.010) included anaerobic mineralizable nitrogen, soil moisture content, and richness of forest floor mesofauna. Old growth had the highest mean values for all variables, and in both models differed significantly from mature stands, while the latter did not differ. Old growth also averaged higher percent soil organic matter, and analysis including that variable was significant but not as strong as without it. Results of the multivariate analyses were mostly supported by univariate analyses, but there were some differences. In univariate analysis, the difference in percent soil organic matter between old growth and thinned mature was due to a single site in which the old growth had exceptionally high soil organic matter; without that site, percent soil organic matter did not differ between old growth and thinned mature, and a multivariate model containing soil organic matter was not statistically significant. In univariate analyses soil mesofauna had to be compared nonparametrically (because of heavy left-tails) and differed only in the Siskiyou Mountains, where they were most abundant and species rich in old growth forests. Species richness of mineral soil mesofauna correlated significantly (+) with percent soil organic matter and soil moisture, while richness of forest floor mesofauna correlated (+) with depth of the forest floor. Composition of forest floor and soil mesofauna suggest the two groups represent a single community. Soil moisture correlated highly with percent soil organic matter, with no evidence for drying in sites that were sampled relatively late in the summer drought, suggesting losses of surface soil moisture were at least partially replaced by hydraulic lift (which has been demonstrated in other forests of the region)