Suchergebnisse

This book looks at the sources and composition of the atmosphere and rainfall, with particular attention on acidifying components and those that affect ecosystems. It further widens the subject to look at trace metals. It includes papers on the impact of deposition on soils and forests and the recovery of the natural environment. Work on critical loads makes a contribution to understanding the degree to which deposition must be reduced to limit its impact.

Summarization: European Union policy on soil threats and soil protection has prioritized new research to address global soil threats. This research draws on the methodology of Critical Zone Observatories (CZOs) to focus a critical mass of international, multidisciplinary expertise at specific field sites. These CZOs were selected as part of an experimental design to study soil processes and ecosystem function along a hypothesized soil life cycle—from incipient soil formation where new parent material is being deposited, to highly degraded soils that have experienced millennia of intensive land use. Further CZOs have been selected to broaden the range of soil environments and data sets to test soil process models that represent the stages of the soil life cycle. The scientific methodology for this research focuses on the central role of soil structure and soil aggregate formation and stability in soil processes. Research methods include detailed analysis and mathematical modeling of soil properties related to aggregate formation and their relation to key processes of reactive transport, nutrient transformation, and C and food web dynamics in soil ecosystems. Within this program of research, quantification of soil processes across an international network of CZOs is focused on understanding soil ecosystem services including their quantitative monetary valuation within the soil life cycle. Further experimental design at the global scale is enabled by this type of international CZO network. One example is a proposed experiment to study soil ecosystem services along planetary-scale environmental gradients. This would allow scientists to gain insight into the responses of soil processes to increasing human pressures on Earth's critical zone that arise through rapidly changing land use and climate. ; Presented on: Vadose Zone Journal

AbstractNutrient imbalances may negatively affect the health status of forests exposed to multiple stress factors, including drought and bark beetle calamities. We studied the origin of base cations in runoff from a small Carpathian catchment underlain by base-poor flysch turbidites using magnesium (Mg), calcium (Ca) and strontium (Sr) isotope composition of 10 ecosystem compartments. Our objective was to constrain conclusions drawn from long-term hydrochemical monitoring of inputs and outputs. Annual export of Mg, Ca and Sr exceeds 5-to-15 times their atmospheric input. Mass budgets per se thus indicate sizeable net leaching of Mg, Ca and Sr from bedrock sandstones and claystones. Surprisingly, δ26Mg, δ44Ca and 87Sr/86Sr isotope ratios of runoff were practically identical to those of atmospheric deposition and soil water but significantly different from bedrock isotope ratios. We did not find any carbonates in the studied area as a hypothetical, easily dissolvable source of base cations whose isotope composition might corroborate the predominance of geogenic base cations in the runoff. Marine carbonates typically have lower δ26 Mg and 87Sr/86Sr ratios, and silicate sediments often have higher δ26Mg and 87Sr/86Sr ratios than runoff at the study site. Mixing of these two sources, if confirmed, could reconcile the flux and isotope data.