Das Projekt "SOM formation: The mycorrhiza-mediated pathway for soil organic matter (SOM) formation and consequences for the SOM turnover under short rotation forestry" wird vom Umweltbundesamt gefördert und von Universität Rostock, Institut für Landnutzung durchgeführt. Arbuscular- (AM) and ectomycorrhizal (EM) fungi influence soil organic matter (SOM) quantity and quality using different mechanisms. So far little is known how changes in the dominating mycorrhiza type occurring after land use change from arable crops to short rotation forestry (SRF) affect the quantity, composition and turnover of SOM. Therefore, we will manipulate the dominating mycorrhiza type in field and lab experiments to test the following hypotheses: (1) A change from AM to EM, expected under SRF, results in SOM storage due to mycelium formation and SOM stabilising hydrophobin production; (2) A back-change to AM in crops after SRF stimulates saprotrophs to decompose the previously stored SOM and forms new SOM using aggregating effects of glomalin. Accordingly, we will sample recent and former long term SRF and their corresponding reference sites. We will investigate the mycorrhizal colonisation, the amount and molecular composition of SOM including markers (chitin, hydrophobin, glomalin). The microbial decomposition of SOM in the presence and absence of EM will be investigated using 13C studies in incubation experiments. This will prove the importance and sustainability of mycorrhizal C for SOM formation.
Das Projekt "Effects of GM wheat cultivation on the decomposition of GM biomass by soil arthropods and annelids" wird vom Umweltbundesamt gefördert und von Universität Bern, Abteilung Synökologie Institut für Ökologie und Evolution durchgeführt. How digestible is transgenic wheat for earthworms? Genetically modified crops are intended to be toxic for the pests that attack them. At the same time, however, they could harm beneficial organisms. Background Crop plants can be genetically modified to make them immune to pathogens such as fungi, or unpalatable or toxic for pests that feed on them. The overriding objective of plant breeders is to reduce the use of crop protection products. The same substances may, however, be harmful to animals that are important for plants, such as woodlice and worms, as they play a central role in decomposing plant material and releasing nutrients into the soil. Objectives The diversity of species and activity of selected soil-dwelling organisms are expected to provide information on the impact of transgenic plants on these important groups of animals. In addition, nutrient uptake and reproduction of selected soil-dwelling organisms will be compared in areas used to grow genetically modified wheat and areas used to grow conventional wheat. Methods Arthropods (such as woodlice) and segmented worms (such as earthworms) are beneficial invertebrates that live in the soil. Their diversity will be investigated using soil samples as part of the field trial with transgenic wheat (cf. Keller project I). Their activity and nutrient uptake will be determined by burying a constant volume of leaf material derived from transgenic wheat plants and conventional wheat plants for a period of several months. The amount eaten by the soil-living organisms will subsequently be measured. Significance Little is known about the effect of substances that may be released into the soil from the transgenic plants being investigated here. The project is using arthropods and annelid worms as an example of how to investigate this question. The ecologically oriented design of the project will also create a basis for assessing the risk of transgenic plants affecting soil fertility in open cultivation.
Das Projekt "Soil degradation and nutrient export in the upper alpine level of the Reuss watershed" wird vom Umweltbundesamt gefördert und von Universität Basel, Umweltgeowissenschaften durchgeführt. Soil degradation of upland soils, especially export of nutrients, influences nutrient content and biogeochemistry of riparian zones and wetlands in catchments significantly. Our hypothesis was that due to the fact that oxic upland soils with a predominantly assimilatory metabolism differ significantly from anoxic wetland soils and riparian zones with dissimilatory metabolism, stable isotopes of sulphur, nitrogen, oxygen and carbon can be used as potential tracers for the erosion of soil material from upland to lowland sites. Gradients from uplands to wetlands were recorded, both for sites influenced by erosion and non-degraded sites. The bulk d18O signal of a soil represents a mixing signature of all components of the soil. Differences between upland and wetland soils are expected to be due to changing mixing ratio and due to fractionation processes in the soil. As stable oxygen isotopes have not often been used in soil sciences so far, a new method had to be developed. Both, carbon and nitrogen isotope signatures are different for upland and wetland sites. For wetlands more negative d13C and d15N values are recorded than for uplands which is principally caused by less decomposed organic matter in the wetland. An influence of soil degradation from the upland site (erosion source) in the wetland (sink area) is detectable in both the d15N and the d13C signal of the wetland. Stable isotope signatures of the top horizons in the wetland are shifted towards heavier values in comparison to an undisturbed site, representing a mixed signal of upland and wetland soil isotopic signature. However, sites which are treated with farmyard manure show heavier d15N values than untreated reference sites. Therefore it is assumed that a possible contribution of erosion to the d15N is masked by the application of manure.
Das Projekt "Protective Function of Snags against Natural Hazards" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Professur für Forstschutz und Dendrologie durchgeführt. Der Schutz gegen Naturgefahren ist eine wichtige Funktion von Gebirgswäldern. Die Fichte (Picea abies) ist in vielen derartigen Ökosystemen eine dominierende Baumart. Fichtenwälder können von Borkenkäfern (Ips typographus) grossflächig zum Absterben gebracht werden. Die abgestorbenen Bäume brechen im Verlauf einiger Jahre häufig ab und es verbleiben sogenannte Stirzel von wenigen Metern Höhe, die für die Schutzfunktion des Bestandes von entscheidender Bedeutung sind. Es wird ein Projekt zur Erfassung der biologischen Abbauprozesse und der mechanischen Stabilität an diesen Stirzeln vorgeschlagen mit dem Ziel, die Schutzfunktion von durch Borkenkäfern geschädigten Fichtenbeständen und die Notwendigkeit von Verbauungsmassnahmen besser beurteilen zu können.
Das Projekt "Umsatz der organischen Substanz in Waldböden unter erhöhtem N-Eintrag: In situ Tracerversuche mit 13C und 15N markierter Buchenstreu" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft, Eidgenössisches Institut für Schnee- und Lawinenforschung durchgeführt. Aims The objectives are to study how increased atmospheric N deposition will affect soil organic matter turnover. We will add large amounts of double-labelled (13C and 15N) beech litter, leafs and wood-chips, to forest soil and to trace the fate of the added C and N through the soil system under ambient and experimentally increased N inputs (+50 kg NH4NO3-N ha-1y-1). Scientific Background Soils contain the largest fraction of the terrestrial carbon pools. Their role as sinks for atmospheric CO2, however, is strongly debated. One of the unknowns is the impact of the currently increased N deposition to forest ecosystems. Nitrogen is the limiting nutrient for many processes in the plant and soil system, and as the cycling of C and N are tightly coupled, increased N deposition affects also the cycling of soil organic matter (SOM). Modelling studies suggest that increased N inputs stimulate the turnover of C due to decreasing C/N ratios. In contrast, many field studies have shown that higher N inputs suppress CO2 effluxes from soils. Recent radiocarbon studies and 13C tracer experiments have indicated that N deposition retards particularly the decomposition of older and stable SOM-pools and thus, increased N inputs might lead to a sequestration of C in the long-term. The underlying mechanisms of this preservation effect, however, are not well known. Methods We will add 13C and 15N-labelled litter (leafs and wood) from a previous CO2 enrichment experiment to soils and we will follow the fate of the added C and N in the litter itself, in mineral soils and their microbial communities, in leached DOC, and in respired CO2. Expected Results The tracing of litter-derived C and N in soils will allow us (1) to identify how increased N deposition affects CO2 effluxes and DOC leaching and (2) to estimate which SOM-pools (labile litter-derived or stabile SOM) respond most sensitive to the increased N inputs. (3) To test if high N inputs in fact retard lignin degradation as hypothesized by some authors, we intend to gain insight into underlying mechanisms by tracing the fate of the labelled lignin monomers in the litter itself, soils, and in DOC and by measuring the activity of lignin degrading enzymes. (4) To elucidate if N deposition changes the microbial communities, e.g. by favouring fast growing microbes specialised on fresh substrate and suppressing slow-growing microbes relying mainly on SOM, we will analyse the 13C in phospholipid fatty acids extracted from soils and from the decomposing litter. (5) To identify how the litter-derived N becomes stabilised in soils, we will trace the 15N signal into physically separated pools of SOM with turnover rates known from their 13C signature.