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The decomposition of belowground and aboveground tree litter was studied on five forest sites across Switzerland, ranging from 480 to 1500 m in altitude, and including calcareous and acidic soils. In addition to decomposition of local litter types (Picea abies, Fagus sylvatica, Castanea sativa), the decomposition of a standard beech litter was studied on all sites. After 2years of decomposition, mass loss ranged from 18 to 71% across the different sites and litter types. The lowest decomposition rates were observed for beech roots, while mass loss was greatest for both spruce needles and spruce roots at the low-altitude site. Mass loss during the first winter correlated best with the content of water-soluble substances. After 1year of incubation, mass loss of the standard litter varied less than did mass loss of local litter, but variance increased during the second year for aboveground litter. These observations indicate a smaller climatic influence on litter breakdown at the beginning of the decomposition process. Litter mass loss could be described using an exponential model with a decay constant depending on either lignin/N ratio or Mn content of the litter and annual soil temperature and throughfall precipitation as climatic variables. Modelling the observed mass loss indicated a strong influence of litter quality in the first 2years of decomposition, confirming the field data from the standard litter experiment. The experiment will continue for some years and is expected to yield additional data on long-term decomposition

Das Ziel dieser Arbeit ist die Entwicklung einer Einsatzoptimierung elektrischer Tagesspeicher zur Maximierung des täglichen Deckungsbeitrags. Es werden sowohl die Erlöse und Kosten der Vermarktung als auch des Betriebs berücksichtigt, sodass die Einsatzentscheidungsrelevanz einzelner Kosten- und Erlöspositionen bestimmt werden kann. Darüber hinaus ist die Einsatzoptimierung technologieneutral gestaltet. Die gewählte Methodik ermöglicht die Verwendung von Wirkungsgradkennfeldern, sodass zulässige Lösungen der Einsatzoptimierung auch bei nicht symmetrischen Betriebsbereichen des Speichers einen technisch möglichen Einsatz darstellen. Die in üblichen Einsatzoptimierungen verwendete Annahme konstanter Wirkungsgrade ist mit einem symmetrischen Betriebsbereich verbunden, der durch die Nennleistung und die minimale Teillast sowie die untere und obere Speichergrenze limitiert ist. Es werden die aktuell relevanten Technologien ausgewählt und untersucht, Pumpspeicherkraftwerke (PSW) und Batteriespeicherkraftwerke, an deren Beispiel die Parameter zur Modellbeschreibung elektrischer Tagesspeicher ausgewählt werden. Für die gewählten Technologien wird zudem die Implementierung von Wirkungsgradkennfeldern mittels der Fuzzy-Logik gezeigt. Neben der technologischen Analyse erfolgt eine energiewirtschaftliche Analyse der Erlöse und Kosten der relevanten Vermarktungsoptionen und des Betriebs elektrischer Tagesspeicher. Die auf der technischen und energiewirtschaftlichen Analyse basierenden mathematischen Problemformulierungen sind nicht linear und nicht konvex, sodass zur Lösung der Optimierungsprobleme der Genetische Algorithmus in Matlab angewendet wird. Der gewählte Optimierungsansatz wird auf die wesentlichen Einflussparameter hinsichtlich Ergebnisgüte und Effizienz untersucht und angepasst. Als ein wesentlicher Einflussfaktor wird neben den Parametern des Genetischen Algorithmus die Anzahl der verwendeten Regeln in der Fuzzy-Logik zur Bildung der Wirkungsgradkennfelder erkannt. Die Anwendungsbeispiele der Tagesspeicher-Einsatzoptimierung zeigen, dass für ein Lithium-Ionen-Batteriespeicherkraftwerk ohne definierte minimale Teillast die Berücksichtigung von Regelleistung in der Vermarktungsstrategie im Gegensatz zu PSW sinnvoll ist. Zudem wird gezeigt, dass bei der Verwendung von konstanten Wirkungsgraden in der Einsatzoptimierung von PSW der Deckungsbeitrag um bis zu 7,8% überschätzt wird. Dies ist durch die mit der Verwendung konstanter Ein- und Ausspeicherwirkungsgrade verbundene Annahme eines symmetrischen Betriebsbereichs bedingt. Als weitere wesentliche Einflussfaktoren auf den Deckungsbeitrag eines Tagesspeichers werden das HT-Zeitfenster des Anschluss-Netzbetreibers, die Startkosten des Tagesspeichers, die Netzzugangsentgelte sowie die Gestaltung des Speichers bezüglich der maximalen durchgängigen Ausspeicherdauer mittels der Tagesspeicher-Einsatzoptimierung untersucht und quantifiziert. Insbesondere die Startkosten zeigen dabei eine hohe Relevanz in der Einsatzoptimierung eines PSW. Bei Berücksichtigung der Wirkungsgradkennfelder erreicht ein beispielhaftes PSW mit drehzahlvariabler Pumpturbine einen mittleren Zykluswirkungsgrad von 81,5%, ein PSW mit drehzahlstarrer Pumpturbine einen mittleren Zykluswirkungsgrad von 81,0% und ein Lithium-Ionen-Batteriespeicherkraftwerk einen mittleren Zykluswirkungsgrad von 79,5%. Der geringe Zykluswirkungsgrad des Batteriespeicherkraftwerks ist insbesondere durch die Struktur des Wirkungsgradkennfelds bedingt, in dem der Wirkungsgrad im Unterschied zu den Kennfeldern der Pumpturbinen mit steigender Last sinkt. The objective of this paper is the development of an optimization approach of electrical storage power plant dispatch to the maximization of the daily contribution margin. Revenues and costs of trading in the potential markets as well as the operational revenues and costs are considered, so that the relevance of single revenue positions and cost positions can be determined. Besides, the optimization approach is designed technology-neutrally. The chosen methodology allows the use of efficiency characteristics, so that feasible solutions of the optimization approach show a technically possible dispatch also with not symmetrical operating ranges of the storage power plant. The assumption used in usual optimization approaches of steady efficiencies or of single load depending efficiency curves is connected with a symmetrical operating range which is limited by the nominal output and the minimum part load as well as the lower and upper storage capacity. The topically relevant technologies are selected and investigated - pumped storage hydropower plants (PSP) and battery storage power plants - at whose example the parameters for the description of a general model of an electrical storage power plant are selected. Besides, for the elected technologies the implementation of the efficiency characteristics is shown by means of the fuzzy logic. Beside the technological analysis an energy-economic analysis of the revenues and costs of trading in the potential markets as well as operational revenues and costs of electrical storage power plant dispatch occurs. The mathematical problems based on the technical and energy-economic analysis are non-linear and not convex. Because of that, for the solution of the optimization problems the genetic algorithm in Matlab is applied. The elected optimization approach is investigated concerning the significant impacting parameters with regard to the quality of the result and efficiency and is adjusted to them. Beside the parameters of the genetic algorithm, the number of the used rules to the implementation of the efficiency characteristics in the fuzzy logic is identified as an essential influencing factor with regard to the quality of the result and efficiency. The examples of use demonstrate that taking into consideration the operating reserve is beneficial for a battery storage power plant without defined minimum part load. Because of the defined part load this trading strategy is much less beneficial for a single PSP. Additionally, it is shown that the use of single efficiency coefficients in the optimization of dispatch of a PSP results in an overestimation of the contribution margin up to 7.8%. This is caused by the assumption of a symmetric operating range, which is especially unrealistic for a PSP. Further significant influencing factors on the contribution margin are peak load time windows of the network operator, the storage power plant‘s individual start-up costs, network access charges and the storage power plant‘s design in reference to the relation between nominal output and storage capacity. Especially start-up costs are highly relevant in the dispatch optimization of a PSP. The use of the efficiency characteristics in this optimization approach shows a mean cycle efficiency of a model PSP with a speed-variable pump turbine of 81.5%. The cycle efficiency of a model PSP with a simple pump turbine averages in about 81.0% and the cycle efficiency of a model battery storage power plant based on lithium ion battery cells averages in about 79.5%. The lower cycle efficiency of the battery storage power plant is caused by the structure of the efficiency characteristics: in contrary to the structure of the efficiency characteristics of a PSP here the efficiency decreases with an increasing output or input load.

Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH4), at forests, grasslands, and croplands across Europe. Biogenic contributions to DIC were estimated by means of its δ13C signature. Leaching of biogenic DIC was 8.3±4.9 g m−2 yr−1 for forests, 24.1±7.2 g m−2 yr−1 for grasslands, and 14.6±4.8 g m−2 yr−1 for croplands. DOC leaching equalled 3.5±1.3 g m−2 yr−1 for forests, 5.3±2.0 g m−2 yr−1 for grasslands, and 4.1±1.3 g m−2 yr−1 for croplands. The average flux of total biogenic carbon across land use systems was 19.4±4.0 g C m−2 yr−1. Production of DOC in topsoils was positively related to their C/N ratio and DOC retention in subsoils was inversely related to the ratio of organic carbon to iron plus aluminium (hydr)oxides. Partial pressures of CO2 in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC relative to soil air CO2. Leaching losses of biogenic carbon (DOC plus biogenic DIC) from grasslands equalled 5–98% (median: 22%) of net ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24–105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small solubility of CO2 in acidic forest soil solutions and large NEE. Leaching of CH4 proved to be insignificant compared with other fluxes of carbon. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems. Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH), at forests, grasslands, and croplands across Europe. Biogenic contributions to DIC were estimated by means of its δC signature. Leaching of biogenic DIC was 8.3±4.9gmyr for forests, 24.1±7.2gmyr for grasslands, and 14.6±4.8gmyr for croplands. DOC leaching equalled 3.5±1.3gmyr for forests, 5.3±2.0gmyr for grasslands, and 4.1±1.3gmyr for croplands. The average flux of total biogenic carbon across land use systems was 19.4±4.0gCmyr. Production of DOC in topsoils was positively related to their C/N ratio and DOC retention in subsoils was inversely related to the ratio of organic carbon to iron plus aluminium (hydr)oxides. Partial pressures of CO in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC relative to soil air CO. Leaching losses of biogenic carbon (DOC plus biogenic DIC) from grasslands equalled 5-98% (median: 22%) of net ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24-105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small solubility of CO in acidic forest soil solutions and large NEE. Leaching of CH proved to be insignificant compared with other fluxes of carbon. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems.

Knowledge about the fate of individual biomolecules during the decomposition process in soil is limited. We used the natural isotopic label introduced by 23 years of continuous maize cropping, together with compound specific 13C isotope analysis, to study lignin monomers in particle size fractions of a Luvisol. Isotope data indicated apparent decadal turnover times for lignin. A kinetic model suggests the existence of a fast and a slow decomposing lignin pool in the soil, reconciling a low stock-to-input ratio with decadal turnover times. We found new, maize-derived lignin primarily in the 63–2000 μm fraction, whereas old, C3-derived lignin from the pre-maize vegetation had accumulated mainly in the silt (2–20 μm) fraction. This distribution of lignin differed from that of total organic carbon, which was concentrated in the

Summary When modelling the carbon dynamics of temperate soils, soil organic carbon (SOC) is often represented by three kinetic pools, i.e. fast, slow and passive/inert. Lignin is often considered to be relatively resistant to decomposition, thus possibly contributing to the passive SOC pool. One way to assess SOC turnover under natural conditions is to follow the fate of 13 C-labelled biomass in soils. We used compound-specific isotope analysis to analyse CuO oxidation products of lignin from grassland topsoils and from an arable topsoil that had received a natural (by C3-C4 vegetation change) or an artificial (by fumigation with labelled CO2) isotopic label for 9–23 years. Results indicate faster apparent turnover for lignin (5–26 years in grassland, 9–38 years in arable soil) compared with bulk SOC (20–26 years in grassland, 51 years in arable soil). Although these calculated lignin turnover times cannot be extrapolated to the whole soil profiles, this paper provides isotopic evidence that lignin in soils is not preferentially preserved, which is a consistent result from both ways of isotopic labelling. It also demonstrates, however, that a considerable proportion of lignin in temperate soils can be stabilized for at least a few decades.