Auswirkungen der Einbringung von Buche (Fagus sylvatica L.) auf die Artendiversität und Naturnähe von Nadelholzbeständen in Niedersachsen

The promotion and extension of continuous cover mixed stands with a simultaneous reduction of conifer-monocultures play a major role in current silvicultural practices in Central Europe. It is assumed that the admixture of the natural dominant beech (Fagus sylvatica) in pure non site-specific conifer stands automatically indicates better conditions in terms of nature conservation and forest management. To test this hypothesis three different conifer-beech-comparisons of pure and mixed stands in Lower Saxony are studied, analyzing plant species diversity and naturalness of understory vegetation as one important indicator for the ecological status of forests. Each comparison includes pure coniferous stands (Picea abies, Pinus sylvestris, Pseudotsuga menziesii), mixed coniferous-beech-stands, and pure beech stands on similar acidic mineral soils where the potential natural vegetation will be an oligotrophic beech forest (L u z u l o - Fa g e t um). The age of stands varies between 50 and 150 years. To specify tree species influence on site conditions and vegetation, the study also includes light climate and soil data of the stands. It is observed that, with regard to all comparisons, the admixture of beech reduces plant species diversity but increases naturalness of the stands. The intensity of beech admixture effects differs. While in Scots pine stands the impact of admixed beech is very noticeable, with the mixed stands being nearly identical with pure beech stands, the species change in Douglas-fir and Norway spruce stands proceeds more slowly. Assuming that the status in nature conservation and forest management is improving with increasing plant species diversity and increasing naturalness, the results of this study show a contrary development on a stand scale, as the potential natural vegetation of the L u z u l o - F a g e t u m is in its self very species poor on vascular plants.Die Förderung und Ausweitung von Mischwäldern bei gleichzeitiger Reduktion reiner Nadelholz-Bestände spielt aktuell eine große Rolle im mitteleuropäischen Waldbau. Gemeinhin wird angenommen, dass die Beimischung der standortsgemäßen Buche (Fagus sylvatica) in standortsfremden Nadelholz Monokulturen die Bedingungen im Sinne des Naturschutzes und der Forstwirtschaft verbessert. Diese Hypothese wird auf der Grundlage von drei unterschiedlichen Nadelholz- Buchen-Versuchsreihen geprüft. Im Mittelpunkt steht dabei die Bodenvegetation als wichtiger und sensitiver Indikator für den ökologischen Zustand von Wäldern. Jede Versuchsreihe umfasst reine Nadelholz-Bestände (Picea abies, Pinus sylvestris, Pseudotsuga menziesii), Nadelholz-Buchen- Mischbestände und reine Buchen-Bestände auf sauren Mineralböden, auf denen von Natur aus nährstoffarme Buchenwälder (L u z u l o - Fa g e t um) vorherrschen würden. Das Alter der Bestände variiert zwischen 50 und 150 Jahren. Schwerpunkte der Analyse sind die Artenvielfalt und Naturnähe der Bodenvegetation. Um den Einfluss der Baumarten auf den Standort und die Vegetation zu bewerten, werden die Licht- und Bodenverhältnisse der Bestände charakterisiert. Es zeigt sich, dass mit der Beimischung der Buche in allen Versuchsreihen die Pflanzenartenvielfalt abnimmt und die Naturnähe zunimmt. Unterschiedlich ist dabei die Intensität der Veränderungen. Zwischen den Kiefern-Buchen-Mischbeständen und den Kiefern-Reinbeständen bestehen sehr deutliche Unterschiede im Aufbau der Bodenvegetation, so dass die Mischbestände den Buchen-Reinbeständen bereits sehr ähnlich sind. In den Douglasien- und Fichten-Versuchsreihen vollzieht sich der Artenwechsel vergleichsweise unauffällig und kontinuierlich. Wenn man davon ausgeht, dass der naturschutzfachliche und waldbauliche Status sich sowohl mit zunehmender Phytodiversität als auch bei zunehmender Naturnähe verbessert, so zeigen diese Ergebnisse auf Bestandesebene eine gegenläufige Entwicklung, da das in der Region der potenziell natürlichen Vegetation entsprechende L u z u l o - Fa g e tum von Natur aus sehr artenarm an Gefäßpflanzen ist

Re-working biographies: Women's narratives of pregnancy whilst living with epilepsy.

This paper explores the multiple ways experiences of pregnancy and early motherhood come to 'rework' the biographies of women living with epilepsy. Pregnancy is explored as a temporarily concurrent status alongside the long-term condition of epilepsy. Narrative interviews were conducted with 32 women from across the UK. Analysis of these narratives suggests that biographical disruption and continuity are both useful in the conceptualisation of women's diverse experiences of pregnancy and epilepsy. Such findings challenge the notion that the presence of a condition over a long period of time leads to the normalisation of illness. Participants' narratives demonstrate that, for some, pregnancy and early motherhood may be disruptive and can raise concerns regarding an ever present condition that may previously have been taken for granted. Findings also indicate the need for a greater consideration of gender and care responsibilities, as well explorations of concomitant conditions, in the theorising of biographies and chronic illness

Market Integration of HVDC Lines

Moving towards regional Supergrids, an increasing number of interconnections are formed by High Voltage Direct Current (HVDC) lines. Currently, in most regions, HVDC losses are not considered in market operations, resulting in additional costs for Transmission System Operators (TSOs). Nordic TSOs have proposed the introduction of HVDC loss factors in market clearing, to account for the cost of losses and avoid HVDC flows between zones with zero price difference. In this paper, we introduce a rigorous framework to assess the introduction of HVDC loss factors in flow-based market coupling. Our results apply to nodal and peer-to-peer markets as well. First, we focus on the identification of an appropriate loss factor. We propose and compare three different models: fixed, linear, and piecewise linear. Second, we introduce formulations to include HVDC losses in market clearing algorithms. Carrying numerical tests for a whole year, we find that accounting only for HVDC losses may lead to lower social welfare for a non-negligible amount of time. To counter this, this paper introduces a framework for including both AC and HVDC losses in a zonal or nodal pricing environment. We show both theoretically and through simulations that such a framework is guaranteed to increase social welfare.Comment: Submitted to "IEEE Transactions on Power Systems" on December 3, 201