Soil seed bank of the invasive Robinia pseudoacacia in planted Pinus nigra stands

Pinus nigra and Robinia pseudoacacia are exotic trees used for afforestation in Hungary. Pinus nigra was non-invasive, however R. pseudoacacia escaped from cultivation and invaded several vegetation types including pine plantations. It has recently been planned to cut P. nigra plantations and replace them by native tree stands, especially in nature reserves. The scattered presence of R. pseudoacacia specimens in pine stands might place constraints on planned tree replacement because of their vegetative resprouting and recolonization from an established seed bank. The aim of this study was to investigate the soil seed bank under the canopy of solitary R. pseudoacacia specimens found in P. nigra plantations. Altogether 250 soil samples were collected from the 0–6 and 6–12 cm soil layers under solitary Robinia trees of varying ages (with basal areas between 62.4 and 1089.3 cm2). Seeds were separated by sieving then scarified and germinated. Seed bank density ranged between 640 and 2285 seedsm–2 with an average distribution of 82.7% and 17.3% in the upper and lower soil layer, respectively. Total density of the seed bank and also the seed bank ratio of the lower soil layer increased with tree age. The accumulated seed bank of R. pseudoacacia should be considered in the careful planning of tree replacement operations in Pinus nigra stands

Conceptual design of a modular EC system for EU-Demo

The DEMO reactor studies within EUROfusion aim to develop a fusion power plant concept. The large Tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) Heating system with up to 130 MW foreseen to reach different regions of plasma for heating, suppression of instabilities and possibly supporting ramp-up and ramp-down phases. The present conceptual design of the system is based on 2-MW coaxial-cavity gyrotron sources in development at IHM-KIT, a transmission line using both circular corrugated waveguides and a quasi-optical evacuated multi-beam transmission line, and mirror antennas located in the Equatorial port. In order to have a modular system, the sources are grouped in “clusters”, which power is combined in the quasi-optical transmission line, up to the Tokamak Building, where they are split and routed as single waveguides. In the launcher, they are combined together again on the launching mirrors, to save space for the apertures in the Breeding Blanket. The present EC system has a certain flexibility to adapt to changing design guidelines, as the foreseen transition to a lower DEMO aspect ratio. The system and the development status of each subsystem will be presented

Role of Lignocellulosic Biomass Composition to Regulate Microbial Mutualism for Organic Mineralization and Humification during Digestate Composting

This study investigated the performance of lignocellulosic wastes to regulate microbial interactions to improve the composting of digestate from the anaerobic digestion of food waste regarding organic mineralization and humification. Garden waste, rice husk, and cornstalks with diverse lignocellulosic biomass compositions and structures were representatively selected for comparison. High-throughput sequencing was integrated with a modular network analysis to decipher microbial community structures and their interactions. Results showed that mixing 15% of cornstalks and garden waste with digestate (wet weight) was more effective than rice husk to enrich functional microbes (e.g., Tepidimicrobium and Mortierella) to promote the microbial interkingdom for lignocellulosic degradation and humus formation. In particular, a stronger bacterial intrakingdom mutualism was observed with cornstalk addition to facilitate the progressive succession of bacteria in digestate from anaerobic to aerobic and thus inhibit the activities of anaerobic and denitrifying microbes to reduce the emissions of methane and nitrous oxide by 14.2–49.1%. Furthermore, garden waste with more lignin could effectively strengthen intrakingdom mutualism within fungi and their interkingdom interaction with bacteria to mitigate organic carbon mineralization and reduce carbon dioxide emission by 39.8–42.7%. By contrast, rice husk weakened microbial interkingdom mutualisms to retard organic biodegradation and humification during digestate composting. Results from this study provided fundamental understanding on selecting lignocellulosic wastes to regulate organic biotransformation and to improve humification and simultaneously mitigate gaseous emissions in digestate composting

From W7-X Towards ITER and Beyond: 2019 Status on EU Fusion Gyrotron Developments

In Europe, the research and development with main focus on achieving robust industrial designs of series gyrotrons for electron cyclotron heating and current drive of today's nuclear fusion experiments and towards a future DEMOnstration fusion power plant is constantly progressing. The R&D is following two different paths. Both are complementing each other: Firstly, it is the adaption of the physical design and basic mechanical construction of the reliably operating 140 GHz, 1 MW CW (spec.: 920 kW, 1800 s) gyrotron of the stellarator Wendelstein 7-X (W7-X), Greifswald, Germany. With regards to time and costs it is the target to perform reliable developments of fusion gyrotrons with advanced specifications for today's plasma fusion experiments. Main focus is on the development of the first EU 170 GHz, 1 MW CW (3600 s) gyrotron for the installation in ITER, Cadarache, France. Another adaption is the dual-frequency 126/84 GHz 1 MW (2 s) gyrotron upgrade for the medium size TCV tokamak, Lausanne, Switzerland. Finally, it is the upgrade of the W7-X gyrotron design towards an RF output power per unit of up to 1.5 MW and possible dual-frequency operation by keeping the basic mechanical construction. Additional to the proven design it allows to fit the new 1.5 MW gyrotron into the already existing infrastructure and to reuse existing W7-X gyrotron auxiliaries, e. g. the high-power voltage supply (HV PS) and the superconducting (SC) magnet. The second R&D path is defined by the complementary approach with regards to development risks towards a future gyrotron which shall fulfil the significant more advanced specifications of a future EU DEMO. The starting point is the 2 MW EU/KIT coaxial-cavity gyrotron design. Main requirements are an RF output power of 2 MW CW at above 200 GHz, multiple operating frequencies, frequency step-tunability and a total efficiency above 60 %

Conceptual Design of a Modular EC Heating System for EU-DEMO

The European DEMO (EU-DEMO) reactor studies within EUROfusion aim to develop a fusion power plant concept. The large tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) heating system with up to 130 MW foreseen to reach different regions of plasma for heating, suppression of instabilities and the possibility to support ramp-up and ramp-down phases. The present conceptual design of the system is based on 2-MW coaxial-cavity gyrotron sources, a transmission line using both circular corrugated waveguides and quasi-optical evacuated multi-beam transmission lines, and mirror antennas located in the Equatorial Port. In order to create a modular system, the sources are grouped in “clusters”, whose powers are combined in the quasi-optical transmission line, up to the tokamak building, where they are split and routed as single waveguides. In the launcher, they are combined together again on the launching mirrors, to save space for the apertures in the Breeding Blanket. The present EC heating system has a certain flexibility to adapt to changing design guidelines. The development status of the system is presented