Recent theoretical studies have shown that spatial redistribution of surface water may explain the occurrence of patterns of alternating vegetated and degraded patches in semiarid grasslands. These results implied, however, that spatial redistribution processes cannot explain the collapse of production on coarser scales observed in these systems. We present a spatially explicit vegetation model to investigate possible mechanisms explaining irreversible vegetation collapse on coarse spatial scales. The model results indicate that the dynamics of vegetation on coarse scales are determined by the interaction of two spatial feedback processes. Loss of plant cover in a certain area results in increased availability of water in remaining vegetated patches through run-on of surface water, promoting within-patch plant production. Hence, spatial redistribution of surface water creates negative feedback between reduced plant cover and increased plant growth in remaining vegetation. Reduced plant cover, however, results in focusing of herbivore grazing in the remaining vegetation. Hence, redistribution of herbivores creates positive feedback between reduced plant cover and increased losses due to grazing in remaining vegetated patches, leading to collapse of the entire vegetation. This may explain irreversible vegetation shifts in semiarid grasslands on coarse spatial scales.
In this paper ongoing software projects among the European radio astronomy observatories are reviewed. In particular, I report on the progress in the ALBUS project which aims to enhance the data products, as well as the tools for radio astronomy data processing. In particular the capabilities of ParselTongue will be discussed. This is a programmable Python interface to classic AIPS that is now publicly available. The options for work on future data reduction packages will be discussed as well. A new effort is the FABRIC project which is part of the ECfunded collaboration EXPReS. This prepares for the next generation of e-VLBI and includes a pilot project on distributed correlation, implementing the correlation in software on standard computing environments, employing the Grid.
The progress achieved over the last three years with e-VLBI has paved the way for the development of the VLBI implementation of the future. At least for the EVN, it is argued that at some point all VLBI operations should be done in e-VLBI mode. This is based on the scientific ambitions of the EVN, which are described in the EVN2015 science vision. At the same time, it should be taken into account that the long-term future of radio astronomy is tied to the SKA. The consensus in the community is that there is a scientific case for Very Long Baseline Interferometry in the next decade, and synergy with technology development for the SKA and its pathfinders should be explored to enhance the VLBI capabilities. I review the progress with e-VLBI, and the options to enhance the sensitivity and operational efficiency of the EVN and global VLBI arrays, including the options for future correlators. New ways are introduced to enhance e-VLBI operations further to the level that all experiments can benefit from an e-VLBI component. It is anticipated that these components will be included in a new proposal to the EC, which will be an important step on the long-term roadmap of the EVN.
No abstract
With the exceptional progress e-VLBI has achieved over the last three years, the VLBI of the future has already started. At least for the EVN, it is argued that at some point all VLBI operations should be done in e-VLBI mode. This ambition is based on the scientific case that is described in the EVN2015 science vision. At the same time, it should be taken into account that the long-term future of radio astronomy is connected to the development of the SKA. The consensus in the community is that there is a scientific case for Very Long Baseline Interferometry in the next decade, and synergy with the technology development for the SKA and its pathfinders should be explored to enhance the VLBI capabilities. It is noteworthy that e-VLBI has been recognised as a SKA pathfinder. Here, I review the progress with e-VLBI, and the options to enhance the sensitivity and operational efficiency of the EVN and global VLBI arrays, including the options for future correlators. In the coming years, through the new NEXPReS effort, new ways are about to get introduced to enhance e-VLBI operations further to the level that all experiments can benefit from an e-VLBI component.
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