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Liu L.,China Agricultural University | Xu Z.X.,Beijing Normal University | Reynard N.S.,CEH Wallingford | Hu C.W.,China Institute of Water Resources and Hydropower Research | Jones R.G.,UK Met Office
Journal of Flood Risk Management | Year: 2013

Changes in precipitation can be expected to have a major influence on the frequency and severity of flooding in the Taihu Basin. As part of an integrated assessment of flood risk in the Taihu Basin, this paper addresses the hydrological conditions and the potential impacts of climate change on Taihu Lake water levels. The hydrological system is simulated by using the distributed hydrological model VIC (Variable Infiltration Capacity), with future climate scenarios generated by the regional climate model PRECIS (Providing Regional Climates for Impacts Studies). The results indicate that maximum and mean flood water levels under the A2 and B2 scenarios for 2021-2050 will be higher than the levels during the baseline period (1961-1990), with larger increases under the B2 scenario than for the A2 scenario. The storm return periods leading to extreme water levels in the Taihu Lake in the future is projected to decrease significantly in comparison to the baseline period, implying the potential for the more frequent occurrence of major floods. These results indicate the importance of planning for future flood control in the Taihu Basin. © 2012 Blackwell Publishing Ltd and The Chartered Institution of Water and Environmental Management (CIWEM). Source

Thomas J.A.,University of Oxford | Simcox D.J.,CEH Wallingford | Hovestadt T.,University of Oxford | Hovestadt T.,CNRS Mechanical Adaptation and Evolution
Journal of Insect Conservation | Year: 2011

Few results of research aimed at solving questions arising from butterfly conservation are rigorously tested by manipulating populations and habitats in the field. Some factors common to successful conservation projects are analysed. In most non-migratory species, population density may vary by up to two orders of magnitude between sites or over time, and is primarily determined by the extent to which a subset of each species' foodplant (or ant host) exists in the optimum growth-form or micro-habitat preferred by its larvae. Successful conservation projects have identified the optimum subset of each species' larval resource before managing sites to increase its representation. In contrast, short-term fluctuations around a site's carrying capacity or equilibrium level are mainly attributable to variation in weather, and are generally two orders of magnitude smaller than that attributable to larval habitat quality. There is little evidence that changing the abundance of adult resources, apart from shelter, influences population size or trends. The main constraint of the adult stage is the inability of many species to track the generation of new habitat patches that arise across modern landscapes. Within-patch larval habitat quality is again critical at the meta-population scale, explaining slightly more examples of patch occupancy than site isolation. This is because the higher density populations supported by optimum habitat are less likely to go extinct, and immigrants to new high-quality patches have a higher probability of founding new populations. Such patches may also generate up to a hundred times more emigrants per hectare than low-quality source patches. © 2010 Springer Science+Business Media B.V. Source

Nicholls J.A.,University of Edinburgh | Preuss S.,University of Edinburgh | Hayward A.,University of Edinburgh | Hayward A.,University of Oxford | And 7 more authors.
Molecular Ecology | Year: 2010

Little is known about the evolutionary history of most complex multi-trophic insect communities. Widespread species from different trophic levels might evolve in parallel, showing similar spatial patterns and either congruent temporal patterns (Contemporary Host-tracking) or later divergence in higher trophic levels (Delayed Host-tracking). Alternatively, host shifts by natural enemies among communities centred on different host resources could disrupt any common community phylogeographic pattern. We examined these alternative models using two Megastigmus parasitoid morphospecies associated with oak cynipid galls sampled throughout their Western Palaearctic distributions. Based on existing host cynipid data, a parallel evolution model predicts that eastern regions of the Western Palaearctic should contain ancestral populations with range expansions across Europe about 1.6 million years ago and deeper species-level divergence at both 8-9 and 4-5 million years ago. Sequence data from mitochondrial cytochrome b and multiple nuclear genes showed similar phylogenetic patterns and revealed cryptic genetic species within both morphospecies, indicating greater diversity in these communities than previously thought. Phylogeographic divergence was apparent in most cryptic species between relatively stable, diverse, putatively ancestral populations in Asia Minor and the Middle East, and genetically depauperate, rapidly expanding populations in Europe, paralleling patterns in host gallwasp species. Mitochondrial and nuclear data also suggested that Europe may have been colonized multiple times from eastern source populations since the late Miocene. Temporal patterns of lineage divergence were congruent within and across trophic levels, supporting the Contemporary Host-tracking Hypothesis for community evolution. © 2010 Blackwell Publishing Ltd. Source

Fagan K.C.,CEH Monks Wood | Pywell R.F.,CEH Monks Wood | Bullock J.M.,CEH Wallingford | Marrs R.H.,University of Liverpool
Restoration Ecology | Year: 2010

Assessments of restoration are usually made through vegetation community surveys, leaving much of the ecosystem underexamined. Invertebrates, and ants in particular, are good candidates for restoration evaluation because they are sensitive to environmental change and are particularly important in ecosystem functioning. The considerable resources currently employed in restoring calcareous grassland on ex-arable land mean that it is important to gather as much information as possible on how ecosystems change through restoration. We compared ant communities from 40 ex-arable sites where some form of restoration work had been implemented between 2 and 60 years previously, with 40 paired reference sites of good quality calcareous grassland with no history of improvement or cultivation. A total of 11 ant species were found, but only two of these were found to be significantly different in abundance between restoration and reference sites: Myrmica sabuleti was more likely to be present in reference sites, whereas Lasius niger was more likely to be found in restoration sites. Myrmica sabuleti abundance was significantly positively correlated with age of restoration sites. The potential number of ant species found in temperate grasslands is small, limiting the information their assemblages can provide about ecosystem change. However, M. sabuleti is a good indicator species for calcareous grassland restoration success and, alongside information from the plant community, could increase the confidence with which restoration success is judged. We found the survey to be quick and simple to carry out and recommend its use. © 2008 Society for Ecological Restoration International. Source

Hancock S.,University of Swansea | Baxter R.,Durham University | Evans J.,CEH Wallingford | Huntley B.,Durham University
Remote Sensing of Environment | Year: 2013

This paper compares three global snow water equivalent (SWE) products, SSM/I (NSIDC), AMSR-E (NSIDC) and Globsnow (v1.0, ESA) to each other, snow covered area (SCA), ground measures of snow depth and meteorological data in an attempt to determine which might be most suitable for testing and developing land surface models. Particular attention is paid to which gives the most accurate peak accumulation, seasonal SWE changes and first and last dates of snow cover.SSM/I and AMSR-E are pure earth observation (EO) derived products whilst Globsnow is a combination of EO and ground data. The results suggest that the pure EO products can saturate in deeper snow (SWE>80-150. mm), can show spurious features during melt and can overestimate SWE due to strong thermal gradients and erroneous forest cover correction factors. Along with the comparison to ground data (only a single point) this suggests that Globsnow is the more accurate product for determining peak accumulation and seasonal SWE cycle.The snow start and end dates of the three SWE products were compared to an optically derived SCA (MOD10C1, taken as truth) and found to give large errors of snow start date (root mean square error of 20. + days, though SSM/I was correct on average). The snow end dates had lower errors (a bias of 1-6. days) although the spread was still on the order of three weeks.During the investigation, occasional abrupt changes in Globsnow were observed (in the v1.0 and v1.2 daily and v1.2 weekly products). These only occurred in around 1% of cases examined and seem to be spurious. Care should be taken to corrector avoid these jumps if using Globsnow to validate land surface models or in an assimilation scheme. © 2012 Elsevier Inc. Source

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