Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity

Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial- or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a meta-data analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric datasets overall consisting of 837 lakes. Our results indicate that in most of our datasets summer temperature (Tjul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing Tjul in regions with present day Tjul between 2.5-14 °C. In some areas with Tjul >14 °C chironomid diversity stabilises or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (~15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites

Engineering geology of British rocks and soils : Lambeth Group

The report is the fourth of a series that examines the distribution, lithostratigraphy, lithology, engineering properties and regional variation of the geological units that are significant to engineering geology, civil engineering construction and land-use in Britain. In this volume the Lambeth Group is described by its lithological variation, mineral composition, geophysical characterisation methods, geotechnical properties and engineering behaviour. The first section describes the geology including the deposits below and above, the named units, sequence stratigraphy and the lithological variation. The next chapter discusses the mineralogy, in particular the clay mineralogy and changes due to pedogenesis, which are illustrated with electron micrographs. Geophysical methods applicable to the Lambeth Group are described and discussed in the next section. This is followed by two sections on the geotechnical characteristics, the former describing the data acquisition, storage in the database, access and analysis and the latter the interpretation and presentation of the geotechnical data. The final chapter, on the engineering geology of the Lambeth Group, draws on the preceding chapters. A comprehensive cited reference list and bibliography are provided. The first three appendices provide extra information on the variability and distribution of the Lambeth Group and includes the type borehole, various cross-sections and an analysis of the described lithology type from borehole descriptions. The final appendix provided statistical summaries of the more commonly carried out geotechnical tests. The lithology of different boreholes are presented as in cross-sections and as with all nonconfidential boreholes held by the BGS are available, free to download (http://www.bgs.ac.uk/data/boreholescans/home.html). The individual items of data in the database are not attributed. The authors would like to thank all those who have contributed data to the BGS including clients, consultancies, contractors, authorities and individuals. It is hoped that this report will provide a useful sources of information to a wide range of engineers, planners, scientists and other interested parties concerned with the Lambeth Group. It is stressed that whilst data are included in this report, these indicate the variability of the particular parameter of each unit and might be used to identify hazards or risk; they are not a substitute for an appropriate ground investigation for the project, including desk study and site investigation. This is the case for all the ‘Engineering geology of UK rocks and soils’ reports but is more important for the Lambeth Group, which is often lithologically variable

Engineering geology of British rocks and soils : Gault Clay

The Gault is a sequence of clays, mudstones and thin siltstones with bands of phosphatic nodules of Middle and Upper Albian age. Its outcrop stretches south-westward fron1 East Anglia through Wessex to west Dorset and surrounds the Weald in an arc from North East Kent westwards through Surrey to Hampshire where it turns south and returns· eastward through west and east Sussex. The Gault clay thickens to the south and reaches its maximum developlnent of over 100 m in the Weald and thins to the west as it passes into Hampshire and Dorset. The Gault clay contains both clay and non-clay mineralso The major non-clay minerals are quartz and calcite. Quartz usually makes up about 20% or more of the Gault and its distribution is fairly uniform. Calcite is present as fossil debris and as a cementing agent. The Gault is more calcareous in the north east than the south and west

The distribution and abundance of chironomids in high-latitude Eurasian lakes with respect to temperature and continentality: development and application of new chironomid-based climate-inference models in northern Russia

The large landmass of northern Russia has the potential to influence global climate through amplification of climate change. Reconstructing the climate in this region over millennial timescales is crucial for understanding the processes that affect the climate system. Chironomids, preserved in lake sediments, have the potential to produce high resolution, low error, quantitative summer air temperature reconstructions. Canonical correspondence analysis (CCA) of modern surface sediments from 100 high-latitude lakes, located in northern European Russia to central Siberia, showed chironomid distribution was primarily driven by July air temperatures. The strong relationship enabled the development of chironomid-inference model based on 81 lake and 89 taxa to reconstruct July air temperature. Analysis of a range of chironomid-inferred temperature model suggest the best to be a two component weighted averaging and partial least squares (WA-PLS model) with r2jack = 0.92 and RMSEP = 0.89°C. Comparison of species responses to July temperature with the Norwegian training set showed the temperature optima of individual species was 1-3°C in the Russian data regardless of modelling technique. This suggests that chironomid-based inference models should only be applied to sediment cores collected within the geographic source area of the training set. The differing responses between the Norwegian and Russian faunas led to the development of a 149 lake, 120 taxa chironomid-continentality inference model. The 2-component WA-PLS model was the minimal adequate model with r2jack = 0.73 and RMSEP = 9.9. Recent warming in the Arctic has been spatial and seasonal heterogeneous; in many areas warming is more pronounced in the spring and autumn leading to a lengthening of the summer, while summer temperatures have remained relatively stable. A continentality model has the potential to detect these seasonal changes in climate. The Russian inference model also improves the representation of a number of taxa, such as Corynocera oliveri-type, Constempellina and Paracladius, which frequently occur in subfossil assemblages from arctic Russian lakes, but are poorly represented in European training sets. These are cold-adapted taxa and their absence from the training sets could lead to overestimations of July temperatures in fossil samples where these taxa form a major component (for example see Andreev et al. 2005). Comparison of reconstructed July air temperatures and continentality indices from a tundra lake in north-east European Russia showed close agreement with local instrumental records over the past 70 years and suggests the models may produce reliable estimates of past climate