Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 62

Report on recovery of acidified ecosystems focusing on the use of space-for-time analogues to predict future conditions given scenarios of global change and acid deposition

The technique of analogue matching has been used almost solely for the process of environmental reconstruction over the Quaternary time scale. Analogue matching and the identification of modern analogues is a long established palaeoecological technique for environmental reconstruction from fossil pollen spectra. However, the use of the technique can be applied to the more recent past in order to investigate the problems of recent anthropogenic environmental disturbance. This report describes the work undertaken applying the analogue matching approach in Work Package 4 of the Euro−limpacs programme. Part II describes work undertaken to improve the model by making use of a wider part of the biological remains preserved in lake sediments. Sub−fossil remains of diatoms and Cladocera are used in a dual proxy analogue matching approach to identify modern analogue lakes for the pre−industrial period of sites in the UK Acid Waters Monitoring Network (AWMN). Having identified close modern analogues, analysis of aquatic macrophytes and macro−invertebrates from the modern analogue sites is performed to assess the suitability of the sites as modern analogues and to assess the performance of the new methodology. Despite the majority of the work on modern analogues being developed for use with biological palaeoecological data, the general concept may be applied to any data for which suitable similarity coefficients or distance measures are available. For example, in Part III, the methodology is applied to hydrochemical data from the MAGIC model, where the objective is to select from among a range of potential analogue sites for lakes with the most similar hydrochemical properties to those same properties predicted by the MAGIC model for 1850 AD. Here though, we use a generalised similarity coefficient as the hydrochemical parameters on which the matching is based are not measured in the same units. This flexibility also allows us to include categorical or factor constraints to the matching process, and we describe the use of lake area and lake altitude classes as constraints within the matching process. As MAGIC can also be used to provide predictions of future hydrochemistry, we also demonstrate how one might use analogue matching to identify close modern analogues for sites based on future hydrochemistry given future changes in acid emissions and deposition and climate change.

Much of the hydrochemical matching work is still work−in−progress and will be developed as part of the Work Package 4 science programme. The dual proxy biological matching described in Part II is largely complete for UK sites, with the exception of increasing the size of the analogue matching training set from which matches are made. It is not the intention to improve this training set for UK lakes in Euro−limpacs. The work described in Part II has recently been written up as a paper in the Journal Environmental Pollution.

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