A natural experiment suggests little direct temperature forcing of the peatland palaeoclimate record

An important uncertainty in the interpretation of peat-based Holocene climate reconstructions is what aspect of climate is recorded. Testate amoeba palaeoecological records have generally been interpreted in terms of water table depth but an increasing weight of experimental evidence shows that testate amoeba communities may respond to temperature independent of hydrological variability. In most ombrotrophic peatlands, variability in water table depth is driven by a combination of both temperature and precipitation, making it difficult to isolate any direct forcing by temperature. An unusual peatland ecosystem in which water tables are extremely stable offers an approach to this question. If testate amoeba communities show variability through time in these percolation bogs this implies a direct influence of temperature. This study presents a late Holocene testate amoeba record from the Imnati percolation bog in western Georgia. Below a phase of recent eutrophication results show essentially no variability in testate amoeba community composition or inferred water table depth through more than 4m of peat representing over 2000 years. It is improbable that there has been no temperature variability over this period and the data therefore imply that direct temperature forcing of the palaeoecological record is minimal, at least for this region and time-scale. Copyright (C) 2014 John Wiley & Sons, Ltd.