Hydrological Dynamics, Fire History and Carbon Accumulation in the Last Millennium in Western Siberia Reconstructed from a High Resolution Ombrotrophic Peat Archive
Wednesday, 17 December 2014
Northern peatlands are important sinks of carbon. However, ongoing climate change and human impact trigger emission of the stored carbon into the atmosphere. Because of the progressive disturbances there is an urgent need to recognize these processes in space and time. We investigated a profile from a Mukhrino bog located close to the Mukhrino Field Station, about 20 km from Khanty-Mansiysk (60°54’ N, 68°42’ E). One meter peat core was subsampled in one-centimeter intervals. Pollen, testate amoebae, plant macrofossils, bulk density and carbon content were analyzed in high-resolution to reconstruct hydrology, droughts and carbon accumulation rates during the last 1200 years. We hypothesize that continental bogs of Siberia have been existing in under summer drought stress during the last millennium and hydrological change (dry shift) is also reflected in local fires. Palaeoecological work was accompanied by surface sampling to collect testate amoebae training set for transfer function development. These microorganisms have been scarcely studied in this part of the world. Redundancy analysis (RDA) showed that 23.7% of variance is explained by the model. Furthermore, water table appeared to be the most significant variable for sampled communities. Testate amoebae calibration data set performed the reliably using weighted averaging model (RMSEPboot=7.9, R2boot=0.74). According to our quantitative reconstruction, higher charcoal influx was inferred between AD 1975 and 1990 what suggests higher fire frequency. However, water table was the lowest between AD 1150 and AD 1965. The data show lack of correlation between peatland wetness and regional fires. Consequently, it suggests that peatland hydrological dynamics might be independent from fires frequency, as fires were caused by recent human activities in concomitance with the positive Arctic Oscillation Index during the last decade.