Linear regression analysis of Australian lacustrine sediments using geochemical and remote sensing techniques

Abstract

Our understanding of carbon cycling is based on a short time period of satellite or instrumental monitoring, which are limited with respect to understanding long term patterns in terrestrial carbon cycle. Our understanding of past changes in terrestrial biomass has been primarily derived from pollen and plant macrofossils preserved within sediments. Geochemical tracers offer a different perspective on past land cover and provide important constraints on source and deposition of sedimentary organic matter in the catchment area for the purpose of regional palaeoenvironmental reconstruction. We combine stable isotope analysis, source rock pyrolysis and remote sensing techniques to see whether we can observe a shift in geochemical signatures of lake sediments in response to changes in vegetation density and catchment hydrology. We hypothesize that we should see an increase in terrestrial organic carbon concentrations in catchments with higher vegetation density. Simultaneously increased rates of precipitation have been associated with increase in vegetation abundance and therefore hydrological shifts should also be reflected in geochemical signatures of sediments. Our results confirm that there is a positive correlation between vegetation density and terrestrial organic carbon concentrations, with sediments from heavily vegetated catchments showing high concentrations of terrestrially derived organic matter. On the other hand, shifts in precipitation appear to only effect geochemical signatures of sediments from semi-arid regions with low vegetation densities.