Carbon stable isotopes as a palaeoclimate proxy in vascular plant dominated peatlands

Carbon stable isotope (δ13C) records from vascular plant dominated peatlands have been used as a palaeoclimate proxy, but a better empirical understanding of fractionation processes in these ecosystems is required. Here, we test the potential of δ13C analysis of ombrotrophic restiad peatlands in New Zealand, dominated by the wire rush (Empodisma spp.), to provide a methodology for developing palaeoclimatic records. We took surface plant samples alongside measurements of water table depth and (micro)climate over spatial (six sites spanning>10° latitude) and temporal (monthly measurements over 1year) gradients and analysed the relationships between cellulose δ13C values and environmental parameters. We found strong, significant negative correlations between δ13C and temperature, photosynthetically active radiation and growing degree days above 0°C. No significant relationships were observed between δ13C and precipitation, relative humidity, soil moisture or water table depth, suggesting no growing season water limitation and a decoupling of the expected link between δ13C in vascular plants and hydrological variables. δ13C of Empodisma spp. roots may therefore provide a valuable temperature proxy in a climatically sensitive region, but further physiological and sub-fossil calibration studies are required to fully understand the observed signal. © 2015.

The International Tropical Peatlands Center