Determining the growth rate of Sphagnum magellanicum Brid. in the Falkland Islands using radiocarbon dating

Introduction The growth rate of Sphagnum L. is of great interest due to the key role it plays in carbon sequestration in peatlands. Methods currently used to determine this growth rate all have limitations. The present study uses radiocarbon dating and age-depth modelling, both common methods in palaeoecology, to determine Sphagnum growth rates, since this approach avoids some common shortcomings of the currently available alternative techniques.Methods Long shoots of Sphagnum magellanicum Brid. were collected from East Falkland. Short sections were cut out at known positions, and each of these sections was radiocarbon dated. The dates were calibrated using a post-bomb calibration curve. The resulting dates were used to construct a Bayesian age-depth model to model the growth rate of this plant. Growth rates were compared with mean temperature, precipitation and insolation, using multiple linear regression.Key results and conclusions The top 21 cm of the 23-cm shoot analysed grew over a period of 20 years. Median modelled growth rates are 1.0–1.5 cm per year, with slower growth between 2015 and 2020 CE. The strongest predictor of growth rate was insolation (sunshine hours month−1). A significant positive effect from precipitation was also found. These results show that radiocarbon dating and age-depth modelling are useful methods for determining the growth rate of Sphagnum at high resolution.