Using the Tea Bag Index to characterize decomposition rates in restored peatlands

Peatlands characteristically accumulate organic matter due to low decomposition rates, but peatland disturbance alters local physicochemical conditions often resulting in loss of soil organic matter and emission of CO2. Restoration may reduce peat oxidation, but traditional measurements of decomposition are time-consuming. The Tea Bag Index (TBI) is a simple, standardized method to measure decomposition rates in soils. We used the TBI to measure decomposition rate at four restored peatland sites across Canada that were used for peat extraction or disturbed by oil extraction (former well-sites), comparing to undisturbed and unrestored sites. We measured environmental conditions including soil temperature, water table position and peat pH from May to August 2016. Litter bags were buried for one year alongside tea bags at one site for a direct comparison of decomposition rates between the methods. There were no significant differences for TBI decay constant (kTBI) between treatments of restored, unrestored or undisturbed sites across the whole data set, but some differences were found among treatments within the same peatland site for sections restored at different times in the past. Soil temperature, pH, and water table were not significantly related to kTBI, but were negatively correlated with the stabilization factor (S). The kTBI and litter bag k were significantly different but positively correlated. The TBI is not easily comparable to traditional litter bags, but is less costly in both time and money, and may be used in conjunction with additional parameters to determine decomposition patterns with potential for use as a metric for evaluating restoration outcomes.