Title: Using the tea bag index to measure decomposition rates in Icelandic rangelands

This study was conducted in Audkuluheidi and Theistareykir where grazing is practiced during summer. The tea bag index (TBI) method was used to measure decomposition rates in those Icelandic highlands with exclosure experiments with the following objectives: (1) to estimate decomposition rates in grazed and non-grazed areas, in heath and gravelly desert in Audkuluheidi and Theistareykir, and (2) to learn the method of TBI for measuring decomposition rates. Initial weights for tea bags were taken before installation, then tea bags were taken to the field and buried in pairs (green and rooibos) at a depth of 5 cm in the experimental plots, organised in six pairs in two habitats. That part of the work was done by other members of the research team. The tea bags were collected in June 2022 after 12 months of incubation and dried in an oven for 48 hours at 70°C. The tea bags’ final weights were recorded and analysed to determine the effects of grazing exclusion, habitats, and sites on mass loss of the two tea types. The results showed that there were significant differences between habitats and sites in tea mass loss. There was no significant difference in mass loss in grazed/non-grazed plots, meaning that grazing did not have any effect on decomposition processes. By using TBI it is possible to collect information about land health through measuring decomposition rates in order to identify strategies for sustainable management of ecosystems, such as rangelands.