| Summary: | Soil is an important resource for all terrestrial organisms and their ecosystems. It contains diverse and complex microbial communities that have a major role in the decomposition of plant litter. This thesis circulated around a specific research question regarding there being a difference in decomposition rates between rangeland habitats at varying degradation stages, and how those rates differed between study sites and sheep grazing regimes within the chosen habitat types. The objective of this study was to investigate decomposition rates in soils of two habitat types at different states of degradation, Betula nana dwarf-shrub heaths and gravel deserts, and their responses to excluded grazing, using the Tea Bag Index (TBI) approach. Two study sites were identified for this research, Auðkúluheiði and Þeistareykir. Two types of tea, green and rooibos, that had been weighted prior, were buried at the sites in each habitat, and allowed to be incubated for three months. After retrieving the tea bags, they were weighted again for mass loss estimation. From the data collected, the decomposition rate constant (k) and stabilization factor (S) could be calculated. Statistical analyses were performed from the collected and calculated data using Linear Mixed Effect Models (LMM). There was no significant difference between the different treatments, habitats and sites with the responses of the decomposition rate (k). However, there was significant difference between all differences in relation to responses of the stabilization factors (S). In three months, the k is not affected by habitats at different degradation stages nor show any responses to grazing.
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