We compared leaf, root, cellulose filter paper and wood decomposition rates over 38 months in acidic tussock tundra under increased nutrient availability (10 g N m^-2 y^-1, 5 g P m^-2 y^-1) and air temperature (5-6^oC) at Toolik Lake, Alaska. Nutrient additions and elevated growing season air temperature have been on going since 1989. Five treatments were compared: control (CT), warmed (GH), fertilized since 1996 (NP11), fertilized since 1989 (NP18), and warmed plus fertilized since 1989 (GHNP). The experiment began in July 2003; samples were collected in August of each year between 2003 and 2006. Betula nana leaf litter from treatment plots was placed in both treatment plots and a common garden to examine how environmental changes associated with treatments altered decomposition rates. The greatest impact was that GH and GHNP litter in treatment plots had reduced decomposition rates (20% more mass remaining) compared to the same litter within a common garden suggesting environmental conditions within the greenhouses slowed decomposition. Comparing decomposition rates between a common Betula nana litter and treatment litter within treatment plots NP11 litter in NP11 plots had 5% less mass remaining compared to the common litter.  However, little difference was observed in the NP18 plots.  Overall litter in GH and GHNP plots decomposed more slowly with 15% greater mass remaining.  Filter paper place aboveground decomposed very slowly in the GH and GHNP plots with 10-20% mass loss, respectively. Filter paper decomposition rates were greatest both above and belowground in NP11 and NP18 plots. Betula wooden dowels placed both above and belowground decomposed slowly with 3-10% mass loss. Dowels placed aboveground had a greater mass remaining compared to belowground samples. Betula nana roots decomposition varied little between treatments with 25% mass loss.  In conclusion, litter and soil characteristics in GH and GHNP plots decreased decomposition rates.