Natural ecosystems are based on litter decomposition; but if animals graze there decrease litter decomposition? Also topography influences soil characteristics and plant communities; due to soil fertility bottom slopes produce more biomass and litter. Does the litter have different decay rate when is produced at different topographic levels? If so, could grazing animals interact with topography and modify decay rate? Will grazing affect ecosystem sustainability? Two experiments conducted in a rangeland, Alberta, Canada, will answer these questions. Litter was mixed and placed at upper (U), middle (M), and lower (L) topographic levels in grazed (G) and ungrazed (UG) plots in a random block design. Also U, M, and L litter, from G and UG plots, was placed in the same conditions in a nested design with six incubation times; decomposition is determined utilizing litterbags. As litter chemical composition is related to decomposition, non-polar (NPC), water-soluble carbon (WSC), holocellulose, lignin, and ashes were determined. These results refer to 66 days of incubation. Decomposition was faster (P<0.05) in L (14.9%) than in M or U levels (12.8% and 11.4%). Water filled porosity influenced this; it was higher in L (0.6) than in M or U (0.3) levels. Graze negatively effected (P<0.0001) litter decay. M and L had faster decomposition in UG (19.2% and 27.5%) than in G (11.5% and 22.1%). G and UG had similar values (13.2%, 15.7%) in U location. Differences in litter quality explain this. G litter had less (P<0.05) NPC than UG litter (38.7 vs. 54.6 mg g^-1) and more (P<0.05) holocellulose (633.4 vs. 610.9 mg g^-1) and lignin (139.6 vs.127.9 mg g^-1) in M location. A similar trend was detected in L level. Ecosystem's implications are slow down nutrient cycling, and decrease available nutrients; this will decrease NPP; over time less C will be allocated to the soil.