The adaptive use of resources by plants is an important topic in ecology, and is generally expressed as a resource-use efficiency. Nitrogen-use efficiency (NUE), in particular, has been the subject of several studies, as nitrogen (N) is the primary growth-limiting factors in many terrestrial systems. in chapter three, we examined how anthropogenic increases in N and phosphorus (P) availability may affect plant NUE response at multiple ecological scales due to carbon and N allocation within the entire plant (the leaf, woody tissue, above- and belowground, and whole-plant) and changes in species composition within the community. We examined plant nutrient efficiency indices in fertilization experiments (6 g N m-2 yr-1, 2 g P m-2 yr-1, or a combination of N and P) in nutrient-limited peatland ecosystems in the Upper Peninsula of Michigan. We further examined the evolutionary tradeoff of parameters such as N-productivity and the mean residence time (MRT) of N in biomass, and subsequent effects on NUE. Lastly, we examined the plant community response to environmental nutrient availability and N-uptake efficiency (plant N uptake/soil N availability). We found that N and P fertilization generally increased aboveground net primary productivity (ANPP) and tissue N concentration, although NUE response to nutrient addition was not straightforward. NUE differed by plant species, and across the ombrotrophic-minerotrophic gradient, and was often affected by the evolutionary tradeoff between N-productivity and MRT, where plants and communities were phenotypically and genetically adapted to maximize either N-productivity or MRT, but not both concurrently. However, N and P fertilization ubiquitously affected plant community N-uptake efficiency, and ultimately N-response efficiency, though the response to each nutrient was dependent on the plant species and community examined. Thus, plant community response to soil N availability may exert more important ecosystem controls than NUE, as significant changes in N-uptake efficiency at various ecological scales may affect ecosystem carbon and nutrient cycling processes.