Molecular assays of soil environments reveal tremendous microbial diversity, but it remains unclear how this diversity might be mechanistically linked to the ecology of the organisms and their biogeochemical function. Methane consumption in upland soils is arguably the simplest biogeochemical function, and there are emerging patterns in the diversity and biogeography of the organisms that carry out soil methane consumption. This simplicity may allow methane uptake in upland soils to be a model system for merging microbial ecology, diversity and biogeochemistry. Five key traits appear critical for methanotroph ecology: enzyme kinetics, nutrient demand, pH tolerance, ammonium sensitivity and desiccation tolerance. Unfortunately, few studies to date have examined the functional consequences these traits may have on methane consumption. Here, I present analysis of methanotroph community composition and Michaelis-Menten kinetics of methane uptake across three North American temperate grassland sites of differing soil moisture regimes. Across this gradient, I observed distinct variation in community composition, and significant changes in enzyme kinetics. In addition, I find that differences in field estimates of methane activity parallel the patterns of Michaelis-Menten assays, which in turn correlate with differences in methanotroph community composition. These correlations suggest that methanotroph community composition alters ecosystem function.