Annual Variability and Regional Fluxes Derived from a 100-Year Site Cluster

Using a growing number of multi-site flux clusters, bottom-up quantification and scaling of regional scale fluxes is achievable while also quantifying the variation in fluxes from land cover differences across the landscape. With long-term flux records, quantifying variation in regional fluxes caused by interannual variation in environmental flux drivers is possible. Using ~100 site-years of data from a ~160 km watershed in Michigan, regional scale variability of fluxes and their drivers are quantified by separate land cover type. This site cluster contains a total of 12 flux sites with 7 sites having long-term (>10 years) of data. With the region predominately consisting of agriculture, forest, urban, and wetland land-cover, we can directly measure the interannual variability of water and carbon fluxes based on land-cover type. For water fluxes, we show annual sums to have a small degree of interannual variability, while carbon fluxes can switch between net annual sources and sinks for all land-cover types besides wetlands, which was recorded for three years as a carbon sink. Once interannual variability per land-cover type is accounted for, estimates of regional scale fluxes can be compiled from a bottom-up scaling approach. Ultimately, a regional scale flux estimate can be used to scale fluxes from relatively small footprint to regional scales, to be used for modeling or remote sensing comparisons, as well as examining spatial and temporal controls of regional scale flux estimates.