Climate-induced changes in biome distribution, NPP, and hydrology in the Upper Midwest U.S.: A case study for potential vegetation

We investigated the impacts of recent climate change on potential vegetation distributions and carbon and water cycling across the Upper Midwest from 1948 to 2007. We used the Agro-IBIS dynamic vegetation model driven by a newly developed gridded daily climate data set at 5 min x 5 min spatial resolution. Trends in climate variables were spatially heterogeneous over the study period and were associated with an overall increase in net primary productivity (NPP). We observed an average regional change in total NPP of 41 +/- 30 g C m(-2) (8%). Increased summer relative humidity and increased annual precipitation were key variables contributing to the positive trends. Mechanisms for increased productivity included a reduction in soil moisture stress as well as increased stomatal conductance resulting from an increase in summertime humidity. Model simulations also showed an average total increase in annual groundwater recharge throughout the region of 39 +/- 35 mm (45%) driven by increases in annual precipitation. Evapotranspiration had a highly variable spatial trend over the 60 year period, with an average total change of 5 +/- 21 mm (1%) across all grid cells. The location of the Tension Zone, a broad ecotone dividing northern mixed forests and southern hardwood forests and prairies, was not observed to migrate using analysis of meteorological variables. Citation: Motew, M. M., and C. J. Kucharik (2013), Climate-induced changes in biome distribution, NPP, and hydrology in the Upper Midwest U. S.: A case study for potential vegetation, J. Geophys. Res. Biogeosci., 118, 248-264, doi:10.1002/jgrg.20025.