Patterns of Primary Productivity in a Semiarid Montane Forest

Abstract

Global forests are projected to be impacted by changing climate, but the scientific community is working to constrain considerable uncertainty in the extent of these impacts. In the southwestern United States, semiarid forests are important natural and social resources, but they face a decline in productivity. One challenge associated with modeling and projecting changes to forest function into the future is understanding controls on current processes at the sub-landscape scale. Because many of these southwestern forests are found in mountainous regions, complex terrain adds to the challenge of characterizing this productivity beyond individual trees. In this study, we attempt to quantify the effect imposed by topographic aspect on primary productivity by observing three co-dominant native species. Repeated measurements of net carbon assimilation demonstrate that P. ponderosa and P. strobiformis respond to natural differences in volumetric water content across opposing north and south aspects, while P. menziesii does not behave this way. The implications of these results are important to modeling potential carbon uptake and transpirative water demand in regions where these species dominate.