Conclusions
In this study the growing season carbon and water dynamics of a subalpine wetland located in complex terrain was characterized, filling a gap in research on carbon source/sink dynamics in alpine wetlands and in understanding their controlling variables. This work showed that horizon shade, caused by the local complex terrain, had a significant and substantial effect on water and carbon fluxes, reducing ET and potentially enhancing GPP during peak growing season. This resulted in increased WUE at the site during periods of increased shading. In addition to Rg, temporal variability in ET was related to temporal variability in soil temperature and VPD. Shade impacted the curvature and intercept of the nonlinear ET-Rg relationship at our site. In contrast, temporal variability in GPP at our site was dependent largely on Rg only. Complex topography and shading can create a large range in ET for similar mountain wetland types at similar elevations. Reduced evaporative losses from such ecosystems could help support late season runoff in downstream communities, where water supplies are needed.