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.