1. Southern Sierra Critical Zone Observatory Integrating measurements for advances in hydrology & geochemistry A research platform for studying Earth surface processes in the “critical zone”, extending from the top of vegetation down through groundwater Roger Bales, UC Merced Beth Boyer, UC Berkeley Martha Conklin, UC Merced Mike Goulden, UC Irvine Jan Hopmans, UC Davis Dale Johnson, U Nevada Jim Kirchner, UC Berkeley Christina Tague, UC Santa Barbara Carolyn Hunsaker, USFS-PSW 9 graduate students Field hydrologist/geochemist Data manager Education/communications scientist CZO team The rain-snow transition zone is particularly vulnerable to large & rapid changes in climate & landcover. While this zone undergoes rapid seasonal changes, going from snowcoverto wet soil to dry soil over a 1-2 month period, climate warming will shift this transition period earlier or eliminate it entirely. The result will be major changes in seasonal-to-interannualcritical zone processes involving water, nutrients and ecosystem response of the largely mixed conifer forest found in the rain-snow transition zone. Forest density & the threat of catastrophic fire in the zone are very high, leading to the further likelihood of changes in longer-term critical zone processes. Steep gradients in precipitation patterns, along both elevation and aspect, plus rapid seasonal changes, make this zone an excellent natural laboratory for studying how critical zone processes respond to perturbations, & particularlyhow the water cycle drives critical zone processes. Also, the characteristic spatial differences along gradients offer the opportunity to substitute space for time. Background Research support: National Science Foundation Research partner: Pacific Southwest Research Station, U.S. Forest Service CZO –meteorology & snowpack –soil moisture & temperature –groundwater levels & temperature –erosion & sedimentation –snowmelt, rain, stream, groundwater & soil chemistry CZO measurements –water cycle & response to perturbations –coupled hydrologic & (bio)geochemical processes/cycles –extreme hydrologic events in hydrologic & (bio)geochemical cycles –vegetation control over fluxes of water & nutrients –pathways for transport of water, heat & mass –role of seasonal snowpack in determining critical zone processes Planned investigations CZO is located in the N. Fork of the Kings R., in the Southern Sierra Nevada. The CZO catchments cross the rain-snow transition, in the mixed conifer forest. PSW measurements –meteorology –stream stage & discharge –stream condition & physical habitat –erosion & sedimentation –geology, soils & litter –snowmelt, rain, stream & soil chemistry –riparian & upland vegetation –stream invertebrates, algae & periphyton Stream major ions Cumulative discharge for 3 catchments, WY 2004 Installing Echo probes for soil moisture & temperature sediment basin stream discharge groundwater snow depth satellite snowcover More information Sierra Nevada Research Institute http://snri.ucmerced.edu CZO home: http://snri.ucmerced.edu/CZO Data: http://eng.ucmerced.edu/snsjho stream instrumentation met station