The Southern Sierra Critical Zone Observatory (CZO) is establishing a rain-snow transition research platform for research by investigators from multiple disciplines and a research program aimed at yielding general knowledge and tools for understanding the interactions between water, atmosphere, ecosystems and landforms in the critical zone. A primary, overarching goal is to understand how critical zone processes control fluxes and stores of water across the landscape, and how the water cycle modulates (bio)geochemical, biological, geomorphological and soil processes in the critical zone. Five science questions define and focus the core measurement and research program: i) how do coupled hydrologic and biogeochemical fluxes vary across the rain-snow transition, ii) what is the role of extreme hydrologic events in water and biogeochemical balances, iii) to what extent does vegetation modulate or actively control the primary subsurface fluxes of water and nutrients, iv) over what time and space scales, and during what seasons, are short-circuit pathways dominant in the critical zone, and v) how does the presence of a seasonal snowpack affect the subsurface, critical zone, soils, geomorphology, biogeochemistry and hydrology, and how will the system respond as climate warms and snowpacks recede. Some unique features of the Sierra Nevada system as compared to more mesic sites include: i) hydrophobic soils, ii) islands of fertility in soils, iii) dominant role of catastrophic events, e.g. fire, and iv) spatial decoupling of decomposition from root uptake in soil profile. The rationale for measurement design, including the value of high-frequency data will be illustrated, as will the strategy for providing community data and information, and educational programs.
Bales, R. (2007): Southern Sierra Critical Zone Observatory: Integrating water cycle & biogeochemical processes across the rain-snow transition . Fall meeting, American Geophysical Union, December 10, 2007; Abstract H13A-0962 .