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October 12, 2005
Ecosystem research conducted at Sky Oaks by John Gamon's group at CalState LA using HPWREN
We are conducting research at San Diego State University's Sky Oaks Biological Field Station to understand the controls of the key ecosystem processes under different disturbance regimes (e.g., extreme drought, ENSO, fire) using a combination of ecophysiological measurements, in situ sampling, and remote sensing techniques. Our primary focus is on the fluxes of carbon dioxide and water vapor between the biosphere and the atmosphere (i.e. photosynthesis, respiration, and evapotranspiration). This "breathing of the planet" helps to control the Earth's atmospheric composition and climate. This study is conducted with a combination of direct flux measurements (from SDSU's eddy covariance tower) and optical remote sensing at leaf, ecosystem and regional scales. Additionally, we have installed arrays of sensors that monitor soil temperature and moisture to help us understand how these variables affect fluxes. Satellite sensors provide large spatial patterns of remotely sensed signals of the ecosystem with regional or global coverage. These signals are used in models to estimate biosphere-atmosphere fluxes. However, the coarse resolution of satellite sensors is problematic, particularly for patchy landscapes (e.g. chaparral). These sensors need validation from field studies (ground truthing). A key tool in this validation is an automated "tram system" comprised of a robotic cart on a rail, elevated above the vegetation canopy, and located near the primary sampling region ("footprint") of the flux tower. The tram enables spatially explicit and multi-temporal sampling, and carries a spectrometer, surface temperature sensor, digital camera, as well as micrometeorological sensors that measure the condition of the vegetation and the nearby atmosphere. By comparing these tram measurements to flux measurements provided by SDSU's eddy covariance tower, we are able to explore the relationships between remotely sensed optical signals and CO2 and water vapor fluxes. Additionally, by comparing tram measurements to satellite signals, we are able to evaluate the accuracy of satellite products used for estimating carbon and water vapor fluxes. With HPWREN support, we are able to connect the data from Sky Oaks biological field station to distant computers via the Internet, facilitating continuous monitoring. The fast Internet connection, allows us to ensure that data are collected and the data quality is good, and allows the development of classroom applications. The "remote lab" gives students a real sense of what the ecosystem is experiencing.
Yufu Cheng and John Gamon
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