Net Ecosystem Exchange, Evapotranspiration and Canopy Conductance in a Riparian Forest

In conjunction with the Cosumnes Research Group, we performed a field study along the. A 21m tall eddy-covariance tower was installed within a seasonally flooded twenty year old cottonwood forest (Populus Fremontii) and bio-micrometeorological data was recorded from January, 2004 through July 2005. Evapotranspiration, canopy conductance, and net ecosystem exchange of CO2 (NEE) are among the half-hour mean values we calculate from this data. We look at diurnal and seasonal trends in NEE, canopy conductance and evapotranspiration. We also analyze the relationship between these ecosystem responses and various forcing variables such as flood duration, water availability, air temperature, solar radiation and vapor pressure deficit (VPD). Preliminary results suggest that the ecosystem does not experience any water stress during the observation period, having continuous access to a shallow water table. VPD has very little control over NEE, while increasing temperature shows a strong relationship with increased NEE levels (due in part to higher temperatures occurring concurrently with higher levels of solar radiation) and canopy resistance clearly decreases with increasing radiation. More in depth analysis involves the use of multivariate statistics in an attempt to examine the degree of cross-correlation in forcing micrometeorological conditions.