After returning from ESA in Baltimore, I traveled with Jonathan again to Harvard Forest for our August measurements (only September left!). We again used "Bucky" the canopy lift to obtain leaf-level measurements of photosynthesis and fluorescence which will use to scale to the canopy, and regional levels.
Some photos of us 60 feet up waiting for the fluorescence values to stablize before taking a measurement. We looked at Fluorescence in leaves that were dark adapted, adapted to ambient light conditions and high-light adapted (PAR = 1500+). Using a response from these variables, we can construct a model of fluorescence under different light conditions in Oak, Maple, and Beech across the growing season.
In addition to our monthly monitoring of leaf fluxes, we were able to collaborate with Jim Kellner and his graduate studetn Carlos Silva, who are using hyperspectral high-resolution imaging to observe and analyze the same parcel of forest that we are monitoring with NDVI and RGB imaging, and solar-induced fluorescence. This multi-layered approach will allow us to correllate fluxes across scales and better quantify actual real-time GPP values of Harvard Forest.
The equipment that Carlos and Jim brought up to the top of the tower was incredibly impressive - they can obtain 1 cm2 resolution of all wavelengths of reflectance from leaves - and at that scale multiple measures from a single leaf! They repeated these scans every 15 minutes for the entire day to see how photoperiodic variation in PAR and temperature impacts these measures.