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Harvard Forest Symposium Abstract 2012

• Title: Canopy Phenology, Remote Sensing, and Microclimate
• Primary Author: Mark Friedl (Boston University)
• Abstract:

  The goal of this research project is to develop improved methods for monitoring phenology from remote sensing, and to use data acquired through this effort to improve models of phenology at scales commensurate with large-scale ecosystem models. Field efforts at Harvard Forest are based at the walk-up tower site adjacent to the EMS tower, and are examining how seasonality in canopy leaf area is controlled by local climate. To achieve this goal, we are collecting long-term measurements that quantify how above and below canopy radiation fluxes vary as a function of seasonal leaf dynamics. Specifically, we are continuously measuring above- and below-canopy radiation fluxes in a variety of spectral bands (shortwave, photosynthetic). Time series of these measurements provide surrogate measures of canopy leaf area dynamics, and directly characterize the shortwave radiation component of the surface energy balance. These measurements also complement ongoing microclimate and eddy covariance measurements of water, energy, and carbon exchange at the EMS tower. Core measurements being collected focus on photosynthetically active radiation (PAR) measured using LI190SB LI-COR quantum radiation sensors. Five below-canopy sensors mounted on posts approximately 0.5 meters above the ground surface and located roughly 20-m from the walk-up tower at equidistant spacing measure downwelling PAR below the forest canopy. Above-canopy quantum sensors measure upwelling and downwelling PAR, and are mounted on a boom extended from the tower at a height of 23-m. Downwelling and upwelling solar radiation measurements are also recorded using a Kipp and Zonen thermopile pyranometer, and global (total) and diffuse PAR measurements are measured using a BF3 sunshine sensor (both at 23-m). BF3 sensor photodiodes are cosine corrected and calibrated for the measurement of PAR quanta. Soil temperatures at 20-cm depth are measured with Campbell Scientific 107-L probes in four locations distributed around the walk-up tower and co-located with PAR sensors. Air temperatures are measured using a shaded CS107-L probe at 23-m. These data are being used in combination with visual observations of phenology collected by Harvard Forest staff, webcam imagery collected by Andrew Richardson’s group, and remote sensing measurements from both Landsat and MODIS.

• Research Category: Forest-Atmosphere Exchange