Estimating Understory Temperatures Using Modis Lst In Mixed Cordilleran Forests

Satellite remote sensing provides a rapid and broad-scale means for monitoring vegetation phenology and its relationship with fluctuations in air temperature. Investigating the response of plant communities to climate change is needed to gain insight into the potentially detrimental effects on ecosystem processes. While many studies have used satellite-derived land surface temperature (LST) as a proxy for air temperature, few studies have attempted to create and validate models of forest understory temperature (T-ust), as it is obscured from these space-borne observations. This study worked to predict instantaneous values of T-ust using daily Moderate Resolution Imaging Spectroradiometer (MODIS) LST data over a 99,000 km(2) study area located in the Rocky Mountains of western Alberta, Canada. Specifically, we aimed to identify the forest characteristics that improve estimates of T-ust over using LST alone. Our top model predicted T-ust to within a mean absolute error (MAE) of 1.4 degrees C with an overall model fit of R-2 = 0.89 over two growing seasons. Canopy closure and the LiDAR-derived standard deviation of canopy height metric were found to significantly improve estimations of T-ust over MODIS LST alone. These findings demonstrate that canopy structure and forest stand-type function to differentiate understory air temperatures from ambient canopy temperature as seen by the sensor overhead.