Author(s)

Hidenori Furuuchi, Michael W. Jenkins, Randy S. Senock, James L. J. Houpis, James C. Pushnik

Department of Biological Sciences, California State University, Chico, USA.
Department of Earth and Environmental Sciences, East Bay, USA.
Department of Geological and Environmental Sciences, California State University, Chico, USA.

This research developed estimates of plant crown transpiration and water-use-efficiency using reflectance and derivative indices extracted from remotely sensed chlorophyll fluorescence measurements under natural conditions. Diurnal changes of leaf-level gas exchange (carbon assimilation rate (A), stomatal conductance (g_s), transpiration rate (E)), chlorophyll fluorescence and canopy-scale remote sensing were measured on top crown of valley oak (Quercus lobata) in the foothills of central California, USA. The results indicated Q. lobata experienced saturating irradiance (PAR), which induced photoinhibition indicated by a decrease in the quantum efficiency of photosystem II (r² = 0.648 with F_v ′/F_m′ and r² = 0.73 with F_PSII) and open reaction centers (qP; r² = 0.699). The excess absorbed quantum energy was dissipated as heat through the Xanthophyll cycle and other processes (photorespiration and the water-water cycle) rather than energy emission as steady state chlorophyll fluorescence (F_s). An increase in leaf temperature caused by the activity of Xanthophyll cycle was correlated to a decrease in F_s (r² = 0.381) and an increase in evaporative cooling through E (r² = 0.800) and water use efficiency (WUE; r² = 0.872).

Crown Transpiration; Remote Sensing; Chlorophyll Fluorescence; Reflectance; Quercus lobata

Furuuchi, H. , Jenkins, M. , Senock, R. , Houpis, J. and Pushnik, J. (2013) Estimating plant crown transpiration and water use efficiency by vegetative reflectance indices associated with chlorophyll fluorescence. Open Journal of Ecology, 3, 122-132. doi: 10.4236/oje.2013.32015.