Seasonal Changes in the Spectral Properties of Mountain Laurel (Kalmia latifolia L., Ericaceae) in North East Alabama

ABSTRACT
Absorptance of visible light (400-700 nm) by mountain laurel (Kalmia latifolia L.) was highest during May followed by April. Compared to May and April, light absorptance decreased 19 and 25% during June and August, respectively. The same results were obtained for light absorptance during December with the exception that during June and August the percentage of light absorptance in the range 562-594 nm was reduced to 56%. Near-infrared light (750-800 nm) absorptance decreased sharply in comparison to the absorption of visible light each sampling time. The lowest absorptance value for the near-infrared light was obtained during June and August (39%), followed in increasing order by December (53%), May (71%) and April (75%). Chlorophyll concentrations gradually increased starting in February and continued through August. In general, reflectance for the visible and near-infrared ranges was lower than 10% for all the sampling period with an exception in April when a sharp increase, in near-infrared reflectance to slightly above 30%, was detected. Evaluation of the light saturation curve showed that CO2 assimilation reached limited CO2 level near 600 μEEm-2s-1.