M. Lamontagne et al., PHOTOSYNTHESIS OF BLACK SPRUCE, JACK PINE, AND TREMBLING ASPEN AFTER ARTIFICIALLY INDUCED FROST DURING THE GROWING-SEASON, Canadian journal of forest research, 28(1), 1998, pp. 1-12
Light-saturated photosynthesis following artificial frosts was monitor
ed for black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus bank
siana Lamb.), and trembling aspen (Populus tremuloides Michx.). None o
f the species exposed to -9 degrees C in May or to a and -9 degrees C
in August recovered within the 23- and 14-day monitoring periods, resp
ectively. Black spruce and jack pine treated at -6 degrees C in May re
covered within 5 and 23 days, respectively. Black spruce treated at -3
degrees C in August recovered within 10 days. Frosts were applied to
the upper and lower canopies of mature black spruce and jack pine in J
une and to mature trembling aspen in July. For black spruce, the lower
canopy did not recover whereas the upper canopy partially recovered o
ver the 10-day monitoring period. For jack pine and trembling aspen, t
here were no differences in recovery between canopy levels. Jack pine
treated at -5.5 degrees C recovered within the 10-day monitoring perio
d whereas at -8.5 degrees C, it only partially recovered. Although rec
overy period varied with species, phenological state, and frost temper
ature, gradual recovery of photosynthesis over 5-21 days seems a reaso
nable modelling algorithm for boreal tree species when growing season
frosts lower than -3 degrees C occur. However, cooling rates in our ex
periments were greater than those that normally occur in nature.