EFFECTS OF ELEVATED CO2, NUTRITION AND CLIMATIC WARMING ON BUD PHENOLOGY IN SITKA SPRUCE (PICEA-SITCHENSIS) AND THEIR IMPACT ON THE RISK OFFROST DAMAGE
Mb. Murray et al., EFFECTS OF ELEVATED CO2, NUTRITION AND CLIMATIC WARMING ON BUD PHENOLOGY IN SITKA SPRUCE (PICEA-SITCHENSIS) AND THEIR IMPACT ON THE RISK OFFROST DAMAGE, Tree physiology, 14(7-9), 1994, pp. 691-706
Effects of elevated CO2, clone and plant nutrition on bud dormancy of
Sitka spruce (Picea sitchensis (Bong.) Carr.) were examined. Sitka spr
uce seedlings were fumigated with ambient or elevated (ambient + 350 m
umol mol-1) concentrations of CO2 in open-top chambers for three growi
ng seasons. In 1991 and 1992, elevated CO2 delayed bud burst in the sp
ring and advanced bud set in the autumn. The effect of the open-top ch
amber on the thermal requirement for bud burst was greater than the ef
fect of elevated CO2 (50 and 30 day degrees (D(d)), respectively). In
a second study, four clones of Sitka spruce taken from two provenances
, at 43 and 54-degrees-N, were fumigated with ambient or elevated CO2.
There was a large natural variation in the timing of bud burst and bu
d set among the clones. Elevated CO2 had no effect on bud dormancy of
the Skidegate a clone, but it reduced the growing season of the North
Bend b clone by 20 days. In a third study, Sitka spruce seedlings grow
ing in ambient or elevated CO2, were supplied with one of three nutrie
nt regimes, low (0.1 x potential), medium (0.5 x potential) or high (2
.0 x potential), using a method and solution based on the Ingestad tec
hnique. Elevated CO2 did not affect bud dormancy in the high-nutrient
treatment, but it reduced the growing season of plants in the low-nutr
ient treatment by 22 days. Increasing plant nutrient supply lengthened
the growing season, plants flushed earlier in the spring and set bud
later in the autumn. The effects of elevated CO2 plus a 0, 2 or 4-degr
ees-C climatic warming on the timing of bud burst and the subsequent r
isk of frost damage were assessed using a simulation model and meteoro
logical data from three sites, Edinburgh, Braemar and Masset. The mode
l predicted that (i) doubling the CO2 concentration in die absence of
climatic warming, will delay the onset of bud burst at all three sites
, (ii) climatic warming in ambient CO2 will hasten bud burst and (iii)
climatic warming in elevated CO2 will hasten bud burst at Edinburgh a
nd Braemar but to a lesser extent than climatic warming alone. At Mass
et, a 4-degrees-C warming was required to advance the date of bud burs
t of seedlings in the elevated CO2 treatment. At all three sites, elev
ated CO2 and climatic warming increased the mean daily temperature on
the date of bud burst, thus reducing the risk of subsequent frost dama
ge.