Environmental and Genetic Control of Dormancy in Picea abies

Abstract

The effects of temperature, photoperiod and chilling on the leafing‐out of Norway spruce, Picea abies (L.) Karst. were studied. High temperature promotes breakage of post‐dormancy, long photoperiods having no such effect. Photoperiod and chilling cause the breakage of true dormancy. However, under field conditions, photoperiod will have no effect on leafing‐out date in the spring. By use of clonal material it was possible to show substantial genetic differences between individuals in response to temperature and photoperiod. When the effect of clones was accounted for, treatments could be compared more precisely. Differences between clones were apparent in heat‐sum required for leafing‐out, in rapidity of response to favorable post chilling conditions, and in chilling requirement This latter quantity was given a new definition, applicable when both chilling and post chilling temperatures are controlled and specified. This is that period beyond which a further 10 days of chilling accelerates leafing‐out by less than one day, i.e. the point at which the slope of the line relating days till leafing‐out to chilling period, is equal to minus 0.10. Differences in leafing‐out date were shown between provenances taken from throughout the range of Picea abies. These differences were related to latitude with provenances of high latitude leafing‐out first.

Northern geometrid forest pests (Lepidoptera: Geometridae) hatch at lower temperatures than their southern conspecifics: Implications of climate change

“…However, Hibbard & Elkinton (2015) did not fi nd any such differences between introduced O. brumata populations on Vancouver Island and in Massachusetts in North America. The pattern recorded might be an adaptation to match larval eclosion with bud burst of host trees, a critical synchrony for many spring folivores (Visser & Holleman, 2001;van Asch & Visser, 2007), with trees from high-latitude populations frequently requiring a lower temperature sum for fl ushing in spring than their southern conspecifi cs (Worrall & Mergen, 1967;Myking & Heide, 1995). Southern moth species spreading northwards would be subject to the risk of a mismatch between budburst and egg hatching in spring unless they can adapt to hatch at a lower temperature sum (Tikkanen et al, 2006;Saikkonen et al, 2012).…”

Effect of accumulated duration of the light period on bud burst in Norway spruce (Picea abies) of varying ages

“…Long days compensate partially for a lack of chilling during rest break in Pinus sylvestris L. (Jensen andGatherum 1965, Hoffman andLyr 1967), Picea abies (L.) Karst. (Nienstaedt 1967, Worrall andMergen 1967) and several other tree species (Nienstaedt 1966, Farmer 1968, Campbell and Sugano 1975, Hinesley 1982, Garber 1983. Some results indicate that there is a critical photoperiod for bud burst in beech (Fagus sylvatica L.) seedlings, even when they are fully chilled (Heide 1993a).…”

“…After transplanting, the seedlings and cuttings were moved outdoors and exposed to natural chilling and freezing temperatures until December 5, 1997. On this date the material was presumed to be fully chilled (Worrall and Mergen 1967, Sarvas 1974, Hänninen 1990). The pots were isolated from each other with sand.…”

Foliation of spruce in the Giant Mts. and its coherence with growth and climate over the last 100 years

“…The temperatures in March and October -the period at the beginning and end of bud formation -had a significant impact on annual needle production (r = 0.36, a = 0.05, figure 9). Worral and Mergen [33] report on the control of bud break by temperature. Gruber [11] describes the parallel development of the shoot and its buds and found that the final needle primordia can be initiated in October.…”