Журнал Сибирского федерального университета: Серия Биология (Dec 2011)
Distribution of Frost Damages in Siberian Spruce (Picea Obovata Ledeb.) on the Two Different Slope Aspects at the Upper Tree Line Ecotone of the Southern Urals
Abstract
The analysis of extreme weather events provides an opportunity to study the microclimate characteristics on different slope aspects of the mountains. About 540 samples of wood of Siberian spruce (Picea obovata Ledeb.) on the north-eastern faced slope and 250 samples on south-western faced slope from 34 study plots on three altitude levels in the upper tree line ecotone of the Iremel massif (Southern Urals, 54 30 -34 N 58 49 -54 E) were collected with the purpose to investigate and date frost damages in tree rings. Differences in tree age when frost damage formation reduces up to 95% (age of their sensibility to frost), as well as in the frequency and synchronism of the frost damage formation, their position in the limit of annual ring and the intensity of damage to trees during the XXth century were revealed. The older trees (till 100 years old) were damaged more often by frost on the north-eastern slope aspect than in the south-west facing one (till 50-70 years old). Frost damages coincide mainly with the first half of the earlywood on both slopes, by reason of late spring frosts. During the XXth centuries 12 years with frost damages of first half of early wood were revealed on both slopes and all altitudinal levels with tree line ecotone (1927, 1943, 1952, 1961, 1964, 1965, 1966, 1967, 1970, 1982, 1995 and 1999). Synchronicity and mass injuries formation in the first half of the earlywood on both slopes along the upper tree line ecotone are probably caused by the advection of cold air masses. Increasing of the frost damage amount in the latewood at the lower level of the upper tree line ecotone on the north-eastern slope is probably due to advective-radiation frost of tree surfaces in the second half of the growth season, because of night cooling, and a runoff of cold air mass from the upper parts of the slopes. The reasons of revealed asynchronal formation of frost damage require further investigation of annual, monthly and daily temperatures, annual and monthly precipitations and dates of the growth period start.
