Сибирский лесной журнал (Dec 2018)
The influence of temperature on biomechanical properties of woody plants in the conditions of protected and open grounds
Abstract
The study is focused on the influence of ambient temperature on biomechanical properties of tissues in the treesgrowing in the conditions of protected and open grounds. The investigations were carried out on 11 plant species growing in the greenhouse of Donetsk Botanical Gardens and 11 tree species growing in open grounds in the conditions of the city of Donetsk. The experiment included two series of trials: 1) calculating the Modulus of Rupture (MOR) of woody tissue for species from the fig Ficus L. genus at +23 ºС; 2) finding temperature dependence of the Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) for the Illawarra flame tree Brachychiton acerifolius A. Cunn. ex G. Don Macarthur et C. Moore and ceiba Ceiba pentandra (L.) Gaertn., and calculating the same dependences for 11 open ground plants. The values of MOR for 7 greenhouse species averaged 4.9 ± 0.7 МН/m2, i.e. circa 20 times lower than in natural environments. Such species as Haroni fig Ficus vallis-choudae Delile and banyan fig Ficus benghalensis var. krishnae (C. DC.) had the lowest MOR values. The study of the influence of low temperatures showed that in the sample pretreated by –23 °C freezing and then heating, MOE dropped simultaneously with slowing of the temperature shift. The altering of MOE is of a stepwise character. The common temperature breakpoint for all the curves is T = 0 °C, i. e. freezing point. According to the values of MOE and MOR, the most resistant species are rubber fig Ficus elastica Roxb. ex Hornem. and Benjamin fig Ficus benjamina L. (for greenhouses), and northern red oak Quercus rubra L., common oak Quercus robur L., and silver birch Betula pendula Roth (for open grounds). The studies allow us to recommend temporary outdoor tub-gardening in summertime for greenhouse trees with proper for each plant shading. Open ground trees should be protected from irreversible trunk bending and breakage preventing or reducing exposure of the lower part of their trunks to light using protective fiber wraps or special cases.
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