Cold Hardiness of Needles of Pinus strobus L. as a Function of Geographic Source

Author： Maronek Dale M. Flint Harrison L.

Publisher： Society of American Foresters

ISSN： 0015-749X

Source： Forest Science, Vol.20, Iss.2, 1974-06, pp. : 135-141

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Abstract

Cold hardiness of needles was determined in 14-year-old trees of Pinus strobus L. from 15 different seed sources on a single site. Hardening was first apparent in September, increased in fall and early winter, and reached a maximum by midwinter. Needles from northern sources were hardier than those from southern sources at all sampling dates. By late April, differences in hardiness among sources had disappeared. Trees dehardened readily in response to one week of high temperature following the December 14 sampling date. Inclusion of either latitude or average annual minimum temperature in a multiple linear regression equation along with longitude and elevation resulted in the best prediction of hardiness. All needles attained levels of hardiness greater than would be required to escape cold injury in the natural habitat. Forest Sci. 20:135-141.