Winter Survival of Grasses and Legumes in Subarctic Alaska as Related to Latitudinal Adaptation, Pre-Winter Storage of Food Reserves, and Dry-Matter Concentration in Overwintering Tissues
Leslie J. Klebesadel, Emeritus Professor of Agronomy
Agricultural and Forestry Experiment Station; Palmer, Alaska
Bulletin 94; September 1993 (21 pages)
Summary
Objectives of this study, consisting of two separate but similar experiments, were to (a) compare winter hardiness in subarctic Alaska of numerous plant species and ecotypes from various latitudinal sources within most species, and (b) seek a better understanding of certain aspects of pre-winter physiologic changes in plants that are associated with successful or with unsuccessful winter survival in this northern area. Both experiments were conducted at the University of Alaska's Matanuska Research Farm (61.6°N) near Palmer in southcentral Alaska.
Latitudinal ecotypes of bromegrass1, timothy, Kentucky bluegrass, red fescue, slender wheatgrass, alfalfa, and red clover, planted in rows in late June of two successive years, were thinned as small seedlings to individual plants. Seven other legumes (six native Alaskan) were also planted in the second experiment. Plants were compared for storage of food reserves (three samplings/year) during late summer and autumn of the year planted, for pre-winter dry-matter concentration in overwintering tissues, for indications of dormancy, and for subsequent winter survival.
· No entries exhibited stored reserves when sampled 9-11 August, but reserves were present in all entries sampled 22-23 August and later until the final sampling in mid-October during both seasons.
·Overwintering tissues of northernmost-adapted ecotypes increased in dry-matter concentration during the pre-winter hardening period more rapidly than those of southern-adapted ecotypes.
·Northernmost ecotypes within each species generally possessed highest dry-matter concentration in storage tissues and highest level of stored food reserves at the final sampling each season (9-12 October) just prior to freeze-up; they also survived the winters best. Southernmost ecotypes were lowest in percent dry matter, stored lowest levels of food reserves, and were poorest in winter survival. Ecotypes of intermediate-latitudinal origin usually were intermediate in these characteristics.
·Evidence of onset of dormancy (slow expression of stored reserves as etiolated growth in a warm, dark chamber) was detected in legumes more than in grasses; this characteristic was frequently, but not invariably, associated with superior winter survival.
·Grasses generally were more winter hardy than the legumes, although certain of the most winter-hardy legumes surpassed nonhardy ecotypes within grass species.
·Best winter hardiness was noted in (a) Alaska cultivars of bromegrass, Kentucky bluegrass, and red fescue, (b) timothy from northern Norway, (c) naturalized strains of slender wheatgrass and Siberian alfalfa, and (d) native Alaskan ecotypes of pumpelly brome, slender wheatgrass, Harrington milkvetch, and alpine sweetvetch.
·A locally adapted ecotype of foliose oxytrope displayed significantly better winter survival than an ecotype of the same species adapted much farther north in arctic Alaska.
·Native Alaskan large-leaf lupine, that grows commonly in habitats supplied with insulating snow cover, winter-killed 100% in the more exposed field environment.
·The very slow growth of native Alaska legumes evaluated preclude their practical use as forages, but their superior north-latitude adaptation and nitrogen-fixation capabilities favor their use for revegetation purposes in subarctic areas.
·Of the introduced grasses from Canada and northern states, species with primarily subterranean overwintering tissues (bromegrass, Kentucky bluegrass, red fescue) generally survived well, but species with primarily above-ground overwintering tissues (timothy, slender wheatgrass) did not. None of the introduced legumes (alfalfa, red clover, sweetclover) from Canada or northern states exhibited good winter survival.