ABSTRACT: Presence of marcescent leaves during winter is a common phenomenon in northern-temperate deciduous forests across the Holarctic, but the ecological significance of marcescence on woody vegetation has received little attention. Especially, implications for browsing by cervids during winter have not been determined. Therefore, I conducted a feeding trial using free-roaming red deer (Cervus elaphus), fallow deer (Dama dama), and sika deer (Cervus nippon) to evaluate effects of marcescent leaves on herbivory of European beech (Fagus sylvatica), hornbeam (Carpinus betulus), and common oak (Quercus robur) during winter. The feeding trial was conducted in Jaegersborg Dyrehave, Denmark, during February 1992. Forty small-diameter (< 6 mm) branches of each tree species with ≤ 2 years of growth and marcescent leaves present were divided into 2 groups. One group had their leaves removed (treatment) and the other group had the leaves retained (control). Branches were labeled, weighed, and randomly placed in a grid (0.5 x 0.5 m apart) in the field. After 7 days, branches were counted and weighed to determine amount of browse removed. In addition, 12 branches of each species were collected for biomass and chemical analyses. Stems and leaves were analyzed separately for crude protein, neutral-detergent fiber, acid-detergent fiber, lignin, and cellulose. Both beech and hornbeam were browsed significantly more by weight and by number of branches when the leaves were removed. Oak branches were browsed the same regardless of leaf presence. Biomass of marcescent leaves of beech and hornbeam were a significantly greater proportion of the overall branch biomass compared with oak. Chemical analyses showed that stems of hornbeam and beech, when compared with their marcescent leaves, had somewhat higher food quality when fiber and crude protein were compared, but marcescent leaves had a higher lignin content. Leaves compared with stems of common oak had a higher protein and lower lignin content compared with other species. These results indicate that marcescent leaves greatly reduced the nutritive value of winter browse, which was reflected in the lower browse preference for their leaves. Therefore, marcescent leaves may be viewed as an anti-herbivore mechanism.

ALCES VOL. 37 (2): 475-482 (2001)

Keywords: beech, Cervidae, deer, food quality, food selection, foraging ecology, hornbeam, marcescent leaves, oak, plant defenses, plant-herbivore interactions

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During winter, presence of marcescent leaves (senescent leaves still attached to the branches), on beech, hornbeam, and common oak is a striking phenomenon of hardwood forests in northern Europe. Marcescence is a juvenile trait in young trees or lower branches of larger trees (Schaffalitzky de Muckadell 1962), where leaves are retained up to a height of about 3 m during the entire winter, and not shed until spring. The ecological significance of marcescent leaves on woody vegetation has received little attention in the past century. Mostly, interest has concentrated on physiological aspects of marcescence in plants (Berkeley 1931, Hoshow and Guard 1949, Addicott 1982) or its evolutionary implications for the development of deciduousness (Wanntorp 1983). Implications for herbivory, however, have not been determined. A few explanations have been presented to explain why dead...