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4.4 Hard and Soft Mast

4.4.1 Southern Species that Produce Mast

Mast refers to specific kinds of fruits of woody species. Hard mast possesses a hard exterior, as in acorns, while soft mast has fleshy fruits as in berries. Both forms of mast are important in the diets of southern wildlife. Many southern woody plants produce mast (Table 11). Mast yields are unpredictable from one year to the next, and vary according to species, location, and weather.


Pomes are fruits that have several tough, papery-walled cavities that house seed; the cavities are surrounded by thick flesh. These fruits may be large like apples or small like serviceberries. Fresh pomes have a high moisture and carbohydrate content, but are low in crude protein (Halls 1977).


A drupe is a pulpy fruit with an inner ovary wall that encloses a seed. Drupes are extensively eaten by wildlife. The fruits tend to be low in crude protein and high in carbohydrates; nutrient content varies considerably among species. Drupe producers in the South include wild cherries, plums, hackberry, and red mulberry (Halls 1977).


Berries are fruits with fleshy ovaries that envelop one or more seeds. Most species are eaten by wildlife. Fruits are usually high in carbohydrates and low in crude protein. Species that produce berries include persimmon, blueberry, and grape.


Hard mast includes nuts and one-seeded fruits (or kernels). Most have concentrations of crude fat, and some also are relatively high in crude protein (Halls 1977). Characteristic species include hornbeam, hickory, beech, walnut, black gum, and several species of oaks.


4.4.2 Selected Species that Utilize Mast in Their Diet


Mast is an essential component in the diets of many vertebrates in the South (Jensen 1982, Combs and Frederickson 1996, Doherty and others 1996, Wolff 1996). Table 12 lists several mast-consuming mammals, including mice, voles, woodrats, rabbits, raccoons, and foxes. Several birds also consume mast (Table 13) including game birds (doves, quail, pheasant, grouse, turkey), waterfowl (mallards, wood ducks), woodpeckers, and songbirds (finches, thrushes, jays, and towhees). The relationship between mast and the food habits of several game species, such as deer, bear, and squirrels has been documented extensively (Kirkpatrick 1989, Kurzejeski 1989, Pelton 1989, Wentworth and others 1989, Fridell and Litvaitis 1991).


White-tailed deer. Hard mast is often an important component of the fall and winter diet of white-tailed deer. Nutrition, reproduction, weight, and antler characteristics of individual animals are influenced by acorn availability (Wentworth and others 1989). In poor mast years, reproduction rates may be low and conception may be delayed. Postnatal survival also can decline following years of minimal acorn production. Fawn weight also can be directly related to the size of the acorn crop.


Black bear. The abundance and distribution of oak mast,(particularly white oak), also can influence black bear natality, mortality, and dispersal. Shifts in home range sometimes occur in response to fluctuations in hard mast availability. The birth and survival of young bears can be directly associated with oak mast crops (Pelton 1989). Poor mast years often result in increased bear movement, which can result in increased mortality due to vehicular accidents and human-bear interactions. The loss of the American chestnut likely had a significant influence on the population dynamics of black bears in the Southern Appalachians (Pelton 1989).


Squirrels. The availability of hard mast also can influence squirrel populations. Poor mast crops can result in population declines, while abundant mast crops may result in substantial population increases (Kurzejeski 1989). Mast comprises the majority of the fall, winter, and spring diets of red, gray, and fox squirrels. Acorns, walnuts, and hickory nuts are major food sources for these squirrels as well as for the eastern chipmunk.


Gamebirds. Hard mast provides a high-energy resource for ruffed grouse, wild turkey, bobwhite quail, and several waterfowl. These species consume acorns in proportion to their availability throughout the year; foraging for mast requires little energy expenditure (Kirkpatrick 1989). Red oak acorns have an elevated phenolic content and are less palatable than white oak species.


4.4.3 Factors Affecting Mast Supply Availability


In recent years, there have been concerns about the decline of mast-producing species (particularly oaks) in the South. Chapter HLTH-1 presents trend information from the FIA on oak and other overstory mast producing trees. In addition, an examination of oak decline in the South is presented in Chapter HLTH-3. The factors that may have contributed to the decline, and the subsequent reduction in hard mast production, are briefly mentioned here.


Many variables, including disease, insect infestation, advanced stand age, drought, and disturbance influence oak forests. Mature oaks are quite susceptible to disease and drought conditions. As these forests age, tree vigor is reduced. They become susceptible to windthrow and ice storms. Longevity varies by species and site characteristics. Lack of natural disturbance is another factor. Fire suppression has resulted in an increase in other species in former oak-dominated areas.


Chestnut blight had a dramatic influence on the American chestnut (Chapter HLTH-3). Chestnut oaks, which replaced chestnuts in many places, are an important source of hard mast for wildlife populations. Gypsy moth infestations on the poor sites occupied by chestnut oaks often inhibit oak regeneration. Infested trees have a reduced capability for stump sprouting and their acorns lack the energy reserves to remain viable. Repeated defoliation kills many oaks. When this happens, yellow-poplar often captures the site.


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created: 21-NOV-2001