Mast (botany)

Mast is the fruit of forest trees and shrubs, such as acorns and other nuts. The term derives from the Old English mæst, meaning the nuts of forest trees that have accumulated on the ground, especially those used historically for fattening domestic pigs, and as food resources for wildlife. In the aseasonal tropics of Southeast Asia, entire forests, including hundreds of species of trees and shrubs, are known to mast at irregular periods of 2–12 years. More generally, mast is considered the edible vegetative or reproductive parts produced by woody species of plants, i.e. trees and shrubs, that wildlife and some domestic animals consume as a food source. Mast is generated in large quantities during long-interval but regularly recurring phenological events known as mast seeding or masting. Such events are population-level phenomena hypothesized to be driven by a wide variety of factors, depending on the plant species involved, including availability of nutrients, economies of scale, weather patterns, and as a form of predator satiation. In turn, these pulses of masting contribute to many ecosystem-level functions and dynamics. Mast can be divided into two basic types: hard mast and soft mast. Tree species such as oak, hickory, and beech produce a hard mast—acorns, hickory nuts, and beechnuts. It has been traditional to turn pigs loose into forests to fatten on this form of mast in a practice known as pannage. Other tree and shrub species produce a soft mast, such as raspberries, blueberries, and greenbriar. Mast seeding (or mast reproduction) is defined as the highly variable annual production of fruit by a population of trees or shrubs. These intermittent pulses of food production drive ecosystem-level functions and forest dynamics. The difference between a mast seeding year and a non-mast seeding year can be thousands of acorns, hickory nuts, beech nuts, etc. Mast seeding predominantly occurs in wind-pollinated tree species, but has also been observed in grasses and Dipterocarps.