Mast (botany)

Fruit of forest trees like acorns and other nuts
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 seeding (or mast reproduction) is defined as the highly variable annual production of fruit by a population of trees or shrubs.

The predator satiation hypothesis states that predator populations may be effectively controlled from year to year by inconsistent pulses of food made available by their prey. For predators of plant communities whose prey are the fruits and seeds produced by the plants, it has been proposed that periodic mast seeding events may be an example of this strategy. Producing excessive quantities of fruits and seeds in mast seeding years may over satiate seed predators to the point that a small proportion of seeds can escape consumption, while a lack of seed production keeps predator populations low in the intervening years. In plant communities with a local abundance of frugivores, large seed releases can effectively exceed seed predation and improve the chance of successful establishment of seeds in future seasons. This hypothesis is especially relevant for wind pollinated species, which many mast seeding species are. Both hypotheses are based on the assumption that large and variable reproductive effort is more efficient than small, consistent reproductive effort, The main limiting resources include water, carbon in the form of nonstructural carbohydrates, and nutrients such as nitrogen and phosphorus. such cues included spring temperature, summer drought, and spring frost. or that rats will invade nearby fields in what is called a "rat flood". Mast seeding has been shown to have both positive and negative effects on ecosystems. An example of this is the white footed mouse. When a mast seeding event occurs, the population of white footed mice also increases, which has been shown in turn to increase instances of Lyme disease, since these mice are hosts for ticks, the disease's primary vector. A positive effect of increased white footed mouse population is that they prey on gypsy moths, which are a major forest pest in the eastern United States. found significantly higher densities of white spruce in stands originating from fires that coincided with mast years than from fires coinciding with years of low cone crops. While noting that previous studies had assessed a three to five year window of opportunity for obtaining white spruce regeneration after fire before seedbed deterioration closed it, Peters et al. (2005)

Many mast seeding species are considered foundation species. Predicting how the intensity and frequency of mast seeding may be altered by climate change will help researchers to determine shifts in the availability of food resources to wildlife and forest dynamics. although the drivers of these long term changes in mast seeding have not been fully identified. For example, in Europe, mast seeding intensity appears to be linked to the mode of the North Atlantic Oscillation, and in tropical south Asia, mast events appear to be linked to the El Niño–Southern Oscillation.