{{Short description|Fruit of forest trees like acorns and other nuts}} thumb|Knocking down acorns to feed pigs. 1300s England.'''Mast''' is the fruit of forest trees and shrubs, such as acorns and other nuts.<ref name="Swartz">{{cite book |last1=Swartz |first1=Delbert |title=Collegiate dictionary of botany |date=1971 |publisher=The Ronald Press |page=284 |oclc=473041137 }}</ref> 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.<ref name="OED mast">{{OED|mast}}</ref><ref>{{cite web |title=mast |url=https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED27027 |website=Middle English Compendium |publisher=University of Michigan }}</ref> 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.<ref name="VisserJongejans2011">{{cite journal |last1=Visser |first1=Marco D. |last2=Jongejans |first2=Eelke |last3=van Breugel |first3=Michiel |last4=Zuidema |first4=Pieter A. |last5=Chen |first5=Yu-Yun |last6=Rahman Kassim |first6=Abdul |last7=de Kroon |first7=Hans |title=Strict mast fruiting for a tropical dipterocarp tree: a demographic cost-benefit analysis of delayed reproduction and seed predation: Demographic cost-benefit analysis of masting |journal=Journal of Ecology |date=July 2011 |volume=99 |issue=4 |pages=1033–1044 |doi=10.1111/j.1365-2745.2011.01825.x |s2cid=83983871 |hdl=2066/92377 |hdl-access=free }}</ref><ref name="Kelly & Sork 2002">{{cite journal |last1=Kelly |first1=Dave |last2=Sork |first2=Victoria L. |title=Mast Seeding in Perennial Plants: Why, How, Where? |journal=Annual Review of Ecology and Systematics |date=November 2002 |volume=33 |issue=1 |pages=427–447 |doi=10.1146/annurev.ecolsys.33.020602.095433 |bibcode=2002AnRES..33..427K |s2cid=31807259 }}</ref>
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.<ref name="Koenig & Knops 2014">{{cite journal |last1=Koenig |first1=Walter D. |last2=Knops |first2=Johannes M. H. |title=Environmental correlates of acorn production by four species of Minnesota oaks |journal=Population Ecology |date=January 2014 |volume=56 |issue=1 |pages=63–71 |doi=10.1007/s10144-013-0408-z |bibcode=2014PopEc..56...63K |s2cid=3355276 }}</ref> 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.<ref name="Pearse Koenig Kelly 2016">{{cite journal |last1=Pearse |first1=Ian S. |last2=Koenig |first2=Walter D. |last3=Kelly |first3=Dave |title=Mechanisms of mast seeding: resources, weather, cues, and selection |journal=New Phytologist |date=November 2016 |volume=212 |issue=3 |pages=546–562 |doi=10.1111/nph.14114 |pmid=27477130 |bibcode=2016NewPh.212..546P |doi-access=free }}</ref> In turn, these pulses of masting contribute to many ecosystem-level functions and dynamics.<ref name="Kelly & Sork 2002" /> == Types of mast == 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.<ref name="Kelly & Sork 2002" /> It has been traditional to turn pigs loose into forests to fatten on this form of mast in a practice known as pannage.<ref name="Norton & Kelly 1988" /> Other tree and shrub species produce a soft mast, such as raspberries, blueberries, and greenbriar.<ref>{{cite journal |last1=Beeman |first1=Larry E. |last2=Pelton |first2=Michael R. |title=Seasonal Foods and Feeding Ecology of Black Bears in the Smoky Mountains |journal=Bears: Their Biology and Management |date=1980 |volume=4 |pages=141–147 |doi=10.2307/3872858 |jstor=3872858 }}</ref>
== Mast seeding == alt=|thumb|An abundance of acorns on the ground often occurs during mast seeding years Mast seeding (or mast reproduction) is defined as the highly variable annual production of fruit by a population of trees or shrubs.<ref name="Norton & Kelly 1988" /> These intermittent pulses of food production drive ecosystem-level functions and forest dynamics.<ref name="Ostfeld Jones Wolff 1996" /> The difference between a mast seeding year and a non-mast seeding year can be thousands of acorns, hickory nuts, beech nuts, etc.<ref name="OED mast" /> Mast seeding predominantly occurs in wind-pollinated tree species, but has also been observed in grasses and Dipterocarps.<ref name="Norton & Kelly 1988" /><ref name="Kelly & Sork 2002" />
Hypotheses for the evolution of mast seeding can broadly be assigned to three categories: economies of scale, resource matching, and proximate cues (i.e. weather).<ref>{{cite journal |last1=Burns |first1=K. C. |title=Masting in a temperate tree: Evidence for environmental prediction? |journal=Austral Ecology |date=2012 |volume=37 |issue=2 |pages=175–182 |doi=10.1111/j.1442-9993.2011.02260.x |bibcode=2012AusEc..37..175B }}</ref>
One study proposes disease as a new hypothesis for the evolution of seed masting.<ref>{{Cite journal |last1=Davies |first1=T. Jonathan |last2=MacPherson |first2=Ailene |date=2024-02-26 |title=Seed masting as a mechanism for escape from pathogens |journal=Current Biology |volume=34 |issue=4 |pages=R120–R125 |doi=10.1016/j.cub.2023.12.027 |pmid=38412815 |issn=0960-9822|doi-access=free }}</ref>
=== Economies of scale === 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.<ref>{{cite journal |last1=Koenig |first1=Walter D. |last2=Knops |first2=Johannes M. H. |title=The Mystery of Masting in Trees: Some trees reproduce synchronously over large areas, with widespread ecological effects, but how and why? |journal=American Scientist |date=2005 |volume=93 |issue=4 |pages=340–347 |doi=10.1511/2005.4.340 |id={{Gale|A143252608}} {{ProQuest|215262264}} |jstor=27858609 |citeseerx=10.1.1.610.6239 }}</ref> 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.<ref name="Kelly & Sork 2002"/>
The pollination efficiency hypothesis suggests that mast seeding may optimize successful pollination and thus fertilization if all individuals within a population are reproductively synchronized.<ref>{{cite journal |last1=Kelly |first1=Dave |last2=Hart |first2=Deirdre E. |last3=Allen |first3=Robert B. |title=Evaluating the Wind Pollination Benefits of Mast Seeding |journal=Ecology |date=2001 |volume=82 |issue=1 |pages=117–126 |doi=10.1890/0012-9658(2001)082[0117:ETWPBO]2.0.CO;2 |jstor=2680090 }}</ref> 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,<ref name="Kelly & Sork 2002"/><ref name="Pearse Koenig Kelly 2016"/> which ultimately leads to higher fitness for the masting population.<ref name="Kelly & Sork 2002"/>
=== Resources and weather === The resource matching hypothesis states that reproduction varies with availability of the resources necessary to reproduce, which is often an energetically and nutritionally expensive action.<ref name="Norton & Kelly 1988">{{cite journal |last1=Norton |first1=D. A. |last2=Kelly |first2=D. |title=Mast Seeding Over 33 Years by ''Dacrydium cupressinum'' Lamb. (rimu) (Podocarpaceae) in New Zealand: The Importance of Economies of Scale |journal=Functional Ecology |date=1988 |volume=2 |issue=3 |pages=399–408 |id={{INIST|7368270}} |doi=10.2307/2389413 |jstor=2389413 |bibcode=1988FuEco...2..399N }}</ref> The main limiting resources include water, carbon in the form of nonstructural carbohydrates, and nutrients such as nitrogen and phosphorus.<ref name="Pearse Koenig Kelly 2016"/> These resources have been shown to be depleted after mast seeding across multiple species.<ref name="Pearse Koenig Kelly 2016"/>
Weather is categorized as a proximate driver of mast seeding, meaning that in combination with resources and economies of scale, various weather parameters can have an effect on the probability of mast seeding occurring in any given season.<ref name="Pearse Koenig Kelly 2016"/> The effects of local weather on mast seeding are highly variable depending on species and geographic location. For some species of oak, mast seeding was shown to be influenced by regional weather-related cues on phenology;<ref name="Sork Bramble Sexton 1993">{{cite journal |last1=Sork |first1=Victoria L. |last2=Bramble |first2=Judy |last3=Sexton |first3=Owen |title=Ecology of Mast-Fruiting in Three Species of North American Deciduous Oaks |journal=Ecology |date=1993 |volume=74 |issue=2 |pages=528–541 |id={{INIST|4677408}} {{ProQuest|219021659}} |doi=10.2307/1939313 |jstor=1939313 |bibcode=1993Ecol...74..528S }}</ref> such cues included spring temperature, summer drought, and spring frost.<ref name="Sork Bramble Sexton 1993"/> These weather variables are associated with critical times for fruit maturation and fertilization.
== Consequences == thumb|Image of wood cross section, showing tree-ring chronologies, which are affected by the interaction of mast seeding, climate, and tree growthMast seeding provides an abundant food source not only for wildlife but also for domestic animals and animals prone to population explosions such as mice, rats, and stoats, whose populations can increase significantly during a mast year, having been reduced by a lack of food in previous non-mast years.<ref name="OED mast" /> In turn, this makes it more likely that birds subsequently will be targeted by the pests,<ref>{{cite news |title=Trappers face pest population explosion |url=https://www.stuff.co.nz/nelson-mail/news/797905/Trappers-face-pest-population-explosion |work=Stuff |date=31 January 2009 }}</ref> or that rats will invade nearby fields in what is called a "rat flood".<ref>{{cite journal |last=Normile |first=D. |title=Holding back a torrent of rats |journal=Science |volume=327 |issue=5967 |pages=806–7 |date=February 2010 |pmid=20150483 |doi=10.1126/science.327.5967.806|bibcode=2010Sci...327..806N |doi-access=free }}</ref>
Mast seeding has been shown to have both positive and negative effects on ecosystems. An example of this is the white-footed mouse.<ref name="Ostfeld Jones Wolff 1996">{{cite journal |last1=Ostfeld |first1=Richard S. |last2=Jones |first2=Clive G. |last3=Wolff |first3=Jerry O. |title=Of Mice and Mast |journal=BioScience |date=1996 |volume=46 |issue=5 |pages=323–330 |id={{Gale|A18417481}} |doi=10.2307/1312946 |jstor=1312946 |s2cid=89496723 |doi-access=free }}</ref> 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.<ref name="Ostfeld Jones Wolff 1996"/>
The interaction between disturbance by fire and mast seeding is key to white spruce regeneration and subsequent stand dynamics in the boreal mixed-wood forest. Peters et al. (2005)<ref name="pete">{{cite journal|last1=Peters|first1=Vernon S.|last2=Macdonald|first2=S. Ellen|last3=Dale|first3=Mark R. T. |year=2005 |title=The interaction between masting and fire is key to white spruce regeneration |journal=Ecology |volume=86 |issue=7 |pages=1744–1750 |doi=10.1890/03-0656 |jstor=3450618|bibcode=2005Ecol...86.1744P |s2cid=84033364 }}</ref> 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)<ref name="pete" /> adduced three lines of evidence to support their claim that the importance of the fire × mast-year interaction hinges on the rapid deterioration of the seedbed, even within one year after fire. Rapid seedbed deterioration is likely to augment the mast-year effect for white spruce as compared with species that are less dependent on short-lived, disturbance-created regeneration microsites. Seed limitation, as well as seedbed deterioration, influences age structure in white spruce. Mast-year effects on the density of white spruce are long-lasting; 40 years after fire, mast-year fires still had 2.5 times more spruce regeneration than non-mast-year fires.<ref name="pete" />
The interaction of mast seeding, climate, and tree growth creates notable effects in tree ring chronologies, and in many tree species reduced growth has been observed in mast years.<ref>{{cite journal |last1=Selås |first1=Vidar |last2=Piovesan |first2=Gianluca |last3=Adams |first3=Jonathan M |last4=Bernabei |first4=Mauro |title=Climatic factors controlling reproduction and growth of Norway spruce in southern Norway |journal=Canadian Journal of Forest Research |date=1 February 2002 |volume=32 |issue=2 |pages=217–225 |id={{INIST|13569450}} |doi=10.1139/x01-192 |bibcode=2002CaJFR..32..217S |citeseerx=10.1.1.570.9347 }}</ref><ref>{{cite journal |last1=Hacket-Pain |first1=Andrew J. |last2=Ascoli |first2=Davide |last3=Vacchiano |first3=Giorgio |last4=Biondi |first4=Franco |last5=Cavin |first5=Liam |last6=Conedera |first6=Marco |last7=Drobyshev |first7=Igor |last8=Liñán |first8=Isabel Dorado |last9=Friend |first9=Andrew D. |last10=Grabner |first10=Michael |last11=Hartl |first11=Claudia |last12=Kreyling |first12=Juergen |last13=Lebourgeois |first13=François |last14=Levanič |first14=Tom |last15=Menzel |first15=Annette |last16=Maaten |first16=Ernst van der |last17=Maaten-Theunissen |first17=Marieke van der |last18=Muffler |first18=Lena |last19=Motta |first19=Renzo |last20=Roibu |first20=Catalin-Constantin |last21=Popa |first21=Ionel |last22=Scharnweber |first22=Tobias |last23=Weigel |first23=Robert |last24=Wilmking |first24=Martin |last25=Zang |first25=Christian S. |title=Climatically controlled reproduction drives interannual growth variability in a temperate tree species |journal=Ecology Letters |date=2018 |volume=21 |issue=12 |pages=1833–1844 |doi=10.1111/ele.13158 |pmid=30230201 |pmc=6446945 |bibcode=2018EcolL..21.1833H }}</ref>
=== Mast seeding under climate change === Many mast seeding species are considered foundation species.<ref>{{cite journal |last1=Mcshea |first1=William J. |last2=Healy |first2=William M. |last3=Devers |first3=Patrick |last4=Fearer |first4=Todd |last5=Koch |first5=Frank H. |last6=Stauffer |first6=Dean |last7=Waldon |first7=Jeff |title=Forestry Matters: Decline of Oaks Will Impact Wildlife in Hardwood Forests |journal=Journal of Wildlife Management |date=July 2007 |volume=71 |issue=5 |pages=1717–1728 |doi=10.2193/2006-169 |bibcode=2007JWMan..71.1717M |s2cid=38714201 }}</ref> 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.<ref>{{cite journal |last1=Graumlich |first1=Lisa J. |title=Response of tree growth to climatic variation in the mixed conifer and deciduous forests of the upper Great Lakes region |journal=Canadian Journal of Forest Research |date=1 February 1993 |volume=23 |issue=2 |pages=133–143 |doi=10.1139/x93-020 |bibcode=1993CaJFR..23..133G }}</ref><ref name="Koenig & Knops 2014"/> Mast seeding has become more variable globally during the last century,<ref>{{cite journal |last1=Pearse |first1=Ian S. |last2=LaMontagne |first2=Jalene M. |last3=Koenig |first3=Walter D. |title=Inter-annual variation in seed production has increased over time (1900–2014) |journal=Proceedings of the Royal Society B: Biological Sciences |date=6 December 2017 |volume=284 |issue=1868 |article-number=20171666 |doi=10.1098/rspb.2017.1666 |pmid=29212721 |pmc=5740272 }}</ref> 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,<ref>{{cite journal |last1=Fernández-Martínez |first1=Marcos |last2=Vicca |first2=Sara |last3=Janssens |first3=Ivan A. |last4=Espelta |first4=Josep Maria |last5=Peñuelas |first5=Josep |title=The North Atlantic Oscillation synchronises fruit production in western European forests |journal=Ecography |date=July 2017 |volume=40 |issue=7 |pages=864–874 |doi=10.1111/ecog.02296 |bibcode=2017Ecogr..40..864F |s2cid=89225514 |hdl=10067/1448460151162165141 |url=https://ddd.uab.cat/record/163016 |hdl-access=free }}</ref><ref>{{cite journal |last1=Ascoli |first1=Davide |last2=Vacchiano |first2=Giorgio |last3=Turco |first3=Marco |last4=Conedera |first4=Marco |last5=Drobyshev |first5=Igor |last6=Maringer |first6=Janet |last7=Motta |first7=Renzo |last8=Hacket-Pain |first8=Andrew |title=Inter-annual and decadal changes in teleconnections drive continental-scale synchronization of tree reproduction |journal=Nature Communications |date=December 2017 |volume=8 |issue=1 |page=2205 |doi=10.1038/s41467-017-02348-9 |pmid=29263383 |pmc=5738406 |bibcode=2017NatCo...8.2205A }}</ref> and in tropical south Asia, mast events appear to be linked to the El Niño–Southern Oscillation.<ref>{{cite journal |last1=Williamson |first1=G. Bruce |last2=Ickes |first2=Kalan |title=Mast fruiting and ENSO cycles - does the cue betray a cause? |journal=Oikos |date=June 2002 |volume=97 |issue=3 |pages=459–461 |doi=10.1034/j.1600-0706.2002.970317.x |bibcode=2002Oikos..97..459W |s2cid=54720692 }}</ref>
==See also== *Phenology *Seed tree
==References== {{reflist|30em}}
==External links== {{wiktionary|mast}} *[http://www.mast-producing-trees.org/ Mast Tree Network] *[https://www.youtube.com/watch?v=w5aH8oH_9fo Ash Tree Mast Year]
*Mast seeding Category:Fruit morphology Category:Acorns