browsing (herbivory)

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The plant material eaten is known as browseOxford English Dictionary: Browse. and is in nature taken directly from the plant, though owners of livestock such as goats and deer may cut twigs or branches for feeding to their stock.St. John's College, Oxford: [http://info.sjc.ox.ac.uk/forests/glossary.htm Forest Glossary]: Browse, Browsewood. In temperate regions, owners take browse before leaf fall, then dry and store it as a winter feed supplement. In time of drought, herdsmen may cut branches from beyond the reach of their stock, as forage at ground level. In the tropical regions, where population pressure leads owners to resort to this more often, there is a danger of permanent depletion of the supply. Animals in captivity may be fed browse as a replacement for their wild food sources; in the case of pandas, the browse may consist of bunches of banana leaves, bamboo shoots, slender pine, spruce, fir and willow branches, straw and native grasses.[http://www.animalsasia.org/emailupdate/html/emailUpdate_HK_02052010_valentine.html?tkn=m1020994&eid=689&sou=AL10MBRVANEM&b=html Buy a bunch of browse for the bears], Animals Asia {{webarchive|url=https://web.archive.org/web/20110718162448/http://www.animalsasia.org/emailupdate/html/emailUpdate_HK_02052010_valentine.html?tkn=m1020994&eid=689&sou=AL10MBRVANEM&b=html |date=2011-07-18 }}

If the population of browsers grows too high, all of the browse that they can reach may be devoured. The resulting level below which few or no leaves are found is known as the browse line.Texas Parks & Wildlife, "[http://tpwd.texas.gov/landwater/land/habitats/hillcountry/vegetation/browse_line.phtml Browsing Pressure]"; accessed 2016.02.16. If over-browsing continues for too long, the ability of the ecosystem's trees to reproduce may be impaired, as young plants cannot survive long enough to grow too tall for browsers to reach.University of Pennsylvania, "[http://www.upenn.edu/paflora/id13.htm Special Issue: Deer eating the future of Pennsylvania's Forests!] {{Webarchive|url=https://web.archive.org/web/20161005085842/http://www.upenn.edu/paflora/id13.htm |date=2016-10-05 }}"; accessed 2016.02.16.

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Overbrowsing occurs when overpopulated or densely-concentrated herbivores exert extreme pressure on plants, reducing the carrying capacity and altering the ecological functions of their habitat.{{Cite web|url=https://scholar.google.ca/scholar?q=Relationships+between+Introduced+Black-tailed+Deer+and+the+Plant+Life+of+the+Queen+Charlotte+Islands,+British+Columbia.&btnG=&hl=en&as_sdt=0,5|title=Relationships between Introduced Black-tailed Deer and the Plant Life of the Queen Charlotte Islands, British Columbia. - Google Scholar|website=scholar.google.ca|access-date=2017-03-08}}{{Cite journal|last1=Côté|first1=Steeve D.|last2=Rooney|first2=Thomas P.|last3=Tremblay|first3=Jean-Pierre|last4=Dussault|first4=Christian|last5=Waller|first5=Donald M.|date=2004-01-01|title=Ecological Impacts of Deer Overabundance|jstor=30034112|journal=Annual Review of Ecology, Evolution, and Systematics|volume=35|pages=113–147|doi=10.1146/annurev.ecolsys.35.021103.105725}}Pojar, J., Lewis, T., Roemer, H., and Wilford, D.J. 1980. Relationships between Introduced Black-tailed Deer and the Plant Life of the Queen Charlotte Islands, British Columbia. Unpublished Manuscript, Ministry of Forests, Smithers, B.C. 63 p. Examples of overbrowsing herbivores around the world include koalas in Southern Australia, introduced mammals in New Zealand, and cervids in forests of North America and Europe.{{Cite journal|last1=Wardle|first1=David A.|last2=Barker|first2=Gary M.|last3=Yeates|first3=Gregor W.|last4=Bonner|first4=Karen I.|last5=Ghani|first5=Anwar|date=2001-01-01|title=Introduced Browsing Mammals in New Zealand Natural Forests: Aboveground and Belowground Consequences|jstor=3100037|journal=Ecological Monographs|volume=71|issue=4|pages=587–614|doi=10.2307/3100037}}{{Cite journal|last1=Whisson|first1=Desley A.|last2=Dixon|first2=Victoria|last3=Taylor|first3=Megan L.|last4=Melzer|first4=Alistair|date=2016-01-06|title=Failure to Respond to Food Resource Decline Has Catastrophic Consequences for Koalas in a High-Density Population in Southern Australia|journal=PLOS ONE|volume=11|issue=1|pages=e0144348|doi=10.1371/journal.pone.0144348|issn=1932-6203|pmc=4703219|pmid=26735846|bibcode=2016PLoSO..1144348W|doi-access=free}}

Moose exclosures (fenced-off areas) are used to determine the ecological impacts of cervids, allowing scientists to compare flora, fauna, and soil in areas inside and outside of exclosures.{{Cite journal|url=https://www.treesearch.fs.fed.us/pubs/3874|title=Deer browsing in northern hardwoods after clearcutting. Effect on height, density, and stocking of regeneration of commercial species|journal=Res. Pap. Ne-57. Upper Darby, Pa: U. S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 15 P|volume=057|last=Jordan|first=James S.|date=1967-01-01}} Changes in plant communities in response to herbivory reflect the differential palatability of plants to the overabundant herbivore, as well as the variable ability of plants to tolerate high levels of browsing. The heights of plants preferred by herbivores can give indications of the local and regional herbivore density.{{Cite journal |last1=Koh |first1=Saewan |last2=Bazely |first2=Dawn R. |last3=Tanentzap |first3=Andrew J. |last4=Voigt |first4=Dennis R. |last5=Da Silva |first5=Eric |date=March 2010 |title=Trillium grandiflorum height is an indicator of white-tailed deer density at local and regional scales |url=https://doi.org/10.1016/j.foreco.2010.01.021 |journal=Forest Ecology and Management |volume=259 |issue=8 |pages=1472–1479 |doi=10.1016/j.foreco.2010.01.021 |bibcode=2010ForEM.259.1472K |issn=0378-1127}} Compositional and structural changes in forest vegetation can have cascading effects on the entire ecosystem, including impacts on soil quality and stability, micro- and macro- invertebrates, small mammals, songbirds, and perhaps even large predators.{{Cite journal|last=Flowerdew|first=J.R.|date=2001-01-01|title=Impacts of woodland deer on small mammal ecology|journal=Forestry|language=en|volume=74|issue=3|pages=277–287|doi=10.1093/forestry/74.3.277|issn=0015-752X|doi-access=free}}

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There are several causes of overabundant herbivores and subsequent overbrowsing. Herbivores are introduced to landscapes in which native plants have not evolved to withstand browsing, and predators have not adapted to hunt the invading species. In other cases, populations of herbivores exceed historic levels due to reduced hunting or predation pressure. For example, carnivores declined in North America throughout the 19th century and hunting regulations became stricter, contributing to increased cervid populations across North America.{{Cite journal|last1=Chollet|first1=Simon|last2=Martin|first2=Jean-Louis|date=2013-04-01|title=Declining woodland birds in North America: should we blame Bambi?|journal=Diversity and Distributions|language=en|volume=19|issue=4|pages=481–483|doi=10.1111/ddi.12003|s2cid=86531297 |issn=1472-4642|doi-access=free|bibcode=2013DivDi..19..481C }} Also, landscape changes due to human development, such as in agriculture and forestry, can produce fragmented forest patches between which deer travel, browsing in early successional habitat at the periphery.{{Cite journal|last1=Alverson|first1=William S.|last2=Waller|first2=Donald M.|last3=Solheim|first3=Stephen L.|date=1988-01-01|title=Forests Too Deer: Edge Effects in Northern Wisconsin|jstor=2386294|journal=Conservation Biology|volume=2|issue=4|pages=348–358|doi=10.1111/j.1523-1739.1988.tb00199.x|bibcode=1988ConBi...2..348A }} Agricultural fields and young silvicultural stands provide deer with high quality food leading to overabundance and increased browsing pressure on forest understory plants.

File:Youngbullantlers.JPG browsing on alders]]Overbrowsing impacts plants at individual, population, and community levels. The negative effects of browsing are greater among intolerant species, such as members of the genus Trillium, which have all photosynthetic tissues and reproductive organs at the apex of a singular stem.{{Cite journal|last1=Augustine|first1=David J.|last2=Decalesta|first2=David|date=2003-01-01|title=Defining deer overabundance and threats to forest communities: From individual plants to landscape structure|journal=Écoscience|volume=10|issue=4|pages=472–486|doi=10.1080/11956860.2003.11682795|bibcode=2003Ecosc..10..472A |s2cid=88837457|issn=1195-6860}} This means that a deer may eat all the reproductive and photosynthetic tissues at once, reducing the plant's height, photosynthetic capabilities, and reproductive output. This is one example of how overbrowsing can lead to the loss of reproductive individuals in a population, and a lack of recruitment of young plants. Plants also differ in their palatability to herbivores. At high densities of herbivores, plants that are highly selected as browse may be missing small and large individuals from the population. At the community level, intense browsing by deer in forests leads to reductions in the abundance of palatable understory herbaceous shrubs, and increases in graminoid and bryophyte abundance which are released from competition for light.{{Cite journal|last1=Chollet|first1=Simon|last2=Baltzinger|first2=Christophe|last3=Saout|first3=Soizic Le|last4=Martin|first4=Jean-Louis|date=2013-12-01|title=A better world for bryophytes? A rare and overlooked case of positive community-wide effects of browsing by overabundant deer|journal=Écoscience|volume=20|issue=4|pages=352–360|doi=10.2980/20-4-3627|bibcode=2013Ecosc..20..352C |s2cid=84448035|issn=1195-6860}}

The intensity of browsing pressure often varies depending on the palatability of plant species to herbivores. Some plant species may be heavily browsed due to their high palatability, while others may be avoided or less affected.{{Citation |last1=Burņeviča |first1=Natālija |title=Chapter 12 - Vertebrate herbivore browsing and impact on forest production |date=2023-01-01 |volume=3 |pages=251–261 |editor-last=Asiegbu |editor-first=Fred O. |url=https://www.sciencedirect.com/science/article/pii/B9780443186943000134 |access-date=2024-04-13 |series=Forest Microbiology |publisher=Academic Press |isbn=978-0-443-18694-3 |last2=Ozoliņš |first2=Jānis |last3=Gaitnieks |first3=Tālis |editor2-last=Kovalchuk |editor2-first=Andriy}}{{Cite journal |last1=Borowski |first1=Zbigniew |last2=Gil |first2=Wojciech |last3=Bartoń |first3=Kamil |last4=Zajączkowski |first4=Grzegorz |last5=Łukaszewicz |first5=Jan |last6=Tittenbrun |first6=Andrzej |last7=Radliński |first7=Bogusław |date=2021-09-15 |title=Density-related effect of red deer browsing on palatable and unpalatable tree species and forest regeneration dynamics |journal=Forest Ecology and Management |volume=496 |pages=119442 |doi=10.1016/j.foreco.2021.119442 |issn=0378-1127|doi-access=free |bibcode=2021ForEM.49619442B }}

Browsing can affect plant reproduction by reducing the availability of leaves for photosynthesis and flowers for pollination. Overbrowsing can lead to a decrease in seed production, hinder the recruitment of new individuals and alter the genetic diversity of plant population.{{Cite web |title=Impacts of Browsing and Grazing Ungulates on Plant Characteristics and Dynamics |url=https://www.researchgate.net/publication/337204564}}{{Cite journal |last1=Spotswood |first1=Erica |last2=Bradley |first2=Kate L. |last3=Knops |first3=Johannes MH |date=2002-02-12 |title=Effects of herbivory on the reproductive effort of 4 prairie perennials |journal=BMC Ecology |volume=2 |issue=1 |pages=2 |doi=10.1186/1472-6785-2-2 |doi-access=free |pmid=11876828 |issn=1472-6785|pmc=77412 }}{{Cite web |title=Browsing_and_Grazing_Ungulates_on_Plant_Characteristics_and_Dynamics |url=https://www.researchgate.net/publication/337204564}}

Overbrowsing can change near-ground forest structure, plant species composition, vegetation density, and leaf litter, with consequences for other forest-dwelling animals. Many species of ground-dwelling invertebrates rely on near-ground vegetation cover and leaf litter layers for habitat; these invertebrates may be lost from areas with intense browsing.{{Cite journal|last=Stewart|first=A.J.A.|date=2001-01-01|title=The impact of deer on lowland woodland invertebrates: a review of the evidence and priorities for future research|journal=Forestry|language=en|volume=74|issue=3|pages=259–270|doi=10.1093/forestry/74.3.259|issn=0015-752X|doi-access=free}} Further, preferential selection of certain plant species by herbivores can impact invertebrates closely associated with those plants. Migratory forest-dwelling songbirds depend on dense understory vegetation for nesting and foraging habitat; reductions in understory plant biomass caused by deer can lead to declines in forest songbird populations.{{Cite journal|last1=Jirinec|first1=Vitek|last2=Cristol|first2=Daniel A.|last3=Leu|first3=Matthias|date=2017-05-01|title=Songbird community varies with deer use in a fragmented landscape|journal=Landscape and Urban Planning|volume=161|pages=1–9|doi=10.1016/j.landurbplan.2017.01.003|bibcode=2017LUrbP.161....1J }} Finally, loss of understory plant diversity associated with ungulate overbrowsing can impact small mammals that rely on this vegetation for cover and food.

Overbrowsing can lead plant communities towards equilibrium states which are only reversible if herbivore numbers are greatly reduced for a sufficient period, and actions are taken to restore the original plant communities. Management to reduce deer populations has a three-method approach: (1) large areas of contiguous old forest with closed canopies are set aside, (2) predator populations are increased, and (3) hunting of the overabundant herbivore is increased. Encouragement of tree recovery by promoting seed sources of native trees is an important aspect of managing recovery from overbrowsing.{{Cite journal |last1=Tanentzap |first1=Andrew J. |last2=Bazely |first2=Dawn R. |last3=Koh |first3=Saewan |last4=Timciska |first4=Mika |last5=Haggith |first5=Edward G. |last6=Carleton |first6=Terry J. |last7=Coomes |first7=David A. |date=January 2011 |title=Seeing the forest for the deer: Do reductions in deer-disturbance lead to forest recovery? |url=https://doi.org/10.1016/j.biocon.2010.09.015 |journal=Biological Conservation |volume=144 |issue=1 |pages=376–382 |doi=10.1016/j.biocon.2010.09.015 |bibcode=2011BCons.144..376T |issn=0006-3207}} Refugia in the form of windthrow mounds, rocky outcrops, or horizontal logs elevated above the forest floor can provide plants with substrate protected from browsing by cervids.{{Cite journal|last1=Chollet|first1=Simon|last2=Baltzinger|first2=Christophe|last3=Ostermann|first3=Lukas|last4=Saint-André|first4=Flore|last5=Martin|first5=Jean-Louis|date=2013-02-01|title=Importance for forest plant communities of refuges protecting from deer browsing|journal=Forest Ecology and Management|volume=289|pages=470–477|doi=10.1016/j.foreco.2012.10.043|bibcode=2013ForEM.289..470C }}{{Cite journal|title=Over-browsing in Pennsylvania creates a depauperate forest dominated by an understory tree: Results from a 60-year-old deer exclosure|journal=The Journal of the Torrey Botanical Society|volume=138|issue=3|pages=322–326|doi=10.3159/torrey-d-11-00018.1|year = 2011|last1 = Kain|first1 = Morgan|last2=Battaglia|first2=Loretta|last3=Royo|first3=Alejandro|last4=Carson|first4=Walter P.|s2cid=85648031}}{{Cite journal|last1=Long|first1=Zachary T.|last2=Carson|first2=Walter P.|last3=Peterson|first3=Chris J.|date=1998-01-01|title=Can Disturbance Create Refugia from Herbivores: An Example with Hemlock Regeneration on Treefall Mounds|jstor=2997303|journal=The Journal of the Torrey Botanical Society|volume=125|issue=2|pages=165–168|doi=10.2307/2997303}} These refugia can contain a proportion of the plant community that would exist without browsing pressure, and may differ significantly from the flora found in nearby browsed areas. If management efforts were to reduce cervid populations in the landscape, these refugia could serve as a model for understory recovery in the surrounding plant community.

• Consumer–resource interactions
• Silvopasture
• Tree shelter
• Yellow-cedar decline

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Category:Herbivory

Category:Fodder