Tree

==Ecology==
{{further|Forest}}

Trees are an important part of the terrestrial [[ecosystem]],<ref name=Lowman>{{cite journal |last=Lowman |first=M D |title=Canopy research in the twenty-first century: a review of arboreal ecology |journal=Tropical Ecology |volume=50 |year=2009 |pages=125–136 |issn=0564-3295}}</ref> providing essential habitats including many kinds of forest for communities of organisms. [[Epiphyte|Epiphytic]] plants such as [[fern]]s, some mosses, liverworts, [[orchid]]s and some species of [[parasite|parasitic]] plants (e.g., [[mistletoe]]) hang from branches;<ref>{{cite book |last=Zotz |first=Gerhard |title=Plants on Plants – The Biology of Vascular Epiphytes |url=https://books.google.com/books?id=hIP2DAAAQBAJ |year=2016 |publisher=Springer |isbn=978-3-319-39237-0 |access-date=14 November 2017 |archive-date=19 August 2020 |archive-url=https://web.archive.org/web/20200819114740/https://books.google.com/books?id=hIP2DAAAQBAJ |url-status=live }}</ref> these along with arboreal lichens, algae, and fungi provide micro-habitats for themselves and for other organisms, including animals. Leaves, flowers and fruits are seasonally available. On the ground underneath trees there is shade, and often there is undergrowth, [[leaf litter]], and decaying wood that provide other habitat.<ref>{{cite web|title=The structure of a forest|url=http://enviropol.com/index.php/forest-structure|publisher=Enviropol|access-date=14 November 2017|archive-date=15 November 2017|archive-url=https://web.archive.org/web/20171115083431/http://enviropol.com/index.php/forest-structure|url-status=live}}</ref><ref>{{cite web|title=Forest Layers, Stories, And Stratification|url=http://www.worldatlas.com/articles/forest-layers-stories-and-stratification.html|publisher=WorldAtlas|access-date=14 November 2017|archive-date=15 November 2017|archive-url=https://web.archive.org/web/20171115083445/http://www.worldatlas.com/articles/forest-layers-stories-and-stratification.html|url-status=live}}</ref> Trees stabilise the soil, prevent rapid run-off of rain water, help prevent desertification, have a role in climate control and help in the maintenance of [[biodiversity]] and ecosystem balance.<ref>{{cite web |url=http://www.fao.org/docrep/005/y2328e/y2328e00.htm |title=Trees outside forests |author1=Bellefontaine, R. |author2=Petit, S. |author3=Pain-Orcet, M. |author4=Deleporte, P. |author5=Bertault, J-G |year=2002 |publisher=Food and Agriculture Organization of the United Nations |access-date=25 July 2012 |archive-date=31 January 2019 |archive-url=https://web.archive.org/web/20190131070800/http://www.fao.org/docrep/005/Y2328E/y2328e00.htm |url-status=live }}</ref>

Many species of tree support their own specialised [[invertebrate]]s. In their natural habitats, 284 different species of insect have been found on the English oak (''[[Quercus robur]]'')<ref>{{cite web |url=http://www.oldknobbley.com/woodland_ecology/trees/trees_oak_english.php |title=English oak |year=2007 |work=Old Knobbley |access-date=25 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120908010458/http://www.oldknobbley.com/woodland_ecology/trees/trees_oak_english.php |archive-date=8 September 2012}}</ref> and 306 species of invertebrate on the Tasmanian oak (''[[Eucalyptus obliqua]]'').<ref>{{cite web |url=http://www.outreachecology.com/go/deliver/YoavDanielBarNessICE2004.pdf |title=Tiny animals, titan trees |author=Bar-Ness, Yoav Daniel |year=2004 |work=ICE: Canopy Invertebrate Fauna of Tasmanian Eucalyptus obliqua |access-date=25 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121204021347/http://www.outreachecology.com/go/deliver/YoavDanielBarNessICE2004.pdf |archive-date=4 December 2012 }}</ref> Non-native tree species provide a less biodiverse community, for example in the United Kingdom the sycamore (''[[Acer pseudoplatanus]]''), which originates from southern Europe, has few associated invertebrate species, though its bark supports a wide range of lichens, bryophytes and other epiphytes.<ref>{{cite web |url=http://members.multimania.co.uk/WoodyPlantEcology/docs/QJF87-143.pdf |archive-url=https://web.archive.org/web/20130221090223/http://members.multimania.co.uk/WoodyPlantEcology/docs/QJF87-143.pdf |archive-date=21 February 2013 |title=The conservation value of sycamore |author=Binggeli, Pierre |access-date=25 July 2012 |url-status=dead}}</ref> {{anchor|Tree apparency}}Trees differ ecologically in the ease with which they can be found by herbivores. Tree apparency varies with a tree's size and [[semiochemical]] content, and with the extent to which it is concealed by [[nonhost resistance|nonhost]] neighbours from its [[insect herbivore|insect pests]].<ref name="Jactel-et-al-2021">{{cite journal | last1=Jactel | first1=Hervé | last2=Moreira | first2=Xoaquín | last3=Castagneyrol | first3=Bastien | title=Tree Diversity and Forest Resistance to Insect Pests: Patterns, Mechanisms, and Prospects | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=66 | issue=1 | date=7 January 2021 |doi=10.1146/annurev-ento-041720-075234 |pages=277–296| pmid=32903046 | s2cid=221621050 | doi-access=free }}</ref>

In ecosystems such as mangrove swamps, trees play a role in developing the habitat, since the roots of the mangrove trees reduce the speed of flow of tidal currents and trap water-borne sediment, reducing the water depth and creating suitable conditions for further mangrove colonisation. Thus mangrove swamps tend to extend seawards in suitable locations.<ref>{{cite web |url=http://ocw.unu.edu/international-network-on-water-environment-and-health/unu-inweh-course-1-mangroves/Importance-of-mangroves.pdf |archive-url=https://web.archive.org/web/20140904153735/http://ocw.unu.edu/international-network-on-water-environment-and-health/unu-inweh-course-1-mangroves/Importance-of-mangroves.pdf |archive-date=4 September 2014 |title=Importance of Mangrove Ecosystem |last=Kathiresan |first=K. |publisher=Annamalai University |access-date=6 September 2014 |url-status=dead}}</ref> Mangrove swamps also provide an effective buffer against the more damaging effects of cyclones and tsunamis.<ref>{{cite web |url=http://www.nepa.gov.jm/policies/draft/Mangroves%20and%20Coastal%20Wetland%20Protection/MANGROVE%20AND%20COASTAL%20WETLANDS%20PROTECTION%20part%201%20to%203.htm |title=Mangroves and coastal wetlands protection |publisher=University of Jamaica |access-date=6 September 2014 |archive-date=23 November 2020 |archive-url=https://web.archive.org/web/20201123124810/https://www.nepa.gov.jm/policies/draft/Mangroves%20and%20Coastal%20Wetland%20Protection/MANGROVE%20AND%20COASTAL%20WETLANDS%20PROTECTION%20part%201%20to%203.htm |url-status=live }}</ref>