Canopy (biology)

The canopy of a forest in Sabah, Malaysia
© Vyacheslav Argenberg / http://www.vascoplanet.com/, CC BY 4.0
Canopy of tropical evergreen forest, Andaman Islands
© Vyacheslav Argenberg / http://www.vascoplanet.com/, CC BY 4.0
Canopy layers of primary tropical forest, Thailand
Macrocystis pyrifera – giant kelp – forming the canopy of a kelp forest

In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns.[1][2][3]

In forest ecology, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms (epiphytes, lianas, arboreal animals, etc.).[4] The communities that inhabit the canopy layer are thought to be involved in maintaining forest diversity, resilience, and functioning.[5]

Sometimes the term canopy is used to refer to the extent of the outer layer of leaves of an individual tree or group of trees. Shade trees normally have a dense canopy that blocks light from lower growing plants.

Observation

Early observations of canopies were made from the ground using binoculars or by examining fallen material. Researchers would sometimes erroneously rely on extrapolation by using more reachable samples taken from the understory. In some cases, they would use unconventional methods such as chairs suspended on vines or hot-air dirigibles, among others. Modern technology, including adapted mountaineering gear, has made canopy observation significantly easier and more accurate, allowed for longer and more collaborative work, and broadened the scope of canopy study.[6]

Canopy structure

A monkey-ladder vine canopy over a road

Canopy structure is the organization or spatial arrangement (three-dimensional geometry) of a plant canopy. Leaf area index (LAI), leaf area per unit ground area, is a key measure used to understand and compare plant canopies.

The canopy is taller than the understory layer. The canopy holds 90% of the animals in the rainforest. They cover vast distances and appear to be unbroken when observed from an airplane. However, despite overlapping tree branches, rainforest canopy trees rarely touch each other. Rather, they are usually separated by a few feet.[7]

Canopy layer of forests

Dominant and co-dominant canopy trees form the uneven canopy layer. Canopy trees are able to photosynthesize relatively rapidly due to abundant light, so it supports the majority of primary productivity in forests. The canopy layer provides protection from strong winds and storms, while also intercepting sunlight and precipitation, leading to a relatively sparsely vegetated understory layer.

Forest canopies are home to unique flora and fauna not found in other layers of forests. The highest terrestrial biodiversity resides in the canopy of tropical rainforests.[8] Many rainforest animals have evolved to live solely in the canopy, and never touch the ground.

The canopy of a rainforest is typically about 10m thick, and intercepts around 95% of sunlight.[9] The canopy is below the emergent layer, a sparse layer of very tall trees, typically one or two per hectare. With an abundance of water and a near ideal temperature in rainforests, light and nutrients are two factors that limit tree growth from the understory to the canopy.

In the permaculture and forest gardening community, the canopy is the highest of seven layers.

The canopy can get as high as 40meters with different animals.

Forest canopy ecology

Forest canopies have unique structural and ecological complexities and are important components of the overall forest ecosystem. They are involved in critical functions such as rainfall interception, light absorption, nutrient & energy cycling, gas exchange, as well as providing habitats for a diverse range of wildlife.[10] The canopy also plays a role in modifying the internal environment of the forest by acting as a buffer for incoming light, wind, and temperature fluctuations.[10]

Species diversity

The forest canopy layer supports a diverse range of flora and fauna. It has been dubbed “the last biotic frontier” as it provides a habitat that has allowed for the evolution of countless species of plants, microorganisms, invertebrates (e.g. insects), and vertebrates (e.g. birds and mammals) that are unique to the upper layer of forests.[11] Due to this, forest canopies are arguably considered some of the most species-rich environments on the planet.[12] It is now believed that the communities found within the canopy layer play an important role in the functioning of the forest, as well as maintaining diversity and ecological resilience.[11]

Climate regulation

Forest climate

Forest canopies contribute to forest microclimate by controlling and buffering variations in climatic conditions. Forest canopies intercept rain and snowfall, thereby buffering the effects of precipitation on the local climate.[13] Forest canopies also buffer the effects of temperature within forests by creating vertical light gradients.[14] Variations in forest microclimate are also driven by the structure and physiology of canopy trees and epiphytes. This produces feedback loops where forest microclimate both determines and is determined by the species identity, growth traits and forest stand composition of canopy trees.[13]

Global climate

Forest canopies are significantly involved in maintaining the stability of the global climate. They are responsible for at least half of the global Carbon dioxide exchange between terrestrial ecosystems and the atmosphere. Forest canopies act as carbon sinks which reduce the increase of atmospheric CO2 caused by human activity. The destruction of forest canopies would lead to the release of carbon dioxide which would result in an increased concentration of atmospheric CO2. This would then contribute to the greenhouse effect, thereby causing the planet to become warmer.[15]

See also

  • Canopy (grape)
  • Canopy research
  • Canopy soils
  • Canopy walkway
  • Crown shyness
  • Hemispherical photography
  • Size-asymmetric competition
  • Stratification (vegetation)
  • Treefall gap
  • Tropical forest
  • Wildfire

References

  1. ^ Campbell, G.S.; Norman, J.M. (1989). "The description and measurement of plant canopy structure". In Russell, Graham; Marshall, Bruce; Jarvis, Paul G. (eds.). Plant Canopies: Their Growth, Form and Function. Cambridge University Press. pp. 1–19. doi:10.1017/CBO9780511752308.002. ISBN 978-0-521-39563-2. LCCN 87032902.
  2. ^ Moffett, Mark W. (December 2000). "What's "Up"? A Critical Look at the Basic Terms of Canopy Biology". Biotropica. 32 (4): 569–596. doi:10.1646/0006-3606(2000)032[0569:WSUACL]2.0.CO;2. S2CID 45947367.
  3. ^ Hay, Robert K.M.; Porter, John R. (2006). The Physiology of Crop Yield (Second ed.). Blackwell Publishing. ISBN 978-1-4051-0859-1. LCCN 2006005216.
  4. ^ Parker, Geoffrey G. (1995). "Structure and microclimate of forest canopies". In Lowman, Margaret D.; Nadkarni, Nalini M. (eds.). Forest Canopies (First ed.). Academic Press. pp. 73–106. ISBN 978-0124576506. LCCN 94041251.
  5. ^ Nadkarni, Nalini M. (February 1994). "Diversity of Species and Interactions in the Upper Tree Canopy of Forest Ecosystems". American Zoologist. 34 (1): 70–78. doi:10.1093/icb/34.1.70 – via Oxford Academic.
  6. ^ Lowman, Margaret D.; Wittman, Philip K. (1996). "Forest Canopies: Methods, Hypotheses, and Future Directions" (PDF). Annual Review of Ecology, Evolution, and Systematics. 27: 55–81. doi:10.1146/annurev.ecolsys.27.1.55. JSTOR 2097229. Archived (PDF) from the original on 7 February 2019.
  7. ^ Butler, Rhett (30 July 2012). "The Rainforest Canopy". Mongabay. Archived from the original on 5 May 2020.
  8. ^ Lowman, Margaret D.; Moffett, Mark (March 1993). "The ecology of tropical rain forest canopies" (PDF). Trends in Ecology & Evolution. 8 (3): 104–107. doi:10.1016/0169-5347(93)90061-S. PMID 21236120. Archived (PDF) from the original on 2 February 2020.
  9. ^ "Light in the Rain Forest". garden.org. Archived from the original on 23 November 2015. Retrieved 23 November 2015.
  10. ^ a b Forest canopies. Margaret Lowman, H. Bruce Rinker (2nd ed.). Amsterdam: Elsevier Academic Press. 2004. ISBN 978-0-12-457553-0. OCLC 162129566.{{cite book}}: CS1 maint: others (link)
  11. ^ a b Nadkarni, Nalini M.; Merwin, Mark C.; Nieder, Jurgen (1 January 2013), "Forest Canopies, Plant Diversity", in Levin, Simon A (ed.), Encyclopedia of Biodiversity (Second Edition), Waltham: Academic Press, pp. 516–527, doi:10.1016/b978-0-12-384719-5.00158-1, ISBN 978-0-12-384720-1, retrieved 26 February 2022
  12. ^ Erwin, Terry L. (1 January 2013), "Forest Canopies, Animal Diversity", in Levin, Simon A (ed.), Encyclopedia of Biodiversity (Second Edition), Waltham: Academic Press, pp. 511–515, doi:10.1016/b978-0-12-384719-5.00057-5, ISBN 978-0-12-384720-1, retrieved 26 February 2022
  13. ^ a b Nakamura, Akihiro; Kitching, Roger L.; Cao, Min; Creedy, Thomas J.; Fayle, Tom M.; Freiberg, Martin; Hewitt, C. N.; Itioka, Takao; Koh, Lian Pin; Ma, Keping; Malhi, Yadvinder (1 June 2017). "Forests and Their Canopies: Achievements and Horizons in Canopy Science". Trends in Ecology & Evolution. 32 (6): 438–451. doi:10.1016/j.tree.2017.02.020. ISSN 0169-5347. PMID 28359572.
  14. ^ Pfeifer, Marion; Gonsamo, Alemu; Woodgate, William; Cayuela, Luis; Marshall, Andrew R.; Ledo, Alicia; Paine, Timothy C. E.; Marchant, Rob; Burt, Andrew; Calders, Kim; Courtney-Mustaphi, Colin (8 January 2018). "Tropical forest canopies and their relationships with climate and disturbance: results from a global dataset of consistent field-based measurements". Forest Ecosystems. 5 (1): 7. doi:10.1186/s40663-017-0118-7. ISSN 2197-5620. S2CID 31219827.
  15. ^ Didham, R. K.; Fagan, L. L. (1 January 2004), "ECOLOGY | Forest Canopies", in Burley, Jeffery (ed.), Encyclopedia of Forest Sciences, Oxford: Elsevier, pp. 68–80, doi:10.1016/b0-12-145160-7/00013-2, ISBN 978-0-12-145160-8, retrieved 26 February 2022

Further reading

External links

Media files used on this page

Havelock Island, Canopy of tropical moist evergreen forest, Andaman Islands.jpg
© Vyacheslav Argenberg / http://www.vascoplanet.com/, CC BY 4.0
The Andaman Islands have a tropical rainforest canopy, made of a mixed flora with elements from Indian, Myanmar, Malaysian and endemic floral strains. Havelock Island, Andaman Sea, Andaman and Nicobar Islands, India.
Khao Sok primary tropical rainforest, southern Thailand.jpg
© Vyacheslav Argenberg / http://www.vascoplanet.com/, CC BY 4.0
This is a photo of a natural heritage site in Thailand, id:
Monkey Ladder Vine canopy.jpg
A picture of a Monkey Ladder Vine taken 2007/08/29 at the McBryde Garden in Hawaii on the island of Kauai. The picture was stitched from two photos and cropped, otherwise is in its original state.
JigsawCanopy.jpg
(c) Mark Fisher - markfisher.photo, CC BY-SA 3.0
The canopy in Sepilok Orangutan Rehabilitation Centre in the Malaysian Sabah District of North Borneo.
Bamboo Canopy.jpg
(c) Anand2202, CC BY-SA 4.0
Canopy formed by the Bamboos, Periyar National Park and Wildlife Sanctuary, India