In
biology
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditar ...
, the canopy is the aboveground portion of a
plant cropping or
crop
A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropo ...
, formed by the collection of individual
plant crowns.
In
forest ecology
Forest ecology is the scientific study of the interrelated patterns, processes, flora, fauna and ecosystems in forests. The management of forests is known as forestry, silviculture, and forest management. A forest ecosystem is a natural woodland ...
, canopy also refers to the upper layer or
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
zone, formed by mature
tree
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
crowns and including other biological organisms (
epiphytes,
liana
A liana is a long- stemmed, woody vine that is rooted in the soil at ground level and uses trees, as well as other means of vertical support, to climb up to the canopy in search of direct sunlight. The word ''liana'' does not refer to a ...
s,
arboreal animals
Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose num ...
, etc.). The communities that inhabit the canopy layer are thought to be involved in maintaining forest diversity, resilience, and functioning.
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 tree
A shade tree is a large tree whose primary role is to provide shade in the surrounding environment due to its spreading canopy and crown, where it may give shelter from sunlight in the heat of the summer for people who seek recreational needs ...
s 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 forestry and ecology, understory (American English), or understorey (Commonwealth English
The use of the English language in current and former member countries of the Commonwealth of Nations was largely inherited from British co ...
. In some cases, they would use unconventional methods such as chairs suspended on
vine
A vine ( Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners thems ...
s 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.
Canopy structure
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
In forestry and ecology, understory (American English), or understorey (Commonwealth English
The use of the English language in current and former member countries of the Commonwealth of Nations was largely inherited from British co ...
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.
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
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity' ...
resides in the canopy of
tropical rainforest
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
s. Many rainforest animals have evolved to live solely in the canopy, and never touch the ground.
The canopy of a
rainforest
Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfo ...
is typically about 10 m thick, and intercepts around 95% of sunlight.
The canopy is below the
emergent layer
Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfore ...
, a sparse layer of very tall trees, typically one or two per
hectare
The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
. 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 40 meters 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.
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.
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.
Due to this, forest canopies are arguably considered some of the most species-rich environments on the planet. 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
In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windst ...
.
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.
Forest canopies also buffer the effects of temperature within forests by creating vertical light gradients. 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.
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 CO
2 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 CO
2. This would then contribute to the greenhouse effect, thereby causing the planet to become warmer.
Canopy interception
See also
References
Further reading
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External links
International Canopy Access Network
{{Authority control
Biology terminology
Forest ecology
Habitat
Rainforests