In ecology, a light gap is a break in

forest canopy In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, the canopy is the upper layer or habitat zone, formed by mature tree crowns and includ ...

or similar barrier that allows young

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s to grow where they would be otherwise inhibited by the lack of light reaching the seedbed. Light gaps form predominantly when a tree falls, and thus produces an opening in the forest canopy. Light gaps are important for maintaining diversity in species-rich ecosystems.

Occurrence

There are many ways in which light gaps can form. A major occurrence is through previously mentioned

treefall gap A treefall gap is a distinguishable hole in the canopy of a forest with vertical sides extending through all levels down to an average height of above ground. These holes occur as result of a fallen tree or large limb. The ecologist who develop ...

s. The death of a full-grown tree initiates a treefall gap, where light is exposed to the soil and creates resources for seeds and younger trees. Treefall gaps have been proven to maintain tree diversity by increasing stem density, which in turn can lead to species richness. Juvenile stems, or

sapling 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, e.g., including only woody plants with secondary growth, only pla ...

s, do an exceptional job at increasing stem density which increases

species diversity Species diversity is the number of different species that are represented in a given community (a dataset). The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundan ...

as a result. Species compete for resources in order to regenerate. Succession can begin when treefall occurs because the newly lit area provides an area for a new population to grow. Trees that will grow in a treefall gap are not necessarily the most suited for that particular environment, but rather, grow by chance. Therefore, different organisms may experience a greater attraction to certain environments over others, which can also have an effect on the extent to which an area flourishes. An interesting example of gap formation comes from Japanese Black Bears and their effects on the forest canopy. When Japanese Black Bears are looking for fruit, they break off branches when climbing trees and as a result, small light gaps form in the canopies. Therefore, their search for food is improving the light conditions of

understory In forestry and ecology, understory (American English), or understorey (English in the Commonwealth of Nations, Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the Canopy (biology), forest ca ...

plants, which in return benefits the bears, as this helps fruit they eat to grow more abundantly.

Selected areas

On a report done in a Neotropical forest, the process of gap-phase regeneration is studied. Through conducted experiments, conclusions are confirmed about the gap-phase regeneration process. A tree fall forms a light gap, which stimulated growth, resulting in an increase in the stem density on the forest floor. Thus, in turn, allows multiple trees to grow back and ecosystems to prosper. Studies of

gap dynamics Gap dynamics refers to the pattern of plant growth that occurs following the creation of a forest gap, a local area of natural disturbance that results in an opening in the canopy of a forest. Gap dynamics are a typical characteristic of both temp ...

have provided evidence for understanding many small disturbances in an ecosystem. Caldera de Taburiente La Palma

In a uniform and discontinuous conifer forest canopy, solar energy is projected at certain angles in the light gaps, which determine soil conditions and amount of snow accumulation. Depending on the time of year, the variety of tree species and the size of the light gap will determine how much light hits the forest floor and what kind of temporal and spatial

heterogeneity Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

will form. In the coastal areas of south-eastern Australia, large

brown kelp Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing and painting, brown is usually made by combining the colors orange and black. In the RGB color model ...

, another kind of canopy, formed by ''

Ecklonia radiata ''Ecklonia'' is a genus of kelp (brown algae) belonging to the family Lessoniaceae. The genus name of ''Ecklonia'' is in honour of Christian Friedrich Ecklon (1795–1868), who was a Danish botanical collector and apothecary. The genus was ...

'', dominates the existing temperate reefs.

Climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

in the area poses a direct effect on the underwater canopy cover, reducing its overall quality. Climate change is causing patches in the canopy layer and because of this loss of coverage, the understory becomes a prime place for

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

to grow. This affects other organisms, such a sponges and encrusting algae that are trying to grow on the reefs. This discovery has shown that although light gaps oftentimes produce positive outcomes, they can also negatively effect some members of the biotic community. Kelp at Middle Bank P2277214

In the

Amazon rainforest The Amazon rainforest, also called the Amazon jungle or Amazonia, is a Tropical and subtropical moist broadleaf forests, moist broadleaf tropical rainforest in the Amazon biome that covers most of the Amazon basin of South America. This basin ...

, light gaps are extensively studied. However, ways in which the

is affected by light gaps there, remains mostly a mystery. Overall

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

in the light gap areas is directly impacted by the size of the light opening, the type of roots that pre-existed its formation, and the type of tree that fell to create the light gap. The quality of biomass determines the level of regrowth in the environment. All types of canopy structures rely on the quality that

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s experience when developing. Seeds can grow better when they are protected, however, they also flourish to a greater extent when they are not in a shaded environment. In fact, some seeds are so sensitive that even a slight change in light can prevent it from surviving.

Light gap herbivores

Light gap herbivores are animals that contribute to the creation of light gaps by feeding on the older plants. Some herbivorous animals include algae and bacteria in their diet. Insect

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s target the shade-tolerant tree species. They cause a substantial amount of damage to the leaves of plants. There is more herbivory in tropical forests than in temperate forests.

Effects on organisms and their ecosystems

Many organisms are directly affected by the formation of light gaps. In a tropical forest, butterflies, which are great

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

indicators, exemplify this notion. Out of twenty various species, each has ecological and behavioral requirements that can be found in both opened and closed canopy gaps. Males will claim certain gaps as their territory to protect the patch from other males, in hopes to attract their female counterpart. Twelve species of butterflies had a positive phototactic response, while four species had a negative response and the remaining four did not express any sort of preference. Overall, butterfly species in a

tropical rainforest Tropical rainforests are dense and warm rainforests with high rainfall typically found between 10° north and south of the Equator. They are a subset of the tropical forest biome that occurs roughly within the 28° latitudes (in the torrid zo ...

were, on average, occupying open canopy gaps more frequently. Butterfly assemblage is determined by the amount of light and temperature that penetrates the canopy. Newly created light gaps are avoided in a lot of situations by species that would normally replenish them through

seed dispersal In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

. However, the aid of the wind for seed dispersal in the light gap has a positive effect on plants, taking them further from the parent plant and decreasing predation.

Frugivores A frugivore ( ) is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance ...

such as birds and bats find recently created gaps dangerous because they pose a hazard on their overall well-being. Birds find no place to perch, and bats are more susceptible to predators when they fly in this area. Large monkeys, toucans, and guans perch in the tops of the canopy, and therefore release their seeds under the canopy and as a result, the seeds do not get dispersed where most needed. Wind initiates seed movement into the canopy gap. As the gap matures, it begins to grow trees that bear fruit, and growth of shrubs draw in more animals as they provide better protection from the open canopy above. Overall, there are many advantages and disadvantages of a light gap disturbance. Some species benefit, and others are threatened. Through more research and investigation, scientists hope to uncover all aspects of the occurrence. It is only then that laws may be implemented to reduce harmful outcomes and increase further ecological sustainability.

References

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