Forest dynamics describes the underlying physical and biological forces that shape and change a

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

. The continuous state of change in forests can be summarized with two basic elements:

disturbance Disturbance and its variants may refer to: Math and science * Disturbance (ecology), a temporary change in average environmental conditions that causes a pronounced change in an ecosystem * Disturbance (geology), linear zone of faults and folds ...

and

succession Succession is the act or process of following in order or sequence. Governance and politics *Order of succession, in politics, the ascension to power by one ruler, official, or monarch after the death, resignation, or removal from office of ...

Disturbance

Forest disturbances are events that cause change in the structure and composition of a forest ecosystem, beyond the growth and death of individual organisms. Disturbances can vary in frequency and intensity, and include natural disasters such as

fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. At a certain point in the combustion reaction, called the ignition point, flames ...

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environmen ...

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...

, volcanic eruptions, rare meteor impacts, outbreaks of insects, fungi, and other pathogens, animal-caused effects such as

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and ot ...

and

trampling Trampling is the act of walking on something repeatedly by humans or animals. Trampling on open ground can destroy the above ground parts of many plants and can compact the soil, thereby creating a distinct microenvironment that specific species ...

, and

anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human i ...

disturbances such as warfare,

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply cha ...

, pollution, the clearing of land for urbanization or agriculture, and the introduction of

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

. Not all disturbances are destructive or negative to the overall forest ecosystem. Many natural disturbances allow for renewal and growth and often release necessary nutrients. Small-scale disturbances are the key to creating and maintaining diversity and heterogeneity within a forest. Small-scale disturbances are events such as single-tree blowdowns, which create gaps that let light through the canopy to the understory and forest floor. This available light allows early-successional shade-intolerant species to colonize and maintain a population within the dominant forest, leading to the complex spatial mosaic forest structure recognized as old-growth. This process is referred to as

patch dynamics Patch dynamics is an ecological perspective that the structure, function, and dynamics of ecological systems can be understood through studying their interactive patches. Patch dynamics, as a term, may also refer to the spatiotemporal changes wi ...

or gap dynamics and has been described across many types of forests, including tropical, temperate, and boreal. The sets and patterns of natural disturbances that characterize a particular area or ecosystem are referred to as the ecosystem's ''disturbance regime''. A natural community is closely linked with its natural disturbance regime. For example, temperate and boreal rainforests typically have a disturbance regime consisting of high-frequency but small-scale events, resulting in a highly complex forest dominated by very old trees. In contrast, forests that have a disturbance regime consisting of high-severity stand-replacing events, such as frequent fires, tend to be more uniform in structure and have relatively young tree stands.

Succession

Forest succession is the process by which species recover and regenerate after a disturbance. The type of disturbance, the climate and weather conditions, the presence of colonizing species, and the interactions among species all influence the path that succession will take. Species diversity and composition fluctuate throughout succession. The classic model of succession is known as ''relay floristics'' and refers to a relay of dominant species. After a stand-replacing disturbance, shade-intolerant species colonize and grow into a dominant canopy, but due to their shade-intolerance they are unable to regenerate under their own canopy; the understory (composed of shade-tolerant species) gradually replaces the canopy, and due to its shade-tolerance it can regenerate under its own canopy and therefore becomes the dominant species. Often succession is not so complete or directed as the relay floristics model describes. Species can be mid-tolerant of shade and survive by taking advantage of small amounts of light coming through the canopy, and further disturbances can create small gaps. These and other factors can lead to a mixture of dominant species and a not so obvious “end” to succession ( climax community). Many successional trajectories follow a basic four-stage development pattern. The first of these stages, ''stand initiation'', occurs after a major disturbance and involves many species arriving in the area of abundant light and nutrients. The second stage, ''stem exclusion'', describes the growth and

competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, ind ...

of these species as resources become less available; likely one or a few species outcompetes and becomes stand-dominating. The third stage, ''understory reinitiation'', involves further disturbance and the creation of gaps; at this point stratification develops, with layers of canopy, midstory, and understory appearing. The final stage, known as ''old-growth'', is the extension and completion of the understory reinititation; a complex multi-aged and multi-layered forest has developed.

Considering climate change

Forests are sensitive to climate, and so

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

can have a great effect on the dynamics of the ecosystem. Rising carbon dioxide levels can increase the productivity and growth of trees, which will then decrease as other nutrients become limiting. Changes in temperature and precipitation can affect the success of various species and the resulting species assemblage. Many factors of climate change can also affect an ecosystem’s disturbance regime, making the forest more or less susceptible to different disturbances and altering or even preventing recovery after a disturbance.

Importance

Forests offer many

ecosystem services Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. ...

including

timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...

, fresh water, carbon storage, and areas of recreation. To conserve these services, along with the natural

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 ...

and

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'') ...

that forests provide, understanding the dynamics that are creating and maintaining the forests is a priority.

Forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forests, woodlands, and associated resources for human and environmental benefits. Forestry is practiced in plantations and natural stands. ...

and silviculture operations require a thorough comprehension of forest dynamics in order to implement effective management and conservation techniques.

References

{{Reflist Forest ecology

Disturbance

Succession

Considering climate change

Importance

See also

References