Understory

In forestry and ecology, understory (or understorey, underbrush, undergrowth) comprises plant life growing beneath the forest canopy without penetrating it to any great extent, but above the forest floor. Only a small percentage of light penetrates the canopy so understory vegetation is generally shade tolerant. The understory typically consists of trees stunted through lack of light, other small trees with low light requirements, saplings, shrubs, vines and undergrowth. Small trees such as holly and dogwood are understory specialists.

In temperate deciduous forests, many understory plants start into growth earlier than the canopy trees to make use of the greater availability of light at this time of year. A gap in the canopy caused by the death of a tree stimulates the potential emergent trees into competitive growth as they grow upwards to fill the gap. These trees tend to have straight trunks and few lower branches. At the same time, the bushes, undergrowth and plant life on the forest floor become more dense. The understory experiences greater humidity than the canopy, and the shaded ground does not vary in temperature as much as open ground. This causes a proliferation of ferns, mosses and fungi and encourages nutrient recycling, which provides favorable habitats for many animals and plants.

Celandine Sward
Lesser celandine (Ranunculus ficaria) on forest floor in spring
Moss tree bark coverage
Tree base showing moss understory limit
Summer understory growing near the Angel Springs Trailhead of Myra-Bellevue Park

Understory structure

The understory is the underlying layer of vegetation in a forest or wooded area, especially the trees and shrubs growing between the forest canopy and the forest floor. Plants in the understory comprise an assortment of seedlings and saplings of canopy trees together with specialist understory shrubs and herbs. Young canopy trees often persist in the understory for decades as suppressed juveniles until an opening in the forest overstory permits their growth into the canopy. In contrast understory shrubs complete their life cycles in the shade of the forest canopy. Some smaller tree species, such as dogwood and holly, rarely grow tall and generally are understory trees.

The canopy of a rainforest is typically about 10m (33ft) thick, and intercepts around 95% of the sunlight.[1] The understory receive less intense light than plants in the canopy and such light as does penetrate is impoverished in wavelengths of light that are most effective for photosynthesis. Understory plants therefore must be shade tolerant—they must be able to photosynthesize adequately using such light as does reach their leaves. They often are able to use wavelengths that canopy plants cannot. In temperate deciduous forests towards the end of the leafless season, understory plants take advantage of the shelter of the still leafless canopy plants to "leaf out" before the canopy trees do. This is important because it provides the understory plants with a window in which to photosynthesize without the canopy shading them. This brief period (usually 1–2 weeks) is often a crucial period in which the plant can maintain a net positive carbon balance over the course of the year.

As a rule forest understories also experience higher humidity than exposed areas. The forest canopy reduces solar radiation, so the ground does not heat up or cool down as rapidly as open ground. Consequently, the understory dries out more slowly than more exposed areas do. The greater humidity encourages epiphytes such as ferns and mosses, and allows fungi and other decomposers to flourish. This drives nutrient cycling, and provides favorable microclimates for many animals and plants, such as the pygmy marmoset.[2]

See also

References

  1. ^ "Light in the Rain Forest". garden.org. Retrieved 8 January 2016.
  2. ^ Kramer, D. M., G. Johnson, O. Kiirats, G. E. Edwards. 2004. New fluorescence parameters for the determination of Q redox state and excitation energy fluxes. Photosynthesis Research 79:209-218

https://www.eolss.net/sample-chapters/C10/E5-03-01-08.pdf

Aspen parkland

Aspen parkland refers to a very large area of transitional biome between prairie and boreal forest in two sections, namely the Peace River Country of northwestern Alberta crossing the border into British Columbia, and a much larger area stretching from central Alberta, all across central Saskatchewan to south central Manitoba and continuing into small parts of the US states of Minnesota and North Dakota. Aspen parkland consists of groves of aspen poplars and spruce interspersed with areas of prairie grasslands, also intersected by large stream and river valleys lined with aspen-spruce forests and dense shrubbery. This is the largest boreal-grassland transition zone in the world and is a zone of constant competition and tension as prairie and woodlands struggle to overtake each other within the parkland.This article focuses on this biome in North America. Similar biomes also exist in Russia north of the steppes (forest steppe) and in northern Europe.

Browsing (herbivory)

Browsing is a type of herbivory in which a herbivore (or, more narrowly defined, a folivore) feeds on leaves, soft shoots, or fruits of high-growing, generally woody plants such as shrubs. This is contrasted with grazing, usually associated with animals feeding on grass or other low vegetation. Alternatively, grazers are animals eating mainly grass, and browsers are animals eating mainly non-grasses, which include both woody and herbaceous dicots. In either case, an example of this dichotomy are goats (which are browsers) and sheep (which are grazers); these two closely related ruminants utilize dissimilar food sources.

Canopy (biology)

In biology, the canopy is the aboveground portion of a plant community or crop, formed by the collection of individual plant crowns.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.).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.

Citrus garrawayi

Citrus garrawayi, the Mount White lime, is a tree native to the Cape York region of northern Queensland in Australia. It is an understory tree in tropical rainforests.Citrus garrawayi is a shrub or small tree up to 15 m, with broad lanceolate leaves. Fruits are elongated, yellowish-green with green pulp. The fruits are edible but the species is rare and grows in an isolated location, so there has to date been no commercial use of the species.

The species is often included in the genus Microcitrus rather than in the genus Citrus.

Elklick Woodlands Natural Area Preserve

Elklick Woodlands Natural Area Preserve is a 226-acre (91 ha) Natural Area Preserve located in Fairfax County, Virginia. Owned by the Fairfax County Park Authority, it is protected with a local conservation easement, and preserves a globally rare natural community known as a "northern hardpan basic oak-hickory forest". This kind of forest occurs on diabase soil with an underlay of dense plastic clay; such terrain is called "shrink-swell soil" due to extreme variations in moisture availability exhibited throughout the year. Trees which grow in such an environment are stunted, and their relatively open canopies encourage the growth of a wide variety of grasses and herbs in the understory. Such forests were once common around northern Virginia, but many have been lost due to increasing suburbanization of the area.The forest found within Elklick Woodlands Natural Area Preserve is one of the most diverse upland forests types in Virginia. The forest's overstory is composed of several species of oaks (particularly white oak) and hickories (particularly pignut hickory); other canopy trees include white ash, tulip poplar, eastern red cedar, and Virginia pine. These trees are somewhat stunted and reach heights that are, on average, about 20 feet (6.1 m) shorter than typical forest trees in the region. The understory contains redbud, ironwood, flowering dogwood, and hawthorn.The preserve is owned and maintained by the Fairfax County Park Authority. It does not include improvements for public access, and visitors must make arrangements with the Fairfax County Park Authority prior to visiting. The preserve is part of a larger tract of county-owned parkland known as the Elklick Preserve. It is continuous with other county-owned and privately conserved greenspace, as well as the nearby Manassas National Battlefield Park.

Forb

A forb (sometimes spelled phorb) is an herbaceous flowering plant that is not a graminoid (grasses, sedges and rushes). The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory.

Laurel Lake Wildlife Management Area

Laurel Lake Wildlife Management Area is located between Dingess and Lenore in Mingo County, West Virginia. Located on 12,856 acres (5,203 ha) of steep terrain with narrow valleys and ridgetops, the WMA contains second growth mixed hardwoods and hemlock with thick understory of mountain laurel and rhododendron.To reach Laurel Lake WMA from Lenore, follow Old Norfolk & Western Railroad Bed Road (County Route 3/5) east about 6 miles (9.7 km) to Laurel Lake.

Lewis Wetzel Wildlife Management Area

Lewis Wetzel Wildlife Management Area (WMA) is located in Wetzel County, West Virginia, USA, about 0.75 miles (1.21 km) south of Jacksonburg on County Route 82. It is located on 13,590 acres (5,500 ha) of steep terrain with narrow valleys and ridgetops. The WMA second growth mixed hardwoods and hemlock with a thick understory of mountain laurel and rhododendron.The wildlife management area and Wetzel County are named for Lewis Wetzel, an early settler and frontiersman in this area of West Virginia.

Navajo State Park

Navajo State Park is a state park of Colorado, USA, on the north shore of Navajo Lake. Touted as Colorado's answer to Lake Powell, this reservoir on the San Juan River begins in Colorado's San Juan Mountains and extends 20 miles (32 km) into New Mexico. Its area is 15,000 acres (6,100 ha), and it has 150 miles (240 km) of shoreline in two states. Park activities include boating, houseboating, fishing, camping, and wildlife viewing. There is a New Mexico state park at the southern end of the lake.

Old-growth forest

An old-growth forest — also termed primary forest or late seral forest — is a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community. Old-growth features include diverse tree-related structures that provide diverse wildlife habitat that increases the biodiversity of the forested ecosystem. The concept of diverse tree structure includes multi-layered canopies and canopy gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris.

Old-growth forests are valuable for economic reasons and for the ecosystem services they provide. This can be a point of contention when some in the logging industry may desire to cut down the forests to obtain valuable timber, while environmentalists seek to preserve the forests for benefits such as maintenance of biodiversity, water regulation, and nutrient cycling.

Persoonia bargoensis

Persoonia bargoensis, commonly known as the Bargo geebung, is a shrub native to New South Wales in eastern Australia. It is currently classified under Commonwealth legislation as vulnerable, and is listed in New South Wales legislation as threatened.Lawrie Johnson and Peter Weston of the New South Wales Herbarium described the Bargo geebung as Persoonia bargoensis in 1991, having previously considered it an intermediate form between Persoonia nutans, which is found 40 km (25 mi) to the north, and P. oxycoccoides, which is found 25 km (16 mi) to the south. However further study found no evidence of intermediate forms between it and the other two species.Within the genus, it is classified in the Lanceolata group, a group of 58 closely related species with similar flowers but very different foliage. These species will often interbreed with each other where two members of the group occur.The Bargo geebung grows as a shrub with an upright habit, reaching 0.6 to 2.5 m high. The new growth is hairy. The leaves are alternately arranged along the stems. The leaves are linear-lanceolate (spear-shaped) to lanceolate, and measure 0.8 to 2.4 cm long by 1 to 2.3 mm wide. Flowering takes place in December and January. The flower heads are auxotelic, which means each stalk bears an individual flower that is subtended by a leaf at its junction with the stem. There are 1 to 20 individual flowers in a flower head (rachis), which can be up to 25 cm long. The flowers are followed by the development of the green drupes.The Bargo geebung is found in small scattered patches in an area bordered by Picton and Douglas Park to the north, Yanderra to the south, Cataract River to the east and Thirlmere to the west. It grows on Hawkesbury Sandstone and Wianamatta Shale soils, 100–300 m (300–1,000 ft) above sea level. It grows in dry sclerophyll eucalypt forest, under forest red gum (Eucalyptus tereticornis) and broad-leaved red ironbark (E. fibrosa) with a grassy understory of kangaroo grass (Themeda triandra), or more open woodland with such trees as red bloodwood (Corymbia gummifera), scribbly gum (Eucalyptus sclerophylla), grey gum (E. punctata), narrow-leaved stringybark (E. sparsifolia) and small-leaved apple (Angophora bakeri) with a shrubby understory of plants such as wreath bush-pea (Pultenaea tuberculata). The increased light and lack of competing plants means the species adapts preferably to (and can be found on) road verges.

Persoonia myrtilloides

Persoonia myrtilloides, commonly known as myrtle geebung, is a shrub species that is endemic to New South Wales in Australia. It grows to between 0.5 and 2.5 metres (1.6 and 8.2 ft) in height and has leaves that are between 12 and 50 millimetres (0.47 and 1.97 in) long and 4 to 30 millimetres (0.16 to 1.18 in) wide. Yellow flowers appear between December and April in the species native range.Persoonia myrtilloides was first formally described in 1827. Two subspecies are currently recognised, distinguished by the shape of leaves and tepals:

P. myrtilloides subsp. cunninghamii (R.Br.) L.A.S.Johnson & P.H.Weston which has broader leaves and reflexed tepal tips.

P. myrtilloides Sieber ex Schult. & Schult.f. subsp. myrtilloides which has narrower leaves and recurved tepal tips.Hybrids with P. acerosa, P. levis and P. recedens have been reported where the parent species both occur.The species occurs in the Blue Mountains from Wentworth Falls northwards to Capertee. Subspecies cunninghamii is found in the Wollemi National Park and the catchment of the Cudgegong River.Both subspecies are understory plants in open forests on sandstone-based soils. Subspecies myrtilloides is associated with trees such as sydney peppermint (Eucalyptus piperita), narrow-leaved peppermint (E. radiata) and silvertop ash (E. sieberi), and a shrubby

understory of old man banksia (Banksia serrata), Phyllota squarrosa, paperbark teatree (Leptospermum trinervium) and mountain devil (Lambertia formosa). It is also found in heath. Subspecies cunninghamii is associated with the trees scribbly gum species Eucalyptus rossii and E. sclerophylla, rough-barked apple (Angophora floribunda), Callitris species, and mallees such as Eucalyptus multicaulis and narrow-leaved mountain mallee (E. apiculata).Currawongs and possibly kangaroos and possums are thought to eat the fruit, the seeds of which are then scattered in droppings. Insects recorded foraging at flowers of subspecies myrtilloides include members of the genera Exoneura, Hylaeus and Odyneurus, Homalictus holochorus, colletid bees of the genus Leioproctus subgenus Cladocerapis, including Leioproctus carinatifrons, L. raymenti, L. speculiferus and Trigona carbonaria.

Rainforest

Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between 250 and 450 centimetres (98 and 177 in), and definitions varying by region for temperate rainforests. The monsoon trough, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the Earth's tropical rainforests.

Around 40% to 75% of all biotic species are indigenous to the rainforests. There may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered there. Rainforests are also responsible for 28% of the world's oxygen turnover, sometimes misnamed oxygen production, processing it through photosynthesis from carbon dioxide and consuming it through respiration.

The undergrowth in some areas of a rainforest can be restricted by poor penetration of sunlight to ground level. If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines, shrubs and small trees, called a jungle. The term jungle is also sometimes applied to tropical rainforests generally.

Rainforests as well as endemic rainforest species are rapidly disappearing due to deforestation, the resulting habitat loss and pollution of the atmosphere.

Stratification (vegetation)

Stratification in the field of ecology refers to the vertical layering of a habitat; the arrangement of vegetation in layers. It classifies the layers (sing. stratum, pl. strata) of vegetation largely according to the different heights to which their plants grow. The individual layers are inhabited by different animal and plant communities (stratozones).

Temperate coniferous forest

Temperate coniferous forest is a terrestrial habitat type defined by the World Wide Fund for Nature. Temperate coniferous forests are found predominantly in areas with warm summers and cool winters, and vary in their kinds of plant life. In some, needleleaf trees dominate, while others are home primarily to broadleaf evergreen trees or a mix of both tree types. A separate habitat type, the tropical coniferous forests, occurs in more tropical climates.

Temperate coniferous forests are common in the coastal areas of regions that have mild winters and heavy rainfall, or inland in drier climates or montane areas. Many species of trees inhabit these forests including pine, cedar, fir, and redwood. The understory also contains a wide variety of herbaceous and shrub species. Temperate coniferous forests sustain the highest levels of biomass in any terrestrial ecosystem and are notable for trees of massive proportions in temperate rainforest regions.Structurally, these forests are rather simple, consisting of 2 layers generally: an overstory and understory. However, some forests may support a layer of shrubs. Pine forests support an herbaceous groundlayer that may be dominated by grasses and forbs that lend themselves to ecologically important wildfires. In contrast, the moist conditions found in temperate rain forests favor the dominance by ferns and some forbs.Temperate rain forests only occur in 7 regions around the world - the Pacific Northwest, the Validivian forests of southwestern South America, the rain forests of New Zealand and Tasmania, the Northeastern Atlantic (small, isolated pockets in Ireland, Scotland, and Iceland), southwestern Japan, and those of the eastern Black Sea).Forest communities dominated by huge trees (e.g., giant sequoia, Sequoiadendron gigantea; redwood, Sequoia sempervirens; mountain ash, Eucalyptus regnans), an unusual ecological phenomena, occur in western North America, southwestern South America, as well as in the Australasian region in such areas as southeastern Australia and northern New Zealand.The Klamath-Siskiyou ecoregion of western North America harbors diverse and unusual assemblages and displays notable endemism for a number of plant and animal taxa.

Theobroma

Theobroma is a genus of flowering plants in the mallow family, Malvaceae, that is sometimes classified as a member of Sterculiaceae. It contains roughly 20 species of small understory trees native to the tropical forests of Central and South America. The generic name is derived from the Greek words θεός (theos), meaning "god," and βρῶμα (broma), meaning "food". It translates to "food of the gods."

Theobroma cacao, the best known species of the genus, is used for making chocolate.

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 equatorial evergreen rainforest. True rainforests are typically found between 10 degrees north and south of the equator (see map); they are a sub-set of the tropical forest biome that occurs roughly within the 28 degree latitudes (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest (or tropical wet forest) that also includes the more extensive seasonal tropical forests.

Woodland

A woodland (listen) or wood (or in the U.S., the plurale tantum woods) is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of primary or secondary succession. Higher density areas of trees with a largely closed canopy that provides extensive and nearly continuous shade are referred to as forests.

Extensive efforts by conservationist groups have been made to preserve woodlands from urbanization and agriculture: the woodlands of Northwest Indiana being an example, having been preserved as part of the Indiana Dunes.

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