Pit and mounds are small, persistent microtopographical features that present themselves after a disturbance event occurs and uproots trees via windthrow. The uprooted tree falls, and a pit forms in the forest floor where the root mass and associated soil matrix used to be. Eventually after a period of time in which the roots decay, the associated soil matrix that was pulled out of the ground with the roots falls back to the ground, creating a corresponding mound. [1]
A pit, as defined above, is formed when pressure is applied to the trunk and crown of the tree that is more powerful than the root and associated soil's ability to hold the tree upright and in place and knocks the tree down. This toppling of the tree can be caused by a multitude of different types of forest disturbance. Wind may blow the tree down; snow may accumulate and put excessive weight on the tree; the tree's roots may have decayed to a point where they are not strong enough to hold the tree upright. Soil conditions also play a role in the ability of the tree to remain upright. Wet soil can loosen the hold a tree's roots have on the soil, and dry soil can help hold the tree in place. [1] [2]
A mound, as defined above, is formed on average from five to ten years after the formation of a pit. The root mass must decay to an extent where the soil matrix that was suspended with it when it toppled over can slough off on to the ground near the corresponding pit. The necessity of the decay of the root mass is what causes this lag time. In more cold or dry climates, the rate of decay is slower and this time lag may be extended. [3] [2]
Pit and mounds always occur on a fine spatial scale, being the result of only one tree felling. Commonly they are a product of windthrow, but they can also be caused by other factors. Large amounts of snow accumulation on tree boughs or extensive root decay are other possible causes for tree uprooting. Pit and mounds have been analyzed on both on a small scale and larger scale forest systems. It has been observed that they can act as important soil disruptors and microsites for biodiversity and plant establishment. [4]
It has been observed that pit and mounds on an individual basis generally have specific climatic and pedological characteristics. Mounds are generally observed to be warmer and drier than the forest floor or the corresponding pit; Similarly, the pit is generally found to be colder and have a higher soil moisture content than either the forest floor or the mound. One notable instance where there is an exception to the general observation is when a snow layer has fallen. The pit becomes insulated by the snow layer and then in some instances is observed to be warmer than the mound.[ citation needed ]
Mounds receive the highest amount of photosynthetically active radiation (PAR) and pits the lowest amount. Pits also have much higher amounts of leaf litter than mounds, who have high tendencies to erode.[ citation needed ]
Studies on pit and mounds generally have at least five sampling sites per each pit and mound sampled. These areas, generally, are the top of the mound, bottom of the pit, side of the mound, edge of the pit, and an undisturbed forest floor area. [5] Studies have observed that both pits and mounds generally have lower carbon and nitrogen soil content than the undisturbed forest floor, although they have carbon to nitrogen ratios that are not significantly different from the ratios observed on the forest floor. [6]
Mounds are observed to be generally more nutrient poor and fewer plants establish on them in comparison to pits for several reasons. Mounds tend to erode and thus are more unstable than the forest floor or the pit. The surface of the mound also contains very little organic matter because it is mainly soil that was uprooted from the mineral horizons of the soil layer. This coupled with the observation that seed deposition rates are lower for mounds than pits, makes plant establishment on mounds unlikely and problematic for the plant. [6]
Conversely, many studies have found that species richness and overall number of established plants is found to be statistically higher on mounds than in pits. It was experimentally determined that the leaf litter accumulation that occurs within a pit has a large effect on the lack of species diversity or establishment that occurs there. In fact, when scientists removed the leaf litter and monitored the species establishment within the pit, it was found that the diversity and number began to resemble that that occurred on mounds. Multiple studies have found that on the forest floor a high or dense amount of leaf litter or dead organic matter corresponds to a low amount of species diversity as well. [7]
Little information is available on how macrofauna are affected by the presence of pit and mounds in a forested landscape. One would believe they would benefit from the presence of coarse woody debris as habitat and new flora that establish in the pit and mounds, but there is a lack of published evidence.[ citation needed ]
One macrofauna species that has received attention is the earthworm population in a lowland temperate rainforest of Belgium. It was observed that both earthworm speciation and biomass differed based on location within the pit and mound microsites examined. Undisturbed sites near the pit and mounds had the highest amount of species diversity and biomass compared to either a pit or a mound. The undisturbed sites contained species of earthworm that were not present in either the pit or mound sample site. An explanation towards why there were less earthworms present in the pit or mound was that within the mound there was more dry, mineralized soil present and less organic matter due to the uprooting of the tree. The pits examined were found to generally only contain one species of earthworm that was known to inhabit very moist soils. It was concluded that the pit microhabitat was too humid and water containing for most other species of earthworm. [8]
What aspects of pit and mounds can be generalized and what effects they exert of the dynamism of the forest can be generalized is a currently evolving narrative. As more scientific literature crops up from around the world, it becomes more apparent what aspects of the pit and mounds occur in most any biome they are found in. As it is, there is not enough scientific data to allow much extrapolation from forest to forest in regard to pit and mound knowledge.[ citation needed ]
Virtually all of the scientific knowledge about pit and mounds and their impact on forest heterogeneity and other dynamics comes from the Northern Hemisphere, particularly the Relic forests of Europe and the Temperate rainforests of Eastern Canada and Southeast Alaska. It can be argued that because pit and mounds occur on such a small scale, they may impact forest in the southern hemisphere in a different way. Until information is collected, it will be unknown.[ citation needed ]
Studies of pit and mound on a large time scale may be affected by the presence of herbivores in the area. A herbivore may preferentially browse certain seedlings that grow on either a pit or a mound and will mask any other variables that might be contributing to why those seedlings are establishing in a pit or mound by skewing the final counts of the growing plants. [7]
One would assume that on a microbial level a disturbance that results in a pit and mound event would lead to a greater heterogeneity on the microbial level as multiple soil horizons are uplifted and mixed. However, little scientific data exists on the microbial population and its changes due to a pit and mound creation.[ citation needed ]
There is no scientific data on the effects, if any, of either the synthetic or natural creation of pit and mounds in a managed forest and the effects it has on the growth or health of the forest.[ citation needed ]
Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoeing, and raking. Examples of draft-animal-powered or mechanized work include ploughing, rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth).
Lumbricus terrestris is a large, reddish worm species thought to be native to Western Europe, now widely distributed around the world. In some areas where it is an introduced species, some people consider it to be a significant pest for out-competing native worms.
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 ; they are a sub-set of the tropical forest biome that occurs roughly within the 28-degree latitudes. Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest that also includes the more extensive seasonal tropical forests.
Silviculture is the practice of controlling the growth, composition/structure, as well as quality of forests to meet values and needs, specifically timber production.
An old-growth forest, sometimes synonymous with primary forest, virgin forest, late seral forest, primeval forest, first-growth forest, or mature 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. The Food and Agriculture Organization of the United Nations defines primary forests as naturally regenerated forests of native tree species where there are no clearly visible indications of human activity and the ecological processes are not significantly disturbed. Barely one-third of the world's forests are primary forests. Old-growth features include diverse tree-related structures that provide diverse wildlife habitats that increases the biodiversity of the forested ecosystem. Virgin or first-growth forests are old-growth forests that have never been logged. 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.
Clearcutting, clearfelling or clearcut logging is a forestry/logging practice in which most or all trees in an area are uniformly cut down. Along with shelterwood and seed tree harvests, it is used by foresters to create certain types of forest ecosystems and to promote select species that require an abundance of sunlight or grow in large, even-age stands. Logging companies and forest-worker unions in some countries support the practice for scientific, safety and economic reasons, while detractors consider it a form of deforestation that destroys natural habitats and contributes to climate change. Environmentalists, traditional owners, local residents and others have regularly campaigned against clearcutting, including through the use of blockades and nonviolent direct action.
In forestry, windthrow refers to trees uprooted by wind. Breakage of the tree bole (trunk) instead of uprooting is called windsnap. Blowdown refers to both windthrow and windsnap.
The soil food web is the community of organisms living all or part of their lives in the soil. It describes a complex living system in the soil and how it interacts with the environment, plants, and animals.
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 unit consisting of all plants, animals, and micro-organisms in that area functioning together with all of the non-living physical (abiotic) factors of the environment.
A hydrosere is a plant succession which occurs in an area of fresh water such as in oxbow lakes and kettle lakes. In time, an area of open freshwater will naturally dry out, ultimately becoming woodland. During this change, a range of different landtypes such as swamp and marsh will succeed each other.
The Atlantic titi monkey or masked titi is a species of titi, a type of New World monkey, endemic to Brazil.
A tree throw or tree hole is a bowl-shaped cavity or depression created in the subsoil by a tree.
Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface. These organisms include earthworms, nematodes, protozoa, fungi, bacteria, different arthropods, as well as some reptiles, and species of burrowing mammals like gophers, moles and prairie dogs. Soil biology plays a vital role in determining many soil characteristics. The decomposition of organic matter by soil organisms has an immense influence on soil fertility, plant growth, soil structure, and carbon storage. As a relatively new science, much remains unknown about soil biology and its effect on soil ecosystems.
Rhamnus cathartica, the European buckthorn, common buckthorn, purging buckthorn, or just buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. It is native to Europe, northwest Africa and western Asia, from the central British Isles south to Morocco, and east to Kyrgyzstan. It was introduced to North America as an ornamental shrub in the early 19th century or perhaps before, and is now naturalized in the northern half of the continent, and is classified as an invasive plant in several US states and in Ontario, Canada.
Plant litter is dead plant material that have fallen to the ground. This detritus or dead organic material and its constituent nutrients are added to the top layer of soil, commonly known as the litter layer or O horizon. Litter is an important factor in ecosystem dynamics, as it is indicative of ecological productivity and may be useful in predicting regional nutrient cycling and soil fertility.
Invasive species of earthworms from the suborder Lumbricina have been expanding their range in North America. Their introduction can have marked effects on the nutrient cycles in temperate forests. These earthworms increase the cycling and leaching of nutrients by breaking up decaying organic matter and spreading it into the soil. Since plants native to these northern forests are evolutionarily adapted to the presence of thick layers of decaying organic matter, the introduction of worms can lead to loss of biodiversity as young plants face less nutrient-rich conditions. Some species of trees and other plants may be incapable of surviving such changes in available nutrients. This change in the plant diversity in turn affects other organisms and often leads to increased invasions of other exotic species as well as overall forest decline. They do not require a mate to reproduce, allowing them to spread faster.
Hügelkultur, literally mound bed or mound culture is a horticultural technique where a mound constructed from decaying wood debris and other compostable biomass plant materials is later planted as a raised bed. Adopted by permaculture advocates, it is suggested the technique helps to improve soil fertility, water retention, and soil warming, thus benefitting plants grown on or near such mounds.
Dendrodrilus rubidus is a species of earthworm in the family Lumbricidae. It is native to Europe, and it is a widespread introduced species, occurring on every continent except Antarctica, as well as many islands. It is often invasive. It is sometimes used as fishing bait, and is marketed under many nonspecific names, including red wiggler, jumping red wiggler, red trout worm, jumbo red worm, and pink worm. Other common names include bank worm, tree worm, and gilt tail.
The Japanese temperate rainforest is well sustained and maintains a high biodiversity. One method that has been utilized in maintaining the health of forests in Japan has been afforestation. The Japanese government and private businesses have set up multiple projects to plant native tree species in open areas scattered throughout the country. This practice has resulted in shifts in forest structure and a healthy temperate rainforest that maintains a high biodiversity.
Mor humus is a form of forest floor humus occurring mostly in coniferous forests. Mor humus consists of evergreen needles and woody debris that litter the forest floor. This litter is slow to decompose, in part due to their chemical composition, but also because of the generally cool and wet conditions where mor humus is found. This results in low bacterial activity and an absence of earthworms and other soil fauna. Because of this, most of the organic matter decomposition in mor humus is carried out by fungi.