Rated 4. Awesome Book - by Reema , book. Buy it at best price from here Rs. Click Here. Refresh Refresh Prices. Store Price Buy Now How long would it take for you to read The Herbaceous Layer in Forests of Eastern North America Life Sciences Depending on your reading style, this is how much time you would take to complete reading this book. Openings are a result of tree death due to small impact disturbances such as wind, low-intensity fires, and tree diseases.
Old-growth forests are unique, usually having multiple horizontal layers of vegetation representing a variety of tree species , age classes, and sizes, as well as "pit and mound" soil shape with well-established fungal nets.
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Thus, sometimes higher biological diversity can be sustained in old-growth forest, or at least a biodiversity that is different from other forest stages. The characteristic topography of much old-growth forest consists of pits and mounds. Mounds are caused by decaying fallen trees, and pits tree throws by the roots pulled out of the ground when trees fall due to natural causes, including being pushed over by animals. Pits expose humus -poor, mineral -rich soil and often collect moisture and fallen leaves, forming a thick organic layer that is able to nurture certain types of organisms.
Mounds provide a place free of leaf inundation and saturation, where other types of organisms thrive. Standing snags provide food sources and habitat for many types of organisms. In particular, many species of dead-wood predators such as woodpeckers must have standing snags available for feeding. In North America, the spotted owl is well known for needing standing snags for nesting habitat. Fallen timber, or coarse woody debris , contributes carbon -rich organic matter directly to the soil , providing a substrate for mosses , fungi, and seedlings , and creating microhabitats by creating relief on the forest floor.
In some ecosystems such as the temperate rain forest of the North American Pacific coast , fallen timber may become nurse logs , providing a substrate for seedling trees. Intact soils harbor many life forms that rely on them. Intact soils generally have very well-defined horizons, or soil profiles. Different organisms may need certain well-defined soil horizons to live, while many trees need well-structured soils free of disturbance to thrive.
Some herbaceous plants in northern hardwood forests must have thick duff layers which are part of the soil profile.
Fungal ecosystems are essential for efficient in-situ recycling of nutrients back into the entire ecosystem. Stand age can also be used to categorize forest as old-growth. This method is useful, because it allows quick and objective determination of forest stage.
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However, this definition does not provide explanation about forest function. It just gives a useful number to measure. So, some forests may be excluded from being categorized as old-growth even if they have old-growth attributes just because they are too young. Also, older forests can lack some old-growth attributes and be categorized as old-growth just because they are so old. The idea of using age is also problematic, because human activities can influence the forest in varied ways. From a forest dynamics perspective, old-growth forest is in a stage that follows understory reinitiation stage.
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Of importance is that while the stand switches from one tree community to another, the stand will not necessarily go through old-growth stage between those stages. Some tree species have relatively open canopy. That allows more shade-tolerant tree species to establish below even before understory reinitiation stage. The shade-tolerant trees eventually outcompete the main canopy trees in stem-exclusion stage. Therefore, the dominant tree species will change, but the forest will still be in stem-exclusion stage until the shade tolerant species reach old growth stage.
Tree species succession may change tree species' composition once the old-growth stage has been achieved. For example, an old boreal forest may contain some large aspen trees, which may die and be replaced by smaller balsam fir or black spruce. Consequently, the forest will switch back to understory reinitiation stage. However, in some forest ecosystems, this can lead to decisions regarding the preservation of unique stands or attributes that will disappear over the next few decades because of natural succession processes.
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Consequently, using stand dynamics to define old-growth forest is more accurate in forests where the species that constitute old-growth have long lifespans and succession is slow. Common cultural definitions and common denominators regarding what comprises old-growth forest, and of the variables that define, constitute and embody old-growth forests include:.
The debate over old-growth definitions has been inextricably linked with a complex range of social perceptions about wilderness preservation, aesthetics, and spirituality, as well as economic or industrial values. In logging terms, old-growth stands are past the economic optimum for harvesting — usually between 80— years, depending on the species.
The Layers of a Forest From Floor to Canopy
Old growth forests were often given harvesting priority because they had the most commercially valuable timber, they were considered to be at greater risk of deterioration through root rot or insect infestation, and they occupied land that could be used for more productive second-growth stands. A scientific symposium in Canada found that defining old growth in a scientifically meaningful, yet policy-relevant, manner presents some basic difficulties, especially if a simple, unambiguous, and rigorous scientific definition is sought.
Symposium participants identified some attributes of late-successional, temperate-zone, old-growth forest types that could be considered in developing an index of "old-growthness" and for defining old-growth forests: .
Old-growth forests provide ecosystem services that may be far more important to society than their use as a source of raw materials. These services include making breathable air, making pure water, carbon storage, regeneration of nutrients, maintenance of soils, pest control by insectivorous bats and insects, micro- and macro-climate control, and the storage of a wide variety of genes.
The effects of old-growth forests in relation to global warming has been contested in various studies and journals. Forest Ecology and Management 1 : Barkman J. Doing H. Segal S. Acta Botanica Neerlandica BULiGL Chapin F. The mineral nutrition of wild plants. Annual Review of Ecology and Systematics Dafni A. Cohen D.
Noy-Mier I. Life-cycle variation in geophytes. Annals of the Missouri Botanical Garden 68 4 : Dixon R. Brown S. Houghton R. Solomon A. Trexler M. Wisniewski J. Carbon pools and flux of global forest ecosystems. Science Gilliam F. Interactions of fire with nutrients in the herbaceous layer of a nutrient-poor Coastal Plain forest. Bulletin of the Torrey Botanical Club 4 : The ecological significance of the herbaceous layer in temperate forest ecosystems.
Bioscience Roberts M. The herbaceous layer in forests of eastern North America. New York. Oxford University Press. ISBN: Studia Naturae Jurko A. Estimation of the above-ground biomass of the herb layer in forest communities. Folia Geobotanica et Phytotaxonomica