References Abstract Habitat fragmentation is the process by which habitat loss results in the division of large, continuous habitats into smaller, more isolated remnants.
See Article History Ecological disturbance, an event or force, of nonbiological or biological origin, that brings about mortality to organisms and changes in their spatial patterning in the ecosystems they inhabit. Disturbance plays a significant role in shaping the structure of individual populations and the character of whole ecosystems.
Minor disturbances include localized wind events, droughtsfloodssmall wildland firesand disease outbreaks in plant and animal populations. The notion of ecological disturbance has deep historical roots in ecological thinking; the first conceptual disturbance-related model in modern ecology was ecological successionan idea emphasizing the progressive changes in ecosystem structure that follow a disturbance.
Characteristics of disturbance and recovery The ecological impact of a disturbance is dependent on its intensity and frequency, on the spatial distribution or the spatial pattern and size of the disturbed patches, and on the scale the spatial extent of the disturbance.
Disturbance intensity and the pace of Pattern in ecological community The change a terrestrial ecosystem experiences as it recovers from a disturbance depends on the intensity and magnitude of the disturbance.
The major mechanisms of recovery in such ecosystems are primary and secondary succession. Primary succession occurs in a landscape that previously was devoid of life.
For example, following the retreat of the ice sheets in North America and Eurasia, plants invaded, and a biological recovery was initiated across regions that once had been incapable of sustaining life. In secondary successionwhich follows a disturbance in an area with existing communities of organisms, biological remnants such as buried seeds survive, and the recovery process begins sooner.
For example, the blast from the eruption of Mount St.
Helens devastated some square km some square miles. Some areas were effectively sterilized, but in other areas organisms survived underground or in patches covered by snow. Primary successionPrimary succession begins in barren areas, such as on bare rock exposed by a retreating glacier.
The first inhabitants are lichens or plants—those that can survive in such an environment. These grasses further modify the soil, which is then colonized by other types of plants.
Each successive stage modifies the habitat by altering the amount of shade and the composition of the soil. The final stage of succession is a climax community, which is a very stable stage that can endure for hundreds of years.
Secondary successionSecondary succession follows a major disturbance, such as a fire or a flood. The stages of secondary succession are similar to those of primary succession; however, primary succession always begins on a barren surface, whereas secondary succession begins in environments that already possess soil.
In addition, through a process called old-field succession, farmland that has been abandoned may undergo secondary succession. Although the complex mechanisms of succession in marine ecosystems are not well understood, the recovery of these ecosystems is likewise affected by disturbance intensity.
However, some of these communities needed to be recolonized by propagulesspores in this case other kinds of propagules include seeds and eggscoming from other beds hundreds of miles away. In both terrestrial and marine ecosystems, the spatial scale of natural disturbances, which is known to span about 10 orders of magnitude, is important.
For example, a drought that might devastate protozoans in a temporary pond would be inconsequential to an elephant. A single tree uprooted by a hurricane is a disaster for the resident antsbut it may become a necessary resource for forest frogs as sufficient water collects around the root cavity.
Likewise, while a fire may decimate wildlife populations and scorch large areas of land, the cones of the northern jack pine Pinus banksianawhich are tiny in comparison, require the presence of fire to open.
For instance, Jamaican coral reefs were subjected to an extended period of anthropogenic human-caused disturbance during the 20th century, which was characterized primarily by the overharvesting of herbivorous fishes and by pollution. Superimposed on this pattern of persistent degradation was a series of large natural disturbances, including intense hurricanes in and and the near-total die-off of Diadema antillarum a species of sea urchin that began in This crowding of the sunlight-infused layer of the ocean creates an alternative state for the ecosystem that can only support small numbers of D.
Conversely, disturbance-dependent species suffer when disturbance frequency declines. The unusual sea palm Postelsia palmaeformis is a kelp found on marine rocky shores of North America that are exposed to extreme wave scouring.
Winter waves produce patches or gaps in the surrounding beds of the California mussel Mytilus californianus.
If these bouts of winter disturbance are frequent enough, the sea palm flourishes. However, at sites characterized by minimal or infrequent wave scouring, it is absent. The biology of pin cherries Prunus pensylvanica illustrates an extension of this theme.Handout Understanding Children in Context: The Ecological Model of Human Development Socialization always occurs in a context and any specific context is embedded in a web of.
Habitat fragmentation is the process by which habitat loss results in the division of large, continuous habitats into smaller, more isolated remnants. Community ecology, study of the organization and functioning of communities, which are assemblages of interacting populations of the species living within a particular area or habitat.
As populations of species interact with one another, they form biological communities.
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Department of Independent Studies. A Pattern Language of Sustainability Ecological design and Permaculture. By Joanne Tippett. April, The assessment for this Achievement Standard will involve you carrying out a practical investigation to collect and interpret data to discuss the presence of observable community heartoftexashop.com community patterns will be selected from succession, stratification and/or zonation.
Moving from pattern to process in fungal symbioses: linking functional traits, community ecology and phylogenetics A growing appreciation of the ubiquity of plant–fungal sym-bioses and their fundamental importance to plant communi-ties (Smith & Read, ; Rodriguez et al., ) has led to.