Ecosystem - Wikipedia
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into This would, in turn, limit the abundance of animals that feed. Figure 1 Distribution of current protected areas in relation to intact forest . Data availability and gaps for species diversity. are incorporated into the Key Biodiversity Area approach, including the Red List of Species, the Red List. Species interactions form the basis for many ecosystem properties and processes such as nutrient cycling and food webs. These are not the only types of species interactions, just the most studied . An important difference between herbivory and predation is that herbivory does . 2, (Sineaur Associates, Inc. , ).
Decomposition The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production and returns carbon dioxide to the atmosphere or water where it can be used for photosynthesis.
In the absence of decomposition, the dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem and are considered lost to it.
Leaching is more important in wet environments and much less important in dry ones. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or barkand cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.
Freeze-thaw cycles and cycles of wetting and drying also fragment dead material. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down ligninwhich allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources. It also affects soil moisture, which slows microbial growth and reduces leaching.
Freeze-thaw cycles also affect decomposition—freezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.
Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen this is especially true in wetlandswhich slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow albeit at a slower rate even after soils become too dry to support plant growth. Nutrient cycle and Biogeochemical cycle Biological nitrogen cycling Ecosystems continually exchange energy and carbon with the wider environment.
Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixationis deposited through precipitation, dust, gases or is applied as fertilizer.
Nitrogen cycle Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production. Nitrogen-fixing bacteria either live symbiotically with plants or live freely in the soil.
Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophswhich carry out photosynthesis.Roles of Species in Ecosystems
Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi, and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil.
This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes especially in the tropics.
Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter. Ecosystem diversity Loch Lomond in Scotland forms a relatively isolated ecosystem.
The fish community of this lake has remained stable over a long period until a number of introductions in the s restructured it's food web. Biodiversity plays an important role in ecosystem functioning.
Ecological effects of biodiversity
The nature of the organisms—the species, functional groups and trophic levels to which they belong—dictates the sorts of actions these individuals are capable of carrying out and the relative efficiency with which they do so. Ecologically distinct species, on the other hand, have a much larger effect.
Similarly, dominant species have a large effect on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.
The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply.
These changes play out in changes in net primary production decomposition rates, and other ecosystem processes. Many governments maintain unrealistically low taxes on rural land, while allowing settlers to establish title to 'virgin' land by converting it to farmland. Thus wealthy landowners can keep huge, underused estates at little or no cost, while land-hungry peasants are encouraged to clear forests to establish marginal holdings.
Reforms of tax and tenure systems could increase productivity on existing holdings and reduce the pressures to expand cultivation into forests and upland watersheds.
Well-designed ecosystem conservation contributes to the predominant' goals of sustainable development in a number of ways. Safeguards for critical tracts of wildlands can serve also to safeguard agricultural land, for example. This is particularly true for upland forests of the tropics, which protect valley fields from floods and erosion, and waterways and irrigation systems from siltation.
A case in point is the Duraoga-Bone Reserve in Indonesia's northern Sulawesi, covering some 3, square kilometres of upland forest.
It protects large populations of most of Sulawesi's endemic mammals, and many of the island's 80 endemic bird species. It also protects the Dumoga Valley Irrigation Scheme, funded by a World Bank loan, set up in the flatlands below to achieve a tripling of rice production on more then 13, hectares of prime agricultural land.
One conclusion from this connection is that governments could think of 'parks for development', insofar as parks serve the dual purpose of protection for species habitats and development processes at the same time.
Does greater species diversity lead to greater stability in ecosystems | gtfd.info
National efforts to anticipate and prevent the adverse consequences of development policies in any of these areas would surely yield much more for species conservation than all the measures of the past 10 years in support of park building, ranger patrols, anti-poaching units, and the other conventional forms of wildlife preservation. The 3rd World Congress on National Parks, held in Bali, Indonesia, in Octoberbrought this message from protected area managers to the policy makers of the world, demonstrating the many contributions that protected areas managed in the modern way are making to sustaining human society.
International Action for National Species Species and their genetic resources - whatever their origins - plainly supply benefits to all human beings. Wild genetic resources from Mexico and Central America serve the needs of maize growers and consumers globally.
The principal cocoa-growing nations are in West Africa, while the genetic resources on which modern cocoa plantations depend for their continued productivity are found in the forests of western Amazonia. Coffee growers and drinkers depend for the health of the crop on constant supplies of new genetic material from coffee's wild relatives, principally located in Ethiopia. Brazil, which supplies wild rubber germplasm to Southeast Asia's rubber plantation, itself depends on germplasm supplies from diverse parts of the world to sustain its sugar-cane, soybean, and other leading crops.
Without access to foreign sources of fresh germplasm year by year, the nations of Europe and North America would quickly find their agricultural output declining. The Earth's endowment of species and natural ecosystems will soon be seen as assets to be conserved and managed for the benefit of all humanity. This will necessarily add the challenge of species conservation to the international political agenda. At the heart of the issue lies the fact that there is often a conflict between the short-term economic interest of the individual nations and the long-term interest of sustainable development and potential economic gains of the world community at large.
A major thrust in actions to conserve genetic diversity must therefore be directed at making it more economically attractive both in the short term and in the longer perspective to protect wild species and their ecosystems. Developing countries must be ensured an equitable share of the economic profit from the use of genes for commercial purposes. Some Current Initiatives A number of international measures are already being tried.
But they are limited in scope, only partially successful, and reactive in nature. Its World Heritage Fund supports the management of a handful of exceptional ecosystems around the world, but all these activities receive small budgets.
UNESCO has sought to establish a global system of Biosphere Reserves representing the Earth's 'biotic provinces' and harbouring sample communities of species.
But their combined activities are tiny in the face of the large needs. Among national agencies, the U. Agency for International Development leads the field in recognizing the value of species conservation.
Legislation passed by the U. This service, which is available to all, can help ensure that development projects are designed with full information available about the species and ecosystems that might be affected. Technical assistance is also available for nations, sectors, and organizations interested in establishing local data bases for their own applications.
Species problems tend to be perceived largely in scientific and conservationist terms rather than as a leading economic and resource concern. Thus the issue lacks political clout. One important initiative that attempts to put conservation more squarely on the agenda of international development concerns has been the Tropical Forestry Action Plan.
The broad-based effort proposes the formulation of national forestry reviews, national forestry plans, identification of new projects, enhanced cooperation between development aid agencies at work in the forestry sector. Establishing norms and procedures with respect to resource issues is at least as important as increased funding. Precedents for such norms include the Convention on Wetlands of International Importance, the Convention on Conservation of Islands for Science both of which safeguard prime habitats and their speciesand the Convention on International Trade in Endangered Species.