Life across secession environments

Succession Ecological succession" is the observed process of change in the species structure of an ecological community over time. Within any community some species may become less abundant over some time interval, or they may even vanish from the ecosystem altogether. Similarly, over some time interval, other species within the community may become more abundant, or new species may even invade into the community from adjacent ecosystems. This observed change over time in what is living in a particular ecosystem is "ecological succession".

Every species has a set of environmental conditions under which it will grow and reproduce most optimally. In a given ecosystem, and under that ecosystem's set of environmental conditions, those species that can grow the most efficiently and produce the most viable offspring will become the most abundant organisms. As long as the ecosystem's set of environmental conditions remains constant, those species optimally adapted to those conditions will flourish.

Ecological succession may occur when the conditions of an environment suddenly and drastically change. A forest fires, wind storms, and human activities like agriculture all greatly alter the conditions of an environment. These massive forces may also destroy species and thus alter the dynamics of the ecological community triggering a scramble for dominance among the species still present.

Stages of succession Primary succession Secondary Succession Climax community

Pond A: Cattails, bulrishes, and water lilies grow in the pond. These plants have their roots in the bottom of the pond, but they can reach above the surface of the water. This pond is an ideal habitat for the animals that must climb to the surface for oxygen. Aquatic insect larvae are abundant. They serve as food for larger insects, which in turn are food for crafish, frogs, salamanders, and turtles. Pond B: Plankton growth is rich enough to support animals that entered when the pond was connected to the lake. Fish make nests on the sandy bottom. Mussels crawl over the bottom. Pond C: Decayed bodies of plants and animals form a layer of humus over the bottom of the pond. Chara, a branching green algae, covers the humus. Fish that build nests on the bare bottom have been replacedby those that lay their eggs on the Chara. Pond D: The pond is so filled with vegetation that there are no longer any large areas of open water. Instead, the pond is filled with grasses. The water dries up during the summer months

The climax community in the area of Michigan is a beech-maple forest. After the ponds are filled in, the area will undergo another series of stages of succession. This is illustrated below. Briefly explain what is happening in the diagram below.

Primary Succession Primary succession begins when organisms move into a landscape previously devoid of all living things following a major disaster, such as the eruption of a volcano that completely destroys the prior environment. This succession involves a total rebuilding of the ecosystem. For example, primary succession requires the regeneration of nutritive soil, which can take centuries and which means the first generation of new plants will mostly be small shrubs and grasses.

Dune building Pioneer plants Grasses with long roots Pioneer Plants

Grey dunes The dunes by now have a more or less continuous plant cover, effectively anchoring the dune sand in one place. Where a series of dunes has formed at the back of the beach, this stage will be on the dunes further inland. Dune shrubs The build-up of humus from all the decaying vegetation of previous stages, means that the sand has by now developed into a poor sandy soil, capable of supporting pasture grasses and bushes. Bushes will develop on the tops and in the hollows of the dunes. These will include species such as

Trees climax ecosystem The final stage in dune stabilization is often achieved by planting conifers, such as Corsican Pine, which is very tolerant of salt. Even in the absence of tree planting, the dunes will eventually develop into woodland.

Secondary Succession Secondary succession also involves the influx of organisms, but in this case they are entering an environment damaged but not devoid of life. This would include, for example, an ecosystem harmed by wild fire or aggressive logging. In this scenario, plants return more rapidly and more robustly. For example, in addition to grasses and shrubs, hardwood trees would begin to grow much earlier. As a result, a full secondary succession progresses much more quickly.

The Major Points: The species living in a particular place gradually change over time as does the physical and chemical environment within that area. Succession takes place because through the processes of living, growing and reproducing, organisms interact with and affect the environment within an area, gradually changing it. Each species is adapted to thrive and compete best against other species under a very specific set of environmental conditions. If these conditions change, then the existing species will be outcompeted by a different set of species which are better adapted to the new conditions. The most often quoted examples of succession deal with plant succession. It is worth remembering that as plant communities change, so will the associated micro-organism, fungus and animal species. Succession involves the whole community, not just the plants.

Change in the plant species present in an area is one of the driving forces behind changes in animal species. This is because each plant species will have associated animal species which feed on it. The presence of these herbivore species will then dictate which particular carnivores are present. The structure or 'architecture' of the plant communities will also influence the animal species which can live in the microhabitats provided by the plants. Succession is directional. Different stages in a particular habitat succession can usually be accurately predicted. These stages, characterised by the presence of different communities, are known as 'seres'

Communities change gradually from one sere to another. The seres are not totally distinct from each other and one will tend to merge gradually into another, finally ending up with a 'climax' community. Succession will not go any further than the climax community. This is the final stage. This does not however, imply that there will be no further change. When large organisms in the climax community, such as trees, die and fall down, then new openings are created in which secondary succession will occur. Many thousands of different species might be involved in the community changes taking place over the course of a succession. For example, in the succession from freshwater to climax woodland.

The actual species involved in a succession in a particular area are controlled by such factors as the geology and history of the area, the climate, microclimate, weather, soil type and other environmental factors. For example, the species involved in a succession from open freshwater to climax woodland in Central Africa, would be quite different to those which have been quoted in these pages as occurring in Britain. However, the processes involved would be the same.

Succession occurs on many different timescales, ranging from a few days to hundreds of years. It may take hundreds of years for a climax woodland to develop, while the succession of invertebrates and fungi within a single cow pat (cow dung), may be over within as little as 3 months. By this time, the dung has been transformed into humus and nutrients and has been recycled back into the soil. The holes clearly visible in the cow pat (right) have been made by the animals which have colonized it.

Climax communities Characteristics The vegetation is tolerant of environmental conditions. It has a wide diversity of species, a well-drained spatial structure, and complex food chains. The climax ecosystem is balanced. There is equilibrium between gross primary production and total respiration, between energy used from sunlight and energy released by decomposition, between uptake of nutrients from the soil and the return of nutrient by litter fall to the soil. Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium. It is an index of the climate of the area. The life or growth forms indicate the climatic type.

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Animal life also exhibit changes with changing communities. In lichen stage the fauna is sparse. It comprises few mites, ants and spiders living in the cracks and crevices. The fauna undergoes a qualitative increase during herb grass stage. The animals found during this stage include nematodes, insects larvae, ants, spiders, mites, etc. The animal population increases and diversifies with the development of forest climax community. The fauna consists of invertebrates like slugs, snails, worms, millipedes, centipedes, ants, bugs; and vertebrates such as squirrels, foxes, mice, moles, snakes, various birds, salamanders and frogs.

What Animals Live in the Redwood Forest? There are numerous large animals that live in the redwood forest, some of which hikers must watch for as they can be dangerous. There are mountain lions, bobcats, black-tailed deer, elk, black bear and coyotes to name a few. Bobcats may be seen in the forest or open areas, and are active day and night. They have a bobbed tail, pointy ears with tufts and are gray to reddish in color. Mountain lions are a larger cat than bobcats and are tan in color with a long tail. Black bear are also active in the forest and open areas. If you see a black bear do not run, but stop and slowly back away while making noise. Most of these animals have no intention of hunting down humans, but can react harmfully if frightened or when threatened

Midsize animals are not as much of a worry to your safety as they are to your belongings. Leave your lunch out or your pack unattended and you may find that an animal--a raccoon for example--has claimed some of your goods as his own. There are gray foxes--one of the only canines that can climb trees--Coho Salmon, northern spotted owls, turkey vultures, river otters and beavers in the redwood forest. Some are specific to water, such as salmon otters and beavers, while others can be seen roaming all sorts of areas. Owls of course are mostly nocturnal but if you keep a watch during dusk you may be lucky enough to spot one. The northern spotted owl is an endangered species

A few of the many small animals that live in the redwood forest are the pacific giant salamander (which feed on banana slugs and are not much bigger than a quarter), Sonoma chipmunks, dusky-footed woodrat, western gray squirrels, Steller's jays and banana slugs, which are bright banana yellow. Water striders, also called water skaters, are just one of hundreds of insects inhabiting the forest and can be seen gliding atop water. Water striders eat other smaller insects and are themselves food for many others, such as the pacific giant salamanders. Many of the smaller animals feed on things such as nuts, seeds, fruit, buds and mushrooms as they are near the bottom of the food chain.

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