Describe ways in which plants and animals reshape the landscape during succession?

Question

How the process of succession results in the cicling of matter

Answer 1

Weed species from the Crucifer and the Goosefoot families, being annuals, are the first to colonize in many cases because they tolerate disturbed soils with altered pH and moisture content. They do not form symbiotic relationships with the fungi or beneficial soil bacteria that die with heavy soil disturbance. These soil bacteria & fungi (soil biota) are partially dependent on the carbohydrate exudate perennial plants secrete from their roots as food. As the surrounding perennial plants disperse seeds to recolonize in subsequent years the soil biota also become reestablished. In general plants that grow together support the same group of beneficial fungi and bacteria. They work together to suppress the pathogen populations.

This root zone relationship area is called the rhizosphere; the region influenced by roots. The fungus that is symbiotic provides protection from pathogens and soil nutrients the pant 's roots do not reach. This is means all the plants become interconnected underground through their roots to these fungi. Seedlings quickly establish connections so are supported by the established plants feeding the symbionts that extend a seedlings limited reach.

These types of fungus are called mycorrhizal partners. The species of plant is adapted to a specific species of fungus and together the are adapted to certain habitat conditions.

For example the sponge mushrooms like the morel (Morchella) form mycorrhizae with trees including Larix occidentalis, Pinus contorta, Pinus ponderosa, and Pseudotsuga menziesii (all members of the pine family, Pinaceae). The fungus also feeds itself by decomposing detritus so it also helps build soil structure that effects water retention. The decomposers, both fungi and bacteria, close the nutrient cycles returning organics to their inorganic components.



Another example, in a chaparral with alkaline to neutral soil that has a low rainfall, the bacterial actinomycetes will be found in climax associations with the non-leguminous plants (important species are bitterbrush, mountain mahogany, cliffrose, and ceanothus). There they decompose organic detritus (plant or animal) and fix nitrogen. hence these bacteria are also decomposers critical in creating soil structure or tilth.

Detritus is any dead animal or plant, whole or in parts including manure. Those that eat this material are the reducers including detritivores & decomposers.

Do not confuse soil dwelling detritivores, pillbugs, earthworms & springtails, that have the ability to swallow & digest dead plants or animals with decomposers. They are not decomposers. Decomposers breakdown organic compounds into inorganic forms outside their bodies then absorb what they need. This is the work of fungi and bacteria that other organisms cannot complete. They do work on dead material so these are a subclass of detrital feeders. The difference that sets them apart is mostly how far they break the organics down and the method of doing it that allows them to break molecules down to inorganics.

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