Presentation on theme: " Succession is usually described as the orderly succession of communities to a climax community (biome) over time or as a sequence of communities (a."— Presentation transcript:
Succession is usually described as the orderly succession of communities to a climax community (biome) over time or as a sequence of communities (a sere) with each transitory community as a seral stage.
There are two main types of succession: 1. Primary succession which begins with bare rock exposed by geologic activity eg. sere: rock -> lichen -> moss -> grass -> shrub -> trees -> maple-beech -hemlock forest 2. Secondary succession which begins on soil from which a previous community has been removed (by fire, agriculture, etc.)
Secondary succession can proceed much faster because the soil has already been prepared by the previous community
Pioneer CommunityClimax Community Unfavorable environmentfavorable environment biomass increases quicklybiomass is generally stable energy consumption inefficient energy consumption efficient some nutrient lossNutrient cycling and recycling r - strategistsK - strategists low species diversity, habitat diversity, genetic diversity high species diversity, habitat diversity, genetic diversity
One thing that limits the carrying capacity, during succession for many organisms, is that the presence of these organisms (themselves) essentially alters the environment (eg. shade, pH, moisture, temperature, chemical composition) sufficiently so that it is no longer suitable for their own offspring to continue.
That is, the populations change the environment so drastically, both biotically and abiotically that it is now more suitable for other populations and less suitable for itself. This leads to the succession of one sere after another until a climax is reached and the changes in the environment are now not so drastic as to produce any further major changes.
Ecosystem characteristic Trends in ecological succession Food chainsSimple food chains becoming more complex food webs Relative Species abundance Changes rapidly first, changes slower in the later stages. Total biomassIncreasing Humus (non- living organic matter) Increasing Species diversity Low diversity in the early stages, then increasing in the intermediate stages and then stabilizing in the final stages as an equilibrium is approached
Ecosystem characteristicTrends in ecological succession Gross productivity (GP)Increasing during early stages of primary succession then little or no increase during final stages of secondary succession Net productivity (NP)Decreasing Respiration (R)Increasing
Ecosystem characteristicTrends in ecological succession Mineral cycles Becomes more self-contained in later stages Nutrient recycling Increases in later stages