Changes in Communities Succession Changes in Communities

What is Succession? The orderly process of change over time in a community. Occurs both on land and water

Primary Succession Succession in a newly formed area Occurs in new lakes, ponds, cooled lava, sand dunes and bare rock Takes place in areas that have never previously supported life Ex - rock -> lichen -> moss -> grass -> shrub -> trees -> oak hickory forest

Secondary Succession Sometimes an storms or fire destroy the species growing in a community. Succession resumes again until there is a climax community. Succession that occurs where an area has been disturbed. Ex - grass -> shrub -> trees -> oak hickory forest

Secondary Succession Human activities usually cause secondary succession. Cutting for timber Clearing for farming Construction Some Natural Causes Forest fires Volcanoes Hurricanes Tornados

Stages of Succession Pioneer Community First inhabitants of the area r-strategists Ex. Lichen and mosses

Sere A set of communities that succeed one another over the course of succession at a given location Succession from start to finish

Stage of Successsion Seral Stages – stages at which species are replaced through competition Ex – grasses, small herbs, shrubs, coniferous trees Climax Community – final stage of succession. Ecosystem has stopped changing Reached a state of permanence

Climax Community High stability High species diversity Complex food chains K-strategists Ex. oak - hickory trees

To sum up During succession species modify the environment making it more suitable for new species Pioneer species are often poor competitors and are replaced by stronger competitors with greater environmental demand Later communities are more complex than the communities they replace. Animated link

Zonation The sub-classification of biomes into smaller zones that share unique physical characteristics. A unique habitat that will favor various species will in turn exist in these zones.

Comparison of Structure of Early and Late Succession Immature Ecosystem Small plant size Low species diversity Mostly producers, few decomposers Few ecological niches (generalized) Low community organization Mature Ecosystem Large plant size High species diversity Mixture of producers, consumers and decomposers Many ecological niches (specialized) High community organization

Comparison of Function of Early and Late Succession Immature Ecosystem Low biomass High primary productivity Simple food chains and webs (mostly plants herbivore with few decomposers Low efficiency of nutrient recycling Low efficiency of energy use Mature Ecosystem High biomass Low primary productivity Complex food chains and webs (dominated by decomposers) High efficiency of nutrient recycling High efficiency of energy use