Ecological Succession

Ecological Succession Process by which communities in a particular area change over time Early communities modify the environment causing change to occur This affects biological community as well How?

Each successive (new) community is more favorable for new species Changes in stages until a climax community is established

Composition of the community changes with time Past Community Future Community Present Community Some species in the past community were out-competed, and/or did not tolerate altered abiotic conditions Modifies such abiotic factors as: Light intensity Wind speed Air Temperature Soil composition Light quality Wind direction Soil water Humidity Changes allow new species to become established.

Primary Succession Regions with no existing community Bare rock Receded glaciers Volcanic regions Krakatoa, Glacier Bay Climax Community Lichens, bryophytes And annual herbs Slower growing broadleaf species Grasses and Small shrubs Fast growing trees Bare Rock 100-200 years

Pioneer Species First organisms to live in a new community. Usually brought in by wind or animals

Secondary Succession Takes place after a land clearance Fire, landslide, forest clearing Soil is already there More rapid than primary Climax Community Open pioneer community (annual grasses) Mature woodland mainly oak Primary bare earth Grasses and low growing perennials Scrub: shrubs and small trees Young broad- leaved woodland 150+ 1-2 years 3-5 years 16-30 years 31-150

Gap Succession In a forested area with a thick canopy Reduced light on soil When a tree falls sunlight fills forest floor New communities are formed

Wetland Ecological Succession In open body of water, aquatic plants are introduced Increase in aquatic plants causes sedimentation Swamps may occur and in warmer months may dry off May lead to EUTROPHICATION More production (photosynthesis) Lead to reduced oxygen and fish kills Natural and anthropogenic Type of pollution

Aerial view of Lake 227 in 1994. Note the bright green colour caused by algae stimulated by the experimental addition of phosphorus for the 26th consecutive year. Lake 305 in the background is unfertilized.