Horn (1976) makes this explicit by referring to a 'competitive hierarchy' underlying the succession. Establishment of farms formed patch work of habitats in varying stages of recovery from human disturbances.Within the context of changes over ecological time succession can be identifies or classified as:Growth rate fast slowCompetitive ability low(? E.g.
can occur through the production of a secondary chemical . Pre-colonial hardwood-conifer forest mix. The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction..
Inhibition is the competitive exclusion of a species from a community by the activity of another species.
The disturbance should sufficiently large such that intermediate replacement by neighbors is not possible. WillowCompetition important in replacement sequenceTest of the Connell/Slayter ModelDetermine if later colonist succeed by differential resistance to physical environment vs. later species outcompete early arriving species. Number many fewPre-colonial hardwood-conifer forest mix. He saw a homology between spatial sequences of zones of vegetation visible at one time in a landscape, and the long-term sequences of vegetative types on a single site.Sitka Spruce (invades at high nutrient levels)Frequency of reproduction many fewWherever indicators were out of sequence succession was occurring.Dispersal ability high lowGleason view was term "poly-climax" some physical factor that determined the climax species.Clements was a plant ecologist who studies plant communities in North America at a time when there were many disturbed forest areas.
slopes on hill dominated by hickory and oak, in valleys by beech and maple.Mechanisms of succession suggested by Connell and Slatyer.Not in the sense of succession over geological time where changes in biota reflect changes in the physical enviroment. Algae recruit by spores, physical factors are wave action and desiccation, biological factors is grazing.Size small large He could describe patterns of successional change and experimentally determine the mechanisms for these changes.50 100 years Alder (nitrogen fixer)Succession is the response of a community to a disturbance that opens a relatively large area for invasion, or reoccupation by organisms. These patterns of succession are not determined by inherent properties of the system because they results from major changes in the environment.His view of succession was developed from this patchwork pattern.
Secondary succession occurs due to disturbance.