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Introduction of Habitat Type Classification System(HTCS)

Introduction of Habitat Type Classification System(HTCS). Xuan Yu A student of Forest Ecology, Penn state. Why HTCS?. Old classifications is not applicable for long term usage. advantage of HTCS Ecological based Easy to determine regardless of overstory Permanent. Premises of HTCS.

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Introduction of Habitat Type Classification System(HTCS)

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  1. Introduction of Habitat Type Classification System(HTCS) Xuan Yu A student of Forest Ecology, Penn state

  2. Why HTCS? • Old classifications is not applicable for long term usage. advantage of HTCS • Ecological based • Easy to determine regardless of overstory • Permanent

  3. Premises of HTCS Because of the premises have been researched deeply, so the implications should be examined. • 1 the vegetation reflects the sum of all environmental factors that affect plant growth; • 2 the climax stage of succession reflects the inherent productivity of a site better that any other stage; • 3 the understory vegetation stabilizes more quickly after disturbance than the midstory or overstory, and it is not necessary to have the climax or potential climax overstory in order to identify the habitat type; • 4 the climatic climax or potential climax is the same for all sites that have similar growing environments within a region.

  4. Evolution of Successional Theory • Clements: the predictable, unidirectional, community-oriented theory. • Gleason: Individual species-based environmentally random theory. Two theory of plant dynamics pointed out the importance of chance events. Alternative ideas resulted development of theory of succession.

  5. Challenge to the Clements Theory • the reaction process had not been proved to be as universal • competition between plants had rarely been clearly demonstrated and thus may not be as important as indicated by Clements • allelopathic effects had not been factored in and several of the mechanisms that drive succession can operate simultaneously.

  6. Alternative Theories • timing of species establishment • competition for space and resources • autecological characteristics (longevity, shade tolerance) • There was not a climax stage, no steady state was necessarily reached. • Disturbance -> pervasive and frequent

  7. Alternative Theories • Grime thinks any species with the appropriate strategy is likely to be present, and site quality interacts with sere. • The Vital Attribute Theory incorporated disturbance into the model and explicit demonstrated multiple pathways for a single site-type.

  8. Alternative Theories • no species exists that is capable of forming a climax • dissimilar factors may develop on similar sites. • Resource-Ratio Hypothesis proposed that successional change is driven by the ratio of two resources. • Life History Model relies on competition as driving force, no equilibrium is reached

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