1 / 51

1958: Bryce Canyon National Park

1958: Bryce Canyon National Park. 1970. 1991. Vegetation dynamics. Also known as plant succession Sequence of compositional and structural vegetation changes through time Why study succession?. Succession. Pragmatic reasons: forest management, invasive species, climate change, restoration.

dieter
Download Presentation

1958: Bryce Canyon National Park

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 1958: Bryce Canyon National Park

  2. 1970

  3. 1991

  4. Vegetation dynamics • Also known as plant succession • Sequence of compositional and structural vegetation changes through time • Why study succession?

  5. Succession • Pragmatic reasons: forest management, invasive species, climate change, restoration

  6. Succession • Study of succession raises other questions: • How is nature organized? • Are communities highly integrated or are they more individualistic?

  7. Succession • Two types of succession • Primary • Secondary

  8. Early views on ecological change • Pervasive order, nature as clockwork of God • Nature has telos, a guiding hand to development • Change is to admit imperfection • Succession (and evolution) runs counter to religious doctrine • Nature as a cathedral, holy and timeless, without change, a static view of nature

  9. Early views on ecological change • Darwin • Originally held religious, static views of nature • Observation of competition in nature contradicted the perfection of holy design • Competition, natural selection drives change • Change and flux in nature accepted • No telos: there is no external, god-like entity orchestrating natural selection towards an endpoint in a rigid, predetermined way.

  10. History of plant succession • Holistic, organismal views (Clements) • Individualistic views (Gleason, Whittaker, Watt, Egler) • Ecosystem ecology and resurgence of holistic, organismal views (Odum) • Disturbance and non-equilibrium ecology • Synthesis views that combine holistic and individualistic perspectives

  11. Frederic Clements (1874-1945) Key terms associated with his facilitation model of succession: immutable deterministic equilibrial organismal holistic superorganismal orderly integrated

  12. Contributions of Clements • Defined primary and secondary succession • Popularized a misleading concept often abused: nature will always grow back to its climax state • Immutable pioneer-to-climax sequence brought out critics who saw natural disturbance as overlooked phenomena • Introduced idea that evolution works at higher levels than the individual • Superorganismal concept has been discredited, but he still receives undue criticism---he had a much more nuanced conception of a climax

  13. Henry Allen Gleason (1882-1975) Key terms associated with his continuum concept: individualistic reductionist random contingent non-equilibrial disorganized

  14. Contributions of Gleason • Not acknowledged for 30 years because of the shadow of Clements • Contributed todevelopment of non-equilibrium ecology • His work allowed for a much richer possibility of new and novel plant communities • Idea of loosely organized plant communities has been abused: if nature is unorganized, then why worry about human impacts, right?

  15. The decline of Clementsian dominance and the turn toward Gleasonian individualism • Dust Bowl (1930’s) • Chestnut blight (1950’s) • Scholars • R.H. Whittaker • Frank Egler • A.S. Watt

  16. American chestnut (Castanea dentata)

  17. R.H. Whittaker (1920–1980) IndividualisticGleasonian Mathematical Gradient analysisSmoky Mountains

  18. Individual species, not entire populations, replace each other during succession. • In absence of disturbance or environmental discontinuities (a sudden change in soil type or topography) boundaries between plant communities are not sharp.

  19. A.S. Watt (1947) Gap phase dynamics Endogenous disturbance Stability through constant change Dynamic equilibrium Space time substitution

  20. Gap phase dynamics

  21. Space-time substitution in a chronosequence

  22. F. Egler’s (1954) Initial relay floristics model of succession IndividualisticContingentNovelty Life history traits

  23. Life history traits

  24. Initial relay floristics (Egler) • Grasses and forbs (A) • r-selected, efficient long-distance dispersal, fast-growing, shade intolerant • Pines (B) • Shade intolerant, intermediate growth rate • Oaks ,hickories (C) • C: k-selected, more local dispersal, slow growing, shade tolerant

  25. The rise of ecosystem approaches to the study of succession: revising Clementsian ideas of development and equilibrium Eugene Odum (1913-2002) Systems ecology Ecosystems Holistic Community controlled Equilibrium Biomass Mutualisms Zero growth economy HomeostasisScale

  26. Odum: the strategy of ecosystem development (1969) • Successionis orderly, directional, and predictable • Succession is community-controlled, though physical environment often sets limits • Culminates in a stabilized ecosystem in which a maximum in biomass and mutualisms are maintained for the available energy flow. • Strategy of succession is increased control of, or homeostasis with, the physical environment to achieve maximum protection from its perturbations.

  27. Rejection of equilibrium views and questions about how to incorporate expogenous disturbance

More Related