Plant Ecology EVE 117
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This 2 page Class Notes was uploaded by Raven Connelly on Tuesday September 8, 2015. The Class Notes belongs to EVE 117 at University of California - Davis taught by Staff in Fall. Since its upload, it has received 54 views. For similar materials see /class/187333/eve-117-university-of-california-davis in Evolution And Ecology at University of California - Davis.
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Date Created: 09/08/15
PLBEVE 117 Plant Ecology Fall 2003 1 Topic 16 R Pearcy Succession 1 De nitions and types of succession A De nition the nonseasonal directional and continuous pattern of colonization and extinction on a site by speciespopulations through time B Autogenic versus allogenic succession l allogenic succession is a change due to some externally imposed environmental change a changes in tree line because of a colder climate b example sedimentation in a salt marsh 2 autogenic succession is brought about by internal biological processes a shading by development of a tree canopy b accumulation of litter C Primary versus secondary succession applies primarily to autogenic succession 1 primary succession colonization and change on a previously unvegetated surface a succession around lake shores b succession on unvegetated rock surfaces c vegetation of glacial moraines as an example 2 secondary succession colonization of disturbed areas that were previously vegetated a 0 1e s b re c shifting agriculture 11 Models ofplant succession A the traditional view is l and r 39 leading to a stable endpoint the climax community 2 one speciescommunity paves the way for another B modem view indicates that it is much more complex with no single quotcausequot or pathway C Alternative mechanisms underlying succession 1 Mode of species establishment a only early pioneers able to establish 1 dispersal seed and seedling bank seed dispersal 2 germination and seedling establishment only possible for these pioneers b any species can become established but pioneers better at dispersal c recolonization can occur by vegetative means 2 Modes of species replacement a early species facilitate later species early idea of F E Clements b early species have little or no effect on late species Late species simply persist longer and early species are suppressed c early species may inhibit development of late species delaying succession d relay floristics versus initial floristic composition hypotheses 3 The end point of succession a not an unchanging climax community per se but only a community that is relatively more stable in time a dynamic equilibrium b occurs when there are no more species that can successfully invade c disturbances and quotmicrosuccessionsquot in gaps important in species diversity u n 111 Characteristics of early and late successional plants PLBEVE 117 Plant Ecology Fall 2003 2 Topic 16 R Pearcy A Early successional plants 1 colonizers rapid growth high photosynthetic capacity short lifespan 2 rselected or in G1ime s model ruderals B Late successional plants 1 competitors perennials slower growth large investment in wood 2 kselected or in Grimes model competitive plants 3 Low photosynthetic capacity but large leaf area C An example from hedgerows in Germany IV Community and ecosystem consequences of succession A primary productivity greatest for early to intermediate stages B biomass greatest mid to late succession C diversity greatest in mid succession D accumulation of nutrients in biomass V Community and ecosystem stability A De ne in terms of speciespopulation composition or ecosystem function B Components of stability 1 resistance ability of a community to avoid change in the face of a disturbance 2 resilience ability of a community to recover from change Readings TEXT Chapter 13 The rst part of this chapter covers material on the ecological effects of and adaptation to disturbances such as re and wind The remainder of the chapter provides a good overview of succession and covers pretty much the same topics as in this outline though I will emphasize different examples Whittaker pp 1 71 185 See this section for a description of the bog lake succession and additional material on secondary succession in deciduous forests Study Questions 1 In your travels you come upon a small area in which the plant community clearly differs from the surrounding community You decide it is a successional community and that the surrounding community is closer to a quotclimaxquot community What would you look for to decide if the succession in this area was a primary or a secondary succession 2 Differentiate between an allogenic and an autogenic succession giving an example of each 3 You are able to travel in time and to revisit a farm in Pennsylvania initially established in 1870 To make way for the farm the trees were cleared and the land cultivated Alas by 1880 the farm was deemed uneconomical and abandoned You visit in 1881 1900 1920 1995 and in 2081 During which visit would you expect to see the greatest species diversity the greatest biomass The greatest annual biomass increment What changes would you expect to see from 1881 to 208 1 4 The classical view is that the climax community is stable and represents an undisturbed state Given what we know now how would you modify this statement so that it more clearly matches current thought
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