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Lecture 19

BIOL215 Lecture 19 Notes.pdf

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Biology (Sci)
BIOL 215
Neil Price

BIOL215 Lecture 19 Notes Hyperparasite: Is a parasite of a parasite, often Hymenoptera. It is mainly found in the world of insect Primary succession describes the growth of plants on a substrate that is rock (not living, and never experienced a growth of a community before - i.e. Mt. St. Helene) In the case of Lupinus present on Mt. St. Helene, there were two processes: Chance event (probability) that seeds come in via birds or wind • • Effect of Lupinus as a species that facilitates or helps colonization for other species During primary succession, facilitation is one process where facilitating species modify the environment to make it less suitable for them more suitable for others (i.e. Alder trees fix nitrogen in soils) Another model of succession of how plants change over the course of time is inhibition (i.e. Abandoned tobacco fields in the Piedmont of North Caroline) The example of Broomsedge is a good example of inhibition model. Broomsedge inhibits establishment of aster by scavenging water and nutrients from soil near parent stems. Inhibition is the reverse of facilitation, instead of improving the soil for other species, inhibition species would take up all the resources in that site and exclude other species In all three model of succession, there is an element of chance and an element of what is the constitution of the communities around the place where succession is taking place that will determine which of those pathways will take place Colonization process, movement to newly created volcanic islands is well documented (primary succession): • Krakatoa in Java Straight • Surtsey near Iceland • Mt. St. Helene Indiana sand dunes (primary succession) example Secondary succession: A change in the habitat but a habitat that was already sustaining a biotic community (already a biological substrate) - i.e. Beaver dam forms pond Secondary succession can occur in other conditions. Inhibition is an example of secondary succession. Other examples include cutting down forests, changing wetlands Table 18.1 on physiological and life history characteristics of early and late-successional plants is tied into earlier lectures on the k and r selection in addition to Grim Triangle (stress tolerant, competition, and importance of disturbance) The old view: Climax as the end point of succession is the climax Climax: the final or stable community in a successional series. It is self-perpetuating and in equilibrium with the physical and biotic environment There are three main different views on climax: • Monoclimax (original proposal): In any place in the world, there is just one type of community that can live there; as a function of climate • Polyclimax: Depending on the physical environment (geographic condition, soil moisture, nutrients, rocks, etc.), you would have different communities • Climax-pattern: Responding to a range of ecological factors and with more than one climax type in a region; pattern of changes, seeing climax as quite mobile equilibrium with many species taking over the community depending on precise and specific conditions that have to do with geographic and climate (precipitation) Climax is rarely a deterministic, fixed endpoint of succession, but rather a continuum of endpoints, depending on soil conditions, among others The classical paradigm in ecology views ecosystem as stable The new paradigm views ecosystem as open and in non-equilibrium. Metler's wood (oaks) is an example Different communities can reach different equilibrium based on what is happening In intertidal communities, different succession occurs depending on clearing size. The size of the clearing will send the system to
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