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Geography 1001: Climate & Vegetation Instructor: Andrés Holz Teaching Assistant: Eungul Lee Lecture 12: Wednesday June 28 • Review lecture 11 – Chapter 20 • Tundra: Properties – Arctic vs. Alpine Tundra – Chapter 19 • Basic terms – Ecology & Biogeography – Ecologies of » Individual » Population » Community definition & characteristics » Habitat & niche – Role of scale Lecture 12: Wednesday June 28 • Review lecture 11 • Ecosystem Components – – – – – Plants essential component NPP Abiotic & Biotic components Life zones Limiting factors • Biotic Ecosystem Operations – Producers, Consumers, and Decomposers – Food Chains and (Complex) Food Webs » Biomass consumption & Efficiency » Toxins accumulations Lecture 12: Wednesday June 28 • Lecture 12 – Chapter 19 • Ecosystems and Succession – Ecosystem Stability, Dynamics, and Diversity – Community Ecology & Ecological Succession » Historical views of a community » Conceptual issues » Clements versus Gleason • Changes of a community – Initial Floristic Composition versus Relay Floristics • Primary and Secondary succession Lecture 12: Wednesday June 28 • Lecture 12 – Chapter 19 • Ecosystems and Succession – Vegetation dynamics & Scale – Patch dynamics– role of disturbances (Historical shift…“catastrophic” versus normal process; e.g. fires, floods, etc…) – “Climax” concept – Vegetation dynamics » Terrestrial Succession Ecosystem Stability, Dynamics, and Diversity Stability – Inertia stability and resilience • resistance of an ecosystem to change • ability of an ecosystem to return to normal after a disturbance – What increases the stability of an ecosystem? • Diversity • Dynamics • Growth interaction reduction factors Ecosystem Stability, Dynamics, and Diversity • Diversity – (Bio) Diversity = richness*abundance*genes*habitat diversity • Dynamics (dynamic balance) – Biotic & abiotic factors enhancing growth – Disturbances & its regime • Size, frequency, intensity, severity, etc… Population Controlling Factors Growth interaction Reduction factors Figure 19.21 Ecosystem Stability, Dynamics, and Diversity – (Dynamic) equilibrium, and non-equilibrium • Various aspects of the ecosystem change from day to day, season to season, and year to year • Changes are within limits and are usually small • Only mature ecosystems are stable and in dynamic equilibrium • Mature ecosystems have resilience and inertia Ecosystem Stability and Diversity • The more diverse a community, the more or less stable the community? • The more stable a community, the higher/lower its inertia & resilience? • The higher the species diversity the greater the inertia and resilience of the ecosystem is. Agricultural Ecosystems Increase or decrease the resilience and general stability? At the short-term? At the mid- & long-term? Figure 19.23 Community Ecology & Ecological Succession • Historical views of a community – Conceptual issues • Clements versus Gleason • Changes of a community – Initial Floristic Composition versus Relay Floristics • Primary and Secondary succession • Vegetation dynamics & Scale • Patch dynamics– role of disturbances (Historical shift…“catastrophic” versus normal process; e.g. fires, floods, etc…) • “Climax” concept • Conceptual Issues – What is a community (Clements v Gleason) • Individualistic responses versus super-organism Community as super-organism (Clements) Comm. A B C UP DOWN any environmental gradient • Conceptual Issues – Community integrity (Clements v Gleason) • Individualistic responses versus super-organism INDIVIDUALISTIC RESPONSES (Gleason) UP DOWN any environmental gradient Community change: concepts Initial Floristic Composition Relay Floristics Comm. A B C Late Early Time Community change: concepts Initial Floristic Composition Relay Floristics Early The idea is that all species enter early on, but dominate at different points along the way Ecological Succession Figure 19.26 Ecological Succession • Def.: Succession refers to a directional change in species composition across space and time, • which usually include a change in spatial structure – (e.g. spruce fir regeneration within a lodgepole pine forest) – Primary – Secondary Mount St. Helens Mount St. Helens Mount St. Helens: primary or secondary succession? Forest fires: primary or secondary? Figure 19.27 Other examples of primary & secondary succession? Other examples of primary & secondary succession? Vegetation dynamics & Scale: a brief review of the basic concepts of forest dynamics • Vegetation dynamics – Is less deterministic than succession Patch dynamics “Shifting Mosaic” – includes succession and regeneration/maintenance dynamics Vegetation dynamics concepts • Regeneration/maintenance dynamics refers to: – a spatio-temporal change in structure – keeping the species composition constant (e.g. spruce fir regeneration within a spruce fir forest) Vegetation dynamics concepts • The dynamic part of the concept is emphasized by frequent occurrence of disturbances, which interrupt the successional pathway to a dynamic endpoint, and promote spatial heterogeneity The role of disturbances across scales • Spatial heterogeneity: At a stand scale The role of disturbances across scales • Spatial heterogeneity: At a landscape scale patch dynamics & the “shifting mosaic” Patch Dynamics “Shifting Mosaic” Climax concept – Largely viewed as a dead concept (but still in many books!) – Communities rarely reach a predetermined “equilibrium” – Disturbances promote a constant change, and heterogeneous environment