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Topic 11 Changes in a community Ecological succession Ecological succession: • Natural, gradual changes in the types of species that live in an area Primary Succession Primary Succession Primary Succession Primary Succession Primary Succession Primary Succession Climax Community • A stable group of plants and animals that is the “end” result of the succession process • Does not always mean big trees – Grasses in prairies – Cacti in deserts Succession of species pioneer species lichens & mosses compete well in high sunlight grasses climax forest shade tolerant species stable community bushes & small trees trees What causes succession? • Tolerance of early species • Facilitation & Inhibition – early species facilitate habitat changes – allows other species to out-compete Changes in abiotic factors over time Abiotic factor Soil quantity Soil quality Soil water retention How it changes Why it changes Benefits to later succession Changes in abiotic factors over time Abiotic factor Light availability Temperature Nitrogen or phosphorus How it changes Why it changes Benefits to/ impacts on succession Changes in abiotic factors over time Abiotic factor How it changes Soil quantity Increases Soil quality Improves Soil water retention Increases Why it changes Benefits to succession More detritus increases humus Provides more area for plants to anchor their roots in Gains organic matter Provides more nutrients for plant growth Increased organic matter retains more water; shading decreases evaporation More water is available for plants Changes in abiotic factors over time Abiotic factor How it changes Why it changes Light availability Decreases Shading increases over time Temperature Shading increases over time Decreases Nitrogen or phosphorus Increases Increased N fixation, Increased decomposition Benefits to/ impacts on succession Favors shade-tolerant species and inhibits shade-intolerants Favors heat-intolerant species and inhibits plants that need higher temps. Favors plants with higher N or P requirements Secondary succession • Occurs after a disturbance that leaves the soil intact – – – – Fire Massive storm Forest clear-cutting Death of a large mature tree • Also occurs in abandoned agricultural fields Disturbances as natural cycle - release nutrients - increases biodiversity - increases habitats - rejuvenates community Fire climax species adaptations to survive and reproduce in areas that experience frequent fires Jack pine Scenarios • A massive landslide occurs leaving completely bare bedrock behind. • A forest is completely uprooted by a tornado. • What is the immediate effect on the ecosystem? • What are the ongoing long-term effects on succession? • What is the immediate effect on the ecosystem? • What are the ongoing long-term effects on succession? .
