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LECTURE 21 – ECOLOGY & PLANT SUCCESSIONEcologyEcology: study of the effects of the environment on living organisms, the effect of living organisms on the environment, & the effects of living organisms on each otherPlant ecology: the interaction among plants & between plants and the environmentEcological hierarchyOrganisms  populations  communities  ecosystems  biospherePopulations- members of a single species living togetherCommunity- different populations living togetherEcosystem- community with all of its living & nonliving organismsBiosphere- all areas on earth in which organisms are foundPopulationPopulation: members of a single species living togetherHabitat: location where the population is foundAddress of an organismNiche: the functional role an organism plays in the ecosystemEncompasses habitat + relationships with other organisms in the ecosystemPlant communityPlant community: different populations of plants living together in the same geographical areaDominant species: the most influential species in the communityExample- Redwood forestControl structure & species composition of the community through physical factors & chemical factorsPhysical factors- light (provide shade), wind (wind screen), humidity (higher than in open areas)Chemical factors- nutrients, pHEcosystemEcosystem: community with all its living & nonliving organismsFunctional unit of study in the environmentBiotic- livingAbiotic- nonlivingAbiotic factorsClimate, light, soil, inorganic substancesBiogeochemical cyclesCarbon cycleCarbon dioxide enters plants through photosynthesisCarbon is released back into the air through respiration or combustion of fuelsFossil fuels- formed from remains of ancient organisms- oil, coal, gasHumans upset the balance of the carbon cycle- see greenhouse effectWater cycleWater enters the atmosphere as vapor from the land & transpiration from plantsTranspiration of large plant population like trees in a tropical rainforest can actually alter the rainfall patterns in the areaVapor condenses then turns into rainfall that goes into rivers, streams, & oceansNitrogen cycleNitrogen gas is fixed by bacteria in plant root nodulesPlants assimilate nitrogen & incorporate it into organic nitrogen compoundsAnimals assimilate nitrogen by ingesting plantsAnimal waste & organic nitrogen compounds are broken downNitrogenNot biologically available in the airPee is a useful typeHuman effectWe upset the nitrogen cycle because different pollution releases a lot of nitrogen into the atmosphereAlso excessive use of fertilizer turns into runoff & disturbs the cyclePhosphorus cycleBiosphereBiosphere: areas on earth in which organisms are foundAll of the communities on earthBiomass: the organic material in living organismsEcosphere: interactions among earth’s biosphere, atmosphere, water, & landFood chainsProducers/photosynthetic  1st order consumers/herbivores  2nd order consumers/carnivoresHerbivore- plant eater (primary consumer)Carnivore- meat eaterPrimary producers  primary consumers  secondary consumers  tertiary consumers  quaternary consumersTrophic level: each step in the food chain80-95% of energy is lost at each levelSo only 10% of energy is passed on at each levelBiomass is also reduced at each levelDetritus food chainDetritus- waste material left behind from other biological processesConsumers degrade the remains of plants & animals & their wasteConsumers- fungi & bacteriaFungi & bacteria are decomposers of dead material/nature’s recyclersFood webMore realistic than a food chain- multiple interactions between several food chainsUsually more than 1 producer & more than 1 primary consumerConsumers also have alternative food sourcesGreenhouse effectHumans upset the balance of the carbon cycle throughGlobal deforestation- main wayMore carbon dioxide released due to burning fuelsResult  25% increase in global carbon dioxideCarbon dioxide acts as a heat trap, capturing sunlight/solar energy, reradiates it back to the earth as heat  global warmingConsequence  global warming, earth’s temperature has increased 1 degree Fahrenheit & more is expectedLess agricultural areas, shifting northDiseases such as malaria are affecting more peopleOcean levels increase, increases floods & hurricanesPlant successionPlant succession: a series of predictable changes over time in the kinds of plants growing in an areaEcosystems mature & change with time (not static)Determined by the physical parameters in the environmentAs ecosystems age, the kinds of organisms change until a stable type of community formsInitial stages- unstable, high rate of replacementLater stages- more stable, low rate of changeClimax communityClimax community: relatively stable community at the end of successionIn equilibrium with the environmentPermanent until some major changeVaries depending on conditionsThe climax community may occur hundreds or thousands of years later2 types of succession- primary & secondary (see below)Primary successionPrimary succession: when plants become established on land completely devoid of soil & vegetationExample- new volcanic islandsPrimary succession begins as a pioneer speciesPioneer species: first inhabitants, forms the soilExample- fernsSoil is formed & thickensEventually the community is mature (climax)Forest habitatsPossible primary succession on forest habitatsLichens: very independent, attach to rocks, algae & fungi mixtureLichens  mosses  grasses  shrubs  treesPrimary succession begins as pioneer species (lichens & mosses) invade bare rockClimax community is spruce, fir, & birch forestSoil: portion of earth’s surface of disintegrated rock & organic materialsProvides essential nutrients to all plantsHolds water & mineral nutrientsProduct of the living environmentInfluenced byClimateTopography- mountains, valleys, etc.Parent material- soil particles of naturally occurring inorganic materialTime4.5 billion years ago, earth was a mixture of rocksTexture- all soils contain 3 kinds of particlesSand- small rocky materialSilt- very fine material, small particlesClay- most important, holds nutrients for plantsHumus: decomposing/decaying organic matter in the soilResults in nutrient rich soilSoil pH- acidic (low pH) or basic (high pH)Influences soil fertility & nutrient availabilityBest soil is neutral or slightly acidicSecondary successionSecondary succession: natural forces or human intervention destroy the existing vegetationFire, flooding,


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UMD BSCI 124 - LECTURE 21 – ECOLOGY & PLANT SUCCESSION

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