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Ecosystems: What Are They and How Do They Work? Chapter 3 Sections 5-7 Soils • Origins of soils • Soil horizons: O, A, B, and C • Soil profiles • Infiltration and leaching Oak tree Wood sorrel Lords and ladies Dog violet Earthworm Fern Millipede Honey fungus Mole Grasses and Organic debris small shrubs builds up Moss and Rock fragments lichen O horizon Leaf litter A horizon Topsoil Bedrock B horizon Subsoil Immature soil Regolith Young soil Pseudoscorpion Mite C horizon Parent material Nematode Root system Red earth Springtail mite Actinomycetes Fungus Fig. 3-21, p. 51 Soil Profiles from Different Ecosystems Fig. 3-22, p. 52 Soil Profiles from Different Ecosystems Mosaic of closely packed pebbles, boulders Alkaline, dark, and rich in humus Weak humusmineral mixture Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Desert Soil (hot, dry climate) Clay, calcium compounds Grassland Soil (semiarid climate) Fig. 3-22a, p. 52 Soil Profiles from Different Ecosystems Forest litter leaf mold Acidic lightcolored humus Humus-mineral mixture Light-colored and acidic Light, grayishbrown, silt loam Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Acid litter and humus Humus and iron and aluminum compounds Dark brown Firm clay Deciduous Forest Soil (humid, mild climate) Coniferous Forest Soil (humid, cold climate) pH • Acidity or alkalinity of water or water-bearing samples • Scale 0-14 • Acidic: pH 0-6.9 • Neutral pH 7.0 • Alkaline (basic): pH 7.1-14 pH Scale Matter Cycling in Ecosystems: Biogeochemical Cycles • Nutrient (biogeochemical) cycles • Hydrologic (water) cycle • Carbon cycle • Nitrogen cycle • Phosphorus cycle • Sulfur cycle Simplified Hydrologic (Water) Cycle Condensation Rain clouds Transpiration Precipitation Precipitation to land Transpiration from plants Rapid Surface runoff (rapid) Evaporation Evaporation From ocean Precipitation Evaporation From ocean Precipitatio n to ocean Surface runoff (rapid) Infiltration and percolation Groundwater movement (slow) Ocean storage Fig. 3-24, p. 54 Human Intervention in the Hydrologic Cycle • Large withdraw of surface and ground waters • Clearing vegetation • Pollution The Carbon Cycle (Marine) Diffusion between atmosphere and ocean Carbon dioxide dissolved in ocean water photosynthesis Combustion of fossil fuels aerobic respiration Marine food webs Producers, consumers, decomposers, detritivores incorporation death, into sediments sedimentation uplifting over geologic time sedimentation Marine sediments, including formations with fossil fuels Fig. 3-25a, p. 56 The Carbon Cycle (Terrestrial) Atmosphere (most carbon is in carbon dioxide) Combustion of fossil fuels volcanic action Terrestrial rocks weathering photosynthesis aerobic respiration Land food webs Producers, consumers, decomposers, detritivores combustion of wood (for clearing land; or fuel) deforestaion Soil water (dissolved carbon) death, burial, compaction over geologic time Peat, fossil fuels leaching, runoff Fig. 3-25b, p. 57 Human Interference in the Global Carbon Cycle High projection Low projection Fig. 3-26, p. 56 The Nitrogen Cycle Gaseous Nitrogen (N2) in Atmosphere Nitrogen Fixation by industry for agriculture Food Webs on Land Fertilizers uptake by autotroph s excretion, death, decomposition uptake by autotroph s Nitrogen Fixation bacteria convert N2 to ammonia (NH3); this dissolves to form ammonium (NH4+) NH3, NH4+ in Soil loss by leaching Nitrogenous Wastes, Remains in Soil Ammonification NO3– in Soil by bacteria 2. Nitrification bacteria, fungi convert the residues to NH3; this dissolves to form NH4+ bacteria convert NO2– to nitrate (NO3–) 1. Nitrification NO2– in Soil bacteria convert NH4+ to nitrite (NO2–) Denitrification loss by leaching Fig. 3-27, p. 58 Human Interference in the Global Nitrogen Cycle Nitrogen fixation by natural processes Nitrogen Fig. 3-28, p. 58 The Phosphorus Cycle mining Fertilizer Guano excretion agriculture uptake by autotrophs Marine Food Webs uptake by autotrophs Dissolved in Ocean Water leaching, runoff Dissolved in Soil Water, Lakes, Rivers death, decomposition sedimentation Land Food Webs weathering weathering settling out uplifting over geologic time Marine Sediments Rocks Fig. 3-29, p. 59 The Sulfur Cycle Water Sulfur trioxide Ammonia Ammonium sulfate Oxygen Sulfur dioxide Acidic fog and precipitation Sulfuric acid Hydrogen sulfide Plants Volcano Dimethyl sulfide Animals Industries Ocean Sulfate salts Metallic Sulfide deposits Decaying matter Sulfur Hydrogen sulfide Fig. 3-30, p. 60