Zoology 360 - Lecture Notes 11/9/09 Threats to Ecosystems and their functioning Kathryn Amatangelo Why do we care about ecosystems? -Basic species can?t exist without ecosystems -Conservation efforts Ecosystem function: Water cycle -Atmosphere -> Precipitation -> Soil water, Water bodies -> Evaporation Mineral-Nutrient Cycle (Rock-derived nutrients) -Rock -> Weathering -> Microbes and Soils -> Plants -> Herbivores -> Carnivores -> Decomposition Nitrogen Cycle -Atmosphere -> Microbes and Soils -> Plants -> Herbivores -> Carnivores -> Decomposition Energy Flow -Sun -> Plants -> Herbivores -> Carnivores -> Decomposition -> Microbes and Soils The importance of soil -Transportation -Composition -Holding Capacity -?Leaky? Humus formation -Tree -> leaf -> microbes -> Humus Soil Components -50% air and water -45% minerals -5% organic matter : 10% plants, 10% animals, 80% humus Microbes -99% diversity What leads to distinct ecosystems? -Pine forests -Grasslands -Volcanic flow -Terrestrial vs. Aquatic Species Pool -What species are available to colonize an area? -Higher # of species colonizes closest from mainland -Lower # of species colonize far from mainland Resources -Altering one resource can affect other species even ones with no direct use on that resource Natural disturbance -Fire -> natural fire regimes, ground layer or canopy fires -Fire structured communities -Midwest Prairies (Fires 5-10 yrs) -California Chaparrel (Fires 20 yrs) -Shrub lands -Jack Pine Forests (Fires 120-180 yrs) -Kirkland?s Warbler -Tides -Treefall -Hurricanes -Floods -Vegetation Trampling -Etc. Human Impacts -Altered Ecosystems -Increase with populations of humans -Habitat loss Vulnerable Ecosystems -Temperate Forests -Logging pressures -Only ~ 40% remain -Tropical Forests -Projected vulnerability -Agriculture pressures Deforestation - Soil erosion -Downstream affects on Water quality -Can prevent restoration -Alters suitability for agriculture -Very degraded in mountains -Too much sloping Deforestation - Fragmentation -Different sizes -Edge effects -More weedy Resource changes : water input and timing -Exponential increase -Continental runoff -Precipitation/temperature Example: Middle Rio Grande -Flooding pressures - dams created -Low availability for water -Decreased by ~40% -Invasion by salt-cedar (deep roots) -Real problem due to its deep roots -Accumulates salt in foliage -Allows some other plants to grow in soils -Last flood in 1940 -Trying to restore natural hydrology -However: human settlements Climate Changes: global warming -More of a problem for plants than animals -Animals can move -Plants stuck -Some talk of collecting seeds and transplanting Does diversity affect ecosystem function Extinction -Humans increasing extinction rates Species Invasion -1% left after earthworm invasion Negative impacts in Hawaii -Feral pigs -Insects -> Malaria Jessica Steig ZOO - 11/9/09.pdf
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