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Biology Lecture 1 Article 2.docx

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Scott Browning

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BIOLOGY LECTURE #1 Terrestrial Biomes: Biomes - Organizes large-scale ecological variation - Distinguished primarily by predominant beg - Determined by temp + rainfall (also determines types of plants that grow) - Height, density, species diversity DECREASES from warm wet climates to cool dry climate - RAUKIAER; classified plants based on trains that varied with climate - LOCATION OF PRENNATING ORGAN- tissues that give rise to new growth the following season, sensitive to climate conditions - Life forms vary with climate change - Life form spectra are more alike in similar climates on diff continents than they are in diff climates on same continent TROPICAL FOREST BIOME Where: areas centered on the equator (C + S, AM = ½ EA’s) Climate: little seasonal variation – high yearly rain + relatively constant warm temp Dominant plant: PHANEROPHYTES (trees, lianas, epiphytes) - emergent layer tall trees (40m+), overstory of trees up to 30 m, subcanopy of trees and tall shrubs, and ground layer of herbaceous veg - HIGHEST BIODIV + PRIMARY PRODUCTIVITY: - Net primary productivity: 2-3kgm y (+) -1 - High despite heavily leached, nutrient poor soils BECUZ litter decomp fast + rapid nutrient uptake from mycorrizhae - est. to have over half of the terrestrial species on EA - Composed of diff sub-biomes made from changes in seasonal patterns of rainfall/elevation/substrate (*)SAVANNA BIOME - Represents a transition from tropical forests to desert Where: N + S of tropical biomes (60% AFR) Climate: lower yearly rainfall and longer dry seasons Dominant plant: mix of grasses and small trees (drought decid) - Diff savannas can be distinguished by their trees and grass due to diff rainfall patterns, height of water tables, and soil depth - FIRE: long periods b/w fires INCREASE veg pop - Releases nutrients tied up in dead litter - Seeds + below ground rhizomes protected by soil (good thermal insulator) - HIGH HERBIVORE DIV + PRODUCTION mirrored by huge variety of predators and scav -2 -1 - Net primary productivity: 400-600g m y (depending on local con) - Decomp is fast and year-round + high annual turnover rate (60-80%) - Turnover = aided by rich div of large herb because a lot of biomass consumed + dung beetles help break down poo DESSERT BIOMES - a lot of variability in desert types Where: band around world bw 15-30 N + S lat (26-35% of EA) -1 Climate: low precip (below 250mm yr ) Dominant Plant: perennial shrubs with extensive roots and small leaves - Warm: therophytes (annual) make up species div: survive dry periods as seeds and stay in soil until right temp and rain, then germinate fast - Great deal of variation in biodiversity, productivity, and org in diff desert - Net primary productivity: low and extremely variable (exception: large bloom of annuals) near 0 – 120g m y -2 -1 - Positive relationship bw productivity and precip - Productivity will vary with soil depth and local drainage patterns GRASSLAND BIOME Where: interior continents Climate: large seasonal temp variations, with hot summers and cold winters Precip varies, with a strong summer peak - Grassland community + productivity DEPEND ON PRECIP
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