Lecture_3_Biomes

Lecture_3_Biomes - Inglobalterms, levels McNeill&Winiwarter,2004 Soil Erosion in Alabama Erosionratesfrom to

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In global terms, the past 60 years have brought human-induced  soil erosion and destruction of soil ecosystems to un-precedented  levels.   Soil Erosion in Alabama Soil Erosion in Alabama Photo by Arthur Rothstein Photo by Arthur Rothstein
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“Erosion rates from  conventionally plowed  agricultural fields average 1  to 2 orders of magnitude  (i.e.  100 to 1,000 times)  greater  than rates of soil production”  (Montgomery 2007)  Severe soil erosion in a wheat field near Washington State Severe soil erosion in a wheat field near Washington State     University University Photo courtesy USDA  Photo courtesy USDA  ARS ARS  Photo credit Jack Dykinga  Photo credit Jack Dykinga
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Biomes
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Biome  = a major unit of vegetation, used for  classifying communities at a global scale.   The fundamental characteristic defining the concept  is the growth form of the plants.   Each biome is associated with a particular climatic  regime and soil type. 
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Global distribution of biomes Notice the relationship between precipitation and temperature and  biomes distribution. 
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Profile ten biomes  L = latitude C = climate S = soil B = biota HI = human impact
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1. Desert  20% of the earth’s land surface L: ~30 o C: 0 – 500 mm annual precip.    S: low OM, high salt, caliche ( aridisols ) B: high diversity/low abundance, 4 desert types in AZ: Mojave, Sonoran,  Chihuahuan, Colorado Plateau HI: humans are  increasing  the land area covered by deserts AND decreasing  the diversity of them.
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Photo by Brad Hinkel Photo by Brad Hinkel
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L: ~ 30 – 40  o S: low – moderate fertility, highly erosive  aridisols . B: Many evergreen plants, fire adapted plants and animals
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This note was uploaded on 04/12/2011 for the course BIO 326 taught by Professor Gehring,c during the Spring '08 term at N. Arizona.

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Lecture_3_Biomes - Inglobalterms, levels McNeill&Winiwarter,2004 Soil Erosion in Alabama Erosionratesfrom to

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