Physical Geography by Alan Arbogast. Chapter 10. Plant Geography. Plant Geography. Photosynthesis. Process of photosynthesis

Transcription

1 Physical Geography by Alan Arbogast Chapter 10 Plant Geography Lawrence McGlinn Department of Geography State University of New York - New Paltz Plant Geography Process of photosynthesis Character & distribution of global biomes Local & regional influences on vegetation Human influence on vegetation patterns Photosynthesis Solar radiation converted to chemical energy 6H 2 O + 6CO 2 + light energy = C 6 H 12 O 6 + 6O 2 Water + Carbon Dioxide + Light Energy = Glucose + Oxygen Produces almost all oxygen in Earth s atmosphere 1

2 Photosynthesis, Respiration, and Decomposition Cycles (Follow sequence 1-9) Biomass Dry weight of all living organisms in an area (kg/m 2 ). Global Biomass Character & Distribution of Biomes Most important factor in geographic distribution of vegetation is climate Secondary factors: geology, soils, lanscape position, human behavior Biome geographic region mapped according to dominant vegetation & organisms Ecosystem community of organisms linked by energy and nutrient flows 2

3 Four Categories of Biomes Forest Grassland Desert Tundra Ecotone wide transitional area between biomes more common than sharp boundaries Forest Biomes Tropical Rainforest equatorial region Af & part of Am climate dense, diverse, evergreen vegetation 4 layers of growth Forest Biomes Tropical Deciduous Forest & Scrub Am & humid parts of Aw climate transition forestscrub leaf loss in dry season shrubs Deciduous Forest Scrub 3

4 Forest Biomes Midlatitude Deciduous Forest Cfa & Cwa, Dfa, Dwa, Dwb climates Dense canopy of broadleaf trees in summer Loses leaves in fall In eastern US, oak, maple & elm common In North America, stretches from Gulf of Mexico to SE Canada Forest Biomes Mediterranean Woodland & Shrub Forest Csa & Csb climates lower midlatitude west coasts dense, woody shrubs fire adaptation Forest Biomes Midlatitude Coniferous Forest needleleaf evergreen trees H, Cfa, Cfb, Cfc, Cwa climates west coast & mts of N. America, SE US, Eastern Europe moister regions support temperate rainforest 4

5 Forest Biomes Boreal Forest coniferous forest covering much of Canada, Russia & Alaska Dfc, Dwc, Dwd climates low diversity, low productivity pine, spruce, fir trees stunted on northern edge of biome Grassland Biomes Tropical Savanna low latitude grasslands with isolated trees & shrubs Aw climate moister areas more trees beneficial dry season wildfires Grassland Biomes Midlatitude Grassland dominant vegetation is grass dry parts Dfa, Dwa, Dfb, Dwb climates, and Bsk climate central N. America, South Africa, eastern Europe, central Asia, Argentina 5

6 Desert Biomes Hot & Dry Desert subtropical, centered on 30º N & S Bwh climate Sahara, Kalahari, Mohave Deserts bare ground to xerophytic plants Desert Biomes Semi-Arid & Cold Desert western N. America & central Asia Bwk climate bare patches to low, spiny, wooly plants, e.g. mesquite, sagebrush, creosote bush Tundra Biome Borders Arctic Ocean across N. American & Russia ET climate grasses, shrubs, sedges, mosses, & lichens all short easily damaged 6

7 Geography of Biomes Local & Regional Influences on Vegetation Slope & Aspect Vertical Zonation Plant Succession Riparian Zones Slope & Aspect Slope degree of steepness of an area Steep slopes have drier, thinner soils, less nutrients available Aspect orientation of slope (N, S, E, W) Insolation intensity depends on aspect Slope facing sun warmer & drier Trees more common on slope away from sun Grasses & shrubs more common facing sun 7

8 Slope & Aspect Vertical Zonation Change in vegetation based on elevation rather than latitude H climate Higher elevations cooler/colder than below Treeline is elevation above which conditions too harsh for trees transition to alpine tundra Snow & ice above tundra Vertical Zonation 8

9 Plant Succession Natural changes in a biome over time trend toward more complexity, Climax Vegetation Primary succession on new sediments Secondary succession in an area disturbed by fire or other catastrophic event Initial plants change conditions so each different, later set of plants can establish and thrive Plant Succession Riparian Zones Areas immediately adjacent to streams Greater moisture available for plants In arid or semi-arid regions, riparian zones support denser vegetation than surroundings Trees along a streambed in a semi-arid environment Human Influence on Vegetation Patterns Deforestation large tracts of land cleared of trees for commercial use or for agriculture 2.4% of world forest lost in 1990s (232 million acres) most in tropical Africa & S. America Deforestation may intensify climate change as burning increases atmospheric CO 2 Massive deforestation in US, also Upper Midwest and Northwest 9

10 Deforestation Brazil slash and burn Washington State clear cut Deforestation Human Influence on Vegetation Patterns Agriculture in midlatitude grassland Only 1% to 4% of virgin prairie left in Great Plains The rest has been developed or used for intensive agriculture Overgrazing too many sheep or cattle on too little land vegetation is stripped, slow to come back weeds establish in bare areas & erosion Remote Sensing & the Biosphere 10