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Land and Water Use

Land and Water Use

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Land and Water Use

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  1. Land and Water Use Part 2

  2. Forestry

  3. Ecological Services • Providing wildlife habitat • Carbon sinks • Affecting local climate patterns • Purifying air and water • Reducing soil erosion • Providing energy and nutrient cycling

  4. Tree Plantations • Large, managed commercial farm with uniformly aged trees of one species

  5. Tree Plantations • Primary uses • Trees harvested by clearcutting

  6. Tree Plantations • Species choice

  7. Tree Plantations Pros Cons • Easy to harvest • Economical • More wood production • Little biodiversity • Damage to wetlands • Much smaller food webs • Little decaying wood

  8. Old-Growth Forests • Have not been seriously impacted by humans • Much biodiversity

  9. Old-Growth Forests • Depletion increases risk of climate change • High economic value, but mature slowly • Mahogany, oak

  10. Old-Growth Forests

  11. Forest Fires • Each forest is unique • Number of fires • Frequency of fires

  12. Changes in Forest Fires • Wild fire frequency has increased (4X average 1970-1986) • Area burned has increased (7X previous) • Wild fire season lengthened by 78 days

  13. Reasons for Changes • Appears to be linked to spring and summer temperatures • Fire management has changed

  14. Crown Fires • Occurs where no fires have occurred in long time • Extremely hot • Burn entire tree • Hop from tree to tree • Kills wildlife, increases soil erosion, destroys structures

  15. Yellowstone 1988

  16. Ground Fires • Occur underground and burn partially decayed leaves • Common in peat bogs • Difficult to detect and extinguish • Summer 2008 - Pocosin Lakes National Wildlife Refuge

  17. Surface Fires • Burns undergrowth and leaf litter. • Kills seedlings and small trees • Releases minerals back into soil • Stimulates germination • Control pathogens and insects

  18. Controlling Fires • Prevention • Prescribed burning

  19. Deforestation • Conversion of forested areas to non-forested areas

  20. Deforestation • Natural causes • Human reasons

  21. Results of Deforestation

  22. Methods to Manage and Harvest • Selective cutting • Strip cutting • Clear-cutting

  23. Clear Cutting Pros Cons • Practical method for trees that require full or moderate sunlight • Genetically improved – resist disease, grow faster • Increased economic returns • Produces high yield of timber • Provides jobs • Reduces recreational value of the land • Causes soil erosion, water pollution, flooding on steeply sloped surfaces • Reduces biodiversity • Decaying wood is absent

  24. Effect on Hydrologic Cycle • Decreased evapotranspiration • Lessens downwind precipitation • Increased runoff to rivers/ocean

  25. Causes of Deforestation • Growing number of poor • “Open-access property rights” • Entrepreneurs

  26. Forest Management • Forests cover 1/3 world land surface • Most forests in N. America, S. America, Russia • Forests cover 1/3 of US • 2/3 nonfederal

  27. Forest Management • Forest Service • 1905 • Agency of USDA • Manages public land in national forests and grasslands (193 million acres) • Logging, farming, recreation, hunting, fishing, mining, oil/gas extraction, livestock grazing