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Land and Water Use. Part 2. Forestry. Ecological Services. Providing wildlife habitat Carbon sinks Affecting local climate patterns Purifying air and water Reducing soil erosion Providing energy and nutrient cycling. Tree Plantations.
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Land and Water Use Part 2
Ecological Services • Providing wildlife habitat • Carbon sinks • Affecting local climate patterns • Purifying air and water • Reducing soil erosion • Providing energy and nutrient cycling
Tree Plantations • Large, managed commercial farm with uniformly aged trees of one species
Tree Plantations • Primary uses • Trees harvested by clearcutting
Tree Plantations • Species choice
Tree Plantations Pros Cons • Easy to harvest • Economical • More wood production • Little biodiversity • Damage to wetlands • Much smaller food webs • Little decaying wood
Old-Growth Forests • Have not been seriously impacted by humans • Much biodiversity
Old-Growth Forests • Depletion increases risk of climate change • High economic value, but mature slowly • Mahogany, oak
Forest Fires • Each forest is unique • Number of fires • Frequency of fires
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
Reasons for Changes • Appears to be linked to spring and summer temperatures • Fire management has changed
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
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
Surface Fires • Burns undergrowth and leaf litter. • Kills seedlings and small trees • Releases minerals back into soil • Stimulates germination • Control pathogens and insects
Controlling Fires • Prevention • Prescribed burning
Deforestation • Conversion of forested areas to non-forested areas
Deforestation • Natural causes • Human reasons
Methods to Manage and Harvest • Selective cutting • Strip cutting • Clear-cutting
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
Effect on Hydrologic Cycle • Decreased evapotranspiration • Lessens downwind precipitation • Increased runoff to rivers/ocean
Causes of Deforestation • Growing number of poor • “Open-access property rights” • Entrepreneurs
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
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