Land and Water Use Part 2

Forestry

Ecological Services 1. Providing wildlife habitat 2. Carbon sinks 3. Affecting local climate patterns 4. Purifying air and water 5. Reducing soil erosion 6. 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

Old-Growth Forests

Forest Fires  Each forest is unique  Number of fires  Frequency of fires

Changes in Forest Fires  Wild fire frequency has increased (4X average )  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

Yellowstone 1988

Ground Fires  Occur underground and burn partially decayed leaves  Common in peat bogs  Difficult to detect and extinguish  Summer 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

Results of Deforestation

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 1.Growing number of poor 2.“Open-access property rights” 3.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