Lecture 15 - Forests

how much of land is covered by forests?

25%

What climatic factors are required for forests to grow?

• precipitation

What type of forest biomes exist?

• boreal (taiga)

• temperate

• tropical

Where are forest biomes found?

high latitude - boreal

midlatitudes - temperate

low latitudes - tropical

Boreal Forest (Taiga)

• large terrestrial biome

• high elevation

• low latitudes

• lower temp

• short growing season

• acidic soils

• major trees are evergreens (coniferous trees)

Temperate Forest

• distinct seasons

• fertile soils

  • bc leaves fall

• rich and diverse plant life

• trees are primarily evergreens and deciduous trees (leaf bearing)

• sufferer of habitat fragmentation

Tropical Forest

• similar year-round temps

• dry tropical forests

  • distinct wet and dry seasons

• tropical rainforests wet year round

• soil is thin, acidic, poor in nutrients

  • nutrient cycle happens fast, so much productivity, photosynthesis year round

  • residence time (N in soil) very very short

    • nutrient poor soil

What environmental problems does Haiti suffer that the Dominican Republic is less vulnerable to?

• heavy deforestation

• poverty

• lethal landslides, soil erosion

• can’t regrow

• less water absorbed into the soil

• less shade, more hot

  • soil dries out more

• flooding

Forests provide a range of goods and services. What are they?

• foods

• paper

• furniture

• houses

• habitat for biodiversity

• aesthetic value

• cultural and recreation purposes

cultural role of forests

• over 200 indigenous groups in the Amazon rainforest

• Acadian/Wabanaki forest and Mi’kmaq territory have similar boundaries

urban forests

• oxygen, clean air

• absorb, noise, dust, pollution, CO2

• provide shade/energy conservation/extreme temps

• reduce storm water runoff

• reduce mental health problems and can improve post surgery recovery rates

• habitats for wildlife

over the past 300 years, how much of the world’s forests have been lost?

35%

history of deforestation

• Near East, Greece, and Roman Empire cut forests before modern era

• Removal of forests continued northward in Europe as civilization advanced

• Great Britain’s forests were cut and many forested areas eliminated

• Colonization of the new world, much of North America was cleared (Half of the US was originally forested)

• Today, majority of deforestation is occurring in the developing world

deforestation in North America

• propelled population/societal growth

• land cleared from east to west for agriculture

• wood used to fuel furnaces of industry

• principal cause of deforstation in Canada is agriculture

reasons for deforestation

• Harvesting forests for wood and wood products

• Fuel in developing countries

• Conversion of forests for agriculture

• Urbanization and energy needs in the city

types of harvesting methods

• clear-cut

• selective harvesting

• shelterwood harvesting

clear-cut

cutting all trees in an area - very damaging

• high profit initially

• water muddy - erosion

• tree all same age when they regrow - less biodiversity

selective harvesting

cuts only the highest value trees; remaining trees reseed the plot

• more environmentally sound

• in temperate forests

shelterwood harvesting

cuts all BUT the best trees, which reseed the plot and are then harvested

• more environmentally sound

• genetically superior

• in temperate forests

why clear cut vs selective/shelterwood in the boreal vs temperate forests

clear cut - boreal

• mimics large scale disturbances

  • forest fires

  • insects

selective/shelterwood in temperate

• mimics natural falling and turnover of trees

how does the presence of roads lead to loss of forests?

• opens access to more forests

• fragments the habitat

all methods of forest disturb habitat

• change structure and composition

  • decrease biodiversity

• increase erosion, siltation, runoff, flooding, landslides

Maximum sustainable yield (MSY)

harvesting as much as is sustainably possible (but no more) for the greatest economic benefit

• The early focus of the National Forest Service

Forest ecosystem management (FEM)

a system that focuses on managing the forest as a whole rather than for maximizing yields of a specific product

• Utilizes a variety of techniques for timber harvesting, vegetation removal, and controlled burns

Explain how the sustainable harvesting of forest products, which provides less annual income than harvesting the trees themselves for timber, can be more economically valuable than the wholesale removal of the valuable timber in that forest

• no high profit initially

• long term income

  • as forests regrow, you can cut more trees from the same area

• this saves money as not as much money will be needed to replant/repair the clear cut forest

  • water purification

  • eco tourism