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Chapter 13

ENVS 137 Chapter Notes - Chapter 13: Sustainable Forest Management, Ecosystem Services, Maple Syrup


Department
Environmental Science
Course Code
ENVS 137
Professor
zahina-ramos
Chapter
13

Page:
of 7
CHAPTER 13: FOREST RESOURCES
13.1: The Values of Forests
● Hurricane Jeanne - caused national disaster in Haiti (only 3% forest due to deforestation)
while Dominican Republic (60% forest) was able to recover fairly quickly
● Extreme poverty is one of the causes of deforestation (consumed by immediate needs)
and powerful barrier to forest restoration and sustainable management (doomed cycle)
● Forest contain about 75% of world’s biodiversity
● Ecosystem services forests provide
β—‹ Flood prevention
β—‹ Maintenance of air and water quality
β—‹ Carbon storage
β—‹ Recreation
β—‹ Aesthetic beauty
β—‹ Wood and paper products ($500 billion to world economy every year)
β—‹ Important source of food clothing, medicine
Ecosystem Services
● Most services not assigned monetary value, BUT loss of these services when forests
disturbed/destroyed β†’ economic consequences
● Forests play a key role in hydrologic cycle (roots absorb water, water evaporates from
leaves) β†’ loss of forest often leads to decrease in rainfall
● Forests diminish the direct runoff of rainfall and reduce the risk of flooding, remove
sediments and dissolved chemicals from the runoff water.
● Forests store large amounts of carbon (photosynthesis β†’ remove carbon dioxide from
atmosphere and store) β†’ Deforestation reduces the total global forest carbon storage

β†’
More CO2 in the atmosphere
● Forests provide primary habitat for 60-80% of all terrestrial species(microbes, plants,
animals) β†’ biodiversity provides humans with many foodstuffs, clothing, building
materials, medicinal chemicals
● Ecotourism β†’ adds $200 billion to global economy, major part of GDP of some
developing countries
Wood Products
● Wood extracted from forests primarily used for fuel, paper, building materials
● Fuel from wood:

burned for fuel or made into charcoal β†’ mostly used/consumed/burned
in developing countries to heat homes, food, and water, charcoal burned for fuel
β—‹ Charcoal β†’ more efficient than wood but also releases pollutants (carbon
monoxide)
β—‹ Biofuel development β†’ convert wood cellulose into methanol or ethanol β†’ would
create much greater demand for wood β†’ further deforestation
● Building materials and solid wood products

:
β—‹ 68% of wood harvested for furniture, containers, musical instruments, etc. from
temperate evergreen and deciduous forests (esp. North America and Europe)
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β—‹ #2% from tropical forests (Southeast Asia and South and Central America) β†’
provide more valuable wood from old-growth forests)
● Paper production:
β—‹ Use of paper varies among regions
β—‹ Generally only smaller logs used to make paper β†’ plantations of fast-growing
trees (pine, eucalyptus)
β—‹ Complicated process including chemicals and bleach to make paper white
β—‹ Wood fiber use, ALSO air and water quality impacts β†’ production of 1 ton of
paper requires 7,000-10,000 gallons of water, chemicals used in process pollute
β—‹ Paper relatively easy to recycle β†’ process uses fewer chemicals, saves water
and trees, causes less air and water pollution
Non-Wood Forest Products
● ex. Cork, maple syrup, gums and resins, wild nuts and fruit, ginseng, mushrooms and
truffles, pharmaceuticals
● 80% of people in world’s poorest countries depend on non-wood forest products for
health and nutrition
● Non-wood products important sources of income
● Natural rubber β†’ $14.7 billion extracted from tropical forest trees (mostly from Asia and
Africa) β†’ rubber tree plantations
13.2: Forest Growth
● 3 levels of forest growth:
β—‹ Individual trees

- supported by growth in diameter of their stems
β—‹ Communities of trees (forest stands)

- develop over time, predictable changes in
species composition and structural complexity
β—‹ Large forested landscapes -

natural and human caused disturbances β†’ forest
patches undergoing different stages of development β†’ influence biodiversity,
goods and services
The Life History of a Tree
● Seed - embryo embedded in nutritive tissue and surrounded by a protective coat
● Trees classified in 2 major groups - based on structures in which seeds are produced:
1. Conifers - seeds grow in cones
2. Angiosperms - seeds grow in flowers and are eventually surrounded by fruits
● Seeds mature β†’ dispersed by wind, water, or animals
● Primary growth - upward (leaves) and downward (roots) growth when seed is
germinated β†’ occurs because of rapid cell division at tips of shoots and roots
● Carbohydrates transported down stem to roots in a thin layer of specialized tissue
(phloem - encircles stem just beneath protective bark)
● Water and mineral nutrients from soil transported up the stem in specialized tissue
xylem (most xylem cells are hollow with thick walls of cellulose and lignin β†’ woody
interior portion of stem)
● Secondary growth β†’ increase in girth (additional layers of xylem (wood) β†’ increase in
diameter)
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● Temperate and boreal climates - xylem growing in spring thinner, less dense than those
produced in summer β†’ difference in growth results in rings
● Tropical climates - trees grow year round β†’ xylem cell walls with uniform thickness β†’
annual rings do NOT form
The Life History of a Forest Stand
● 4 stages of succession: (after disturbance like fire/logging)
● Transition times between stages vary, but typically faster in tropical climates, and slower
in cooler climates
1. Establishment stage - tree seedlings germinate on recently cleared ground, abundant
light and soil resources β†’ grow quickly into saplings
a. Leafy branches of fastest growing trees β†’ create dense shade beneath canopy
β†’ intense competition for soil resources, light, water β†’ trees grow more slowly
b. survival of the fittest
2. Thinning stage
a. largest trees continue to grow, biomass of the forest increases
b. BUT total number of trees declines (b/c of intense competition β†’ limits the
establishment of new trees)
c. Even-aged because most trees became established at about the same time
d. End of thinning stage β†’ trees larger and more widely spaced, large trees die β†’
leave openings in forest canopy β†’ total biomass may decline
3. Transition stage (gap phase)
a. Increased light and reduced competition for soil resources β†’ tree seedlings to
become established in the gaps (typically shade tolerant trees)
b. Total biomass for forest remains relatively CONSTANT (new trees replace those
that die)
c. Diversity of trees increases
d. Uneven-aged
4. Old-growth stage
a. Transition forests (if not disturbed) β†’ accumulate more decaying logs and
standing snags
b. Very large, old trees and abundant woody debris
c. Complex structure β†’ variety of unique habitats and niches
d. Rich soil and favorable moisture β†’ diverse herbs
The Life History of a Forested Landscape
● Landscapes have many patches each with different stages of succession
● May extend over thousands of square kilometers β†’ mosaic of individual forest stands in
various stages of development (as a result of past disturbances), patches varied in size
● Biodiversity of transition and old-growth forests tends to DIMINISH if they are small and
fragmented
● Establishment stage patches β†’ store little carbon and have LOWER net ecosystem
production, subject to erosion and nutrient loss (if near streams)
● Thinning stage stands β†’ trees rapidly take up nutrients, small loss of nutrients to
streams, net ecosystem production HIGH, increasing amount of stored carbon
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