COMMUNITY%20AND%20ECOSYSTEM%20BIOLOGY

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COMMUNITY AND ECOSYSTEM BIOLOGY

• Biology 302

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NUTRIENT CYCLING

• READINGS for this lecture series
• KREBS cpt 27. Ecosystem Metabolism III
  Nutrient Cycles
• KREBS cpt 28. Ecosystem Health
• Human Impacts Pp 590 - 600

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NUTRIENT CYCLING

• We are not dealing with
• Energy eventually gets lost
• We are dealing with
• Nutrients these cycle

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Aldo Leopold A Sand County Almanac
The Journey of Atom X
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Thanks for buying my text book
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• 1. Biochemical cycles
• Redistribution within an individual organism
• This really is r- and K-selection from first
  term
•  
• 2. Biogeochemical cycles
• Exchange within an ecosystem
• N, P - rapid exchange
• Ca - long if stored in long-lived tree tissue
•  
• 3. Geochemical cycles
• Exchange of chemicals between ecosystems
• Nutrients and dust
• CO2, SO2, NOx

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• 1. Biochemical cycles
• Redistribution within an individual organism
• This really is r- and K-selection from first
  term
•  
• 2. Biogeochemical cycles
• Exchange within an ecosystem
• N, P - rapid exchange
• Ca - long if stored in long-lived tree tissue
•  
• 3. Geochemical cycles
• Exchange of chemicals between ecosystems
• Nutrients and dust
• CO2, SO2, NOx

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• 1. Biochemical cycles
• Redistribution within an individual organism
• This really is r- and K-selection from first
  term
•  
• 2. Biogeochemical cycles
• Exchange within an ecosystem
• N, P - rapid exchange
• Ca - long if stored in long-lived tree tissue
•  
• 3. Geochemical cycles
• Exchange of chemicals between ecosystems
• Nutrients and dust
• CO2, SO2, NOx

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Krebs Fig. 27.12 p573
SULPHUR CYCLE
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Krebs Fig. 27.17 p579
NITROGEN CYCLE
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Krebs Fig. 28.7 p590
WATER CYCLE
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Krebs Fig. 27.8 p591
CARBON CYCLE
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• These figures have
• All sorts of rates of transfer
• We can compare between systems

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• These figures have
• All sorts of rates of transfer
• We can compare between systems

• More interesting
• What influences the rates?
• What are the impacts of altering the rates?

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• 1. Biochemical cycle
• 2. Biogeochemical cycles
• Exchange within an ecosystem
• 3. Geochemical cycles

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• BIOGEOCHEMICAL CYCLES
• A few major points (general principles)
•  
• Nutrient cycling is never perfect i.e. always
  losses from system
• input and output

Precipitation Runoff stream flow
Particle fallout from atmosphere Wind loss
Weathering of substrate Leaching
Fertilizer pollution Harvesting
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2. Inputs and outputs are small in comparison to
amounts held in biomass and recycled
3. Relatively 'tight' cycling is the norm

1. Disturbances (e.g. deforestation) often uncouples
   cycling
2. Gradient from poles to tropics

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Annual Nitrogen budget for the undisturbed
Hubbard Brook Experimental Forest. Values are
Kg, or Kg/ha/yr
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2. Inputs and outputs are small in comparison to
amounts held in biomass and recycled
3. Relatively 'tight' cycling is the norm

1. Disturbances (e.g. deforestation) often uncouples
   cycling
2. Gradient from poles to tropics

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Stream water nitrate concentrations from Hubbard
Brook watersheds, NH
Krebs Fig. 27.7 p567
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Concentrations of ions in streamwater from
experimentally deforested, and control,
catchments at Hubbard Brook.
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• Disturbances (e.g. deforestation) often uncouples
  cycling, and a consequent
• loss of nutrients (Krebs p567 (Fig 27.7))
• x13 normal loss in Hubbard Brook (become Atom
  X's)
• reduction in leaf area
• 40 more runoff (would have transpired)
• more leaching
• more erosion, and soil loss
• decouples within-system cycling of decomposition
  and plant uptake processes
• all the activities (and products) of spring
  decomposition get washed away

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2. Inputs and outputs are small in comparison to
amounts held in biomass and recycled
3. Relatively 'tight' cycling is the norm

1. Disturbances (e.g. deforestation) often uncouples
   cycling
2. Gradient from poles to tropics

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5. Patterns from
POLAR TROPICS
Decomposition Slow Rapid
Proportion nutrients in living biomass Low (mostly (OM) High
Cycling Slow Rapid

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Relative proportion of Nitrogen in organic matter
components
ROOTS
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Relative proportion of Nitrogen in organic matter
components
SHOOTS
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DECOMPOSITION

• IF SLOW
• Nutrients removed from circulation for long
  periods
• Productivity reduced
• Excessive accumulations have impact on soil

• IF TOO FAST
• Nutrient depletion
• Poor chemistry and physics of soil such as soil
  fertility, soil moisture and resistance to erosion

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• RATE OF DECOMPOSITION
• humid tropical forests about 2 - 3 weeks
• temperate hardwood forests 1 - 3 years
• temperate / boreal forests 4 - 30 yr
• Arctic/Alpine / dryland forests gt40 years
• generally, rate of decomposition increases
  with increase amount of litterfall

Residence time the time required for the
complete breakdown of one years litter fall
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• Decomposition Rates influenced by
• temperature
• moisture
• pH, O2
• quality of litter
• soil type (influences bugs)
• soil animals
• type of fauna / flora
• rapid if bacterial
• slow if fungal

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• Decomposition Rates influenced by
• temperature
• moisture
• pH, O2
• quality of litter
• soil type (influences bugs)
• soil animals
• type of fauna / flora
• rapid if bacterial
• slow if fungal

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Relationship between rate of litter decomposition
and the balance between bacteria and fungi
Plant species weight loss in 1 year C/N ratio bacterial colonies fungal colonies Bact / Fungi ratio
Mulberry 90 25
Redbud 70 26
White Oak 55 34
Loblolly pine 40 43
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• Decomposition Rates influenced by
• temperature
• moisture
• pH, O2
• quality of litter
• soil type (influences bugs)
• soil animals
• type of fauna / flora
• rapid if bacterial
• slow if fungal

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100 90 80 70 60 50 40 30 20 10 0
0.5 mm mesh bags
leaf litter remaining
7.0 mm mesh bags
(J) J A S O N D J F M A
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• Decomposition Rates influenced by
• temperature
• moisture
• pH, O2
• quality of litter
• soil type (influences bugs)
• soil animals
• type of fauna / flora
• rapid if bacterial
• slow if fungal

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Relationship between rate of litter decomposition
and the balance between bacteria and fungi
Plant species weight loss in 1 year C/N ratio bacterial colonies fungal colonies Bact / Fungi ratio
Mulberry 90 25 698 2650 264
Redbud 70 26 286 1870 148
White Oak 55 34 32 1880 17
Loblolly pine 40 43 15 360 42
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• WHAT DETERMINES THE TYPE OF, AND ABUNDANCE OF,
  MICROFLORA / FAUNA IN THE FIRST PLACE?
• activities of soil fauna e.g. earthworms
• species of plant producing the litter
• chemical composition of the litter
• C/N ratio - high gives poor decomposition
• microbes need N to use C
• N often complexed with nasties (tannin)
• optimum is 251
• Douglas fir wood 5481
• Douglas fir needles 581
• alfalfa hay 181
• pH of litter and therefore of the forest floor
• more acid promotes fungi, less bacteria
• moisture and temperature

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• 1. Biochemical cycle
• 2. Biogeochemical cycles
• 3. Geochemical cycles
• exchange between ecosystems
• examples carbon and sulphur

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• CARBON CYCLING
• (Krebs p590-600)
•  
• CO2 is in the atmosphere at 0.03
• 99 locked up in coal, oil, limestone, chalk
  etc.
• Human activity produces about 5-10 of natural
  emissions
• mostly due to fossil fuels
• before industrial revolution 280ppm
• currently about 355ppm
• projected to be 700ppm by 2100 (unless rather
  profound change to human activities)

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• US Energy Information Admin forecast that world
  emissions will increase by 54 above 1990 levels
  by 2015, or x2 CO2 in about 40 years (2030)
• Canada produces only 2 of global greenhouse
  emissions (but with 0.5 of worlds population)
• From 19601990, Canadian emissions increased by
  250
• These GCM (General Circulation Models) predict
  x2 CO2 increase 1.3 to 4.5C

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Next Fig.
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Concentration of CO2 emissions in Hawaii
Krebs Fig. 28.9 p592
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• 1. Lead to 3C at equator, and 5-8C at poles
• a 0.6C increase in world temperatures since
  1900
• 2nd warmest year historically was 1997 warmest
  was 1998
• ice shelf is melting faster than predicted in
  Antarctica
• retreat of glaciers worldwide
• N-ward movement of permafrost in the Mackenzie
  River Basin

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The Greenhouse Effect of CO2 and other trace gases
Krebs Fig. 2814 p597
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An estimate of temperature variations over last
400000 years, obtained by comparing O2 isotope
ratios in fossils taken from ocean cores in the
Caribbean. Dashed line is the ratio from 10000
years ago.
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200
100
400
CLIMATE HAS ALWAYS CHANGED!
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Average temperature 1902-1980
Next Fig.
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Average temperature 1902-1980
Next Fig.
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Estimated mean global surface temperatures, 1860
1990, relative to 1940
1940
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• 2. 25cm sea level
• already rising along the Gulf states
• Louisiana losing approx. 40 ha of coastal
  wetland per day!
• 15 of the worlds largest cities
• (London, New Orleans, Cairo, NY, LA)
• 300m people will be displaced
• Fiji, Tahiti, Bangladesh (disappear in the next
  100 years)

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• 3. 25-50 dry matter production
• agriculture zones
• population zones
• most of prairies and Gt. Plains become desert
• reserves and parks (1 C can shift 60-100 miles)

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1. Plant and animal responses (Krebs pp593-596)

INDIVIDUAL PLANT RESPONSES (p593) i. increased
plant growth x2 CO2 leads to 40 increase
growth in some trees ii. increased water use
efficiency iii. Increased reproductive output
(fruit, seed etc.) IV. influence migration rates
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1. Plant and animal responses

PLANT COMMUNITY RESPONSES (p594) i. Increased
evaporation in the arctic tundra lose much fish
habitat , and migratory birds ii. Release of
enormous C-reserves from boreal forests iii.
Other effects may be quite minimal
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1. Boreal forests
2. Temperate forests
3. Tropical forests

Rate
Photosynthesis
3
2
1
Respiration
Temperature
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1. Boreal forests
2. Temperate forests
3. Tropical forests

1 2.8 increased death rate during El Nino
events
Rate
Photosynthesis
3
2
1
Respiration
Temperature
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1. Plant and animal responses

• INDIVIDUAL ANIMAL RESPONSES
• Migration vertically becomes a problem
• leads to local extinction

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• TWO PROBLEMS
• rate of change is unprecedented and may be too
  fast for adaptation
• major impact will come from extreme events
• heat waves and floods
• prob. that a heat wave of gt5 days at gt35C in
  Washington D.C. will rise from 17 to 47 with
  an increase of 3C
• prob. of drought in mid-West will increase
  1988, 1993, 1994
• more rainfall in India (good), but more
  flooding in Bangladesh
• longer hurricane season
• Boreal forest are vast store houses of carbon
• fires give off carbon
• earlier and drier summers give 50 more fires
• 20 of excess CO2 in atmosphere is from forest
  burning
• 178000 Amazon fires gt1 km2

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• WEIRD WEATHER
• (MacLean's, Jan 1999)
• 1996
• Floods in the Saguenay region
• 10 dead, 2000 displaced from homes
• Vancouver's snowfall of the century
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• 1997
• Devastating floods in Manitoba Red River
• 28000 people displaced from homes

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• 1998
• Ice storm in Quebec and Eastern Ontario (storm
  of the century)
• Chinas floods - Yangtze River burst its banks
• The hottest year on record, worldwide (after
  '97, 94, 89)
• A 200,000 ha fire in Florida - worst ever
• Heat wave in the southern US
• Temperatures over 38OC for over 2 weeks
• Killed over 100 people
• Heat wave in India killed 2500
• and spawned raging bushfires in Australia
• Hurricane Mitch
• most devastating hurricane in 200 years
• killed an estimated 11000
• In US Midwest - spate of tornadoes killed 129

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• 1999
• The Ontario snow storm
• In the state of Maine a record low of - 48OC

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• CENTER FOR CLIMATE MODELING (Environment Canada,
  Victoria)
• violent winter storms will increase from 1
  every 20 years to 1 every 10 years
• in Canadas north, extreme daily max.
  temperatures will peak at 10OC above present
• Record rain and snow storms will deliver 10
  more ppt.
• and become more frequent
• Vancouvers famous drizzle will become
  frequent torrential downpours
• Blizzards in the east will last longer and dump
  more snow
• more avalanches
• more spring flooding
•  Torontos Storm of 99, like Montreals Ice
  Storm of the Century and Winnipegs Great Flood,
  could well turn out to be a mere overture to the
  far greater wrath of the weather to come

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• U.S. NATIONAL OCEANIC AND ATMOSPHERIC
  ADMINISTRATION
• Number of heat waves ?3 days has increased 88
  between 1949 and 1995
• Extreme snow and rainstorms increased 20 since
  1900

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• 1. CLIMATIC "REALITIES"
• The greenhouse effect - real on a planetary
  scale
• Temperature - CO2 correlations - real in
  earth's history
• Atmospheric build-up of radiatively active
  gases - real within human observation
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U.S. Scientists' report doesnt support the
Kyoto treaty (Wall St. Journal November
2001)   Last week the U.S. National Academy of
Sciences released a report on climate change,
prepared in response to a request from the White
House, that was depicted in the press as an
implicit endorsement of the Kyoto Protocol. CNN's
Michelle Mitchell was typical of the coverage
when she declared that the report represented a
unanimous decision that global warming is real,
is getting worse, and is due to man. There is no
wriggle room.
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As one of 11 scientist who prepared the report, I
can state that this is simply untrue. The full
report makes clear that there is no consensus,
unanimous or otherwise, about long-term climate
trends and what causes them. But - and I cannot
stress this enough - we are not in a position to
confidently attribute past climate change to
carbon dioxide or to forecast what the climate
will be in the future.
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One reason for this uncertainty is that, as the
report states, the climate is always changing
change is the norm. Two centuries ago, much of
the Northern Hemisphere was emerging from a
little ice age. A millennium ago, during the
Middle Ages, the same region was in a warm
period. Thirty years ago, we were concerned with
global cooling. Richard S. Lindzen Professor of
Meteorology MIT Member of National Acad. Sciences
panel on climate change.
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• 2. WHAT CAN THE MODELS TELL US?
• GCM's tend to agree on the big picture
• 1.3 to 4.5C for x2 of CO2
• BUT resolution is poor
• they disagree at regional and local levels
• they grossly oversimplify clouds and oceans
• So, there is much uncertainty and ample room
  for doubt and scepticism

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• 3. THE CLIMATIC FUTURE
• some sort of climate change is inevitable
• increased frequency of extreme events and
  greater variability are probable
• general warming is probably, but not certain
• convincing observation are present
• credible models years away

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• SULFUR CYCLE
• (Krebs p572-576)
• Considerable exchange between oceans and
  atmosphere
• mostly in the form of SO2 and H2S
• Humans produce 160 of natural production
• SO2 emitted by plants, seawater, volcanoes
• combustion of fossil fuels and organic matter
• H2S anaerobic decomposition
• H2S is oxidized to SO2
• SO2 combines with atomic O and molecular O2, and
  ozone O3 to produce SO3
• SO2 H2O H2SO3 (sulphurous acid)
• SO3 H2O H2SO4 (sulphuric acid)
• NOx H2O HNO3 (nitric acid)
• NOx can destroy ozone

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Emissions of SO2, NOx, and volatile organic
compounds (e.g.. Methane) in USA.
Krebs Fig. 27.14 p575
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• ACID RAIN
• Horrible topic - much ambiguity
• by definition, rain with pHlt5.6
• 'normal' rain is slightly acidic (carbonic
  acid)
• pH 2.7 is common in Pennsylvania a storm in
  West Virginia had 1.5 pH

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Normal range of pecip.
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Acidity of precipitation over Canada and US in
1982 changed little in past 2 decades
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• In 1979 acid rain was described by the Federal
  Environment Minster (Canada) as the most serious
  and pressing environmental problem Canada has
  ever faced.
• Early evidence - absence of lichens on trees
• on buildings (Parliament House in Ottawa,
• Taj Mahal, Capitol Bldg., Acropolis)
• more insidious - effects on rivers, lakes and
  forests
• some lakes in the Adirondacks
• drop of 2pH units in 30 years i.e. x100!
• 180 lakes are fishless

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• estimated that 150,000 lakes of 700,000 in
  eastern Canada have been damaged
• about 14,000 are believed to be acidified (i.e.
  losing normal life)
• 140 Ontario lakes are fishless
• Nova Scotia, salmon disappearing from streams
• In the Czech Republic nearly 60 of the forests
  d damaged or destroyed
• In US, some high elevation spruce forests
  (Shenandoah and Gt. Smoky Mt) have been
  affected.

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Krebs Fig. 27.15 p577 Effects of acidification
on eastern Canadian Lakes
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Catch of (percentage of average for 1936-1940)
Atlantic salmon in Nova Scotia streams 1935 - 1980
pH gt5
pH lt 5
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PANTHER LAKE
One Rain Three lakes in the Adirondaks
SAGAMORE LAKE
WOODS LAKE
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Mean for Adirondak Lakes 1995 1930s
0 1 2 3 4 5 6 7 8
9 10 11 12 13 14
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Mean for Adirondak Lakes 1995 1930s
0 1 2 3 4 5 6 7 8
9 10 11 12 13 14
Small mouth bass Lake trout Brook trout Yellow
perch Salamander Mayfly Whirligig Water boatman
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Forests in Czech Republic, killed by acid rain
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• but
• damages cuticle (Black Forest)
• interferes with guard cells
• disturbs metabolism and poisoning of cells
• accelerates foliar leaching
• alteration of N-fixation and mycorrhizal fungi
• increased susceptibility to other stresses
•  
• but
• organic forest floor is well buffered
• but accelerates leaching of Ca (the buffer)
• leads to mobilization of Al
• toxic to fine roots
• leads to a reduction in growth or die back
  (Black Forest)

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• ALSO READ p12 of web hand out
• effects of acid deposition
• effects of ozone depletion