biol 302 nutrient cycling1 community and ecosystem biology biology 302
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Biol 302 Nutrient Cycling 1
COMMUNITY AND COMMUNITY AND ECOSYSTEM BIOLOGYECOSYSTEM BIOLOGY
Biology 302Biology 302
Biol 302 Nutrient Cycling 2
NUTRIENT CYCLINGNUTRIENT CYCLING
READINGS for this lecture series:READINGS for this lecture series:
• KREBS cpt 27. Ecosystem Metabolism III: Nutrient Cycles
• KREBS cpt 28. Ecosystem Health:
Human Impacts; Pp 590 - 600
Biol 302 Nutrient Cycling 3
NUTRIENT CYCLINGNUTRIENT CYCLING
• We are not dealing with:
• Energy – eventually gets “lost”
• We are dealing with:
• Nutrients – these cycle
Biol 302 Nutrient Cycling 4
Aldo Leopold “A Sand County Almanac”Aldo Leopold “A Sand County Almanac”“The Journey of Atom X”
Biol 302 Nutrient Cycling 10
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
Biol 302 Nutrient Cycling 11
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
Biol 302 Nutrient Cycling 12
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
Biol 302 Nutrient Cycling 17
These figures have:
• All sorts of rates of transfer
• We can compare between systems
Biol 302 Nutrient Cycling 18
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?
Biol 302 Nutrient Cycling 19
1. Biochemical cycle
2. Biogeochemical cycles:
• Exchange within an ecosystem
3. Geochemical cycles:
Biol 302 Nutrient Cycling 20
BIOGEOCHEMICAL CYCLES: A few major points (general principles): 1. 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
Biol 302 Nutrient Cycling 21
3. Relatively 'tight' cycling is the norm
2. Inputs and outputs are small in comparison to amounts held in biomass and recycled
4. Disturbances (e.g. deforestation) often uncouples cycling
5. Gradient from poles to tropics
Biol 302 Nutrient Cycling 22
Annual Nitrogen budget for the undisturbed Hubbard Brook Experimental Forest. Values
are Kg, or Kg/ha/yr
Biol 302 Nutrient Cycling 23
3. Relatively 'tight' cycling is the norm
2. Inputs and outputs are small in comparison to amounts held in biomass and recycled
4. Disturbances (e.g. deforestation) often uncouples cycling
5. Gradient from poles to tropics
Biol 302 Nutrient Cycling 24Krebs Fig. 27.7; p567
Stream water nitrate concentrations from Hubbard Brook watersheds, NH
Biol 302 Nutrient Cycling 25
Concentrations of ions in streamwater from experimentally deforested, and control, catchments at Hubbard Brook.
Biol 302 Nutrient Cycling 26
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
Biol 302 Nutrient Cycling 27
3. Relatively 'tight' cycling is the norm
2. Inputs and outputs are small in comparison to amounts held in biomass and recycled
4. Disturbances (e.g. deforestation) often uncouples cycling
5. Gradient from poles to tropics
Biol 302 Nutrient Cycling 28
5. Patterns from:
POLAR TROPICS
Decomposition Slow Rapid
Proportion nutrients in living biomass
Low (mostly (OM)
High
Cycling Slow Rapid
Biol 302 Nutrient Cycling 31
DECOMPOSITIONIF 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
Biol 302 Nutrient Cycling 32
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 >40 years
• generally, rate of decomposition increases with increase amount of litterfallResidence time … the time required for the
complete breakdown of one year’s litter fall
Biol 302 Nutrient Cycling 37
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
Biol 302 Nutrient Cycling 38
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
Biol 302 Nutrient Cycling 39
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
Relationship between rate of litter decomposition Relationship between rate of litter decomposition and the balance between bacteria and fungiand the balance between bacteria and fungi
Biol 302 Nutrient Cycling 40
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
Biol 302 Nutrient Cycling 41
(J) J A S O N D J F M A
100
90
80
70
60
50
40
30
20
10
0
% leaf litter
remaining
0.5 mm mesh bags
7.0 mm mesh bags
Biol 302 Nutrient Cycling 42
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
Biol 302 Nutrient Cycling 43
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
Relationship between rate of litter decomposition Relationship between rate of litter decomposition and the balance between bacteria and fungiand the balance between bacteria and fungi
Biol 302 Nutrient Cycling 44
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 25:1
Douglas fir wood 548:1 Douglas fir needles 58:1 alfalfa hay 18:1
pH of litter and therefore of the forest floor more acid promotes fungi, less bacteria
moisture and temperature
Biol 302 Nutrient Cycling 45
1. Biochemical cycle
2. Biogeochemical cycles
3. Geochemical cycles:
• exchange between ecosystems
• examples: carbon and sulphur
Biol 302 Nutrient Cycling 46
CARBON CYCLINGCARBON 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)
Biol 302 Nutrient Cycling 48
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 world’s population)
From 1960–1990, Canadian emissions increased by 250%
These GCM (General Circulation Models) predict x2 CO2 =
increase 1.3 to 4.5C
Biol 302 Nutrient Cycling 55
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
Biol 302 Nutrient Cycling 56Krebs Fig. 28;14; p597
The Greenhouse Effect of CO2 and other trace gases
Biol 302 Nutrient Cycling 57
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.
CLIMATE HAS ALWAYS CHANGED!
400300200100
Biol 302 Nutrient Cycling 61
Estimated mean global surface temperatures, 1860 – 1990, relative to 1940
1940
Biol 302 Nutrient Cycling 63
2. +25cm sea level
already rising along the Gulf states
Louisiana losing approx. 40 ha of coastal wetland per day!
15 of the world’s largest cities
(London, New Orleans, Cairo, NY, LA)
300m people will be displaced
Fiji, Tahiti, Bangladesh (disappear in the next 100 years)
Biol 302 Nutrient Cycling 69
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)
Biol 302 Nutrient Cycling 71
4. 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
Biol 302 Nutrient Cycling 73
4. 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
Biol 302 Nutrient Cycling 74
Rat
e
Temperature
Photosynthesis
Respiration
12
3
1. Boreal forests
2. Temperate forests
3. Tropical forests
Biol 302 Nutrient Cycling 75
Rat
e
Temperature
Photosynthesis
Respiration
12
3
1. Boreal forests
2. Temperate forests
3. Tropical forests1 – 2.8% increased death rate during
El Nino events
Biol 302 Nutrient Cycling 76
4. Plant and animal responses
INDIVIDUAL ANIMAL RESPONSES
i. Migration vertically becomes a problem
leads to local extinction
Biol 302 Nutrient Cycling 77
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 >5 days at >35C 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 >1 km2
Biol 302 Nutrient Cycling 78
WEIRD WEATHER
(MacLean's, Jan 1999)
1996
Floods in the Saguenay region
10 dead, 2000 displaced from homes
Vancouver's snowfall of the century
1997
Devastating floods in Manitoba; Red River
28000 people displaced from homes
Biol 302 Nutrient Cycling 79
1998 Ice storm in Quebec and Eastern Ontario (storm of the century) China’s 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
Biol 302 Nutrient Cycling 80
1999
The Ontario snow storm
In the state of Maine a record low of - 48OC
Biol 302 Nutrient Cycling 81
CENTER FOR CLIMATE MODELING (Environment Canada, Victoria) violent winter storms will increase from 1 every 20 years to 1
every 10 years in Canada’s 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 “Vancouver’s famous drizzle” will become “frequent torrential
downpours” “Blizzards in the east will last longer and dump more snow”
more avalanches more spring flooding
“Toronto’s Storm of ‘99, like Montreal’s Ice Storm of the Century and Winnipeg’s Great Flood, could well turn out to be a mere
overture to the far greater wrath of the weather to come”
Biol 302 Nutrient Cycling 82
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
Biol 302 Nutrient Cycling 83
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
Biol 302 Nutrient Cycling 84
U.S. Scientists' report doesn’t 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.”
Biol 302 Nutrient Cycling 85
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.
Biol 302 Nutrient Cycling 86
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 MeteorologyMITMember of National Acad. Sciences panel on climate change.
Biol 302 Nutrient Cycling 87
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
Biol 302 Nutrient Cycling 88
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
Biol 302 Nutrient Cycling 89
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
Biol 302 Nutrient Cycling 90
Krebs Fig. 27.14; p575
Emissions of SO2, NOx, and volatile organic compounds (e.g.. Methane) in USA.
Biol 302 Nutrient Cycling 92
ACID RAIN: Horrible topic - much ambiguity
by definition, rain with pH<5.6 'normal' rain is slightly acidic (carbonic acid) pH 2.7 is common in Pennsylvania; a storm
in West Virginia had 1.5 pH
Biol 302 Nutrient Cycling 97
Acidity of precipitation over Canada and US in 1982; changed little in past 2 decades
Biol 302 Nutrient Cycling 98
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
Biol 302 Nutrient Cycling 100
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 ddamaged or destroyed
In US, some high elevation spruce forests (Shenandoah and Gt. Smoky Mt) have been affected.
Biol 302 Nutrient Cycling 101
Krebs Fig. 27.15; p577
Effects of acidification on eastern Canadian Lakes
Biol 302 Nutrient Cycling 102
Catch of (percentage of average for 1936-1940) Atlantic salmon in Nova Scotia streams 1935 - 1980
pH >5
pH < 5
Biol 302 Nutrient Cycling 103
PANTHER LAKE
SAGAMORE LAKE
WOODS LAKE
One Rain –
Three lakes in the
Adirondaks
Biol 302 Nutrient Cycling 104
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Mean for Adirondak Lakes 1995 1930s
Biol 302 Nutrient Cycling 105
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
Mean for Adirondak Lakes 1995 1930s
Biol 302 Nutrient Cycling 107
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)