Handouts to accompany lectures on Nutrient Cycling – Roy Turkington - 1 -

NUTRIENT CYCLING

You will be perplexed by the complexity and interconnectedness!

We are not talking 'energy' (eventually lost from system as heat)

  • we are talking matter, nutrients - cycling

READ Krebs Cpt 27 pages 560-582, 590-600

Read parts from Aldo Leopold "A sand county almanac" and continue with:

  • locked in limestone ledge
  • bur-oak root
  • built a flower and an acorn
  • deer
  • Indian (berth in bones)
  • "underground" again
  • bluestem rootlet and then a leaf
  • deer mouse cut leaf for nest
  • nest destroyed by fox
  • "underground" again
  • side-oats grama grass
  • buffalo
  • "underground" again
  • spiderwort, rabbit, owl
  • sporobolus
  • Prairie fire......
  • beaver (dies and flows downstream)
  • ends up in old prison, the sea

Read quote from "Cycling of materials"

1. Biochemical cycles:

  • Redistribution within an individual organism
  • this really is r- and K-selection from first term (no more now)

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

The relative importance of these (see Table)

From here I have various options:

  • totally descriptive
  • all sorts of pathways (including the cycles above)
  • all sorts of rates of transfer
  • comparative among systems
  • try to find a few more interesting things
  • what influences rates?
  • what impact does cycling have on us?

1. BIOGEOCHEMICAL CYCLES: (within the ecosystem)

A few major points (general principles):

1). Nutrient cycling is never perfect i.e. always losses from system

  • input and output

  • precipitation
/
  • runoff and stream flow

  • particle fallout from atmosphere
/
  • wind loss

  • weathering of substrate
/
  • leaching

  • fertilizer, pollution
/
  • harvesting

  • cycling
  • soil/atmosphere/plant (animal)/soil etc.

2). Inputs and outputs are small in comparison to amounts held in biomass and recycled

3). Relatively 'tight' cycling is the norm

4). 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

5). Patterns from:

POLE to / TROPICS
  • decomposition
/ slow / rapid
  • proportion of nutrients in living biomass
/ low (mostly in dead OM) / high
  • cycling
/ slow / rapid

DECOMPOSITION

If slow - nutrients removed from circulation for long periods

  • productivity reduced
  • excessive accumulations have impact on soil
  • too wet, acid, cold
  • poor root development
  • poor nutrition
  • slow growth

If too fast - much lost by leaching

  • nutrient depletion
  • poor physics and chemistry of soils
  • serious for soil fertility
  • serious for soil moisture
  • resistance to erosion drops

Rate of decomposition

  • humid tropical forests about2 - 3 weeks
  • temperate hardwood forests1 - 3 years
  • temperate/boreal forests4 - 30 yr
  • Arctic/Alpine/dryland forests>40 years
  • generally, rate of decomposition increases with increase amount of litterfall

Rates determined (or 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

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
  • makes soil acidic
  • N often complexed with nasties (tannin)
  • optimum is 25:1
  • Douglas fir sapwood548:1
  • Douglas fir heartwood429:1
  • Douglas fir needles58:1
  • alfalfa hay18:1
  • pH of litter and therefore of the forest floor
  • more acid promotes fungi, less bacteria
  • moisture and temperature

I will not go through the descriptions of numerous nutrients. Rather, let's look at a few interesting things about two of them – Carbon and Sulphur.

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 of CO2

  • mostly due to fossil fuels
  • before industrial revolution280ppm
  • currently about 355ppm
  • projected to be 700ppm by 2100 (unless rather profound change to human activities)
  • 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

READ Buddemeir (p6)

  • lead to +3C at equator

+5-8C at poles

  • there has been 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 worlwide
  • northward movement of the permafrost in the Mackenzie River Basin

+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)

+25-50% dry matter production

i.e. changes in worlds climate

  • agriculture zones
  • population zones
  • most of prairies and Gt. Plains become desert
  • preserves and parks may befew hundred km, but a few degrees shift can move zones far greater distances
  • 1C can move 60-100 miles
  • but see Fig 1.4 (p13 of BHT)

If increase in CO2 due only to fuel it would be higher, but buffering:

  • plant growth; +5% net productivity for each 10% increase CO2
  • oceans
  • increase CO2
  • increase in solution in oceans
  • increase sedimentation of CaCO3 (has removed 35% of what we have produced this past 100 years)
  • depends on rate of atmospheric and oceanic stirring
  • cold water at poles dissolve it
  • warm water at tropics release it

READ Buddemeir p2 (2 quotes)

Greenhouse effect

  • incoming short, reradiated as long, trapped
  • increased air temperature
  • causes increased oceanic temperature
  • causes increased dissolved CO2 to be released (+FEEDBACK)
  • causes more evaporation, more clouds, less incoming radiation, .....cooling,more CO2 dissolved (-FEEDBACK)
  • i.e. checks and balances
  • the economy of nature
  • equilibrium
  • the Walt Disney View of the world.

This all ignores lag effects

AND: we can't consider CO2 in isolation e.g. Methane which also contributes to global warming.
Methane:

  • bubbles in ice from Australia and Greenland
  • graph actually can be extended to 27000 yrs BC
  • from 1550ppb (in 1880) to 1720ppb (1989) = 11%

In contributing to global warming, the order:

1st- CO2 (50%)
2nd- CFC chlorofluorocarbons (20%)
3rd- methane (from cattle, sheep, pigs, and rice paddies) (16%)
4th- trace gases (primarily N2O, nitrous oxide (6%), and ozone (8%))

CO2 has the combined effect of the next three, (BUT, methane can protect ozone layer).

From tree (1989) 4:64-68

What will all of this do to animals and plants? (Krebs p593-596)

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 >1km2!!

Plants:

Spruce has migrated at 200km/100 years, 9000 years ago

Most species expanded at 10-40km/100yrs

If:

  • x2 CO2 in 50 yrs we require 500km/100 yrs
  • a 2-3C shift can give a 200 mile boundary shift, then need 1m/hr!
  • several orders of magnitude too fast
  • and, the soil may be all wrong
  • e.g. move from Prairies to Canadian Shield
  • 18000 yrs ago, Spruce grew with sedges in open parkland of American Midwest
  • 10000 in closed canopies in southern Canada
  • 6000 now in Boreal forest association
  • i.e. expect new communities
  • Arctic Tundra may disappear
  • if top 2-3m of permafrost of Arctic and Boreal is lost, the wet coastal tundra will be lost
  • disastrous for migratory birds and mammals for breeding

BUT could lead to +40% wheat seed with x2 CO2

and radishes mature in 12 days instead of 20 in x3 CO2

Animals:

Migrate vertically about 500m to compensate for 3C shift

  • but as we ascend there is less habitable area, and extinction
  • estimates from Gt. Basin Mts. that we would lose 10-50% of current species

Climatic "realities"

  • The greenhouse effect - real on a planetary scale
  • Temperature - CO2 correlations - real in earth's history
  • Atmospheric buildup of radiatively active gases - real within human observation

What can the models tell us?

  • GCM's tend to agree on the big picture
  • 1.3 to 4.5C for x2 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 skepticism

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
  • credible models and convincing observation are years away

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
  • H2Sanaerobic decomposition
  • H2S is oxidized to SO2
  • SO2 combines with atomic O and molecular O2, and ozone O3 to produce SO3
  • SO2 + H2O=H2SO3 (sulfurous acid)
  • SO3 + H2O=H2SO4 (sulfuric acid)
  • NOx + H2O=HNO3 (nitric acid)
  • NOx can destroy ozone

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

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
  • 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 damaged or destroyed
  • In the US, some high elevation spruce forests (Shenandoah and Gt. Smoky Mt) have been affected.

..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)

HAMISH KIMMINS (FOREST ECOLOGY)

Temperature Rising – Climate Change in Southwestern British Columbia

This material has nearly all been taken from a poster prepared for the Geological Survey of Canada (GSC). The authors are Robert J.W. Turner and John J. Clague, and this is Miscellaneous Report #67 (1999) of the GSC. For more information:

In these notes, numbers in parenthesis refer to overheads used in class.

Prediction – by 2050, temp in southwestern BC will be “several degrees warmer than today, and that winters will be wetter and summers drier.” ….. “Such changes would be the largest and most rapid of the last 10,000 years and will have a profound effect on our lives and the ecosystems that support us.”

Is climate changing?

20th century was the warmest of the last 1000 years

1990’s was the warmest decade of the 20th century

(1) general increase over last 140 years

change erratic, but accelerated since 1980s.

(2) nature’s thermometer:

Wedgemont Glacier near Whistler, has retreated 100s of meters, due mostly to melting in warmer summers.

(3) global temperature change

Climate has always changed:

(4) A vast ice sheet covered Vancouver 16,000 years ago.

9000 yrs ago, average temp in southwestern BC was 1-2C warmer than today.

Vikings settled in Greenland during a warm period, the “medieval Warm” period from approx. 1000 – 1200AD.

Europe experienced unusually cold weather during the “Little Ice Age” (13th century to late 1800s).

(5, 6) Earth’s climate much more stable, and warmer, during last 10,000 years than any time in last 100,000 years.

Why is climate changing now?

(7) earth’s solar energy budget

  • (describe fig 7)

Greenhouse effect is the heat-trapping quality of the atmosphere caused by gases that absorb long-wave radiation emitted by the earth.

(8) the Carbon balance

(9) Greenhouse gases

  • the big 3 are CO2, Methane (CH4) and Nitrous oxide (N2O)

(10) CO2 build up

The air we breath

(11) vehicle exhaust produces 30% of greenhouse gas emissions in the lower Fraser Valley.

(12) smog trapped in the Fraser Valley. Vancouver, Penticton, Kelowna and other cities in southern BC lie within valleys whose mountain walls trap polluted air.

Air-borne pollutants normally dispersed by wind, but on calm days they can become concentrated beneath a layer of warmer air.

Worsen asthma and impaired lung function

Will worsen as summers get warmer (and more vehicles)

Coastal floods and failing slopes

(13) Predict that future winters will be wetter and stormier in coastal BC. If so, we can expect more floods.

(14, 15) wetter winters means less stable slopes and more land slides. Of greatest concern are ‘debris flows”

Rising seas

Shrinking glaciers and melting ice caps, and rising sea levels.

Expected rise in sea level over next 100 years is 15-95cm

(16) vulnerable shore lines

shores formed of loose, easily eroded sediments may shift inland

higher seas may also flood deltas, tidal marshes, and other low lying coastal areas

(17) eroding cliffs at Point Grey

  • retreated at up to 60cm per year before 1982.

(18) critical marshes:

  • Fraser Delta marshes are critical habitat for waterfowl, shore birds and salmon fry. Rising sea level may cover the marshes or squeeze them against Delta and Richmond dykes (19).

Salmon in hot water

(20) pacific salmon live in cool ocean waters

(21) southern BC is near the southern limit of their range.

Warming of the north pacific could force salmon northward, reducing their numbers in rivers of southern BC. Warm-water fish such as tuna and mackerel may replace them.

Mackerel have recently been found off Vancouver Island and concern that they may eat young salmon.

(22) problems for salmon moving upstream to spawn (stop eating when they enter fresh water and rely on stored fats).

Low water problems

(23) changing river flow

streams flow in southern Interior has changed over last 30 year.

Spring run-off starts earlier and autumn rains come later, thus extending the period of low summer flow.

More precipitation falls as rain than snow in autumn, therefore snow packs are smaller

Smaller snowpacks results in lower stream flow in summer

These trends will continue if climate continues to warm.

(24) water balance: running in a deficit

summers are dry and hot in the southern Interior valleys e.g. Okanagan

warming will affect the water balance in these valleys

less precipitation may fall as snow

evaporation and transpiration will increase

lake levels may fall – while demand will continue to increase

(25) home water budget

an average, each person uses 300L of water per day at home.

This increases to 600L per day if we include individual use through businesses and services.

Forests in transition.

(26) as climate warms, some plant species in BCs Interior will extend their ranges northwards and to higher elevations

drought-tolerant trees such as Douglas fir and Ponderosa Pine will be favored over spruce.

(28) Dry grasslands may replace Douglas fir

trees may invade alpine meadows

** plants adapted to new climate will first appear in areas disturbed by fire, logging and extreme drought.

(29) effects of climate change on forest sand forestry.

On the farm.

Climate change is expected to bring warmer year-round temperatures, wetter springs and drier summers to Interior valleys such as the Okanagan and the Similkameen.

Vineyards and orchards could spread north to Kamloops.

Severe winter cold may be reduced, but drier, warmer, summer climate will increase drought during the growing season.

Warmer year-round temperatures and drier summers should benefit agriculture in the Fraser Valley and s Vancouver Island; higher yields and more diverse crops – and more insect pests.

How do we measure up?

(30) Canada ranks #2 in per capita CO2 emissions.

Effects of acid deposition.

Natural precipitation varies in acidity but ahs an average pH of 5.6. Acid deposition with a pH value < 5.6 has a number of harmful effects, especially when the pH falls bellow 5.1.

  • damaging statues, buildings, metals, and car finishes.
  • killing fish, aquatic plants, and microorganisms in lakes an streams.
  • reducing ability of salmon and trout to reproduce when the pH falls below 5.5.
  • killing and reducing productivity of many species of phytoplankton when the Ph is bellow their optimum range of 6 – 8.
  • weakening of killing trees, especially conifers at high elevations, by leaching Calcium, phosphorus an other plant nutrients form soil (Fig below).
  • damaging tree roots and killing many kinds of fish by releasing ions of aluminum, lead, mercury, and cadmium from soil and bottom sediments (Fig below).
  • weakening trees and making them more susceptible to attacks by disease, insects, drought and fungi and mosses that thrive under acidic conditions.
  • stunting the growth of crops such as tomatoes, soybeans, snap beans, tobacco, spinach, and cotton increasing populations of giardia, a protozoan that is associated with a severe gastrointestinal disease that afflicts hikers and mountain climbers who drink water from seemingly clear mountain stream waters.
  • leaching toxic metals such as copper and lead from city and home water pipes into drinking water.
  • causing and aggravating many human respiratory diseases and leading to premature death.

Effects of ozone depletion.