|
ecol assignments.htm
requirements.htm
..\schedule.htm
ecol home.htm
lab home.htm
..\pop biology.xls
Reserve items
| |
PRODUCTIVITY OF ECOSYSTEMS
Readings and References
Link to a very useful
site
on productivity at U. Florida
DEFINITIONS:
Productivity - energy fixed/area/time
NOTES
A.
Photosynthesis - light energy is captured
in two steps (the light-dependent and the light-independent [=dark] reactions) and stored as chemical energy (food)
carbon dioxide + water + energy yields glucose (sugar, stored chemical energy) + oxygen
6CO2 + 6H2O yields C6H12O6 + 6O2
264g + 108g (energy input ~ 700Kcal )180g + 192g
B. Requirements for photosynthesis
1. Water, carbon dioxide
2. Energy - light
3. Photosynthetic pigments
chlorophyll absorbs red and violet
carotenoids absorb blue & green
erythrin pigments red algae - in ocean green light goes deepest
4. Enzymes (protein molecules acting as catalysts)
5. Nutrients (coenzymes, etc.) magnesium in chlorophyll
C. Factors influencing rates of photosynthesis
1. Temperature
maximum rate at 30-35oC (90oF)
rate near zero at 50oC (120oF)
2. Water - land plants: 500g water/gm glucose synthesized (less for
C4 and CAM plants)
transpiration - water loss through leaves
drought major factor
freezing limits water availability
3. Nutrients - on land, phosphorus, nitrogen, or N/P ratio
in ocean, iron and silica - low solubility and sinking problems
4. Light - in ocean compensation depth few cm to 100m
daylength on land and sea, but all places get same total illumination time over a year
saturation at 30% full sunlight (10% for leaf perpendicular to light)
photorespiration - like zapping your motherboard - too many electrons
C3 vs C4 plants
and CAM plants
maximum use is 1-5% full sunlight if conditions are good
5. Difference between short and long term factors limiting productivity:
carbon dioxide may limit rate on summer day in moist, fertile cornfield
over a whole summer, water and nutrients limit
D. WORLD PRODUCTIVITY ESTIMATES
From Whittaker, R.H. 1975. Communities and Ecosystems, Ed. 2. New York. Macmillian Publ. Co. 385pp.
to convert to Kcal, multiply by 4.5
|
ECOSYSTEM TYPE |
NPP (grams organic matter per M2 per year) |
World total |
|
|
Mean |
(109metric tons/yr) |
|
Tropical rain forest |
2200 |
37.4 |
|
Tropical seasonal forest |
1600 |
12.0 |
|
Temperate evergreen forest |
1300 |
6.5 |
|
Temperate deciduous forest |
1200 |
8.4 |
|
Boreal forest |
800 |
9.6 |
|
Woodland and shrubland |
700 |
6.0 |
|
Savanna |
900 |
13.5 |
|
Temperate grassland |
600 |
5.4 |
|
Tundra and alpine |
140 |
1.1 |
|
Desert and semidesert |
90 |
1.6 |
|
Extreme desert, rock, ice |
3 |
0.07 |
|
Cultivated land |
650 |
9.1 |
|
Swamp and marsh |
2000 |
4.0 |
|
Lake and stream |
250 |
0.5 |
|
TOTAL LAND |
|
115 |
|
Open ocean |
125 (180) |
41.5 (60) |
|
Upwelling zones |
500 |
0.2 |
|
Continental shelf |
360 |
9.6 |
|
Algal beds and reefs |
2500 |
1.6 |
|
Estuaries |
1500 |
2.1 |
|
TOTAL OCEAN |
|
55.0 (75) |
Non-photosynthetic production
Deep sea hydrothermal vents
Lithosphere, sediments. see: http://news.bbc.co.uk/2/hi/science/nature/4291571.stm
|
