Ecosystem Productivity and Diversity Primary Focus of Ecosystem Ecology

--> examine the exchange of Many Ecologists ENERGY Æ productivity has a pervasive influence on diversity MATTER

Radiant Energy All Ecosystems Producers

- have 3 basic components C o CO2 n CO2 r s O e u O 2 tt m 2 Autotrophs / Primary Producers i n p H O L o t H O 2 f ti io 2 a a n e c L lo Heterotrophs / Consumers s N n ut s a rie ent r nt ri T s ut De Abiotic Components N com pos ition Abiotic Elements Consumers Deposition

Three measure that can be used to define relative importance:

Studying Ecosystems 1) BIOMASS Mass of standing crop of each species First Step Rate of production of new biomass (YIELD) --> determine the food web 2) Flow of Chemical Materials - defines the qualitative movement of ENERGY and Superorganism analogy useful here NUTRIENTS view community as taking in, processing, re-using, discarding nutrients Then eg P molecule: soil--> grass--> grasshopper --> feces --> decide significance of various species to -->bacteria--> soil movement of ENERGY and NUTRIENTS 3) Flow of Energy transform solar energy and transfers it to green plants, consumers… most is lost as heat, requires constant input

1 Primary Production Most ecologists use energy

- chemicals are often tied up in peculiarities of organisms Photosynthesis -

solar energy ----> chemical energy

- energy is not recirculated (easier to measure) 12 H2O + 6CO2 + solar energy --> C6H12O6 + 6O2 + 6H2O

- reduces diverse communities to calories Carbohydrates

Energy enters almost all ecosystems via solar radiation, and is fixed by the process of photosynthesis

Primary Production Compensation Point

Photosynthesis - - P’synthesis = Respiration --> no new production

solar energy ----> chemical energy Gross Primary Production

12 H2O + 6CO2 + solar energy --> C6H12O6 + 6O2 + 6H2O --> energy fixed during photosysnthesis

Respiration - opposite of P’synthesis Net Primary Production C H O + 6O --> 12 H O + 6CO + energy for work and heat 6 12 6 2 2 2 --> energy fixed in photosynthesis - energy lost due to respiration

Daily patterns of CO2 assimilation in Douglas fir during spring and summer How do you measure these 2 aspects of Primary Production?

Terrestrial Systems

--> measure change in CO2 or O2 concentrations around a plant

Daytime P’syn and Resp occurring Light Temperature/

CO2 uptake measures NET production Assimilation

Nighttime only Resp occurring 2

CO2 output measure respiration Net CO

2 Alternative methods Can determine the energetic equivalent using: --> measure uptake of radioactive Carbon (14C)

14 12 H2O + 6CO2 + 709 kcal --> C6H12O6 + 6O2 + 6H2O --> CO2 of known concentration around plant

--> harvest plant at later time

Absorption of 6 moles of CO2 indicates absorption of 709 kcal --> determine amount of 14C in plant tissues

Method is difficult to do in the field.

But can do easily in lab

Measure concentration of Chlorophyll Simplest Method

--> know how much carbon is assimilated per --> measure amount of plant material present at 2 times gram of chlorophyll produced

∆B = B2 -B1 One way, --> collect plant tissue and extract Chlorophyll, B1 = Plant Biomass at time 1 determine how much chlorophyll per gram of tissue B2 = Plant Biomass at time 2 ∆B = change in Biomass from time 1 to time 2 Another way, --> satellite imagery --> use reflectance of light from LOSSES occur due to plants --> different reflectance patterns depending on how much cholorphyll is present death (L) consumption (G)

If you know death rate and consumption rate Convert Biomass to Energy Net Primary Production = ∆B + L + G --> determine caloric equivalent of plant material in bomb calorimeter Can apply this method to individual plants, or above ground production or below ground production, or all plants of one species or of all plants... Mean of 57 species (cal/g dry wt) (J/g dry wt)

Leaves 4,229 17,694 Roots 4,720 19,748 Seeds 5,065 21,192

3 Aquatic Systems - P’syn measured in much the same way Light bottle - Dark bottle method as in terrestrial Water samples (containing the primary producer) But easier to look at CO2 changes --> placed in two bottles Most aquatic primary producers don’t require remaining rooted in order to function --> one bottle transparent (light bottle) --> one bottle opaque (dark bottle) Use a ‘light bottle - dark bottle’ technique

--> measure CO2 and O2 in each bottle at various times

Net primary production --> light bottle

Gross primary production --> light bottle + dark bottle

Prod (g/m2/yr) Ecosystem Area Range Mean World Net (t/yr) Tropical 17.0 1000-3500 2200 37.4 Rainforest Efficiency of Primary Production Temperate 5.0 600-2500 1300 6.5 Coniferous How efficient are plants at converting solar energy to Temperate 7.0 600-2500 1200 8.4 Deciduous biochemical energy? Temperate 9.0 200-1500 600 5.4 Grassland Desert 18.0 10-250 90 1.6 Efficiency = Wetlands 2.0 800-3500 2000 4.0 Energy fixed by plant / energy in incident solar radiation

Lakes 2.0 100-1500 250 0.5 Phytoplankton usually < 0.5%

Open Ocean 332.0 2-400 125 41.5 Forest plants 2.0-3.5% Continental 26.6 200-600 360 9.6 Shelf Estuaries 1.4 200-3500 1500 2.1

Factors that Limit Primary Productivity in Ecosystems dI/dt = -kI Marine Systems

LIGHT - obvious factor

- water absorbs solar radiation

- 1/2 is absorbed in first metre k=0.02

- 5 - 10% reaches 20m in very clear water k=0.1 Relative Light Intensity

Depth (m)

4 Clear Lk Rate of P’synthesis in Three CA Lakes 60

50 Castle Lk 8 40 Lk Tahoe ---> zone of primary productivity at surface 6 0.4 30 4 0.2 20 2 0.1 10

0 0 0 042 02010 30 020 40 60

0 100% If you know: 50% 20 30% --> extinction coefficient, k 20% --> amount of solar radiation 40 Average values for tropical marine --> amount of chlorophyll present 10% 60 locations

Depth (m) Depth ---> Rate of P’synthesis 80 Relative light intensity P = (R/k) * C * 3.7

100 (3.7 - average value - g C fixed by 1 g chl in 1 hour under Gross production light saturation)

P = rate of photosynthesis - g C fixed / m2 ocean / day Example from Gulf of Alaska R = relative rate of P’synthesis for amount of light entering water k = extinction coefficient per metre solar radiation = 229 cal/cm2/day C = grams of chlorphyll per cubic metre k = 0.1/m chlorophyll = 0.0025 g/m3 water R = 14.5

P = 14.5/0.1*0.0025*3.7 = 1.34 g C/m3/day

Measured rate is 1.5 g C/m3/day

--> so formula does good job predicting Relative P’synthesis, of rate R

Total daily surface radiation, kcal/m2

5 Summer Fall Solar radiation varies greatly globally

--> so should primary productivity

20 June

15

Sept 10

Dec 5 Potential productivity Winter Spring 0 0 20406080 North Latitude 0.01 0.3 1.6 8.7 47.0 (mg/m3)

Why are tropical regions under productive when light Nitrogen in bays on Long Island intensity is good year round? Duck farms were common - source of nutrient input Something else must be limiting P’synthesis. P and N --> nutrients --> increased P observed in bays, but not N N and P --> N taken up right away by algae

--> oceans typically low in N and P at surface

Nutrient Enrichment in Sargasso Sea Freshwater Ecosystems Low productivity despite good sun --> solar radiation limits 1o prod’n Addition of Nutrient combinations to algal cultures --> Nutrient limitation also operates Nutrients Uptake of 14C Added (% relative to controls) N+P+metals 1290 N+P 110 N+P+metals (no Fe) 108 N+P+Fe 1200

Addition of Fe alone stimulated Primary P’tion for short time

6 Experimental Lakes Area (ELA) Addition of nutrients to Algonquin Lakes (Langford)

Fertilizer - Nitrogen, Phosphorus, Potassium

2 years

Average # of ‘large’ zooplankton per litre

Lake Pre-Fertilization Post-Fertilization

Brewer 7000 135400 Kearney 47000 74600 McCauley 19100 31100

Dillon and Ringler 1974 Lake 227 - fertilized annually with phosphate and nitrogen Phosphorous and Primary productivity

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Phosphorous (mg/m3)

Lake 226 - split with impermeable barrier )

P, C and N on one side, C and N on the other. 3 Phytoplankton Biomass (mg/m Biomass Phytoplankton

1970 1975 1980 1985 Year

7 Primary Productivity in Terrestrial Systems AET - Actual Evapotranspiration

Solar radiation vs temperature - moisture into atmosphere

--> tightly linked in aquatic systems --> evaporation from ground --> transpiration from plants

--> but, in terrestrial Function of --> large range of temps among areas with same --> solar radiation solar radiation --> temperature --> rainfall eg Arizona - desert to alpine

Tennessee North Carolina

Massachussetts New York Net Primary Production Primary Net Production Primary Net Wisconsin

AET Length of photosynthetic period

Boreal coniferous

Deciduous

Pine

Temperate Coniferous Production Gross Primary

Evergreen Broadleaf

0 10203040 Leaf area duration Net primary production

8 Solar radiation, temperature and moisture Old Growth Forests and Salmon

--> good for predicting global patterns of primary produciton --> nutrient input Local? --> black bears consume tonnes of salmon each year --> nutrients --> 8 dragged 1600kg each from river to forest

--> fertilizer increases yields in crop plants --> up to 100m away --> consume only fraction of each carcass --> feces --> up to half of N in samples originated in ocean

Secondary Production Energy from Plant

Biomass from plants Not Used Consumed

Herbivory Feces Digested Detritus

Urine Metabolizable Energy

Resting E Activity Growth Reproduction Maintenance Production

How can you estimate secondary production in an animal Estimate Respiration community? - measured in a lab

Gross energy intake --> watch the animal Basal metabolic rate

--> not really a good estimate Assimilated energy --> gross E in minus e in urine and feces Maintenance and activity rates can be much higher than basal Assimilated = Respiration + Production --> temperature is very important

9 Ecological Efficiencies

Net Production Net productivity at trophic level n (P) Production Efficiency = --> growth of individuals in a population Assimilation at trophic level n (P+R)

--> Population size

Production = Growth + Birth

BIOMASS --> calories

Group Production Efficiency No. of Studies Insectivores 0.86 6 Birds 1.29 9 Production efficiency --> not constant within a species Small mammals 1.51 8 Other Mammals 3.14 56 Fish and social insects 9.77 22 Other Invertebrates 25.0 73 Herbivores 20.8 15 Carnivores 27.6 11 Detritivores 36.2 23 Nonsocial Insects 40.7 61 Herbivores 38.8 49 Detritivores 47.0 6 Carnivores 55.6 5

Birds and mammals --> 97-99% of assimilated energy Respiration to Proportion

--> RESPIRATION Food Consumption

Community Level Efficiency

Consumption Assimilation at trophic level n Lindeman’s Lindeman’s = Assimilation at trophic level n-1

Intake at trophic level n Consumption = Efficiency Net productivity at trophic level n-1 0 102030 1-2 2-3 3-4 1-2 2-3 3-4 Trophic Level Trophic Level

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