FW364 Ecological Problem Solving Class 3: Ecosystems / Mass Balance Sept. 9, 2013

Housekeeping You will need your textbook/software for lab in two weeks. You will need to turn in your trash log and reflection paper tomorrow via or in lab.

Applications of Mass Balance What are these? What are the effects of zebra mussel invasion? What are zebra mussel effects on fish?  Very difficult to assess the effects of zebra mussels on fish quantitatively  One approach: Food web mass-balance

Applications of Mass Balance Great Lakes Food Web

Applications of Mass Balance Great Lakes Food Web We can build a mass-balance model that uses food web connections to link how zebra mussels affect fish What data are needed? (think about stock and flow models) Biomass of populations Consumption Production Respiration Flow to detritus Predator-prey relationships

Applications of Mass Balance Oneida Lake, New York Major findings: Zebra mussels negatively affect walleye and some life stages of yellow perch Zebra mussels positively affect lake sturgeon and many littoral fish (e.g., bluegill)

Biological Production So far, we have been using stock & flow models for plants like this: Plant biomass Respiration Photosynthesis Where flow rates are represented by arrows: Input to plant biomass is photosynthesis An output to plant biomass is respiration The next step is to relate photosynthesis and respiration to production

Biological Production Definitions: Gross production = Rate of photosynthesis  total amount of C fixed (carbon assimilation) Net production = Photosynthesis – Respiration  the “profit” for plants ~ the carbon that plants can use to add biomass Note: for right now, we are not assuming steady state plant could be growing, or not Primary production can be measured by: 1.Short-term estimates 2.Long-term estimates Plant biomass Respiration Photosynthesis Why do we care about short-term vs. long-term estimates?

Short-term Primary Production We can measure short-term primary production by isolating a plant in a chamber and measuring: increase in O 2 decrease in CO 2 uptake of radioactive C Question: If we measure an increase in O 2 in the light, is this net or gross production? Answer: Net production In the light, photosynthesis is occurring (which produces O 2 ) However, the plant still respires (which consumes O 2 ) So some of the O 2 produced gets consumed The measured increase in O 2 in the light is the difference (i.e., O 2 produced from photosynthesis – O 2 consumed by respiration)

Short-term Primary Production So, then, how do we measure gross production? Need a dark chamber in order to get respiration only: In the dark, no photosynthesis occurs (no production of O 2 ) However, respiration still occurs (which consumes O 2 ) Gross Photosynthesis = (O 2 change in light) – (O 2 change in dark) (gross production) (net production) (loss due to respiration) (always negative, so the math works like addition)

Long-term Primary Production We can measure long-term production much like crop production on a farm Net production is essentially the addition of new biomass (incorporation) So another way to measure net production is to eliminate (or assume) that there are no losses other than respiration (no death, no grazing) and measure the change in biomass over a set length of time e.g., over one season: this works for crops, where losses are minimized This is a cheap (budget) approach for estimating net production

Consumer Production Now on to animal (consumer) production Organisms at the second trophic level, third, etc. Animal production often measured with a budget approach (losses estimated) gut consumption defecation assimilation incorporation respiration Consumer Mass Balance assimilation = gross uptake incorporation = net uptake

Consumer Production Consumer gross production (uptake) is the assimilation rate (how much carbon enters / time) of the organism Assimilation Rate = Consumption Rate * Assimilation Efficiency where assimilation is fraction transfer of currency across the gut wall consumption defecation assimilation incorporation respiration Consumer Mass Balance assimilation = gross uptake incorporation = net uptake gut

Consumer Production consumption defecation assimilation incorporation respiration Consumer Mass Balance assimilation = gross uptake incorporation = net uptake Usually more interested in consumer net production (biomass gain): Consumer Net Production (uptake) = Assimilation Rate - Respiration Rate (since material lost in respiration does not build new biomass) gut

Consumer Production ~ OR ~ Net Production = Consumption Rate * Incorporation Efficiency where incorporation means material incorporated into new biomass (net production is what is left after respiration has been subtracted from what has been assimilated) consumption defecation assimilation incorporation respiration Consumer Mass Balance assimilation = gross uptake incorporation = net uptake gut

Consumer Production consumption defecation assimilation incorporation respiration Consumer Mass Balance assimilation = gross uptake incorporation = net uptake Let’s be more explicit and define some equations… gut

Consumer Production NPR = net production rate A = Assimilation efficiency [0 < A < 1] CR = Consumption rate AR = Assimilation rate RR = Respiration rateI = Incorporation efficiency [0 < I < 1] NPR = CR*A – RR = AR – RR or NPR = CR*I consumption defecation assimilation incorporation respiration Consumer Mass Balance assimilation = gross uptake incorporation = net uptake gut

Video Break! Stretch

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System What quantity are we solving for? Biomass of Herbivores Biomass of Plants SHSH SPSP Herbivore Plant

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System What quantity are we solving for? Biomass of Herbivores Biomass of Plants SHSH SPSP Important note: For this example, we want to use processes that affect biomass directly, i.e., direct flows that add or remove biomass We are not going to need to model respiration explicitly (respiration has already been “accounted for”)

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System What quantity are we solving for? Biomass of Herbivores Biomass of Plants SHSH SPSP T = S F THTH = SHSH FHFH TPTP = SPSP FPFP SHSH = T H * F H SPSP = T P * F P SHSH SPSP T H * F H T P * F P = Let’s set up the equation using only algebra (no numbers)

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP T H * F H T P * F P = Givens: T H = 300 d T P = 30 d

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP 300 d * F H 30 d * F P = Givens: T H = 300 d T P = 30 d

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP 300 d * F H 30 d * F P = Givens: Herbivores consume 60% of NPP (0.6*NPP) 25% gets incorporated (I = 25% = 0.25) We have one (and only one) input to herbivores  consumption Since we are interested in change to herbivore biomass, we need to know how much of the material consumed is incorporated  Our F H needs to be the incorporation flow We can define incorporation to herbivores as: F H = 0.25( Consumption ) F H = 0.25(0.6*NPP) F H = 0.15 NPP This sounds like a flow!

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP 300 d * F H 30 d * F P = We have one (and only one) input to herbivores  consumption Since we are interested in change to herbivore biomass, we need to know how much of the material consumed is incorporated  Our F H needs to be the incorporation flow We can define incorporation to herbivores as: F H = 0.25( Cons. Rate ) F H = 0.25(0.6*NPP) F H = 0.15 NPP F H = 0.15 F P How does NPP relate to F P ? Remember from earlier, NPP is the addition to plant biomass So NPP = F P Givens: Herbivores consume 60% of NPP (0.6*NPP) 25% gets incorporated (I = 25% = 0.25) This sounds like a flow!

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP 300 d * 0.15 F P 30 d * F P = We have one (and only one) input to herbivores  consumption Since we are interested in change to herbivore biomass, we need to know how much of the material consumed is incorporated  Our F H needs to be the incorporation flow We can define incorporation to herbivores as: F H = 0.25( Cons. Rate ) F H = 0.25(0.6*NPP) F H = 0.15 NPP F H = 0.15 F P How does NPP relate to F P ? Remember from earlier, NPP is the addition to plant biomass So NPP = F P Givens: Herbivores consume 60% of NPP (0.6*NPP) 25% gets incorporated (I = 25% = 0.25) This sounds like a flow!

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP 300 d * 0.15 F P 30 d * F P = SHSH SPSP 300 d * d = SHSH SPSP = 1.5 (unit-less quantity) 50% greater herbivore biomass than plant biomass!  Inverted biomass pyramid Herbivores Plants More on this in a moment

Given that herbivores consume 60% of net primary production and incorporate 25% of what they consume (incorporation efficiency = 25%, recall distinction from assimilation efficiency), that T for herbivores is 300 days and that T for plants is 30 days, what is the ratio of herbivore biomass to plant biomass? Exercise C Residence Time in Plant-Herbivore System SHSH SPSP 300 d * 0.15 F P 30 d * F P = SHSH SPSP 300 d * d = SHSH SPSP = 1.5 (unit-less quantity) We can generalize from this exercise to specify this new equation: SHSH SPSP T H * cF P T P * F P = Where c is fraction of net plant production incorporated by herbivores (15% in above example, i.e., = 25% * 60%)

Biomass Pyramids & Turnover Time SHSH SPSP T H * cF P T P * F P = Question 1: What does this general relationship tell us about the amount of herbivore biomass that can be supported per unit of plant biomass? Herbivore Perspective: Think about T H and c ( c is fraction of net plant production incorporated by herbivores)

Biomass Pyramids & Turnover Time SHSH SPSP T H * cF P T P * F P = Question 1: What does this general relationship tell us about the amount of herbivore biomass that can be supported per unit of plant biomass? Answers: (herbivore perspective) As turnover time of herbivores gets longer (large T - slower to turnover), more herbivore biomass can be supported by a given plant biomass ( slow-growing, slow-reproducing, slow-dying herbivore will be more abundant per unit of resource than fast-growing, fast dying herbivore) As herbivores get more voracious and efficient (higher c), more herbivore biomass can be supported by a given plant biomass

Biomass Pyramids & Turnover Time SHSH SPSP T H * cF P T P * F P = Question 1: What does this general relationship tell us about the amount of herbivore biomass that can be supported per unit of plant biomass? Plant Perspective: Think about T P

Biomass Pyramids & Turnover Time SHSH SPSP T H * cF P T P * F P = Question 1: What does this general relationship tell us about the amount of herbivore biomass that can be supported per unit of plant biomass? Answers: (plant perspective) As plant turnover time gets longer (large T– slower to turnover), less herbivores can be supported per unit plant biomass) Concept check: What would lead to plants having a longer T? Anything in environment that is poor for growth (colder / less light / poor nutrients); plants that grow slower; greater investment in poisons

Biomass Pyramids & Turnover Time SHSH SPSP T H * cF P T P * F P = Remember that low biomass (stock) can still mean high production if turnover is rapid (small T) Can generalize from what we have done to any two trophic levels (trophic levels do not have to be adjacent), as long as you know what is going on in between (# of levels, incorporation efficiency of each consumer level) We will be practicing this in Lab 2  Using this guy (or gal)

Notes for Lab Tomorrow The assignment, powerpoint, and notes will be posted online. Bring a calculator, writing utensil, and paper. Bring your plastic trash log and reflection paper.