1 mon. tues. wed. thurs. fri. week of oct. 13 week of oct. 20 wet, muddy outdoor lab – wear...

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Mon. Tues. Wed. Thurs. Fri.Week ofOct. 13

Week ofOct. 20

Wet, muddy outdoor lab – wear closed-toed shoes

Week ofOct. 27

Independent project set-up

Class in LibraryMultimedia Room

Get back to uson Lemna experimentsif necessary

Week ofNov. 3

Forest ecology lab – dress for weather

Exam 2

T lab switch?

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Mistake on exam Key – #15 should be b.

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Outline for ecosystems

Introduction

How does energy move through an ecosystem?

How does matter move through an ecosystem?

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All organisms participate in element cycling. Each group will be assigned one of the following element cycles (C, N, P, S). Describe 5 ways that your everyday activities contribute to the element cycles (hint: think about the indirect effects of your activities). In your answer, include 1 process that transforms an element from inorganic to organic form, 1 process that transforms an element from organic form to inorganic form, and 1 non-biological transformation.

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Carbon cycle

Driving a car, smoking a cigarette, burning oil

Respiration

Growing plants for food

Compost pile in back yard

Carbon from fossil fuel burning dissolves into oceanand precipitates as limestonec

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Nitrogen cycle

Driving a car

Growing plants for food – N fertilizer

Eating plants and excreting excess N

Planting soybeans and clover

Using excess N fertilizer that runs off into streams

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Sulfur cycle

Driving a car

Burning coal produces acid rain

Eating plants and excreting excess S

Planting vegetation

Walking on dirt paths rather than sidewalk

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Phosphorus cycle

Growing plants for food – P fertilizer

Sedimentation and burial of P in lakes

Eating plants and excreting excess P

P in sewage discharged to water stimulates algal growth

Tilling land for agriculture releases P into air

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How does matter move through an ecosystem?

Nutrient recycling in terrestrial andaquatic ecosystems

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Nutrient recycling in terrestrial systems

- where is it happening?

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Nutrient recycling in terrestrial systems

- new weathering of bedrock provides small amount of nutrients taken up by vegetation each year (~10%)

- how do we know that?

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-mass balance

-inputs = outputs

-weathering + precipitation =loss in streams

measurecalculate by difference

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Figure 8.2

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Figure 8.3

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Organic matter decomposition

1. Leaching of soluble compounds by water

2. Consumption by detritus-feeding orgs.- e.g., earthworms, millipedes, etc.

3. Breakdown of rest by fungi and bacteria- how do they decompose?

What factors affect rate of decomposition?

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Effect of rainfall on rate of leaf decomposition

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Litter/living leaf

Soil P/plant P

Soil N/plant N

%of total org C

Tropical Temperate

Which column is larger?

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Land use affects phosphorus retention in a system

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Nitrogen fixation can increase nitrogen avail.

Litter quality (nitrogen content) of different tree species

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Mychorrhizae increase nutrient content ofplants

Fig. 8.7

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Nutrient recycling in aquatic systems

- where is it happening?

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-sediments not in contact with pelagic zone

- most sediments are anaerobic - reactions are slower

Pelagic zone

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Figure 8.12

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Cool (dense) water

Warm (low density) water

Water below the thermocline may becomedepleted of oxygen in summertime

Why?

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Fig. 8.16

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Low oxygen in facilitates recycling ofsome nutrients (P and Fe)

When oxygen is present, P and Fe combine toform insoluble compounds which remain in the sediments

When oxygen is absent, P and Fe are solubleand remain in water – can be mixed upinto pelagic zone and taken up by algae

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Fig. 8.17

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Which nutrient is most limiting to aquaticsystems??

What do I mean by most limiting?

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P - limitation

N-limitation

LIS

Housatonic

Where does P-limitation switchto N-limitation?

How will changes in nutrient loading affect species composition and frequency of algal blooms?

Goal to decreaseN input to LIS by55% in 15 years

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Example of using properties of nutrientrecycling in aquatic systems to reducealgal blooms in freshwater systems

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Thermocline

Fountain

oxygen

How could this reduce algal blooms?

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Nutrient recycling

- Terrestrial systems- soil

- weathering of rock- decomposition of organic matter

- Aquatic systems- sediments and deep water

- reactions slow (anaerobic)- decomposition not near uptake