1

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?

2

Mistake on exam Key – #15 should be b.

3

Outline for ecosystems

Introduction

How does energy move through an ecosystem?

How does matter move through an ecosystem?

4

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.

5

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

6

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

7

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

8

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

9

How does matter move through an ecosystem?

Nutrient recycling in terrestrial andaquatic ecosystems

10

Nutrient recycling in terrestrial systems

- where is it happening?

11

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?

12

-mass balance

-inputs = outputs

-weathering + precipitation =loss in streams

measurecalculate by difference

13

Figure 8.2

14

Figure 8.3

15

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?

16

Effect of rainfall on rate of leaf decomposition

17

Litter/living leaf

Soil P/plant P

Soil N/plant N

%of total org C

Tropical Temperate

Which column is larger?

18

Land use affects phosphorus retention in a system

19

20

Nitrogen fixation can increase nitrogen avail.

Litter quality (nitrogen content) of different tree species

21

Mychorrhizae increase nutrient content ofplants

Fig. 8.7

22

Nutrient recycling in aquatic systems

- where is it happening?

23

-sediments not in contact with pelagic zone

- most sediments are anaerobic - reactions are slower

Pelagic zone

24

Figure 8.12

25

Cool (dense) water

Warm (low density) water

Water below the thermocline may becomedepleted of oxygen in summertime

Why?

26

Fig. 8.16

27

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

28

Fig. 8.17

29

Which nutrient is most limiting to aquaticsystems??

What do I mean by most limiting?

30

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

31

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

32

33

Thermocline

Fountain

oxygen

How could this reduce algal blooms?

34

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