1. Controls and additive series

2. Rule #1
Make sure your control, is actually a control
e.g. non-lethal presence of predators in bromeliads….

4. Caged Predator
Free Predator
No Predator

5. Caged Predator
Free Predator
No Predator

6. Additive controls…
Group exercise:
Read your stream control example, and decide on:
(1) What is wrong with the design?
(2) How you might fix it.

7. Scenario 1
Before
After A B C A B C

8. Scenario 2 B C A
+ pollutant E F D
- pollutant

9. What is the probability that the 3 “worst” streams are randomly assigned to the pollutant treatment?

10. Scenario 3 + chemical in alkaline solution control Before After B C BD D
control

11. Scenario 4 A B C
Before
After D E F
+ pollutant
control

13. Scenario 5 ?

14. Insect abundance =
m1 * width +
m2 * dioxin +
m3 * width*dioxin +
Y-intercept
(and error)

15. Summary of control types
Which scenarios lacked:
Control for initial conditions?
Unmanipulated, contemporaneous control?
Control for side effect of manipulation?
Control for covariates?
Control for non-target response?

16. BACI design Before After Control Impact
Unmanipulated, contemporaneous control
Initial conditions
Eg. Scenario 3
Before
After
+ pollutant
Before
After
control

17. BACI design Before After Control Impact
Unmanipulated, contemporaneous control
Initial conditions
Before
After
control
+ pollutant

18. Example of BACI design: on forest fragments and birds
Ernest Leupin’s study
on forest fragments and birds

19. Sicamous Creek Research Forest
Figure 2. Experimental layout and treatments at the Sicamous Creek Experimental Forest. A- Uncut Reserves, B- 0.1ha openings, C- Selection Cut, D- 10 ha opening, E- 1ha openings . Each Treatment was replicated three times. Dashed line indicates the sampling extension of one uncut reserve.

20. Figure 3. Aerial view (south-west) of the resulting forest matrix after harvest.

21. How can we analyze BACI designs?
Randomized block?
A treatment x date ANOVA?
Before
After
+ pollutant
control A B C D E F
What is n?
What is k?
How many independent experimental units in total?

22. How can we analyze BACI designs?
Randomized block?
A treatment x date ANOVA?
Before
After
+ pollutant
control
What is n?
What is k?
How many independent experimental units in total? A B C G H I D E F J K L

23. How can we analyze BACI designs?
Two separate ANOVAs / t-tests?
Before
After
+ pollutant
control
Different?
Different?

24. How can we analyze BACI designs?
Two separate ANOVAs / t-tests?
Impact sites
Y variable
before after
before after
before after
before after A B C

25. How can we analyze BACI designs?
Need to match the number of datapoints with the number of experimental units
Need to take advantage of built-in control for stream identity

26. How can we analyze BACI designs?
One solution:
Use difference between before and after as the data!
Before
After
Difference
+ pollutant A B C A B C A B C
Before
After
Difference
control D E F D E F D E F