1. ANOVA Seminar #30 (Economic Value of Tropical Forest to Coffee Production) Mike DeDad 12/3/07 Source: http://www.pnas.org/cgi/reprint/0405147101v1.pdf

2. Economic Value of Tropical Forest to Coffee Production Societal benefits are immense Not a big enough motivator Economic value pollination services to agriculture

3. Purpose To “conduct pollination experiments to examine the effects of these patterns on coffee production and quality, and to estimate the resulting economic value of tropical forest fragments to coffee farms.” Previously determined that “bee species richness and visitation rate decline with distance from forest.”

4. Methods Studied a 1,065 hectare coffee farm in the Valle General, Costa Rica Took branches from three types of sites Near, Intermediate, and Far Took 4 branches from each of 5 healthy plants from each site divided randomly between hand-pollination and ambient pollination

6. Methods Explanatory Variables Distance (Near, Intermediate, or Far) Pollination (By hand or ambient) Response Variables seed mass Fruit set peaberry frequency

7. Methods What are some possible confounding variables? Length of the branch number of leaves relative shade Dismissed these because r<.19 Not significantly related

8. What are the hypotheses? Null Hypothesis: population means of each response variable are equal for each explanatory variable Alternative Hypothesis: population means differ

9. Two-way ANOVA DFG= product of the two degrees of freedom for each factor Distance dfg= (I-1)= 3-1= 2 Pollination dfg= (I-1)= 2-1= 1 Two-way ANOVA dfg= 2 x 1= 2

10. F 2,24 = 8.13, P < 0.0001F 2,24 = 2.96, P = 0.0710 F 2,24 = 7.28, P = 0.0034 Reject H 0 Borderline

11. Conclusions Hand pollinating increased seed mass and fruit set for far sites while decreasing peaberry frequency (higher quality) Ambient pollination decreased seed mass and fruit set for far sites while increasing peaberry frequency (lower quality)

12. Conclusions The presence of native tropical forest increased both the quantity and quality of harvested coffee (near and int. sites) The lack of nearby forest decreases quantity and quality of harvested coffee (far sites)

13. What are the consequences of committing error? Type 1: Rejecting the null hypothesis even though it is true Convincing farmers to not expand even though the presence of forests has no effect on coffee production Type 2: Failing to reject the null hypothesis even though it is false Allowing deforestation even though forests have an effect on coffee quality and yield

14. Are there any questions?