Need help with a ecology manuscript

Ecology Lab

Trunk cross-sections from a 50 year-old hardwood forest

Trunk cross-sections from a 100 year-old hardwood forest

Upslope vs. Downslope – do they differ in age of last disturbance as determined by successional stage?

If the forests differ in age, we predict: • The forests will differ in the size of the oldest hardwood trees. • The forests will differ in the proportion of mature hardwoods relative to pines.

Analyses: Part I

2 t-tests for your 2021 data:

1. Does the circumference of the top 10 trees upslope differ from the circumference of the top 10 trees downslope?

2. Does the circumference of the top 25 trees upslope differ from the circumference of the top 25 trees downslope?

Usually larger sample is better, but not always. Why might that not be true here?

Analyses: Part II

2 t-tests for comparing 2019 to 2021 data:

1. Does the 2019 upslope data differ significantly from the 2021 upslope data

2. Does the 2019 downslope data differ significantly from the 2021 downslope data

Do you expect a high or low p-value here?

Note: for Sections 51 & 52 – your data was taken from a different place than the 2019 data. How might this change your hypotheses, interpretations?

Analyses: Part III 3 Fisher’s exact tests (is the number of pines & hardwoods contingent on being upslope vs. downslope?:

1. Is the number of pines & hardwoods over 80 cms in 2019 contingent upon being upslope vs. downslope?

2. Is the number of pines & hardwoods over 80 cms in 2021 contingent upon being upslope vs. downslope?

3. Is the number of pines & hardwoods over 80 cms for both years combined contingent upon being upslope vs. downslope?

Pines Hard

Up X Y

Downs W Z

Contingency Table