Statistical Lab for Earthworm Populations

Earthworm Populations
Week 5 Lab

Based on the reading and the mini lecture we supposed that earthworms would be more abundant in the forest habitats than in the prairie habitat, and that the older forest would be more favorable than the young, regenerating forest. In addition we predict a positive correlation between soil temperature and earthworm abundance because worms would be more active and comfortable in warmer habitat. Litter depth and percent cover were a little bit more difficult to predict. On the one hand the more of these two variables the better the habitat is to support earthworms, especially litter depth. On the other hand the abundance of earthworms has an effect on these variables such that the more worms that are present, the more litter is consumed and the presence of worms could also have a negative effect on the habitat for undergrowth plant species reducing the percent cover. We predict that these variables are more indicators of worm populations so that we expect to find more worms where the litter depth is smaller and there is less plant cover.

Analysis 1.
Prairie Habitat Forest Habitat
Soil Temp C Average LD % Cover # Worms Soil Temp C Average LD % Cover # Worms
MEAN: 9.80555556 12.15 66.25 50.5 11.6851852 1.7025 30.33333 71
STERROR: 0.98169984 3.70129482 15.99153 7.076958 0.71169922 0.68096592 24.96887 18.52026
UpperCE: 12.1158516 20.8604903 103.8839 67.15465 13.7633369 3.69091095 103.2421 125.0789
LowerCE: 7.49525948 3.43950972 28.61612 33.84535 9.60703344 -0.285911 -42.5754 16.9211

The standard errors are huge for most all of the categories which lead to large confidence intervals. We cannot be very confident about our mean values especially for the litter depth, percent cover, and number of worms.
A Welch Modified Two-Sample t-test was done, and no significant differences were found between forest and prairie habitat lands on worm abundance (t=1.03, df= 2.6, p value = .4)

Analysis 2.