Well, this seems pretty clear - there is almost twice as much earthworm biomass (when all are added together and the total weight of worm mass is weighed) per unit area in our experimental plots than in the high grade prairie. This is interesting in a number of ways:
1. This confirms what we were supposing (based upon previous work) that the soil (and the biology of soils) differs after buckthorn has been growing there for some time.
2. It seems to suggest that native prairie is susceptible to invasion. That being stated the biomass is pretty small.
3. Earthworm biomass will be worth monitoring in years to come - it may be a useful index of recovery.

To obtain the above graph I removed the first buckthorn sample from the analysis. I did this, not because it I did not 'like ' the result, but rather because the fact that the soil had clearly been saturated with rain which made it unable to support any earthworms (in fact there were 2 very small worms in the sample). The statistical analysis performed was a two-tailed t-test which was significant (p<0.01), meaning that for us to conclude that there was a difference in biomass between these populations is reasonable.

(If the outlying sample remains in the analysis the results of a one-tailed t-test remain significant).