For the next section of the seminar, I will talk about the effects of our disturbance treatments, the process of natural recovery following that disturbance, and finally the effect of the alginate pellets. In every case the disturbance had a big effect on the biomass. This chart gives the mean chlorophyll a contents of the soils together with p-values, which indicate whether or not there was significant variation among the treatments. Essentially, if the p-value is less than 0.05, it's significant. So some of these are really significant. At Dugway Proving Ground you can see that trampling had a big impact, but the burning was even more severe. At the San Rafael Swell site we have a big trampling effect, and at Fort Bliss we have both big trampling and burning effects, with the tank disturbance being more severe than the burn treatment. You would imagine that a tank does more harm than a couple of scientists jumping around, and it does. Now, at Yuma Proving Ground, we're down near the detection level for chlorophyll a, so we didn't get a significant difference. We use a number of different enumeration methods; I can't go into all of these but we use a most probable number technique, epifluorescence microscopy, plate counts, and a moistened soil method. Using the most probable number technique we found a significant difference in disturbed plots at Yuma. Thus, in all cases we detected disturbance impact.

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