We also detected some impact in nitrogen fixation rates. What we can see is there were big differences at Dugway in terms of the impact of disturbance on nitrogen fixation, the burn treatment again being the most severe treatment. There are also big drops at the San Rafael Swell site and at Fort Bliss. You will also notice there is a big difference in the amount of nitrogen fixation that goes on between these different deserts. At Yuma Proving Ground there is essentially no difference in rates of nitrogen fixation. We're down near detection levels at that site, so it's not really surprising.

What about the effects of disturbance on infiltration and erodibility? Does disturbance have an impact on these soil properties? We found that there was a big impact. People have been speculating that disturbance of the crusts must have an impact on these processes, but they haven't really been documenting it very well. We were able to document impacts in all three of the sites that were crusted. You can see significant differences in total runoff in disturbed areas. At Dugway Proving Ground we've got more runoff in the trampled area, and much more runoff in the burned area. At the San Rafael Swell, again an increase is evident. At Fort Bliss the runoff is quite a bit higher, especially in the tank areas. With more runoff, there is consequently more sediment lost. The sedimentation numbers are larger, indicating that there is a lot more erosion going on in these plots.

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