Conclusions

Initial edaphic conditions:
Edaphic conditions in the 32 upland forest stands varied with soil texture and military use. Less organic layer mass and soil A horizon depth, and greater soil bulk density and organic layer C:N ratios, indicate more soil disturbance in military compartments open to tracked vehicles, and greater response to that disturbance in sandy sites.

Nitrogen cycling in the 32 upland forest stands varied with soil texture and military use. Higher rates of nitrification, but lower pooled organic layer mass, indicate greater nitrogen availability to plants, but less nutrient capital and, possibly, less resilience to disturbance in sandy, compared to clayey, sites.


Burn Responses:
The prescribed fires minimally, but significantly, reduced the soil organic layer. Immediate (< 3 wk) fire effects on soil nutrients varied, with a general trend of no significant effect on extractable mineral soil N or Al, and increase in Ca. We conclude the low-intensity fires had little short-term effect on soil quality.

Over the longer-term (2-3 season), the prescribed fires influenced nitrogen cycling. NH4-N generally increased the growing season following burning. NO3-N increased following fire in stands with heavier military use, but decreased in stands with predominantly dismounted military training.

We conclude that effects of prescribed fire and military training on forest soil biogeochemistry at Fort Benning depend on the temporal scale at which they are evaluated. Initial conditions in our sites suggest, over the scale of decades, military training with tracked vehicles can reduce soil quality, especially on sandy sites. Low-intensity prescribed fire appears to have little immediate effect on soil conditions, but may result in an increase in available ammonium in the first post-fire growing season. Heavier military use may slow soil recovery during the 2-3 season intervals between prescribed fires. Monitoring over multiple temporal scales can help characterize short-term trajectories of ecosystem response to land use disturbance within the longer-term trajectories and cumulative impacts of land use over time.