Wednesday, November 15, 2006 - 10:00 AM

Resilience of the Tallgrass Ecosystem to Military Disturbance.

Peggy Althoff, Kansas State Univ, Dept of Agronomy, 2004 Throckmorton, Crop, Soil & Range, Manhattan, KS 66506-5501

Military training exercises disturb ecosystems primarily through vegetation removal, compaction, and increased erosion.  Evaluating and assessing the disturbance impact of tank maneuvers has been identified as a priority at military installations.  On two different soil types (silty clay loam and silt loam), we sampled physical, chemical, and biotic indicators of soil quality to evaluate soil disturbance resulting from two years of tank maneuvers during wet and dry soil conditions followed by one year of recovery at the Fort Riley Military Installation in Kansas.  Treatment consisted of a 63-ton M1A1 tank making 5 passes (single disturbance) over each plot in a figure-8 pattern in 2003.  In 2004, one-half of the same figure-8 patterns on each plot received 5 additional tank passes (repeated disturbance) during the same conditions (wet or dry) as in 2003.  There was no additional tank disturbance in 2005. Bulk density and penetrometer resistance indicated that compaction remained most severe on curve areas in the silt loam soil. In both soil types, soil carbon measurements, including total carbon, active carbon, and microbial biomass carbon were consistently lower on curve compared to straight-a-way areas.  Earthworm and nematode densities in silt loam also remained significantly lower in curve areas than in straight-a-way sections of the track.  Earthworm densities in silty clay loam continued to be impacted by all treatments and in all areas.  Vegetation biomass in both soil types continued to be reduced in repeated traffic treatments.