SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental Consequencesdestruction of prairie dog habitat would directly affect burrowing owls and mountain plovers if thesespecies were present in the colony, and would reduce suitable habitat in areas not currently occupiedby these species. If prairie dog populations decline on FTC, use of the installation for foraging and/ornesting by bald and golden eagles and ferruginous hawks would decline or be eliminated.Regulatory and Administrative Mitigation 2: Mitigation measures for impacts to threatened andendangered species from maneuver training would be the same as those described under Impacts fromLive-Fire Training.Impact 3: Impacts to vegetation. The number of large-maneuver rotations would not be expected todiffer from the current condition under Alternative C; however, there are qualitative differencesbetween IBCT and SBCT maneuver training. The SBCT would use existing roads and trails morethan the IBCT; however, it requires large training areas. The SBCT causes less surface disturbancedoes less digging during maneuver rotations than the IBCT. There are more vehicles of heavier grossweight in the SBCT, and the quantity of small-unit collective maneuver rotations at FTC would beexpected to increase by 50 percent when comparing the SBCT’s small unit maneuver requirement tothe IBCT it would replace. When looking at all units that would train on FTC or PCMS the increasein maneuver training is less than a 10% increase with the 2/25 th SBCT. The MIMs associated withmaneuver training at both FTC and PCMS would be expected to be nearly double for an SBCT whencompared to an IBCT (49,576 MIMs associated with the IBCT versus 104,898 MIMs associated withthe SBCT). Brigade- and battalion-level training would primarily occur at PCMS, and the frequencyof maneuver training at PCMS is not expected to increase above existing levels.Maneuver activities can have a serious effect on the understory species in the juniper woodlands fromvehicles maneuvering between the larger trees. Decreases in density and cover of woody plants areespecially detrimental in juniper woodlands because they typically occur on steep slopes with lowinitial cover and highly erodible soils. Such effects on woodland vegetation may be less severe atFTC (as compared with the PCMS studies) because there are many established trails on whichvehicles may travel through the woodland areas (USACE 2007a).Indirect impacts from movement of vehicles can result from vegetation loss, soil disturbance,disaggregation, compaction, and consequently erosion, each of which can change the nature andavailability of microsites for seed germination (Shaw and Diersing 1989; Shaw and Diersing 1990;Diersing et al. 1988). Disturbance of the soil crust in arid ecosystems can accelerate erosion, decreasewater retention, disrupt plant nutrient cycling at the microbial level, and expose the reservoir of weedseeds in the soil to conditions favorable for germination (USGS 2002). Reseeding efforts by DECAMand ITAM reduce the overall recovery period at FTC and PCMS by allowing succession to skip theinitial weedy stage.Maneuver Training Area studies have been conducted for the PCMS to assess the effects of trainingactivities on vegetation at the PCMS. These vegetation studies are also applicable to assessing thepotential impacts of mechanized military training at FTC (Shaw and Diersing 1989; Shaw andDiersing 1990). The studies indicate that grasslands, woodlands, and shrublands have been affectedby prior maneuver training based on readily visible imprints of tracks on the soil (tracking) comparedwith untracked sites (Shaw and Diersing 1989; Shaw and Diersing 1990; and Diersing et al. 1988).Direct impacts from the passage of vehicles such as the Stryker include crushing of herbaceous andwoody vegetation that might not resprout or otherwise recover and injury to shallow roots that mightkill the plants or retard development.Pedestrian traffic also can affect vegetation. For grasses and herbaceous cover, these impacts wouldrange from negligible to substantive depending on use factors, such as the number of troopsFebruary 2008 5-171 2/25th SBCT Final EIS