PARENT SESSION
Oral Session # 11: Ecological Studies on Military Installations.
Presiding: B Collins
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 203.
Disturbance of upland soil and vegetation affects the export of nutrients and sediments to streams during storm events.
Houser, Jeffrey1, Mulholland, Patrick 1, Maloney, Kelly2, 1 Oak Ridge National Laboratory, Oak Ridge, TN, USA2 Auburn University, Auburn, AL, USA
ABSTRACT- The inputs of sediments and nutrients to streams are affected by watershed characteristics. The role of riparian zones in buffering streams from watershed disturbance has been well studied. Our objective was to determine the impact of upland soil and vegetation disturbance on nutrient concentrations in streams with largely intact riparian zones. Spatial variability in the intensity of military training (infantry and tank maneuvers) at the Ft. Benning military base (Columbus, GA) results in the uplands of some stream catchments being highly disturbed while others remain relatively undisturbed. The watershed disturbance intensity was quantified as the proportion of the watershed area that consisted of either roads or bare ground on a slope greater than 3 %. We selected 11 headwater streams located in 11 different catchments across this gradient of disturbance intensity: 3 reference sites, 4 sites of low to moderate disturbance, and 4 sites of high disturbance. We examined nutrient concentrations in these streams during baseflow conditions and storm events. Suspended sediments showed the strongest pattern across the disturbance gradient. In streams draining highly disturbed catchments, suspended sediments (dominated by the inorganic fraction) were significantly higher during baseflow conditions and showed larger increases in concentration during storms. Under baseflow conditions PO43- concentrations were lower in the disturbed streams (perhaps due to adsorption by the high level of inorganic sediments in these streams), and NH4+ and NO3- showed no clear pattern across the disturbance gradient. During storm events, PO43-, NH4+ and NO3- generally showed larger increases in concentration in the disturbed streams. These results indicate that streams with intact riparian zones can be affected by upland disturbance.
Key words: nitrogen, sediment, disturbance, phosphorus