PARENT SESSION
Organized Oral Session 46: Ecological indicators at multiple scales
Organizer(s): F Müller and E Hyatt
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 516 C, Level 5, Palais des congrès de Montréal

Soil nutrient flux as an indicator of ecological disturbance.

Ko vacic, David^*,1, Krzysik, Anthony², Zak, John³, Freeman, Carl⁴, Graham, John⁵, Duda, Jeffrey⁶, ¹ University of Illinois, Champaign, IL² Prescott College, Prescott, AZ³ Texas Tech University, Lubbock, TX⁴ Wayne State University, Detroit, MI⁵ Berry College, Mount Berry, GA⁶ Biological Resources Division – Western Fisheries Research Center, Seattle, WA

ABSTRACT- The development of reliable and ecosystem relevant ecological indicators for assessing and monitoring the condition and trends of ecological processes represents a significant advancement for land managers. Our objective was to determine if soil nutrient flux could be used as a biogeochemical indicator of ecosystem resilience and sustainability. In mature oligotrophic forests competition for nutrients is intense and soil leaching losses are low. When forest vegetation is disturbed; nutrient uptake is interrupted, and nutrient losses ensue. Following disturbance nitrate is highly vulnerable and typically exhibits the greatest ecosystem losses because of its high solubility. Losses of K, Ca, and Mg have also been documented after disturbance. We hypothesized that soil solution nutrient concentrations would be directly correlated with training disturbance levels. Nine research sites were selected in the Fall-Line Sandhills of Fort Benning Georgia, three each in three disjunct military training disturbance classes: Low, Medium, and High. Porous cup tension lysimeters installed on the nine sites provided soil solution samples that were analyzed for anions and cations on a seasonal basis. Nutrient concentrations across sites followed our hypothesized trend with low and medium sites exhibiting lower nutrient losses than high intensity sites. High disturbance sites exhibited the highest mean soil solution nutrient concentrations. Average peak nitrate solution concentrations were 1.5, 0.5, and 15.1 mg L^-1 for the Low, Medium and High disturbance classes, respectively. Those for sulfate were 42.3, 25.1, and 68.5 mg L^-1, respectively. Average peak calcium solution concentrations were 8.5, 14.0, and 24.0 mg L^-1 for the Low, Medium and High disturbance classes, respectively. Those for magnesium were 1.8, 2.1, and 5.8 mg L^-1, respectively. Soil solution losses appear to be effective indicators of disturbance and condition on military training lands.

Key words: nutrient losses, ecological indicators, disturbance, soil leaching