Nitrogen and phosphorus removal using tile-treatment wetlands: A 12-year study from the midwestern United States.

Nutrient enrichment from tile-drained agricultural lands to the Mississippi River is a leading cause of hypoxia in the Gulf of Mexico. Small edge-of-field wetlands can effectively treat nitrate-nitrogen (NO3 -N) export from tiles, although less research exists on their capacity to treat phosphorus (P). Additionally, long-term data are needed to incorporate variability of weather and farming practices into assessments of wetland performance longevity. Research conducted over 12 yr quantified size-effectiveness of wetlands to reduce NO3 -N and dissolved P (orthophosphate [ORP]) loadings from subsurface tile systems. Nitrate-N export was significantly higher during corn (Zea mays L.) than soybean [Glycine max (L.) Merr.] production years, during which 80-84% of mean annual loadings were exported during spring. Wetlands representing 3% (W1) of tile-drained farmland area reduced 15-38% of NO3 -N export, with cumulative reductions of 39-49 and 49-57% observed in wetlands representing 6 (W2) and 9% (W3) areas, respectively. Mass NO3 -N removal ranged from 28 to 52%. Twelve-year total ORP load reductions for W1 ranged from 53 to 81%, with cumulative reductions of 35-91% and 32-95% for W2 and W3 wetlands, respectively. Mass ORP removal ranged from 71 to 85%. Results emphasize how incorporating constructed wetlands into state and watershed-level conservation planning can significantly contribute toward reducing excess N and P export to river systems and ultimately to the Gulf of Mexico.

Habitat disturbance and the diversity and abundance of ants (Formicidae) in the Southeastern Fall-Line Sandhills.

We examined habitat disturbance, species richness, equitability, and abundance of ants in the Fall-Line Sandhills, at Fort Benning, Georgia. We collected ants with pitfall traps, sweep nets, and by searching tree trunks. Disturbed areas were used for military training; tracked and wheeled vehicles damaged vegetation and soils. Highly disturbed sites had fewer trees, diminished ground cover, warmer soils in the summer, and more compacted soils with a shallower A-horizon. We collected 48 species of ants, in 23 genera (141,468 individuals), over four years of sampling. Highly disturbed areas had fewer species, and greater numbers of ants than did moderately or lightly disturbed areas. The ant communities in disturbed areas were also less equitable, and were dominated by Dorymyrmex smithi.