This experiment involved the addition of 15N at various distances away from a group of target plants to determine the local pattern of nutrient capture by each of the target species. Twenty plots were laid out in Field C in such a way that the plot centers were at least 2m apart. Plots were chosen so that at least 3 out of 4 species (Schizachyrium scoparium, Poa pratensis, Artemisia ludoviciana, and Ambrosia coronopifolia) were present within an 18cm radius of the center. The plots were randomly assigned the following treatments (replicated 3 times except for the 60cm radius treatment which was replicated twice): 5, 10, 15, 20, 30, 45, and 60cm 15N injection radius. For each treatment, 15N was injected in a circle around the center flag using a wire hoop as a guide. Twenty injections were made at equal intervals around the wire hoop using a syringe connected via tygon tubing to a reservoir of 15N solution. A plastic funnel was used to guide the syringe to each injection point; this prevented foliar contamination by deflecting vegetation away from the syringe. The syringe was pushed to a depth of 10cm at each point and 10ml of 15N solution was injected as the syringe was pulled to the surface. The 15N was injected as 98 atom % 15N (NH4)2SO4 (obtained from Aldrich Chemical Co., Lot no. 037F3755) at the rate of 0.1 g 15N per plot. The plots were injected on July 30, 1987 and harvested August 31 and September 1, 1987. For a list of treatments, see the treatment layouts in file trmte56.