Day, T.A. and Detling, J.K.. 1990. Changes in Grass Leaf Water Relations Following Bison Urine Deposition. American Midlands Naturalist 123. pp. 171-178.
In a northern, mixed-grass prairie in South Dakota, bison urine deposition leads to patches of vegetation having much higer total aboveground plant biomass, root mass and N concentrations. Although Schizachyrium scoparium (C4) dominated the prairie, these increases in total aboveground plant biomass following urine deposition resulted mainly from the large growth response to Poa pratensis (C3). Field experiments were conducted over 2 growing seasons to investigate the effect of urine deposition on leaf water relations of these two grasses. Poa on urine patches had higher leaf conductances and lower water potentials that Poa off patches. During drought stomatal closure began at lower water potentials in Poa on urine patches. Leaf folding was less prevalent in Poa on urine patches. Urine deposition had much smaller and usually insignificant effects on leaf water relations of Schizachyrium.