Changes in grass leaf water relations following bison urine deposition

In a northern, mixed-grass prairie in South Dakota, Bison bison urine deposition leads to patches of vegetation having much higher 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 of Poa pratensis (C₃). Poa on urine patches had higher leaf conductances and lower water potentials than 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 has much smaller and usually insignificant effects on leaf water relations of Schizachyrium. -from Authors