The effects of sheep urine on growing characteristics of different life form plants in a Chinese steppe grassland
羊尿对典型草原不同生活型草地植物生长特性的影响

The effects of sheep urine deposition volume (0, 1, 2 L/m2 or 4 L/m2) and stage of plant growth at deposition (vegetative or reproductive) on the growth characteristics of Stipa bungeana, Artemisia capillaries and Lespedeza davurica in Steppe grassland were determined. Measurements quantified treatment effects on the number and size of tillers or branches, and population biomass. The results indicate that the response of the three plant species to sheep urine deposition differs, and is influenced by both urine volume and stage of growth at deposition. Urine deposition had a short-term (1-4 weeks after application) scorch effect on grassland plant growth, which mainly occurred in the inner zone of urine patches. Application of urine had a long-term positive effect (> 4 weeks after application) on S. bungeana growth and a long-term negative effect on A. capillaries and L. davurica growth, which lasted at least two years and decreased with decreasing urine volume. All species growing in the inner zone of urine patches (equivalent to 4 L/m2) were harmed by sheep urine deposition. While some species from the middle zone of patches (2-4 L/m2) were also harmed, no species were harmed in the outer zones (1-2 L/m2). S. bungeana in higher sheep urine deposition plots (2-4 L/m2) had higher mean annual tiller numbers and aboveground biomass, whereas L. davurica and A. capillaries exhibited an inverse trend. All species growing in urine patches had a higher percentage of dead tillers or branches, and a higher percentage of dead biomass at first harvest. The reproductive and vegetative stages of A. capillaries and the reproductive stages of S. bungeana and L. davurica were sensitive to sheep urine deposition. In addition, S. bungeana growing in urine patches became active earlier in the spring and delayed senescence until later in the growing season than the control.