Mob grazing increases trampling but not litter deposition on a Nebraska Sandhills subirrigated meadow

Abstract

High cattle stocking densities may enhance trampling, litter deposition, and soil organic matter (OM) formation in grasslands. To test this, we measured aboveground vegetation production, standing live and dead mass before and after grazing, vegetation utilization, trampling, litter accumulation, and spring standing dead mass across 2014 and 2015, comparing high [210,343 lb live weight (LW) acre–1] and low (7,011 lb LW acre–1) stocking densities in a Nebraska Sandhills subirrigated meadow. Pregrazing live mass in the cool-season grass-dominated meadow averaged 3,722 and 4,128 lb acre–1 under the low and high densities, respectively. Utilization was greater under the high (93%) than the low (85%) stocking density, resulting in less postgrazing live mass (272 and 521 lb acre–1, respectively). The high stocking density also increased trampling (41%) of live vegetation relative to the low density (25%) but did not affect annual litter accumulation, which averaged 1,957 lb acre–1. Trampling accounted for 97% of annual litter accumulation under the high stocking density but 51% under the low density, indicating the importance of senescence and fall of standing plant material under the latter. Transfer of trampled tissue to the litter pool was 931 and 1,762 lb acre–1 at maximum, whereas the transfer of senescent and detached standing plant material to the litter pool was 1,085 and 136 lb acre–1 at minimum under the low and high densities, respectively. We reject the hypothesis that high stocking densities enhances annual litter deposition and, in turn, soil OM formation in grasslands.