Effects of white-tailed deer on plant populations
Experimental and observational studies by Leland
Russell showed that browsing by white-tailed deer is
essentially preventing the regeneration of oaks (Quercus
buckleyi and Q. fusiformis) in parts of
central Texas: browsing prevents new stems from growing
>0.5m tall. Two current projects continue this
work by examing the joint effects of deer herbivory and fire on other
hardwood species.
David Zippin found that deer also have a substantial negative impact upon the endangered forb Streptanthus bracteatus.
Russell, F.L., and N.L. Fowler. 2004. Effects of white-tailed deer on the population dynamics of acorns, seedlings and small saplings of Quercus buckleyi. Plant Ecology 173:59-72.
Russell, F.L., and N.L. Fowler. 2002. Failure of adult recruitment in Quercus buckleyi populations on the eastern Edwards Plateau, Texas. American Midland Naturalist 148:201-217.
Russell, F.L., D.B. Zippin, and N.L. Fowler. 2001. Effects of white-tailed deer (Odocoileus virginianus) on plants, plant populations, and communities: a review. American Midland Naturalist 146:1-26.
Russell, F. L., and N. L. Fowler. 1999. Rarity of oak sampling in savannas and woodlands of the eastern Edwards Plateau. Southwestern Naturalist 44:31-41.
Zippin, D. Z. 1997. Herbivory and the population biology of a rare annual plant, the bracted twistflower (Streptanthus bracteatus). Ph.D. dissertation, University of Texas at Austin
Effects of grazing upon competition between grass species
An experimental field study found that cattle grazing is the most important factor determining the distribution of tall and short grasses, over-riding topography. But simulated grazing is not able to alter the competitive balance between the native dominant Schizachyrium scoparium (little bluestem grass) and the invasive Bothriochloa ischaemum(King Ranch bluestem grass).
Bothriochloa/Schizachyrium poster (Gabbard & Fowler 2003)
Fowler, N.L. 2002. The joint effects of herbivory, competition, and topographic position upon six grasses. Ecology 83:2477-2488.
Effects of simulated grazing on Bothriochloa ischaemum population dynamics
Nassella (Stipa) leucotricha (Texas winter grass) and its parasite, the epiphytic fungus Atkinsonella texensis
Atkinsonella texensis sterilizes Nassella leucotricha; plants form a fungal fruiting body at the end of what would have been the flowering culm. Marty Maas found that the fungal fruiting body is 'less expensive' than making seeds would have been, which explains why infected plants have more vegetative biomass than uninfected plants. Infection did not affect the incidence of grasshopper herbivory.
Maas, M. M. 2004. The distribution of the epiphytic fungus Atkinsonella texensis and its effects on the performance of its plant host, Nassella leucotricha. Ph.D. dissertation, University of Texas at Austin.
