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theses

Throughout their range, white-tailed deer (Odocoileus virginianus) have significantly altered the diversity and productivity of plants upon which they browse in forest understories as well as the average heights of many of these species, yet traditional vegetation surveys can fail to capture changes occurring at higher levels in the vertical dimension. In Chapter 1 I examine fine-scale understory changes in the vertical dimension by measuring vegetation density and species richness at 20 cm intervals from ground level to two meters at 44 pre-existing deer exclosures of various ages in New Jersey and Maryland forests. I found that vertical vegetation density and species richness were significantly greater at every height when protected from deer. Deer affected density at all heights somewhat evenly but the impact on species richness was significantly greater in the lower heights. The impact on species richness was significantly correlated to exclosure age at virtually every height. My results indicate that multiple heights must be measured to obtain a full picture of deer impacts. In Chapter 2 I explored the relationship of the vertical species richness profile to deer densities by measuring species richness at 20 cm intervals up to two meters across 10 forests in the Washington D.C. region with a gradient of deer densities (5 deer/km2 to 78 deer/km2). Vertical profiles of species richness followed a negative exponential distribution for all sites with the coefficient of the exponential describing the rate of understory species loss in the vertical dimension. This species attenuation coefficient was linearly related to the deer density explaining 31% of the variation. In Chapter 3 I test various floristic quality indicators for their ability to capture the effects of deer on forests. Using data collected at the same exclosures and forests as above, I found that the Floristic Quality Assessment Index (FQAI) and the Plant Stewardship Index (PSI) indicated increased quality inside deer exclosures that increased slowly the longer the plots had been protected from deer browse. FQAI and PSI were also well-correlated to deer densities (r2 = 0.25 and 0.31, respectively) showing decreased quality as deer density increased.

ETD_4654

Ph.D.

Includes bibliographical references

by Linda Rohleder

http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000068950

doi:10.7282/T3Z036R8

ETD doctoral

The author owns the copyright to this work.