Analysis of Vegetation Changes in Rock Creek park, 1991-2007

Hatfield, Jeff; Krafft, Cairn

Rock Creek Park is a 702 ha natural area that lies within the boundaries of Washington, D.C. (Ferebee 2003). Long-term vegetation plots were established by the National Park Service (NPS) in 1991, as part of a region-wide effort to develop a vegetation monitoring plan. One of the goals of the monitoring was to determine the effect of white-tailed deer (Odocoileus virginianus) populations on the native vegetation, since white-tailed deer are known to have a major impact on other native plant communities (Russell et al. 2001, Horsley et al. 2003). Vegetation data collected at Rock Creek Park every 4 years during 1991-2007 were analyzed for differences among 3 regions within the park and among years. The variables measured and analyzed were percentage of twigs browsed, percentage of canopy cover, species richness of herbaceous plants, number of tree seedlings in each of 7 height classes, tree seedling stocking rate for low deer density and high deer density areas, percentage of tree and shrub cover <2 m in height, mean diameter at breast height *DBS) of trees greater than or equal to 1 cm DBH, number of tree stems greater than or equal to 1 cm DBH, species richness of trees and shrubs, and mean height of the 5 tallest trees in each plot quadrant. Repeated measures analysis of variance (ANOVA) was used to test for differences (P?0.01) were found among the 3 regions in the variables discussed above. Many of the variables showed very significant differences (P<0.01) among years, and causative factors should be investigated further. In addition, importance values were calculated for the most important tree species in each region and changes over time were reported. Future sampling recommendations are also discussed.

Analysis of Vegetation Changes in Rock Creek park, 1991-2007

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