.|  Baltimore Ecosystem Study
Vegetation Research Projects

Vegetation analysis of the BES long-term biogeochemical study plots
  • Mary Cadenasso, Cary Institute of Ecosystem Studies
  • Steward T.A. Pickett, Cary Institute of Ecosystem Studies
  • Wayne C. Zipperer, United States Forest Service
Permanent plots are a powerful tool for understanding systems over the long term because of the rigorous quantification of patterns in a spatially refined way and because of the comparability of numerous variables measured in the same place. In 1998, 7 plots were surveyed into 3 forests in the study region of the Baltimore Ecosystem Study (BES): Oregon Ridge Park (4 plots), Hillsdale Park (1 plot), and Leakin Park (2 plots). Plots were surveyed in to correct for slope and to achieve an accuracy of plot side length to within 0.5 cm. Plots are 1600 m2 with the exception of the Hillsdale plot which is 900 m2. The Hillsdale plot is smaller to fit within the confines of the forest patch. Sites were selected 1) to represent urban and non-urban forests, 2) away from obvious habitat boundaries or edges, 3) with consistent drainage lines within the plot, and 4) with at least 80% continuous tree canopy. All vegetation layers were sampled in order to characterize the structure and composition of the plant community. A variety of sampling methods were used for the different layers but all layers were quantified with a high level of detail to minimize variation and to best characterize the plot. Here we present a survey of the patterns found in these plots.

Ninety four species were recorded including 31 trees, 16 shrubs, 9 vines, and 38 herbs. Ninety percent of these species were native. All plots had similar tree density; however, trees in Hillsdale were smaller in basal area and this plot had the highest density of standing dead trees. Living and dead sapling density was highest in the three city plots suggesting that vegetation structure in city plots is more dynamic. Seedling density was greatest in the city plots as well, and the proportion of seedlings that were damaged by mammalian herbivores were lower in the city plots compared to the plots in Oregon Ridge (Fig. 1). The cover of shrubs was greater in Oregon Ridge relative to the city plots but the species richness of the layer was similar in and out of the city. Vines maintained a greater cover in the city than at Oregon Ridge and the species richness of vines was also greater in the city. Exotic vines and shrubs were only found in the city plots. Species richness of the ground layer vegetation was highest in the three city plots compared to Oregon Ridge (Fig. 2). The permanent plots will be continually resampled to monitor changes in the vegetation.

Figure 1. Seedling density and number of seedlings browsed by mammalian herbivores in seven of the BES permanent plots. There are three plots in urban Leakin and Hillsdale parks and two upland plots (OR-u) and two mid-slope (OR-m) plots in rural Oregon Ridge Park.

Figure 2. Species richness of vegetation layers in seven of the BES permanent plots.