Field data for the Vegetation Mapping Inventory Project of Rock Creek Park

This reference is an assemblage of field data collected as part the baseline vegetation inventory for the park unit. Typical files here are vegetation plot data, accuracy assessment data, field photos, PDF showing locations of vegetation plots and accuracy assessment data, and other data for this type. Plots were subjectively placed so as to be most representative of the mapped vegetation unit. All mapped vegetation types were sampled over a range of environmental variation. Additional plots were taken where the vegetation type documented in the field was unclassified or less well known. For example, the ash floodplain map unit polygons were targeted specifically for field verification. This vegetation types was later classified as part of the Platanus occidentalis - Fraxinus pennsylvanica Forest Association. Plot sizes ranged from 20 x 20 m for forests and woodlands, 10 x 10 m for shrublands, and 5 x 5 m for herbaceous vegetation. In some cases, where the polygons were too narrow to reasonably accomodate standard plot sizes, the plots were adjusted accordingly, e.g., 10 x 20 m plots were often used in sampling narrow bands of floodplain forest in the park. The vegetation was visually divided into strata, and all the species of each stratum were listed and percent cover estimated. Additional species within the vegetation unit or polygon that occurred outside of sampled plots were listed separately. Species that were not identifiable in the field were collected for later identification. In addition to floristic information, the following environmental information was recorded on field forms: soil profile description, flooding regime, soil moisture regime, slope, aspect and evidence of disturbance. Latitude and longitude of each plot was recorded using a GPS unit. The vegetation profile in cross-section was sketched by hand to represent the location and setting of the plot. Seventy-seven vegetation plots in total were sampled for this project.