NYC Resources311Office of the Mayor

Scientific Studies and Monitoring

Bronx River Forest Floodplain and River Channel Rehabilitation Project – Vegetation Monitoring

2004-2005

In 2004, construction began on the Bronx River Forest Floodplain and River Channel Rehabilitation Project funded by The New York State Clean Air/Clean Water Bond Act. This project was a pivotal component of on-going efforts by the City of New York/Parks & Recreation’s Natural Resource Group, the Bronx River Alliance, and other community groups to restore the Bronx River and its floodplain in the northern end of Bronx Park.

The project was designed to help address the reduced resource and habitat value in the Park resulting from the impacts of urban development and neglect. The Bronx River Forest Bond Act Restoration Project is located in the Bronx Forest floodplain, at the north end of Bronx Park, and is bordered by ball fields and the Metro North railroad to the west, the Bronx River Parkway to east, and Kazimiroff Blvd to the south.

Vegetation monitoring was conducted to evaluate the success of the plantings (percent survival) and impact of the plantings on plant species diversity, cover, and invasive plant dominance in the forest floodplain.

Methods

Planting Success

Due to the large numbers of plants installed, a complete post-project count was not conducted. Instead, installed plants were counted in a sub-set of all the planting areas, dead plants were counted, and visual assessments were made of plant loss.

Cover and Species Richness

Eleven plots were established in 2002, each measured 3m x 3m: one reference wetland planting area plot (number 14); two control plots (numbers 19 and 20); and two reference plots (numbers 24 and 30). Six new floodplain plots were established in 2005 (number 40-43, 50, 51). The location of all plots was marked with wooden or rebar stakes, drawn on a map and GPSed.

During sampling, temporary stakes were used to mark all corners of the 3m x 3m plots and the meter tape was be strung around the plot. A 1m x 1m plot for herbaceous layer sampling was temporarily demarcated in the NE corner of the 3m x 3m plot. Relative percent cover was estimated at three distinct levels: herbaceous, shrub, and tree canopy. Percent cover at each level was visually estimated for each species found in the plot. At each level all species present as well as dominant species were noted.

Vegetation Communities

An inventory of the vegetation community that has been was conducted using entitation, a process of identifying and describing ecologically distinct plant communities, or entities. Entitation results in a map and database that can be used to identify where certain species are dominant or present, and to help prioritize areas that may be threatened, should be protected, or should be restored. This mapping can serve as a baseline for assessing change.

Results

Due to the large numbers of plants installed, a complete post-project count was not conducted. Instead, installed plants were counted in a sub-set of all the planting areas, dead plants were counted, and visual assessments were made of plant loss.

Planting Success

Planting Area Number of plants installed by January 2005 Additional plants installed spring 2005? Number of Installed plants dead by June 2006 % Survival Known vandalism
Area 1 354 0 100%
Area 2 189 3 98% yes
Area 3 829 6 99%
Area 4 190 yes 1
Area 5 689 yes 2
Area 6 528 0 100%
Area 7 786 yes 16
Area 15a 107 yes 7 yes

The table shows the subset of planting areas that were re-counted in June 2006. On average, in the planting areas with a known number of plants in January 2005 (Areas 1,2,3,6) , the total number plants counted was in total only 64% of the total number of plants counted upon installation. This is probably because the plants could not be relocated, or were planted slightly outside the planting area, since very few dead installed plants were found (at most 2% of total counted). Other plants that had died may no longer have been visible to count and some may have been vandalized (although the small heavily vandalized area near the Burke Ave Bridge was not re-counted here). Most importantly, however, no significant numbers of dead plants were observed after the plant installations. Overall, the qualitative observations suggest that in most planting areas, at least 85% of the installed plants survived.

Plant cover and species richness

The relative percent covers were entered into a spreadsheet (Appendix A) and used to estimate the percentage of the plot covered by each plant species present. Also calculated for each species were the average percent cover if present, number of plots present, and relative frequency. Calculations per plot included total percent cover of all plants, percent cover of plant groups (woodies, graminoids), species richness, the average and standard deviation for each. For a detailed summary of findings, download the Bond Act Project 1-Year Post Project Monitoring and Status Report (Word document, 113 KB).

Vegetation Communities

The entitation in the Bronx River Forest showed that much of the forest has some exotic invasive plant present or dominant in the understory. The recently planted areas, however, have either no significant Japanese knotweed, or only present but not dominant.

— Marit Larson

Downloads

Bond Act Project 1-Year Post Project Monitoring and Status Report (Word document, 113 KB)

Bond Act Vegetation Monitoring Data (Excel file, 51 KB)

Other Monitoring Efforts Related to the Bronx Forest Floodplain Restoration Project

Learn more about the Bronx River Forest Floodplain Restoration Project

Bronx Forest Floodplain Restoration Project – Avian monitoring

Bronx Forest Floodplain Restoration Project – Instream Habitat

Bronx Forest Floodplain Restoration Project – Channel Morphology

Was this information helpful?