New York City Urban Field Station

Urban Forest Restoration

[photo:] NYC forestry interns measures tree height in an urban forest.  Photo by Brady Simmons, NYC Department of Parks & Recreation.  Used with permission.NYC Afforestation Project (NYCAP)

How successfully do constructed, native, urban forests sustain themselves; and how resilient are they to the invasion of non-native invasive plant species?

Rich Hallett and Nancy Falxa Sonti of the Urban Field Station are collaborating with Yale University researchers Alexander Felson, Mark Bradford, and Emily Oldfield to investigate the sustainability of constructed, native, urban forests and their resilience to invasive species. Researchers collected data at their site in Kissena Park for a third year, tracking recruitment from the planted, native vegetation as well as the proliferation of invasive plant species.. Soil quality, water and carbon storage capacity are improving as a result of the afforestation efforts. The research team is investigating the impact of planted species diversity and organic amendments on these ecosystem functions. In addition, buried wood stakes were installed at the research site in 2012 as part of a national study of soil organic matter decomposition and soil productivity. The first set has been dug up by researchers Mary Beth Adams (USFS) and Marty Jurgensen (Michigan Technological University), with more to follow next year.

ULTRA-Ex: Long-term forest restoration study in Pelham Bay Park, Bronx

Can forest restoration efforts encourage the development of closed canopy forests and discourage the establishment of non-native invasive species?

Ecologists from NYC Parks & Recreation and the Forest Service have collaborated to conduct a study on the success of forest restoration in Pelham Bay Park, NYC’s largest public park. Located in the northeast section of the Bronx, Pelham Bay Park hosts a diverse array of habitats and reflects a varied land use history. Portions of the park experienced intense deforestation pressure in the early 20th century.  Rodman's Neck, a section of Pelham Bay, was identified as a restoration site in 1992 after the area was surveyed and deemed severely degraded with invasive vines and an altered forest structure. The objective of this study is to determine if the restoration resulted in a more native and diverse forest than control sites and to understand the effects of a differential maintenance regime across different sites in the restoration area.  Using a nested plot design, forty-eight plots were established to assess the abundance of non-native species, planted tree survival, and native shrub and herbaceous species diversity and abundance. Crown transparency and foliage height diversity were measured with digital camera techniques that allow an examination of the vertical profile of native and non-native species composition.  Control plots were established in neighboring areas that remained degraded.

Preliminary results indicate that total tree basal area is greater in all the treatment plots than in control plots. Native basal area was also greater in several treatment plots than in control plots, including those areas treated with invasive removal alone, and those that were cleared, planted, and maintained for invasive control. Foliage height diversity and canopy closure were both higher in the restored areas compared to control plots.  It has been 20 years since the initial restoration work; and the results of this study show retention of planted trees as well as a closed mature canopy in the restored areas.

The Influence of New York City Urban Soils on Native Tree Seedling Growth and Survival

Urban Field Station researchers Rich Hallett and Nancy Falxa Sonti are collaborating with Clara Pregitzer  of the Natural Areas Conservancy to quantify the performance of four commonly planted native tree species growing in typical urban soils. Soils used in these experiments were collected from reforestation sites in New York City. Using a multi-factorial design, researchers planted red oak, silver maple, serviceberry, and black birch seedlings into thirteen soil types, including one custom-made greenhouse soil and twelve urban soils collected from four typical New York City soil categories (coal ash, urban construction fill, sandy clean fill, and native till). After two growing seasons in a common greenhouse environment, tree health was assessed using height and diameter growth, leaf discoloration, and chlorophyll fluorescence (an indication of photosynthetic performance). These parameters were combined into a single standardized tree health variable, which, in preliminary analyses, was found to be significantly affected by soil type. After data collection, the trees and soil were harvested and dried for subsequent biomass and chemistry analyses.

Innovative Urban Afforestation Strategies at Freshkills Park and Beyond

[image:]Ron Zalesny collecting native poplar twig material at Freshkills ParkAnother project in development at Freshkills Park assesses the potential of phytotechnologies (literally “plant technologies”) to improve the physical, chemical, and biological characteristics of soils imported to a restoration site in the new park as well as similar sites throughout New York City. Plant Geneticist Ron Zalesny (US Forest Service) traveled to New York City to work with the Freshkills Park, and Greenbelt Native Plant Center, and Urban Field Station researchers Rich Hallett and Nancy Falxa Sonti to identify “workhorse” plant species belonging to the Populus (poplar), Salix (willow), and Panicum (switchgrass) genera. The initial plant material was selected from native Staten Island plant populations, including some on the Freshkills site. Specific varieties of plants with the greatest ability to remove inorganic contaminants from the soil will be determined through greenhouse studies at the Institute for Applied Ecosystem Studies in Rhinelander, WI. The long-term goal is to select and plant the most successful plant varieties throughout New York City afforestation sites, creating a more suitable environment for native ecosystems.

Research Products

Simmons, Brady L.; Hallett, Richard A.; Sonti, Nancy Falxa; Auyeung, D.S.N.; Lu, Jacqueline W.T. 2016. Long-term outcomes of forest restoration in an urban park. Restoration Ecology. 24(1): 109-118.

Zalesny, Ronald S.; Hallett, Richard A.; Falxa Sonti, Nancy; Wiese, Adam H.; Birr, Bruce A.. 2014. Propagating native Salicaceae for afforestation and restoration in New York City's five boroughs