COS 80-4 - Temporal changes in leaf area index within an urban brownfield

Wednesday, August 9, 2017: 9:00 AM
B112, Oregon Convention Center
Frank Gallagher, Landscape Architecture, Rutgers University, New Brunswick, NJ, Allyson B. Salisbury, Environmental Science, Rutgers University, New Brunswick, NJ and Jason C. Grabosky, Department of Ecology, Evolution & Natural Resources, Rutgers University, New Brunswick, NJ

While numerous studies over the past several decades have described the impairment of ecological integrity associated with urbanization, few attempts have been made to clearly define and quantify the ecological functions and services of urban “wildlands”. These naturally assembled novel communities have been shown to function in spite of the stress often associated with legacy soil contamination. Such communities, however, develop unique patterns of species
diversity/distribution, models of primary productivity and carbon sequestration that are driven by threshold tolerances and develop along nontraditional guild trajectories. In addition, the degree to which such systems tolerate sudden alterations, such as atypical weather events associated with climate change, is not well understood. This study documents primary productivity within the tree canopy of an urban brownfield over a 7 year period from 2010 through 2016. Of particular interest is the nonlinear
relationship between the rates of recovery after Hurricane Sandy and the stress induced by the total soil metal load (TML)


The land that comprises the study area was originally part of an intertidal mud flat and salt marsh that was filled for use as a rail yard. Due to its industrial history soil metals exceed all screening
criteria and were unevenly distributed. Our earlier work using multispectral imagery had
demonstrated a non-linear threshold relationship between the Normalized Difference Vegetation
Index and TML. These data however, did not have the frequency to examine the temporal
character of the site. Using leaf area index (LAI) as a surrogate for primary productivity we
studied the impacts of TML both higher and lower (pseudo-control) than the previously defined
threshold values. Measurements we taken using a LAI-2200C Plant Canopy Analyzer from May
through September on a biweekly basis. The null hypothesis was that LAI between the two sets
of data would differ significantly and remain consistent over time. After 6 years the data
indicate that TML did not correlate with LAI at the specific site level. The sites above the critical
threshold TML value could have LAI values similar to the pseudo-control sites. In addition, the
occurrence of Hurricane Sandy yielded an opportunity to examine recovery rates. While all of
the sites have not yet recovered to levels before the storm, the results indicate that sites with a
TML above the threshold could have recovery rates equivalent to those of the pseudo-controls.
Soil nutrient and organic matter concentrations have also been examined with similar result.