Current Research

"Management of grassland species diversity on Long Island" (On-Going).

Grasslands, which are early successional plant communities in most parts of the northeastern United States, are rapidly declining in species diversity and areal extent.  A few of the remaining grasslands in the region (such as the Hempstead Plains) are long-term features of the landscape, but most extant grasslands are artifacts of the cultural landscape, with recent human activities serving as replacements for the natural disturbances (mainly fire) that maintained these communities in the past.  These “cultural” grasslands can be roughly divided into two groups:  old-field grasslands that regenerated from former agricultural fields and restored grasslands that were purposely planted to resemble “natural” grasslands.  This complex history of grassland communities, particularly on Long island, raises important questions for conservation and management.  What is the conservation value of old-field grasslands compared to restored and “natural” grasslands?  What is the connection between land use history, soil properties, and grassland species diversity?  And how can we manage Long Island’s grasslands to maintain both characteristic and threatened grassland species?  This project, which focuses on soil properties and their association with both land use history and species diversity, is an expansion of the work of one of my graduate students (Polly Weigand) who painstakingly characterized the species composition of these sites, but had not characterized the physical environmental parameters that we hope are the key to explaining the differences in diversity that we see among Long Island’s threatened grasslands.  Polly Weigand, an MS student at Hofstra University, and the students in my recent upper-level course, The Ecology of Wild and Urban Plants, played a major role in getting the project off the ground, but much work still needs to be done.

"A Revised Site Index for Urban Trees" (On-Going).

Urban tree growth, longevity, and mortality are related to site conditions. Unfortunately, urban landscape managers do not always have the knowledge or resources to adequately identify site problems inhibiting tree growth and health. Practical and accurate site quality indices have been used in agriculture and forestry. These approaches employ site indicators and interpret score values into integrated indices. Given the strong linkage between site quality and plant growth and health, an urban site index would have substantial application for urban forestry, arboriculture, horticulture, urban agriculture, and other areas.  In this work, which is led by collaborator Bryant Scharenbroch (Morton Arboretum and University of Wisconsin S.P.), we are testing a Revised Urban Site Index (RUSI) model in cities around the United States.

"Urbanization induced changes to terrestrial carbon and nitrogen stocks: A chronosequence approach" (On-Going).

Research on changes to carbon (C) and nitrogen (N) stocks due to urbanization has typically focused on comparisons of developed and undeveloped land uses, but comparatively little work has been done to quantify change over time.  We used a chronosequence approach to examine how aboveground C and belowground C and N stocks changed over time for different land use change trajectories in the Greater Boston area.  When we compared our preliminary findings in Boston against results from Baltimore (our previous work), Denver, and Los Angeles and found that developed soils in all regions experienced initial C and N losses relative to pre-development conditions, followed by increases in C and N over time.  Preliminary data from this ongoing research suggest that urban C and N stocks are variable over space, dynamic over time, and that the processes driving these trends are influenced by land use history, management, and regional climactic and edaphic factors.

"An Evaluation of Management, Urbanization and Isolation Effects on Grassland Species Diversity in the Atlantic Coastal Plain" (On-Going)

The grasslands of the Atlantic Coastal Plain have been rapidly declining in areal extent over the past century.  A range of local, state, federal, and private organizations oversee the scattered remnants of this once widespread ecological community, but there is limited information to guide the management of these threatened habitats.  For instance, while it is accepted that frequent disturbance is required to prevent the encroachment of woody vegetation in the region’s grasslands, the extent to which fire is necessary to maintain rare and characteristic species is still unclear.  Similarly, while a number of old field grasslands have been restored through considerable effort and expense, it is unclear whether these restored grasslands are of greater ecological and conservation value than the old field grasslands that they typically replace.  This project examines the abundance and diversity of species in grasslands that vary in their land use history, management, and distance to both urban areas and other grasslands.  The experimental work for this project was conducted primarily through the efforts of Polly Weigand (MS student).

"Conservation of an endangered coastal plant: Seabeach Amaranth" (On-Going).

Sea Beach Amaranth (Amaranthus pumilus) is a federally threatened species under the authority of the Endangered Species Act.  Once abundant, populations of the species declined precipitously during the 20th Century, with the plant all-but-disappearing from the East Coast of the United States.  While the species has made a reappearance in many areas where it was once thought to be extirpated, populations in those areas have been highly volatile and many questions remain about its both habitat preferences and the best management practices for conserving and expanding existing populations.  I am working with a graduate student (Chris Smith) and the Town of Hempstead to determine how changes in disturbance regime, nutrient dynamics, and location of breeding bird populations influence the abundance and vigor of this threatened plant species.

 "Impacts of storms and land use change on tree canopy in the Long Island and NYC Area" (On-Going).

The Raciti Lab is using current and historical satellite imagery to evaluate changes in tree canopy cover over time on Long Island (and potentially NYC).  Urban trees provide a wide range of societal benefits while also increasing the sustainability of our environment.  High densities of urban trees have been associated with a lower prevalence of childhood asthma in cities, reduced summer temperatures, decreased building energy usage, increased property values, lower crime rates, stronger ties among neighbors, more time spent shopping in central business districts, and increased perceptions of aesthetic beauty.  Many of the cities and towns in the New York metropolitan area are pursuing greening initiatives that they hope will allow them to maintain and increase these positive ecosystem services for their citizens.  Unfortunately, these urban greening initiatives face some difficult challenges, including 1) increasing frequency of severe storm events with climate change; 2) continued loss of tree and forest cover due to land development; and 3) potential changes in people’s attitudes towards urban trees in light of damage caused by falling trees during storm events, such as Hurricane Sandy in November of 2012.  Key questions for this research include: A) How much tree canopy does LI have and how is it changing over time?  B) How did Hurricane Sandy and other major storms alter tree canopy in the region?  C) What is the role of land use change in tree canopy losses on Long Island?  D) Is there evidence to support the anecdotally noted phenomenon of “dendrophobia” (a fear of falling trees) that might cause removal of healthy trees or non-replacement of lost trees?  E)  How much are these changes in tree cover altering ecosystem services on Long Island including water and air quality?