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Graduate Studies in Urban Forestry

Dr. Grabosky is currently working with several graduate students on a variety of research projects related to urban and community forestry. A selection of research projects currently in process are listed below:

Forest evapotranspiration (ET) is the dominant term in water budgets over forests, so minor changes in ET have outsize impacts on the behavior of associated water resources. This research uses remote sensing inputs and DisALEXI model outputs to quantify the effect of generalized forest management actions, forest composition, forest density, and other disturbances on ET over the coastal plain pine forest of southern NJ. The water budget in this system is dominated by ET, and almost all precipitation not recycled into the atmosphere moves through the underlying unconsolidated sand and gravel aquifer. Results indicate that long-term changes to forest structure arising from reductions in disturbance cause considerable, and previously ignored, increases in ET. Disturbance-dependent ecosystems experiencing less-frequent disturbance may witness negative consequences for the stability of groundwater resources due to increased landscape-scale water use by vegetation. Regulatory and administrative conditions established to safeguard the forest resource from some of those disturbances may thus be counter-productive for ensuring robust water provisioning.


  • The Allometric Relationship of Tree Diameter and Crown Volume
    Rich Leopold (113k PDF), PhD Student, Ecology & Evolution

The objective of this study is to analyze the allometric relationship between the diameter at breast height (DBH) and crown volume. The question presented is: Does site type influence this relationship?  The species selected for this study are Quercus rubra, Quercus palustris, Acer rubrum, Acer platinoids, Pyrus calleryana, Gleditsia triacanthos, Planatanus X acerifolia, Zelkova seratta,all species of Tilia spp, and Fraxinus spp.  Four different site types have been identified, lawns, pits, small strips, and large strips.  Lawns are classified as areas with non-limited root growth in all directions.  Pits are growing areas that are limited in root growth in all directions, sidewalk cutouts.  Strips are areas with non-limited growth in two directions 180 degrees from one another, areas between the street curb and the sidewalk. Furthermore, strips have been divided into large strips, greater than 4 feet up to 12 feet in the limiting directions, and small strips, less than or equal to 4 feet in the limiting direction.

The DBH is measured, recorded and a bright dot placed at the point of measure to provide a known height for image analysis.  A high resolution digital photograph is then taken.  The image is then processed using software called ImageJ.  This software allows us to scale the pixels of the image to the known height of 4.5 feet based on the location of the dot placed on the tree.  The following image measurements are taken, DBH, total tree height, crown height, and crown diameter at regular intervals of crown height.  Volume of the crown is then calculated by way of analyzing each crown segment as a truncated cone (Cadori et al. 2016, Heger 1965).

Once the crown volumes have been calculated the allometric relationship for each species site combination will be performed.  An analysis will be used to determine if there are significant differences in the allometric scaling relationship of DBH and crown volume between the different site types.  Understanding how site type influences growth patterns can allow us to better employ the concept of the right tree for the right site.  Furthermore, time and money can be saved by predicting multiple measurements while only having to take one measurement.