Department of Environmental Sciences

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Seminar Abstracts
Environmental Sciences Seminar Abstract            

  Hydrological balance in an upland forest of the New Jersey Pine Barrens - five years of investigation
Schäfer KVR1, Clark KL2
1Department of Biological Sciences, Rutgers University
2USDA Forest Service, Silas Little Experimental Forest, 501 Four Mile Road, New Lisbon, NJ

The New Jersey Pine Barrens are in the most densely populated state in the United States, where water replenishment to the groundwater aquifers are crucial for the water needs of the inhabitants there. Most people in the New Jersey Pine Barrens rely on the Kirkwood-Cohansey (KC) aquifer for their water needs, but as the population has grown at the margins of the Pine Barrens, treated water from the Delaware River has recently been imported into the area. In this study, we investigated the hydraulic balance of an upland oak/pine forest in the New Jersey Pine Barrens that is a part of the KC aquifer using sap flux measurements to quantify transpiration, and eddy covariance to estimate evapotranspiration. Data were collected from 2005-2009 under non-disturbed and disturbed conditions, when defoliation by Gypsy moth (Lymantria dispar L.) eliminated foliage for approximately 3 weeks in 2007.

In this forest, transpiration as measured with the sap flux technique was significantly reduced by 19% compared to 2005 but surprisingly similar to 2006, when drought occurred. Prolonged drought has seemingly a stronger effect on the hydraulic balance than reduced foliage or partly seasonal defoliation suggesting compensation through the remaining foliage. Latent heat flux and evapotranspiration measured with the eddy covariance system was also reduced during defoliation (92 mm vs. 193 mm from June 1st to July 15th), and sensitive to drought conditions. On an annual basis, evapotranspiration averaged 646 mm yr-1 in 2005-2006, but only 442 mm yr-1 in 2007. Differences between sap flux and eddy covariance measurements suggested that different controls over biological and physical factors affected water flux in this stand. Under future climate change, frequency and intensity of precipitation may then have a larger influence on local water balance than disturbance effects in the New Jersey Pine Barrens.

Last updated: 03/08/2010