Scales of influence: Evaluating southern pine beetle risk in the New Jersey Pinelands

Although the range of southern pine beetle (Dendroctonus frontalis Zimmermann; SPB) has traditionally included southern New Jersey, outbreaks in that state were rare through the 20^th century. In the early 2000s, an outbreak began in the southern part of the state and has since moved inexorably northward through the state’s pine forests, and SPB has now been detected to the north in Long Island, New York as well as in Connecticut. With this northward movement, SPB transitions from its usual hosts—loblolly and shortleaf pine—to pitch pine (Pinus rigida).  Although pitch pine has been noted as a host species, no previous research has documented the species’ defense mechanisms against SPB, and little is known about how variation in pitch pine forest stand structure characteristics might affect risk of SPB infestation.  The New Jersey Pinelands comprise a 1.1 million acre tract of federally protected land, consisting primarily of pitch pine and mixed pitch pine/oak hardwood forests.  We characterized constitutive resin flow at sites throughout the Pinelands, comparing it against local variables including soil type, topography, forest type and forest structure.  We found that while tree to tree variation was high, some site characteristics provided additional information about locations that might be more susceptible to SPB.  For our forest structure analyses, we combined field data collection in both infested and uninfested stands with GIS data on forest type and infestation locations beyond our field data collection sites.  We found that while many stand and type characteristics that have conventionally been regarded as risk factors in the southern states, such as stand basal area, were also risk factors in New Jersey, the as yet mostly uninfested stands in the northern Pinelands maybe be at even higher risk of SPB infestation due to their unique forest structure.  The development of management strategies for the Atlantic coastal pine barrens in New Jersey and Long Island will require the consideration of all scales of importance in the development of an SPB outbreak, from the tree, to the stand, to the landscape scale.