Pre-logging Treatment of Invasive Glossy Buckthorn (Frangula alnus Mill.) Promotes Regeneration of Eastern White Pine (Pinus strobus L.)

Forests 2017, 8(1), 16; doi:10.3390/f8010016

Author 

Thomas D. Lee ^1,* , Stephen E. Eisenhaure ²

 and Ian P. Gaudreau ³

¹

Department of Natural Resources and the Environment, University of New Hampshire, 56 College Road, Durham, NH 03824, USA

²

Office of Woodlands and Natural Areas, University of New Hampshire, Kingman Farm, Route 155, Madbury, NH 03823, USA

³

Department of Civil and Environmental Engineering, University of New Hampshire, 33 Academic Way, Durham, NH 03824, USA

^*

Author to whom correspondence should be addressed. 

Academic Editors: Timothy A. Martin and Jean-Claude Ruel

Received: 31 October 2016 / Revised: 23 December 2016 / Accepted: 23 December 2016 / Published: 29 December 2016

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Abstract 

Non-native glossy buckthorn (Frangula alnus Mill.) is invasive in forests of the northeastern USA but little is known of its effects on tree regeneration. We tested whether killing buckthorn stems before logging reduces its post-logging abundance and increases the density and height of eastern white pine (Pinus strobus L.) seedlings. Three 0.4 ha plots were clearcut, three were thinned, and three were left as controls. Each plot had previously been divided into three subplots that received different buckthorn treatments during the two years before logging. Buckthorn treatments were (1) stems cut at base five times; (2) stems cut once then heat killed four times; (3) untreated control. Three years post-logging, buckthorn density and stem height were unaffected by logging but equally reduced by the two buckthorn treatments. Buckthorn reduction increased density and height of pine seedlings, and seedling height also increased with logging. In the fifth year post-logging, pine height growth and biomass were greater in clearcut than in thinned treatments, greater in areas of buckthorn removal and, within treated subplots, greater in areas with low buckthorn density than in thickets of recovering buckthorn. Thus, although buckthorn inhibited regenerating pine, pre-logging destruction of buckthorn stems reduced such competition for at least four years. View Full-Text

Keywords: basal cutting;  biological invasion;  competition;  exotic shrub;  flame gun;  glossy buckthorn (Frangula alnus Mill.); eastern white pine (Pinus strobus L.)

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