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

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.

Factors limiting the success of invasive glossy buckthorn (Frangula alnus) in New Hampshire’s eastern white pine – hardwood forests

“…The widespread observation that glossy buckthorn frequently reaches high abundances in eastern white pine stands (Frappier et al 2003a, Frappier et al 2003b, Fagan and Peart 2004, Cunard and Lee 2008, Burnham and Lee 2010, Lee and Thompson 2012, Koning and Singleton 2013, Kozikowski 2016, Lee et al 2016 led to the present research. The main objective of this study was to determine the extent to which tree species composition, light availability (photosynthetically active radiation, PAR), and soil characteristics are associated with buckthorn success.…”

“…Mortality and the final stem heights and number of leaves were recorded. Plants were dried at 95 degrees Celsius using a drying oven (VWR 1350GD, Sheldon Manufacturing Inc, Cornelius, OR) for two days following the protocol used by Lee et al (2016). The dried biomass was weighed on a Mettler AE 163 scale (Mettler Instrument Corporation, Hightstown, NJ).…”

“…Both cutting plants at the base and burning cut stumps have limited effectiveness. Although cutting or cutting-then-flaming buckthorn stumps after a logging event was associated with a reduction in buckthorn abundance, half of the stems alive three years later had survived the treatment (Lee et al 2016). Prescribed burning increased buckthorn re-sprouting two years after treatment (Nagel et al 2008).…”

“…Even seedlings that were established in a buckthorn thicket, such as red oak (Quercus rubra) and sugar maple (Acer saccharum), experienced reduced height and diameter measurements compared to those grown in the absence of buckthorn (Hamelin et al 2016). Lee et al (2016) and Lanzer et al (2017) observed taller and more productive eastern white pine (Pinus strobus) seedlings and saplings where buckthorn had been removed.…”

“…In an attempt to reduce the extent of buckthorn invasion, and in turn, reduce the demand Previous research suggests buckthorn is found more commonly in early and midsuccessional softwood stands than later successional, hardwood or hemlock-hardwood stands (Frappier et al 2003a, Frappier et al 2003b, Fagan and Peart 2004, Cunard and Lee 2008, Burnham and Lee 2010, Lee and Thompson 2012, Kozikowski 2016, Lanzer 2016, Lee et al 2016. In one study, the mean number of buckthorn stems in softwood plots was 17.6, whereas hardwood plots averaged 7.9 stems (Kozikowski 2016).…”