Date of Award

Winter 2016

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Thomas D. Lee

Second Advisor

Mark J. Ducey

Third Advisor

Stephen E. Eisenhaure

Abstract

Invasive glossy buckthorn (Frangula alnus P. Mill) threatens forest communities in southeastern New Hampshire both ecologically and economically by outcompeting native regeneration and hampering forest management. Seventy-five white pine (Pinus strobus L.) seedlings surrounded mainly by buckthorn were identified at the MacDonald Lot property in Durham, NH. In spring 2015, fifty of these pines were encouraged to emerge from and overtop surrounding buckthorn by cutting all neighboring plants within 1 m; targeted herbicide was applied to cut stumps at 25 of these. Pine response was assessed after one growing season. Released pines showed increased diameter growth, foliar biomass, and stem non-structural carbohydrate content. No growth differences between pines treated with herbicide and those not treated were observed; however buckthorn did recover more strongly in untreated plots.

Buckthorn’s response to forest succession is not known, nor is the status of the regional invasion. To determine a) if the invasion is continuing to invade new stands, and b) what successional factors predict buckthorn presence and abundance in forests, I resampled 20 of 22 sites in an old-field chronosequence in Durham, NH initially sampled 17 years prior. Site characteristics such as age since abandonment, overall shade tolerance, and degree of occupation by various vegetation were analyzed. Site age and shade tolerance were the strongest predictors of buckthorn presence and abundance. In these unmanaged old-field sites, the buckthorn invasion seems to have stabilized with no net gain in stands invaded.

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