Canopy gaps facilitate establishment, growth, and reproduction of invasive Frangula alnus in a Tsuga canadensis dominated forest

Abstract

The primary objective of this study was to determine whether the exotic, invasive shrub, glossy buckthorn (Frangula alnus), is more abundant in canopy gaps created by logging than in uncut forests. Secondary objectives were to determine whether buckthorn abundance in gaps is related to gap size, and whether or not buckthorn exhibits advanced regeneration. The abundance of glossy buckthorn was estimated in five patch cuts and three single-tree cuts in a 90 year old eastern hemlock-eastern white pine-sweet birch forest at the Woodman Horticultural Farm in Durham, NH, USA. Glossy buckthorn was 96 times more abundant in logged areas than in uncut control plots. The three largest but youngest gaps ([0.08 ha; 5 years old) had the greatest proportion of tall ([2 m), reproductively mature glossy buckthorn individuals, with 18.4% fruiting. The older, medium-sized gaps (ca. 0.03 ha; 10 years old) contained the highest overall densities of glossy buckthorn, but few stems were flowering (*2%) and none were fruiting at the time of sampling. Small gaps (\0.01 ha; 10 years old) appeared to be sinks for glossy buckthorn, as all individuals were \0.5 m tall and none were [4 years old. As age and size of gaps were correlated, it was difficult to determine which factor played a larger role in the establishment and persistence of glossy buckthorn. However, the greater proportion of individuals[2 m tall and greater reproductive vigor of glossy buckthorn in large gaps relative to small gaps-despite fewer years available for growth-suggest that larger disturbances lead to more resources available for buckthorn growth, survival, and reproduction. Individuals \0.5 m tall were observed in uncut control plots at low density (\30 stems/ha) and 5% of stems in large gaps were older than the gaps themselves, suggesting that gap formation released previously established glossy buckthorn individuals (i.e., advanced regeneration).

Using structured decision making with landowners to address private forest management and parcelization: balancing multiple objectives and incorporating uncertainty

“…Similarly, water quality is high if the forest cover is high, but as more trees are removed, water quality tends to decrease Blinn 2004, Stednick et al 2004). Also, the abundance of exotic species appears to increase as the intensity of the forest use increases (Belote et al 2008, Burnham andLee 2010). The effects of disturbance on the conservation value of the forest for birds (Norris et al 2009, Twedt andSomershoe 2009) and herpetofauna (Semlitsch et al 2009, Strojny and Hunter 2010, Tilghman et al 2012, Hocking et al 2013) may be variable, but generally, the conservation value is expected to decrease as disturbance increases.…”

Invasive glossy buckthorn impedes growth of red oak and sugar maple under-planted in a mature hybrid poplar plantation

“…(Fagan and Peart 2004;Webster et al 2007), an exotic invasive shrub that is now dominant in several ecosystems in Eastern North America. Its spread is facilitated by openings in the forest canopy, even partial ones, resulting from cutting and thinning operations (Burnham and Lee 2009). It is a somewhat shade-tolerant species that out competes native species in the colonization of canopy gaps, where it tends to form a very dense mono-specific stand (Frappier et al 2004;Nagel et al 2008) limiting light availability for native tree seedlings.…”

Aboveground Biomass of Glossy Buckthorn is Similar in Open and Understory Environments but Architectural Strategy Differs

“…Rhamnus frangula L.) is an exotic invasive shrub that is now dominant in several ecosystems in Eastern North America [1]. It is a cause for great concern among forest managers and conservation scientists, because its spread and growth are facilitated by openings in the forest canopy, even partial ones, resulting from cutting and thinning operations [2,3]. Buckthorn is generally not considered particularly shade tolerant.…”

“…Several explanations have been proposed for this question. A first explanation is that the abundant, precocious and bird-dispersed fruit (seed) production of glossy buckthorn allows for the creation of large seed and seedling banks [2,[8][9][10]. Indeed, Mills et al [10] observed seedling densities for glossy buckthorn exceeding more than seven times that of four native shrub species combined.…”