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


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 (similar to 2%) and none were fruiting at the time of sampling. Small gaps ( 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).

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Biological Invasions


Springer Verlag

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