Edge effects of a linear disturbance on the abundance and reproduction of an annual, Melampyrum lineare, in the boreal forest

We examined edge effects of narrow linear openings on the performance of cow-wheat (Melampyrum lineare, Desr.), an herbaceous annual and facultative hemi-parasite, in the boreal forest. Our objective was to determine the edge effects from linear disturbances: (1) on the abundance and performance (height, flower, and fruit production) of cow-wheat at both the population and individual-level; and (2) on abiotic/biotic (vegetation structure) conditions that might influence cow-wheat responses at edges. In jack pine-dominated boreal forests of northern Alberta, Canada we measured cow-wheat height, reproductive success, and abundance in three treatments: on a linear disturbance (6-8 m wide), at the edge of that disturbance, and in the adjacent interior forest. Our results suggest that cow-wheat abundance and seed production at the population level are positively influenced by the creation of openings and associated edge effects, but cow-wheat individual performance was not. In addition, we found evidence of 'edge sealing', with edges characterized by higher tree and sapling density compared to both the interior forest and seismic lines and higher short shrub cover than in the interior forest. Our results provide insight into positive effects of forest openings and associated edges on this hemi-parasitic annual with implications for increased population abundance in the face of increasing fragmentation in the boreal forest.