Autecological response of Kalmia angustifolia to forest types and disturbance regimes

Abstract

Vegetative and reproductive growth of Kalmia angustifolia was studied in eight habitats which differed in vegetation cover, soil type, moisture and disturbance. The shrub was most vigorous, with the highest cover (73%), plant height (55 cm), current year's twig density (283 m −2) and aboveground biomass (1139 gm −2), in the open canopy black spruce forest. Under the closed canopy undisturbed black spruce forest, Kalmia remained mostly vegetative with only 1 twig m −2 producing flowers, whereas in the clear-cut and burned forest site Kalmia flowered profusely (67 flowering twigs m −2). Mean of individual leaf area of older Kalmia growing under a closed canopy black spruce forest was significantly higher (6.88 cm 2) than younger plants developing from sprouts after clearcutting and burning (2.35 cm 2). In the clear-cut and burned site Kalmia produced the highest density of fruits and seeds (806 fruits and 60 630 seeds m −2, respectively) compared with the other sites (10–451 fruits and 1824–1841 592 seeds m −2, respectively). However, more than 50% of the seeds were non-viable. On the other hand, although very few seeds were produced under the closed canopy forest more than 80% of them were viable seeds. Discriminant analysis (DA) of 14 vegetative parameters of Kalmia, measured in the eight sites, classified all the sites that were disturbed by cutting and/or burning in one group irrespective of their soil type, moisture regime and time since disturbance. The undisturbed sites were positioned separately in the DA ordination diagram based on their forest cover type and soil moisture regime. Disturbance-induced spread of Kalmia and its implications for forest management are discussed.