The relative effect of clipping, neighbours, and fertilization on the population dynamics of Lupinus arcticus (Family Fabaceae)

A demographic study was conducted in 1991 and 1992 on replicated field populations of Lupinus arcticus, near Kluane Lake, Yukon. The relative effects of herbivory, neighbours, and soil fertility level were assessed using a factorial experiment of +/- clipping, +/- neighbour removal, and +/- fertilizer (NPK). The main population experiment monitored the dynamics of leaves, however, data on reproduction, survival, and size were also collected from the permanent quadrats. Clipping reduced leaf cohort survivorship, total leaf density, and the incidence of disease on leaves, but resulted in an increased standing crop of leaves. Removing neighbours increased the percent cover of L. arcticus and decreased total leaf mortality. Fertilizing increased the incidence of disease on leaves, and reduce the standing crop of leaves. Significant three-way interactions between treatments affected the plasticity of petiole length distributions for L. arcticus. Between-year differences in the responses to the treatments were also detected, particularly for reproductive investment and output in L. arcticus. Although a number of significant responses to treatments were detected, nevertheless, the overall tendency was for a lack of response, especially pertaining to leaf population dynamics. This low response to the treatments imposed is consistent with Grime’s (1979) arguments that plants growing in low productivity, infrequently disturbed habitats (i.e. stressful sensu Grime 1979) should show little response to short-term changes in local environmental conditions.Science, Faculty ofBotany, Department ofGraduat