Shefferson, Kull, and Tali 2006

		Shefferson, R.P., T. Kull, and K. Tali. 2006. Demographic response to shading
		and defoliation in two woodland orchids. Folia Geobotanica 41:95-106

Abstract Many woodland herbs are long-lived, clonal geophytes that have evolved life
histories favoring survival over reproduction. We examined the life history responses
of natural populations of two woodland orchid species, Cypripedium calceolus and
Cephalanthera longifolia to defoliation and heavy shading conducted early in the
growing seasons of 2002 and 2003. We asked whether, in view of the importance of
growth for the survival of geophytes, treated plants were more likely to exhibit reduced
flowering than reduced vegetative growth in the seasons following treatment. We also
asked whether plants would suffer reduced ramet performance. Both treatments led
to significant declines in flower number per ramet, number of leaves per ramet, and
mean ramet height relative to controls in Cypripedium. However, in Cephalanthera,
only shaded plants exhibited significant declines in flower number per ramet, and only
defoliated plants exhibited declines in mean ramet height. The number of ramets per
plant did not decline relative to controls in either species. Thus, these orchids,
especially Cypripedium, appeared to allocate resources preferentially to vegetative
growth functions over sexual reproduction. Per-plant variation in leaf and flower
number per ramet, as well as in mean ramet height, consistently declined in
response to treatment, significantly so in the case of mean ramet height, suggesting
that ramets became more similar within genets. These results suggest both
similarities and differences in the ways in which Cephalanthera and Cypripedium
mobilize resources in response to stress.

Article copyright notice: © 2006 by the Institute of Botany, Academy of Sciences of the
Czech Republic.

View PDF

Shefferson, Kull, and Tali 2006