An investigation of environmental parameters influencing the distribution of Platanthera blephariglottis (Willdenow) Lindley and P. clavellata (Michaux) Luer (Orchidaceae) in peatlands, and some aspects of their population dynamics

Brown, Cynthia Joan (1995) An investigation of environmental parameters influencing the distribution of Platanthera blephariglottis (Willdenow) Lindley and P. clavellata (Michaux) Luer (Orchidaceae) in peatlands, and some aspects of their population dynamics. Masters thesis, Memorial University of Newfoundland.

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Abstract

Populations of two terrestrial species of orchids, P. blephariglottis and P. clavellata, were investigated for two field seasons (1991-1992) to observe population dynamics and to explore what environmental factors (peat constituents, water pH and water level, endophytic fungi) may influence their distribution within a peatland. The dynamics of the populations were similar to each other and to that observed for other North American and European orchid species. Both populations increased in plant numbers, while showing a marked decline in flowering percentages in 1992. The populations, while having a net gain of individuals, also lost individuals, but it was not determined if these plants had died or returned to a subterranean stage. P. blephariglottis did not set any capsules, and capsule set was very low for P. clavellata due to a late frost at the time of flowering in both years. -- Peat constituent values associated with P. blephariglottis and P. clavellata were, for the most part, not significantly different, although the values associated with P. clavellata tended to be higher and to have a greater range than those associated with P. blephariglottis. Water level values were significantly different between species, suggesting that it is on this basis that these species partition the habitat. This is similar to the results of Boland and Scott (1992) for other peatland orchids. The relationship of water level and crown depth implies that P. clavellata can spend a significant period of time, when actively growing and flowering, with the crown submerged. -- Two mycorrhizal fungi were isolated and found to be associated with both species, suggesting that the fungi do not play a role in the distribution of these species.

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