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Abgeschickt von Chuck Sheviak am 21 Maerz, 2001 um 20:12:59
Antwort auf: Are Lady 's Slipper Endangered in North America? von Glen Lee am 16 Maerz, 2001 um 07:23:21:
I agree with Bill's comments, and would like to add a few thoughts of my own.
In general, most North American Cypripedium species probably have declined in abundance over the years, but it is important to consider the species, their habitats, and the geographic setting.
At one extreme, take for instance Cypripedium candidum. This species is mostly limited to the Midwestern U.S. and originally occurred there in considerable abundance on mesic prairie. The habitat that originally supported vast numbers of these plants has been almost completely converted to the production of grain, and with the loss of habitat went the species. It can still be found in some abundance in limited areas, and it certainly is not in any immediate danger of extinction, but what once was a typical plant of the region is now a precious discovery.
At the other extreme, perhaps, is Cypripedium acaule. This is still a common plant in much of the eastern portion of the continent. It is most abundant in acidic coniferous and oak forests. Today, successional pine forests are ubiquitous across the northeastern U.S., where they have developed on abandoned farm land. Because of the present abundance of these temporary communities, very likely C. acaule is today more abundant in this region than it was 200 years ago, and it certainly is far more common than a century ago when most of the region was still actively farmed.
Most of the other species probably fall between these extremes with regional differences in land use history contributing to a complex picture. To some extent, too, what we or our predecessors have seen in the past were merely temporary manifestations of history and environment. Our observations were made at a moment in a long and continuously varying system.
In the Canadian prairies, the situation around Winnipeg is interesting. A number of years ago I found Cypripedium parviflorum, both var. pubescens and var. makasin, to be abundant and generally distributed across wide areas. They did not occur everywhere, however. I had so grown accustomed to their presence, that when they suddenly disappeared without apparent change in the vegetation, I wondered why. Eventually I stumbled, quite literally, on the likely explanation. I tripped over a strand of barbed wire protruding from the soil. The remains of rotten fence posts could then be detected. The area had been grazed many years earlier. Although the vegetation as a whole had recovered and was not obviously different from the ungrazed communities nearby, not all species had responded similarly. The site apparently remained unsuitable for the Cypripedium, since clearly vast numbers of seeds rained down on it annually.
Certainly it comes as no surprise that as the human population grows at unprecedented levels and the surface of the planet is increasingly modified as a result, Cypripedium species will be affected along with everything else. For the most part the relationship will not be to the benefit of the cypripediums, but it is not a simple relationship.