The white-topped pitcher plant of precarious abundance
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
ORYX VOL 24 NO 4 OCTOBER 1990
The white-topped pitcher plant case
of precarious abundance
George W. Folkerts
White-topped pitcher plants, among the most attractive members of the
genus Sarracenia, are in great demand for floral displays, in the USA and
Europe. It is doubtful whether current levels of exploitation are sustainable;
there is no way of controlling harvesting for the domestic market and the
monitoring of exports is difficult. As well as this pressure, wild populations
are perhaps in even greater danger from changes in land use.
Introduction
11 species may be distinguished. There are at
On the coastal plain of south-eastern North least eight very distinctive types (McDaniel,
America, from south-eastern Virginia south to 1971). Two pitcher plants with very restricted
central Florida and west to east-central Texas, ranges, the green pitcher plant S. oreophila and
there are habitats that support one of the most the Alabama canebrake pitcher plant S. rubra
remarkable assemblages of plants in the alabamensis, have long been known to be
world. Their unique nature partly derives declining (Folkerts, 1977) and are currently
from an unusually high diversity of carnivo- protected by US law. The white-topped pitch-
rous plants. The bog sites where these assem- er plant S. leucophylla, considered by many to
blages are found differ somewhat ecologically, be the most beautiful, is used here to exempli-
but share a number of features, including wet, fy the problems that many of the organisms of
acid soils, frequent fires (at least under the these habitats are encountering. The leaves of
primeval fire regime), and often a low avail- this plant are tubular, up to 90 cm in height,
ability of soil nutrients. Presumably these fea- and taper to a narrow base. The top portion of
tures have promoted the evolution of a num- the leaf and the hood, which overhangs the
ber of unique carnivorous genera, including orifice, are mainly bright white, the areas
the Venus flytrap Dioneae muscipula and the between the veins lacking chlorophyll.
North American pitcher plants of the genus Evolutionarily, this plant seems to have sacri-
Sarracenia. Additionally, although the genera ficed photosynthesis in the upper portion of
have not evolved here and are not endemic, a the leaf, creating the white, flower-like
number of species of butterworts Pinguicula appearance, which is very effective in attract-
spp., bladderworts Utricularia spp., and sun- ing insects from which the plant obtains vital
dews Drosera spp., are present. Several species nutrients. The species ranges from south-east-
in these genera are restricted to bogs in south- ern Georgia through the Florida Panhandle
eastern USA. and southern Alabama to south-eastern
Mississippi.
Pitcher plants
The role of fire in maintaining
Among the most conspicuous plants in the pitcher plant bogs
bogs are the species of Sarracenia, causing the
sites to often be called pitcher plant bogs. Pitcher plant habitats along the Gulf Coast of
Depending on taxonomic opinion, as many as south-eastern North America have been dis-
201
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918ORYX VOL 24 NO 4 OCTOBER 1990
appearing rapidly in the last several decades
(Folkerts, 1982). Although large stands of the
white-topped pitcher plant were once com-
mon, populations are now smaller and much
less abundant than they were 30 years ago.
Many factors are involved. One major factor
relates to fire. There is abundant evidence that
many of the plant communities on the coastal
plain of south-eastern North America were
historically maintained by natural fires
(Komarek, 1974). Writings of early American
naturalists attest to this fact (Brickell, 1737;
Bartram, 1791). Before the American Indians
arrived from Asia, fire in these ecosystems
was started by lightning. In pre-Columbian
times, fire generated by a single strike could
have spread for dozens, perhaps hundreds, of
kilometres, even though the burn was proba-
bly patchy. The only barriers to the spread of
fire would have been watercourses, relatively
infrequent rocky areas, the presence of com-
munities in which natural processes did not
generate sufficient fuel to carry fire, and areas
where litter consisted largely of materials that
did not ignite readily or were slow to burn.
Insect-trapping leaves of the white-topped pitcher
The white-topped pitcher plant and almost plant Sarracenia leucophylla. On the lower left is a
every other species of plant that shares its mature fruit (George Folkerts).
habitat are perennial herbaceous species in
which the perennating portions (generally rhi- strated that the Yellowstone ecosystem was
zomes, bulbs or corms) lie beneath the soil not only harmed very little, but may have ben-
surface and therefore are not harmed by fires. efited significantly (Boyce, 1989). In any event,
Fire destroys only the aerial portions and in fire control and suppression was an accepted
most species these regenerate in a few months practice and still is in many quarters. Only in
or by the next season. It is this adaptation to the last decade has this view begun to change.
fire that may play a major part in spelling the Without frequent fire, the pitcher plant com-
demise of the white-topped pitcher plant and munity rapidly disappears as a result of eco-
many associated plants and animals. From the logical succession. Invasion by fire-intolerant
1930s until recently, fire was viewed as a vines, shrubs and trees, whose propagules are
catastrophe that should be prevented at all dispersed by wind or birds occurs almost
costs. The public education programme, initiat- immediately. As the woody species mature,
ed by the US Forest Service and involving well- shading begins to affect the bog plants detri-
known symbols such as 'Smokey the Bear' suc- mentally, almost all of which are adapted to
ceeded in convincing the biologically naive conditions in full sun. Drying of the bog soil
public that fire was an unnatural event to be occurs as a result of transpiration of large
feared. This campaign has had some drastic amounts of water through the woody plants.
detrimental ramifications. A prime example After a period of from 3-5 years without fire,
exists in the massive public and bureaucratic the accumulated litter is sufficiently deep to
outcry that resulted from the 1988 fires in prevent sexual reproduction in the pitcher
Yellowstone National Park in the western plants, which seem to require areas of bare
United States. The scientific evidence demon- mineral soil for seed germination and seedling
202
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918WHITE-TOPPED PITCHER PLANT
growth. This failure in seedling recruitment is The ability of the white-topped pitcher
aggravated by the fact that stress resulting plant to continue to produce visible vegetative
from the presence of competing woody species parts without reproducing sexually, has
causes the pitcher plants to produce fewer resulted in a dilemma for conservationists
flowers. Eventually the great majority of pitch- concerned about its future. There are approxi-
er plants in a stand may fail to flower. mately 250 known sites at which the species
However, the rhizomes of the white-topped still occurs. Many of these are along public
pitcher plant are very long-lived and seem roads, and a number are well known to local
able to survive for decades in a dormant state people. In cases where the public perceives a
without producing flowers or pitchers, species as relatively abundant, conservation
although inconspicuous phyllodia may be pro- groups and US resource agencies have justifi-
duced. Evidence for this comes from examina- ably been reluctant to propose the plant for
tion of pitcher plant sites planted to pines in formal protection lest they be accused of 'cry-
the early 1960s. During the 1970s and early ing wolf. Nevertheless, most of the popula-
1980s there was no sign of the plants, yet after tions of the white-topped pitcher plant are
the pines were harvested in the late 1980s, functionally extinct because they are not
active plants of S. leucophylla and S. flava with reproducing.
large rhizomes were present. It appears that if It might seem that the solution is obvious:
competing, shading vegetation is removed by merely initiate a programme of burning,
fire or clearance, dormant rhizomes again pro- which would eliminate competing vegetation
duce above-ground parts. The maximum and restore the successional stage that is con-
length of time that the rhizomes can survive in ducive to pitcher plant population health.
dormancy is not known. There are, however, a number of significant
mam
A large drainage ditch in the eastern Florida Panhandle constructed to dry out bog soils to enable the planting
of pine trees (George Folkerts).
203
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918ORYX VOL 24 NO 4 OCTOBER 1990
problems associated with this seemingly sim- ing discing and chopping of the soil may kill
ple answer. First, natural fires no longer most of the pitcher plants before the pines are
spread even if they are allowed to burn. planted. Herbicides are often applied to con-
Roads, railways, canals, drainage ditches, trol competing hardwoods and these may
developed areas and constructed fire breaks eliminate the few remaining living pitcher
all prevent the spreading of fires. Secondly, plants. Under these conditions, prospects for
problems with smoke and possible spread of restoration of a pitcher plant community are
fire into residential areas, agricultural fields poor.
and managed forests make controlled burning
difficult and make burning permits difficult to
obtain. Thirdly, prescribed burning, when it is The trade in pitchers
done by public or private land management
agencies, is traditionally done in the winter. A third major threat to the white-topped
Winter burning will not successfully remove pitcher plant has intensified in the last five
competing woody species from pitcher plant years. Because of their beauty, pitchers of this
habitats unless the site is burned every year species have been cut for use in floral dis-
for a number of years. Circumstantial evi- plays. Until recently, the trade in pitchers was
dence obtained from lightning strike and limited and only a few sites were regularly
thunderstorm records indicates that 'natural' harvested. However, since 1984 pitcher har-
burns probably occurred most frequently in vest has increased. In 1988 the Office of
the spring and summer. Scientific Authority of the US Fish and
Wildlife Service received applications for per-
mits to harvest over three million pitchers of
The effect of land-use changes the white-topped pitcher plant. It is doubtful
that this many pitchers are present in all exist-
If lack of burning were the only problem, the ing populations. The Office of Scientific
future of pitcher plant communities would be Authority approved the export of approxi-
bleak. But several other degrading factors are mately half a million pitchers on the basis of
acting to exacerbate the situation. Intensive its legal authority resulting from agreements
monoculture of pines has become a major under the Convention on International Trade
land use activity in the range of the white- in Endangered Species of Wild Fauna and
topped pitcher plant in the past 30 years. Flora (CITES) (the white-topped pitcher plant
Pitcher plant habitats are too wet for economic is listed in Appendix II of CITES). However,
growth of commercial pine species. The tim- there is currently no method by which pitcher
ber and pulp industry view bogs as sites to be harvest for the domestic market can be con-
drained and converted to profit. In a sense, trolled. In fact it is very difficult even to moni-
the industries can hardly be blamed. They tor export to determine if permit holders are
would contend that they pay taxes on the complying with prescribed limits. The bulk of
land and have been given no economic incen- the exported pitchers end up in floral displays
tives to protect any components of the natural in the UK, the Federal Republic of Germany,
world. To their credit, a few corporations have the Netherlands and Scandinavian countries.
attempted to protect natural communities It seems almost certain that a twice-yearly
when the economic sacrifice was not too great. harvest (the plant produces two crops of
Conversion of bogs to even-aged stands of pitchers during a season) of large numbers of
pine involves drainage, which cause irre- pitchers from a population is detrimental to
versible changes in habitat. In addition to soil this plant. The pitchers are photosynthetic
drying, the closely spaced pines cast heavy structures as well as the means by which the
shade. Eventually a thick layer of shed pine plant attracts and digests insect food. Harvest
needles accumulates, killing any seedlings or is also causing physical damage to the habitat
small plants present. Site preparation involv- as a result of vehicle and human traffic. Even
204
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918WHITE-TOPPED PITCHER PLANT
Harvested pitchers ready to be transported to cold storage for eventual sale in thefloristtrade (Mark Bailey).
though most would agree that the practice is eliminates most of the pitcher plants. Soil
damaging, long-term studies that support this compaction may inhibit recovery if grazing
view have not been done. Even if they were pressure is reduced. Pond construction has
undertaken now many sites might be dam- destroyed a large number of bogs on slopes,
aged irreparably before the results were avail- which depend on seepage for moisture.
able. Harvesters have not been required to Herbicide spraying, urbanization, canal and
show that their activities are not damaging. road construction, off-road vehicle traffic and
mowing are all taking their toll.
A final factor that is affecting survival of the
Other damaging factors white-topped pitcher plant and many other
bog species, especially the carnivorous kinds,
Damage to white-topped pitcher plant popu- is the digging of living plants for sale or trade
lations resulting from fire suppression, forest by commercial operators and the growing
practices and pitcher harvest must be viewed number of carnivorous plant fanciers. These
as catastrophic. Even so, many other degrad- groups often profess a conservation ethic, but
ing processes and damaging practices are also experience indicates that many enthusiasts
occurring. Pitcher plant bogs appear to be cannot resist having one more plant of a
lush. Landowners who do not realize that slightly different type for their greenhouse or
plants growing in areas with low nutrients do artificial bog. As a result, populations of
not make good forage have attempted to turn extremely rare and legally protected species
bogs into pastures. Although cattle do not eat have been decimated. A common but unper-
the pitchers, they do eat the flowers. After a suasive excuse offered by the diggers is that
few years of grazing, trampling by livestock they are rescuing plants that probably would
205
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918ORYX VOL 24 NO 4 OCTOBER 1990
have been destroyed anyway. The white- to maintain openness and protect the source
topped pitcher plant can probably tolerate of the bog moisture are seldom maintained.
current levels of removal, but as the species Clear-cutting, a common practice on many
becomes rarer, each plant will be of more sig- managed public lands, often disturbs the bog
nificance and demand will increase. soil. Replanting is sometimes done right up to
the bog edge. When the stand matures, shad-
ing and needlefall become problems.
The need for protection Additionally, dense stands of trees planted
upslope from bogs may remove much of the
One might assume that stands of white-topped available soil moisture before it can reach the
pitcher plants on public lands are safe, but the bog. Unfortunately, policies on many of the
reverse is often the case. Populations exists in public lands in the US are dictated more by
two national forests, several military bases and bureaucratic inertia, industry pressure and
a number of state forests, parks and other pub- political expedience than by wise and far-
lic properties. National forest populations are sighted resource management principles. In
protected only by administrative initiative, the few cases in which pitcher plant habitats
since the plant has no legal protection. Those have been properly managed, it has been at
that are offered some protection are often the initiative of a few knowledgeable agency
improperly managed, at times as a result of employees who did so in the face of opposi-
insufficient knowledge about the needs of the tion or apathy.
community. Ditches constructed to control pre- Currently the white-topped pitcher plant is
scribed burns result in soil drying. Buffer areas listed in at least some category of endanger-
The area behind the fence has been grazed for two years. Before grazing it resembled the foreground area,
which has never been grazed. Grazing rapidly eliminates nearly all of the bog flora (George Folkerts).
206
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918WHITE-TOPPED PITCHER PLANT
ment or rarity by agencies in all the states in information in this article was obtained during a
its range. This reflects its precarious status, study supported by the US Fish and Wildlife Service
but the lists are seldom backed by legal pro- contract 14-16-0009-1550-RWO-l 4 through the
Alabama Cooperative Fish and Wildlife Research
tection. If they are, enforcement is difficult or Unit (Co-operators: US Fish and Wildlife Service,
impossible. As has been the case with so Alabama Division of Game and Fish, Alabama
many declining species, it seems that we may Agricultural Experiment Station, Auburn
have to wait until the species reaches the University, and Wildlife Management Institute).
point when it qualifies for protection under
federal law. Then we can fight a last ditch bat-
tle and hope that a few remnants can be References
saved. It is ironic that agencies, industries and Bartram, W. 1791. Travels through North and South
groups who strongly object to legal protection Carolina, Georgia, East and West Florida.
for endangered species, because it may inter- Philadelphia.
fere with their traditional endeavours or with Brickell, J. 1737. Natural history of North Carolina.
Published by the author, Dublin, Ireland.
profit, are continually in the process of push-
Boyce, M.S. 1989. Effects of the 1988 fires on ungu-
ing species to the point where legal protection lates in Yellowstone National Park. Proceedings of
is necessary. the 17th Tall Timbers Fire Ecology Conference. Tall
Sarracenia leucophylla is not the only species Timbers Research Station, Tallahassee, Fla. (in
inhabiting the bogs of the south-eastern US. press).
These sites harbour more than 20 other species Folkerts, G.W. 1977. Endangered and threatened
carnivorous plants of North America. In
of carnivorous plants, making them some of Extinction is For Ever: The Status of Threatened and
the most diverse carnivorous plant habitats in Endangered Plants of the Americas (eds G. T. Prance
the world. Many other rare and declining and T. S. Elias), pp. 301-313. The New York
species are present, including the Panhandle Botanical Garden, Bronx, New York.
lily Lilium iridollae, the yellow fringeless Folkerts, G.W. 1982. The Gulf Coast pitcher plant
orchid Platanthera Integra, and the bog spice- bogs. Amer. Scient. 70,260-267.
bush Lindera subcoriacea. Over 12 species of Komarek, E.V. 1974. Effects of fire on temperate
forests and related ecosystems: southeastern
insect are obligate associates of pitcher plants
United Sates. In Fire and Ecosystems (eds T. T.
(Rymal and Folkerts, 1982). The bogs are habi- Kozlowski and C. E. Ahlgren), pp. 251-277.
tat for crayfishes Fallicambarus spp., a number Academic Press, New York.
of which have not yet been scientifically McDaniel, S. 1971. The genus Sarracenia
described. All of these species will share in the (Sarraceniaceae). Bull. Tall Timbers Res. Sta. 9,1-36.
white-topped pitcher plant's fate. At present Rymal, D.E. and Folkerts, G.W. 1982. Insects associ-
there is little cause for optimism. ated with pitcher plants (Sarracenia:
Sarraceniaceae) and their relationship to pitcher
plant conservation: a review. /. Ala. Acad. Sci. 53,
131-151.
Acknowledgmen ts
Bruce MacBryde kindly supplied some of the infor- George W. Folkerts, Department of Zoology and
mation included here. Debbie Rymal Folkerts, Nick Wildlife Science, Alabama Cooperative Fish and
Holler, Dan Speake and Lee Stribling read and criti- Wildlife Research Unit, and Alabama Agricultural
cized the manuscript. Mark Bailey generously Experiment Station, Auburn University, Auburn,
allowed the use of a photograph. A portion of the Alabama 36849-5414, USA.
207
Downloaded from https://www.cambridge.org/core. IP address: 46.4.80.155, on 27 Jul 2021 at 12:56:55, subject to the Cambridge Core terms of use, available at
https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300034918You can also read
