Long-Term Studies: A Case for Orchid Species Survival

2005·2.3 MB·

by  Light, Marilyn H S

Selbyana 26(1,2): 174-188.2005.
LONG-TERM STUDIES: A CASE FOR ORCHID SPECIES SURVIVAL
MARILYN RS. LIGHT* AND MICHAEL MACCONAILL
174 Jolicoeur St., Gatineau, Quebec Canada J8Z lC9.
Email: [email protected]
ABSTRACT. Our understanding of orchid population behavior can be critical to the selection of appropriate
conservation measures, yet less than 50% of North American and 5% of world orchid species respectively
are currently subject to long-term study. Such studies often must be accomplished with limited resources.
Whatever the situation, however, the selected approach should be both comprehensive and well thought
out, if there is to be a conservation pay-off.
Key words: Cypripedium parviflorum, disturbance, time series
INTRODUCTION exceed 20 years, the longest being 41 years,
making this possibly the most concentrated
Long-term study of individual orchids and of time-series treatment of orchid populations in
their populations is essential to further our un North America.
derstanding of the factors affecting their estab Data gathering is an immense task beyond the
lishment and success, yet relatively few such scope of the relatively few field personnel em
studies have been undertaken (Tamm 1972). ployed for the purpose (Freemark et al. 1999).
Vanhecke (1994) reported that for the 227 Eu Most historic time series have been initiated by
ropean orchid species, time-series observations private citizens, groups, or public entities. The
had been recorded for only 17% or 39 species. authors of the Plant Tracking List, published as
More than 40% of these observation periods a technical reference by the New Hampshire
were short (2-5 years), while the longest unin Natural Heritage Bureau (2004), acknowledge
terrupted observation was 41 years for a popu the limited capacity of field biologists to gather
lation of Cypripedium calceolus L. in Denmark. what is required. They solicit the assistance of
Kull (2002) presented data on field-based studies persons who can provide additional locations
of 67 temperate terrestrials, of which some are and other data. The New England Plant Conser
North American and included in this paper. A vation Program of the New England Wild Flow
total of 208 orchid species are listed in Flora er Society (NEWOS), a voluntary association of
North America (2002), which we used as a ref private organizations and government agencies
erence: the majority are terrestrials, and 20% are in each of the six states of New England, are
epiphytes. Time-series observations of North working together to develop management plans
American terrestrial orchids are summarized in for plants identified as at risk. NEWOS (1997)
TABLE 1, where we list 126 studies of 68 taxa published Flora Conservanda, which serves as a
(39%), the longest being of Platanthera leuco reference tool for all New England plants in
phaea (Nuttall) Lindley during a 41-year period. need of conservation, including orchids. Orchid
Of all these studies, 40% are for 10 or less years, research also is challenging because historical
with 70% of these being of species deemed to data are variously published in reports, theses,
be at risk. Either no studies exist or they remain books, and scientific papers. Some of the most
unreported for some 60% of North American comprehensive reports are included in conser
terrestrial orchid species. Some of the notable vation assessments of species that are of special
time series include those of Curtis (1954), who
concern throughout their geographic range, such
reported on a 20-year study (1933-1952) of five
as Cypripedium arietinum R. Brown, which is
species of Cypripedium L. to develop an under
known from ca. 430 localities in North America
standing of the fluctuation in annual flower pro
(Schultz 2003) and Isotria medeoloides (Pursh)
duction. Light et al. (2003) reviewed time series
Raf., for which some 25 sites have been moni
from the Ottawa District and surrounding areas
tored, some for as long as 25 years (New Hamp
in Canada, reporting 38 studies of 32 taxa, the
shire Natural Heritage Bureau 2004). Regretta
majority being those of Reddoch and Reddoch
bly many data sets are never published or remain
(1997), who have tracked 32 of the 43 terrestrial
in private hands. Despite the paucity of time
orchid species found within a 50-km radius of
series data, an abundance of reports state the ob
Ottawa. More than two-thirds of observations
vious: long-term monitoring is needed. We must
be hopeful that many time series have been ini
* Corresponding author. tiated but not yet reported. Also, to measure our
174
TABLE I. Long-term studies of terrestrial orchids in the Continental USA and Canada.
Species Duration (years) Period Source
Amerorchis rotundifolia (Banks ex Pursh) Hulten 38 1959-1996 Reddoch & Reddoch 1997
Unspecified St. Hilaire 2001
Aplectrum hyemale (Muh!. ex Willd.) Nutl. 7 1986-1992 Lavoie 1993
Arethusa bulbosa (L.) 30 1967-1996 Reddoch & Reddoch 1997
Calopogon tuberosus (L.) B. s. P. 9 1970-1978 Reddoch & Reddoch 1997
Calypso bulbosa (L.) Oakes 7 1973-1979 Reddoch & Reddoch 1997
Cleistes bifaria (Fern.) Catling & Gregg 10 1990-1999 Kery & Gregg 2003
Cleistes divaricata (L.) Ames 6 1985-1990 Gregg 1991
Coeloglossum viride (L.) Hartm. 7 1973-1979 Reddoch & Reddoch 1997
Corallorhiza bentleyi Freudenst. 5 1996-2001 Bentley 2004
Corallorhiza maculata (Raf.) Raf. 32 1965-1996 Reddoch & Reddoch 1997
I/J
Corallorhiza striata Lindl. 29 1968-1996 Reddoch & Reddoch 1997 trI
Corallorhiza trifida Chatel. 29 1968-1996 Reddoch & Reddoch 1997 (J
0
Cyclopogon cranichoides (Griesn.) Schltr. 4 1986-1989 Calvo 1990 Z
Cypripedium acaule (Ait.) 4 1984-1987 Primack & Hall 1990 0
11 1984-1994 Plimack & Stacy 1998 >-<
0
25 1997-present W. G. Schmid pers. comm. (J
28 1969-1996 Reddoch & Reddoch 1997 (J
20 1977-J996 Gill 1996 "d
10
Cypripedium arietinum R. Br. 20 1933-1952 Curtis 1954
0
29 1968-1996 Reddoch & Reddoch 1997 (J
Cypripedium candidwn Muhl. ex Willd. 20 1933-1952 Curtis 1954 trI
trI
10 1994-present R. Shefferson pers. comm. 0
Cypripedium Jasciculatum Kellogg ex S. Watson 3 1998-2000 P. Lantham pefs. comm. .Z.....
8 1987-1994 Lichthardt J 995 Cl
Cypripedium montanum Douglas ex Lindl. 5 1992-1996 Seevers & Lang 1998 I/J
9 1990-1998 Kaye 1999
Cypripedium parvijiorum Salisb. 20 1933-1952 Curtis 1954
8 1996-2003 M. From pers. comm.
Cypripedium parvijiorwn Salisb. var. parvijioruml 10 1994-present Shefferson et al. 2003,
pers. comm.
Cypripedium parvifiorum Salisb. var. pubescens (Willd.) Knight 20 1933-1952 Curtis 1954
29 1968-1996 Reddoch & Reddoch 1997
20 1985-present Light & MacConaill this study
Cypripedium X andrewsii A. M. Fuller 10 1994-present R. Shefferson pers. comm.
20 1933-1952 Curtis 1954
Cypripedium passerinum Rich. 2 1995-1996 Nantel & Cantin 1997
Cypripedium reginae Walt. 20 1933-1952 Curtis 1954
20 1985-present Light & MacConaill, this study ,....
12 1980-2001 K. Gregg pers. comm. --l
VI
Dactylorhiza majalis (Rchh.) P. F. Hunt & Summerh. 3 1993-195 Meades 2002
26 1959-1984 S. Meades pefs. comm.
TABLE l. Continued. I-.-..J'
0\
Species Duration (yea,,) Period Source
Epipactis gigantea Douglas ex Hook. 3 1989-1991 Mancuso 1991
8 1994-200]2 Hornbeck et a!. 2003
6 1998-2003 Black Hills National Forest,
USDA Forest Servo 2002
Epipactis helleborine (L.) Crantz 20 1985-present Light et a!. 2003
Galearis spectabilis (L.) Raf. 28 1969-1996 Reddoch & Reddoch 1997
8 19 96-present M. From pers. comm.
Reddoch & Reddoch 1997
Goodyera pubescens (Willd.) R. Br. in Ait. 29 1975-2003 J. Reddoch pers. comm.
5 1985-1989 Keenan 1990
Goodyera oblongifolia Raf. 4 1998-2002 Smith 2002
Goodyera tesselata (Lodd.) 22 1975-1996 Reddoch & Reddoch 1997
Hexalectris nitida L. O. Williams 3 1995-1997 Wolfe et al. 1997
Hexalectris revoluta Correll 9 19 96-present R. Coleman pers. comm.
Hexalectris warnockii Ames & Correll 9 I 996-present R. Coleman pers. comm.
lsotria medeoloides (Pursh) Raf. 3 1995-1997 Wolfe et a!. 1997 [/]
lsotria verticillata (Muh1en. ex Willd.) Raf. 5 1979-1984 Mehrhoff 1989 tn
l'
Liparis Wi ifolia (L.) Rich. ex Lind!. 25 1965-1990 Oldham unpub!. data to
-<
Liparis loeselii (L.) Rich. 13 1977-1989 Whigham & O'Neill 1991 >-
7 1993-1999 McMaster 2001 Z
28 1969-1996 Reddoch & Reddoch 1997 >-
Listeria auriculata Wiegand 11 1967-1977 Reddoch & Reddoch 1997
Listera convallarioides (Sw.) Elliott 8 1987-1994 Hoy 2002
19 1917-1935 Pease 1964
Malaxis abieticola Salazar & Soto Arenas 6 1999-present R. Coleman pers. comm.
Malaxis monophyllos var. brachypoda (A. Gray) F. Moris & E. A.
Eames discontinuous Schultz 20023
Malaxis porphyrea (Rid!.) Kuntze 6 1999-present R. Coleman pers. comm.
Platanthera aquilonis Sheviak f. alba (M. H. S. Light) P.M.Br. 10 1985-1996 Light & MacConaill 19894,
M. Light pers. comm.
Platanthera blephariglottis (Willd.) Lind!. 27 1970-1996 Reddoch & Reddoch 1997 -<
Platanthera ciliaris (L.) Lind!. 8 1996-present Keller & Killingbeck 2003, 0
P. Keller pers. comm. 8"
8
2 1983-1984 Robertson & Wyatt 1990
(D
Platanthera clavellata (Michx.) Luer 28 1969-1996 Reddoch & Reddoch 19 97 tv
Platanthera dilatata (pursh) Lind!. ex L. C. Beck 31 1966-1996 Reddoch & Reddoch 1997 ~,.....
Platanthera grandiflora (Bigelow) Lind!. 28 1969-1996 Reddoch & Reddoch I 997
Platanthera hookeri (Torr. ex A. Gray) Lind!. 26 1978-1996 Reddoch & Reddoch 19 97 ~
Platanthera huronensis (Nutt.) Lind!. 29 1968-1996 Reddoch & Reddoch 1997 tv
0
Platanthera integrilabia (Correll) Luer 2 1988-1989 Zettler & Fairey 1990 0
U1
TABLE 1. Continued.
Species Duration (years) Period Source
Platanthera leucophaea (Nutt.) Lindl. 41 1956-1996 Reddoch & Reddoch 1997
Platanthera orbiculata (Pursh) Lindl. 19 1969-1996 Reddoch & Reddoch 1997
Platanthera praeclara Sheviak and Bowles 8 1987-1994 Sieg & King 1995
8 1996-present (Nebraska) M. From pers.
comm.
5 1996-2000 (Iowa) M. From pers. comm.
5 1984-1988 Bjugstad & Fortune 1989
Platanthera psycodes (L.) Lindl. 28 1969-1996 Reddoch & Reddoch 1997
Platanthera zothecina (L. C. Higgins & S. L. Welsh) Kartesz &
Gandhi 1 on-going Hudson 2001
Cf.l
Pogonia ophioglossoides (L.) Ker. Gawl. 30 1967-1996 Reddoch & Reddoch 1997 trJ
Pteroglossaspis ecristata (Fern.) Rolfe 2 1998-1999 Grace 2000 (1
0
Spiranthes casei Catling & Cruise 25 1972-1996 Reddoch & Reddoch 1997 S
Spiranthes cemua (L.) Rich. 10 1985-1994 Antlfinger & Wendel 1997
9 1995-2003 M. From pers. comm. ......
0
24 1973-1996 Reddoch & Reddoch 1997 (1
Spiranthes delitescens Sheviak 13 1992-present R. Coleman pers. comm. (1
Spiranthes diluvialis Sheviak 12 1992-present Sipes* '"0
8 1993-2000 Fertig 2000 ~
0
2 1999-2000 Moseley & Murphy 2002 (1
5 1996-2000 Heide12001 0
Spiranthes infemalis Sheviak 12 1991-2002 U.S. Fish and Wildlife Servo
......
Status Report pendingt Z
Spiranthes lacera (Raf.) Raf. 29 1968-1996 Reddoch & Reddoch 1997 0
Spiranthes magnicamporum Sheviak 6 1998-present M. From pers. comm. Cf.l
Spiranthes romanzoffiana Cham. 34 1967-2000 J. Reddoch pers. comm.
Stenorrhynchos michuacanum (La Llave & Lexarza) Lindl. 10 1995-present R. Coleman pers. comm.
Tipularia discolor (Pursh) Nutt. 13 1977-1989 Whigham & O'Nei111991
Triphora trianthophora (Sw.) Rydberg subsp. trianthophora 6 1988-1993 Williams 1994
6 1985-1990 Keenan 1992
19 1974-1992 Keenan 1992
12 1986-1997 Wood1iffe unpubl. data
1 Published as Cypripedium calceolus L. subsp. parviflorum (Salisb.) Fern.
2 Baseline monitoring began in 2000.
3 Published as Malaxis brachypoda (A. Gray) Fern.; see Schultz 2002 Appendix B for a comprehensive review of observations.
4 Published as Platanthera hyperborea (L.) Lindl. var. hyperborea f. alba Light.
* http://www.science.siu.edulplant- biologyI faculty/sipes/rareplants.html.
t http://heritage.nv.govI notes03 .htm.
178 SELBYANA Volume 26(1,2) 2005
relative success in meeting a common conser the earliest previous record for this region (Red
vation objective of population-level mainte doch & Reddoch 1997). The behavior of plants
nance, we need tracking and regular reporting of individually and collectively over the study pe
population behavior to a central registry. Long riod is presented.
term studies need not be limited only to demo
graphic behavior of particularly showy orchids
METHODS AND MATERIALS
or those species at risk of extinction.
Cypripedium parviflorum Salisb. var. pubes Research Sites
cens (Willd.) Knight (formerly C. calceolus Sal
Fieldwork was carried out in Gatineau Park,
isb. var. pubescens (Willd.) Corr.) is a self-com
Quebec, Canada (45°27'N, 7?o46'W). Some ~50
patible but pollinator-dependent, long-lived de
flowering genets occupy a 11ght gap measurmg
ciduous perennial orchid locally common over a
21 m X 23 m at the head of a forested valley
wide range in North America (Catling & Catling
that slopes down from west to east. The flow
1991; Curtis 1954; Light & MacConaill 1996,
ering population has been tracked since 2000.
2002a; Tremblay 1994). Previous investigations
The forest canopy surrounding the site is ca. 30
of this spring-flowering orchid in Gatineau Park,
m high and somewhat irregular. Estimated stand
Quebec, Canada, have focused on reproductive
age is 75 years, and blow-downs have been fre
behavior (Light & MacConaill 1996, 1998,
quent, as indicated by a characteristic mound
2002b· Tremblay 1994). Studies of Cypripedium
L. and pit relief (Ouimet et al. 2001). Major canopy
spp. conducted elsewhere have explored ei
species include sugar maple (Acer saccharum
ther the phenology and floral biology or the im
Marsh.) and red oak (Quercus rubra L.). Soil is
pact of habitat alteration on reproductive success
variably shallow over marble parent material
(Curtis 1954, Gill 1996, O'Connell & Johnston
(Hearn & Hogarth 1970). The, Quebec forest
1998, Primack et al. 1994, Primack & Stacy
monitoring network (Reseau d'Etude et de Sur
1998, Tremblay 1994). Failure to re-emerge is
veillance des Ecosystemes Forestiers or RESEF)
often described as a resting state or dormancy,
operates atmospheric monitoring station #11 in
and Shefferson et al. (2003) explored the costs
Gatineau Park, ca. 12 km to the northwest of the
of flowering, dormancy, and sprouting in Cyp
study site. According to RESEF measurements,
ripedium parviflorum Salisb. var. parviflorum
average acid deposition rate for the 1989-1993
(published as C. calceolus var. parvifiorum).
period was 560 and 460 eq·ha-1yr-1, for nitrogen
Their fieldwork identified the costs of dormancy
and sulfur respectively (Ouimet et al. 2001).
and sprouting to survival of orchids in an open
The isolated single genet of Cypripedium par
wet meadow.
viflorum var. pubescens (Site 1), a light gap
Our tracking of Cypripedium parviflorum var.
formed from tree falls, is 1.2-1.8 km from the
pubescens began in 1985, when a single plant
nearest other C. parviflorum sites, including the
was found growing within a population of Epi
colony (Site 2) described above. This plant has
pactis helleborine (L.) Crantz (Site 1, Light &
been tracked annually (1985-2004). Soil depth
MacConaill 2002a). Beginning in 1996, we set
is variable but averages ca. 10 cm over marble
out to elucidate factors affecting seed production
bedrock, where the orchid grows near several
within a large colony of C. parviflorum var. pu
small clumps of Carex sp.
bescens (Site 2) located 1.8 km south of that site
(Light & MacConaill 1996, 1998, 2002a). We
Populatiou Mappiug
first focused our effort on larger genets but ex
panded our study to include increasingly more All flowering genets in the large colony were
genets; until in 2000, the entire flowering pop marked with a numbered plastic stake, mapped,
ulation was tracked, a process which has since and assigned to one of four groups: genets
been repeated annually (Light & MacConaill known in 1991-2000 and those found blooming
2002b). The region recently has been subjected for the first time in 2001, 2002, and 2003 (FIG
to some extreme weather events, including se URE 1). Genets were classified according to the
vere drought in 1991. In July 1996, ca. 3 cm of number of reproductive and vegetative shoots or
hail shredded orchid leaves. An ice storm in Jan as non-emergent. Size classes based on total
uary 1998, the worst on record for eastern North shoots were labeled as non-emergent (A), 1
America, created an estimated 10-20 times the shoot (B), 2 or 3 shoots (C), 4-8 (D), 9-15 (E),
annual production of woody litter in temperate and 16 shoots (F).
deciduous forests (Hooper et al. 2001). Addi
tionally in 1998, the frost-free period was sig
Light and Weather Data
nificantly prolonged, being April 12-0ctober 5
(174 days). In 1998, Cypripedium parviflorum Precipitation and temperature data obtained
var. pubescens began flowering 12 days before from the weather station located at Ottawa In-
SECOND IOCC PROCEEDINGS 179
N
+
•
•
4-"--100
" IJE.m-2.s'
•
• •
+
+ •• +
• ••• +
•
+••. ~ • +
•
:. 4O•
-""'-----1000---
IJE.m-2.s-'
•
•
o
m 5
Scale
•
FlGURE 1. Sketch map of large colony showing distribution of Cypripedium parviflorum var. pubescens plants
in year classes 1991~2000 (e), 2001 (X), 2002 (+) and 2003 (I.). Circled symbols mark 13 plants that changed
from 9 or more stems to absent or vice-versa. Contours of PAR (photosynthetically active radiation) intensity
(/-Lmol·m-2·s-1) indicate the averaged light levels as measured in 2001. Also shown are the location of significant
rocks (triangles), standing trees (grey circles), and fallen tree trunks and branches (grey lines).
ternational Airport, ca. 20 Jan south, was used riod, before and after the overstory closed. Min
to calculate yearly averages and deviations. Dai imum and maximum soil temperatures were
ly minimum and maximum temperature also was measured within the root zone, using a standard
monitored within the site during flowering sea ized probe.
son, and rainfall was measured locally within 2
Jan of both sites. Sunlight, measured as photo RESULTS
synthetically active radiation (PAR), was esti
Tracking of the Isolated Single Genet,
mated at the level of the single plant and at 14
1985-2004
locations representative of the range of habitat
within the large colony, using a LI-COR meter The Site 1 plant has experienced a more or
around noon sun time during the blooming pe- less consistent light regime during a 20-year pe-
180 SELBYANA Volume 26(1,2) 2005
TABLE 2. Behavior of a single plant of Cypripedium parviflorum var. pubescens and deviation from long-term
average precipitation over 20 years (1985-2004) in Site I, Gatineau Park, Quebec.
Stems Rainfall
deviationt
Year Total Flowering Fruits PAR* (mm)
1985 I 0 0 -22.8
1986 1 0 0 297.3
1987 I 0 0 37.7
1988 2 0 0 43.6
1989 2 2 0 99 -14.2
1990 2 2 0 77.2
1991 2 2 0 -133.3
1992 I 0 0 57.6
1993 3 0 0 40.8
1994 2 0 0 87.2
1995 2 1 0 268 136.7:j:
1996 2 0 149.2
1997 2 0 -33.4
1998 2 2 2 18.3:j:
1999 4 3 1 i8.1
2000 9 9 1 130 13.8:j:
2001 8 6 1 356 -7.3
2002 0 0 0 70.3
2003 0 0 0 93.8
2004 8 nla nla
* Photosynthetically Active Radiation (PAR) in f.Lmoj·m-2s-1, as measured with a Ll-COR meter.
i-Deviation from seasonal average precipitation (463 mm) as recorded at Ottawa International Airport 31 May,
1-31 Oct.
:j: Tree fall events.
riod (TABLE 2). Light measurements taken but reemerged with one flower bud on 8 shoots
around noon sun time after the deciduous can in 2004.
opy closed in the spring have been 99-356
j-Lmol·m-2·s-1, but sun fleck at other times on a Tracking the Large Population
sunny day can cause readings to fluctuate 25-
1600 j-Lmol·m-2·s-1 (M. Light unpubl. data). The We have been tracking the Site 2 population
orchid first bloomed in 1989, when it produced since 1996. Transition data for all flowering
two flowering shoots. The plant then bloomed plants began in 2000 with 1295 stems on 269
for 3 years in succession (1989-1991) without genets and followed with 1590 stems on 290
fruiting. The number of emergent orchid shoots genets in 2001, 1724 stems on 326 genets in
declined, and the plant did not flower in 1992- 2002, and 1728 stems on 341 genets in 2003.
1994, possibly because of the 1991 drought, but This includes 21, 36, and ] 5 recruits floweri.ng
flowering resumed in 1995. In June 1995, a 10- for the first time in 2001, 2002, and 2003 re
m tall tree (Ostrya virginiana) located ca. 2 m spectively. Orchid shoot and leaf expansion
to the southeast fell into the site (TABLE 2). The dates varied in 1996-2003, ranging from April
tree had been in declining health. had few leafy 28, 1998, to May 20, 1997. From 1996 to 2003
branches and several large bracket fungus fruit (with the exception of 2001 when no data were
ing structures on its trunk. No significant in collected), the interval between orchid leaf ex
crease in genet size occurred until 4 years after pansion and tree leaf expansion (canopy closure)
that tree-fall event. The ice storm in January was 10-20 days. The interval of flower opening
1998 led to the loss of major limbs from the tops to canopy closure likewise varied 6-18 days
of healthy trees (Acer saccharum) growing during these years. Annual fmit production var
around the light gap. Some limbs and smaller ied 22-75% in the 1996-2003 period (n = 8;
branches fell close to but not onto the orchid; mean 46%; SD 16%, TABLE 3).
they were not removed. The plant doubled in
size each year in 1998-2000, when 2, 4, and 9 Sunlight
shoots respectively were produced. In 2001, it Available light to any genet in the large col
had 6 flowering shoots with one fruit. The plant ony is highly variable mostly because of sun
was then non-emergent for 2 consecutive years fleck. Light remains at moderate but highly var-
SECOND IOCC PROCEEDINGS 181
TABLE 3. Orchid leaf expansion, flowering dates, canopy closing, and percent fruit set of flowers available for
pollination for the large colony of Cypripedium paviflorum var. pubescens (1996-2003).
Orchid
leaves begin First Canopy Fruit set*
Year expanding flowers open closes (%) Remarks
1996 May 15 May 22 May 31 38
1997 May 20 May 28 Jun 9 55
1998 Apr 28 Apr 28 May 16 75 Birch and maple fall; hot, dry spring
1999 May 5 May 8 May 15 25 Hickory falls
2000 May 11 May 12 May 28 50
2001 nJa May 11 May 17 41
2002 May 15 May 17 Jun 1 35
2003 May 16 May 18 May 29 22
* SD 16%.
iable levels (100-1600 j.1mol·m-2·s-1) for many atures recorded from within the rooting zone of
of the plants throughout the spring and summer 32 selected emerging genets were 9.7-16.8°C,
(M. Light unpubl. data). During the blooming mean 12.6°C (Light & MacConaill 2002c).
season in 1998, we observed that flowers in the Those plants rooted in the shade of a fallen tree
sunniest part of the site were affected by sun, trunk had the lowest soil temperature (9.7°C),
heat, and an exceptionally dry season: the flow while those rooted in a sunnier area along the
ers, especially the pouches, were bleached and north side of the colony had soil temperatures
papery. The ice stonn had toppled a paper birch of 15.6-16.9°C. In the lightly shaded southern
(Betula papyijera), which disturbed several or part of the colony, soil temperatures were 11.1-
chids rooted at its foot. A 20-m long piece of 12.0°C. On April 29, 2004, one of the first warm
sugar maple trunk (Acer saccharum) that spring days of 2004, shoots were ca. 5 cm long,
snapped during the 1998 ice storm also lay when we measured soil temperature. While air
across the site. Early in 1999, a 20-m tall bitter temperature at noon was 24.0°C, soil tempera
nut hickory, Carya cordijormis (Wang) K. ture averaged 7°C in the lightly shaded south
Koch, growing just outside the northern colony part of the colony or where a minimum of 5 cm
boundary fell into the site. That year we noted of loose litter covered the soil. Where genets
for the first time that plants in the southeastern were rooted in shallow gravelly soil (>3 cm
part of the colony that previously faced north over rock) or where soil was exposed to direct
now faced west, as if toward a stronger light sunlight, soil temperatures averaged 12.0°C.
source (M. Light unpubl. data). In 2001, light
levels were measured twice: after the orchid
leaves had expanded but before the forest can Behavior of Large Colony
opy closed on May 15; and after the canopy had
closed but before the flowers had faded on May Transitions between Total Stems Size Classes
25. Some genets were exposed to more light Transition matrices for 269, 290, and 326
(max 1600 j.1mol·m-2·s-1) before the canopy plants for 2000-2001, 2001-2002, and 2002-
closed than after (min 40 j.1mol·m-2·s-1). For 2003 seasons respectively showed a preponder
other genets, the opposite was true, where more ance of plants re-emerging in the same or an
light was available after the canopy closed than adjacent size class; the summed absolute num
before (25-2100 j.1mol·m-2·s-1; M. Light unpubl. bers of transitions are shown in TABLE 4. On six
data). The average PAR across the site for May occasions, a large genet (9 or more stems) in one
15, 2001, was 132 ± 25 (n = 14), for May 25, year did not emerge the following year: three of
189 ± 35 j.1mol·m-2·s-1 (n = 14). A map of the these then reappeared as large plants in a sub
light regime (PAR) for the large colony in 2001 sequent year. On five other occasions, other gen
is shown in FIGURE 1. ets re-emerged from a dormant stage as large
plants, while two genets entered the study at this
Soil Temperature size. Six of these 13 plants were clustered within
Soil temperature varied according to season 2 m southwest of the foot of the sugar maple
and across the site according to soil depth and tree that fell during the 1998 ice storm, and five
insolation, but local variation within parts of the other plants were aligned along a NW-SE axis
colony was similar to variation across the colony in the south part of the colony (FIGURE 1). One
(M. Light unpubl. data). On May 8, 2002, when genet growing at the base of a birch tree was
emergent shoots were ca. 7-25 cm, soil temper- disturbed, when the rootstock was uprooted, and
182 SELBYANA Volume 26(1,2) 2005
TABLE 4. Cumulated year-to-year transitions over the 4-year period 2000-2003 (3 transitions) between six plant
size classes based on total stems (flowering and non-flowering).
To From size class
Stems Size class A B C D E F Totals New recruits
0 A 33 19 19 14 3 3 91 nla
1 B 4 55 28 9 1 97 46
2, 3 C 11 48 140 41 3 1 244 23
4-8 D 10 13 56 156 21 3 259 2
9-15 E 5 1 6 34 74 13 133 1
16+ F 3 1 8 16 33 61 1
Total 66 136 250 262 118 53 885 73
another was located at the foot of a birch tree Effect of Flowering on Re-emergence of
seemingly unaffected by the ice storm. Smaller Genets
We also identified ten genets in size classes E The probability of a plant with 1-3 stems
or F, which had emerged at some time in 2000 emerging the following year was independent of
or later with more than 50% vegetative stems. its flowering status (X2 = 2.24 for 8 df, 385
In 2002, all ten were significantly vegetative: in plants). Plants with more than 3 stems composed
nine of the ten, fewer than 50% of the shoots entirely of vegetative shoots were rare.
flowered, while in the tenth genet, 6 of its 17
shoots were non-flowering. This significantly
Precipitation
vegetative state peaked in 2002 with fewer
plants involved in 2001 and in 2003, suggesting Deviation from seasonal average precipitation
a point-in-time response by these plants to some recorded at Ottawa International Airport, May
triggering event. I-October 31 is presented in TABLE 2. In 1998,
the spring was warm and dry until May 31,
Flower Productivity when 14.4 rom precipitation was recorded. In
For this popUlation as a whole, a year-to-year June 1998, rainfall was recorded at 119 rom,
variation was observed in the overall flower-to 50% of which fell over 6 days (June 13-18).
shoot ratio with 93.1 % of 1295 stems flowering Monthly precipitation for May-October 1998 is
in 2000, 79.3% of 1590 stems flowering in 2001, presented in TABLE 5.
and 71 % of 1724 and 1728 stems flowering in
2002 and 2003 respectively. Curiously, the num
ber of flowering stems in the colony remained DISCUSSION
fairly constant during the study period despite
Long-term observations of individual orchid
recruitment of new plants. Flowering stems per
plants and populations are critical to our under
year numbered 1205, 1261, 1225, and 1239 re
standing of factors impacting popUlations in
spectively in 2000-2003. Although overall flow
cluding: 1) Why orchids grow in specific habi
er production of the colony remained relatively
tats and if this is solely because the fungi which
constant during these years, annual flower pro
foster germination can live or once were able to
ductivity in terms of total stems clearly varied.
live there; 2) Why some orchids respond posi
tively to disturbance, and others seemingly do
not; 3) What exactly is happening at the level of
TABLE 5. Deviations from monthly long-term aver
soil microflora and microfauna in response to a
age precipitation as recorded at Ottawa Interna
disturbance or when an open area becomes over
tional Airport, May-October 1998.
grown with shrubs and trees; and 4) What is the
cryptic consequence of management practices,
Precipitation (mm)
including forest stand thinning or the removal of
Month Actual Deviation
woody and other plants presumed to be com
May 33.4 -35.5 peting with orchids for light. The ecological
June 119.0* 20.6 mechanisms that regulate and maintain plant
July 76.1 -7.7 biodiversity and species composition are not
August 50.4 5.8 well understood. They need to be identified to
September 71.6 -20.3
ensure successful management for conservation
October 71.4 44.7
and restoration of diverse natural ecosystems
* 63.4 mID recorded for June 13-18, 1998. (Bakker et at 2002).
SECOND IOCC PROCEEDINGS 183
Founding of a Population same major disturbance events concurrently, we
considered using the longer time series of the
We can estimate the likely period when the single genet to interpret behavior within the
single genet became established. Curtis (1943) shorter tracking situation. Curtis (1954) ob
estimated that 10 or more years are needed be served that the flowering of temperate terrestrial
tween seed germination and first flower produc orchids, especially those of the genus Cypripe
tion, which suggests in this case that the seed dium spp. L., fluctuated annually with some sea
germinated sometime before 1979. Significantly sons being particularly productive. He reported
greater than average seasonal (April I-October that some common factor appeared to affect an
31) and yearly precipitation was recorded at Ot nual flower production across stations but de
tawa International Airport in 1972 (204.21282.2 duced that the factors responsible for annual
mm), in 1973 (72.4/156.7 mm), in 1979 (141.9/ fluctuation were not the same as those causing
227.4 mm), and in 1981 (294.11188.5 mm), plant-to-plant variation within a given site. We
which could have contributed to seedling estab observed a productive season in 2000 when 93%
lishment. The genet gradually increased in size of shoots in the large colony were reproductive.
in 1985-1998 and peaked in numbers of shoots The isolated single genet peaked in size in 2000
in 2000. Given the distance of this plant from when every shoot was reproductive (TABLE 2),
other genets, it seems likely that the five fruits suggesting some common triggering event for
produced since it first flowered have arisen both sites. Each site was subjected to increased
through geitonogamy. litter deposition, but other variables including an
early spring, light, and precipitation at critical
Disturbance in Deciduous Forests times during the growing season remain possi
bilities. Certain larger genets fluctuated between
Deciduous forests of the northeastern United appearance and dormancy, but light or even
States and Canada have been variably affected chance alone does not seem to be responsible
by natural and human events. Wind and ice for this behavior. The 13 genets in the large col
storms, herbivory, selective harvest, and clear ony that showed similar behavior were clustered
cutting have influenced forest structure in dif (FIGURE 1). The behavior of both the single plant
ferent ways and, at many sites, have resulted in and the large colony of Cypripedium parviflo
regenerated single cohort stands aged 60-120 rum var. pubescens discussed in this paper,
years (Fajvan & Wood 1996, Hooper et al. 2001, where some large multi-flowered genets were
Ouimet et al. 2001). Minor disturbances result present, disappeared, and then re-appeared,
ing in localized overstory mortality accelerate seems to be much more complex than simple
forest changes by either increasing growing models and explanations suggest.
space or by initiating a new cohort of regener KulI (1995) investigated genet and ramet dy
ation. In Gatineau Park, many trees were har namics of Cypripedium calceolus L. during a
vested in the 1930s, giving us a present forest lO-year period and concluded that fluctuations
aged ca. 75 years. Repeated canopy opening in effective population size were related to dif
caused by wind (blow downs), ice, lightning ferences in the light regime. Primack et al.
strike, and death of tree(s) from diseases and (1994) concluded that one episode of fruit pro
insects has been a frequent occurrence. duction decreased future plant size, when plants
were subjected to experimental defoliation; but
Explaining a Delayed Response no increase was detected in photosynthetic rate
to Disturbance coincident with partial defoliation. Outbreaks of
herbivorous insects have been associated with
Stoutamire (1991), Kaitala and Kull (2002), the resurgence of Cypripedium colonies (Gill
and Kull (1995, 1997) clarified what we and oth 1996). He noted that for two successive sum
ers have speculated: that a delayed response in mers following the loss of tree foliage to insects,
Cypripedium spp. to environmental variables "the forest floor was exposed to full sunlight
may result from prolonged development of buds, and was hotter and drier than in the previous
reserve buds, and replacement or sympodial decades." We have observed that colonies of
buds at least one growing season before expres blooming Cypripedium spp. in forested sites ex
sion. Which environmental variables are respon ist in highly variable but remarkably consistent
sible, however, remains unclear. Part of the prob light regimes across species. Are light, soil
lem with disturbance interpretation is the noise moisture, or temperature implicated in what has
level of data saturated with random environmen been observed by other investigators or does
tal effects: data sets are often too short to reveal disturbance or the loss of trees or their leaves
pattern. Since both sites discussed in this paper affect tree root microflora in some cryptic man
are close enough to have been exposed to the ner and thence the orchids?