Biology of the Study Species
Silene acaulis (Caryophyllaceae; “moss campion”) is a long-lived cushion plant
found in alpine and arctic tundra throughout the circumboreal zone (Hultén 1974). Each
cushion has a single taproot, and branches do not root adventitiously, so individuals are
easy to distinguish. Moss campion flowers are insect pollinated and produce fruits at the
end of the growing season.
Polygonum viviparum (Polygonaceae; “bistort”) is a circumboreal geophyte. Each
ramet consists of 1-4 basal leaves and 0-2 inflorescences (occasionally more) that arise
from a single unbranched rhizome (Diggle 1997). Bistort produce asexual bulbils instead
of flowers at most inflorescence nodes (Bauert 1993, Diggle et al. 1998). Dispersed
bulbils may root to produce new recruits (“bulblings”), which is the only form of
reproduction we have observed at any of our sites.
The Study Populations
The names and locations of all sites for which
demographic data are included in the archive are given in
Table 1 (see Fig. 1 for a map of sites). All populations
were censused every year between the first and last
census. We began following populations of moss campion
in Alaska’s Wrangell Mountains in 1995. Data prior to
2001 are not included in the archive, but are available
from the authors upon request; this includes data for
three additional moss campion populations in the
Wrangell mountains that were censused annually from
1995 to 2001, but then discontinued). Two Wrangells
populations (PA and RI) begun in 1995 continue to be
censused annually, and three additional populations
begun in 1998 are still being censused. In 2001, we
initiated 12 additional moss campion populations (four
each at Toolik Lake, Banff National Park, and Niwot
Ridge) and we initiated 16 bistort populations (4 each at
Toolik, Wrangells, Banff, and Niwot). Censuses of all
populations of both species in Banff National Park were
discontinued after the 2006 census. Finally, two
populations of each species were initiated at Latir Peaks
Wilderness in New Mexico, one in 2007 and one in 2008.
In each region, we chose study populations based
on several criteria. First, populations were placed
sufficiently far apart as to render significant seed or bulbil
dispersal extremely unlikely over yearly or decadal timescales. The minimum distance between study populations
Fig. 1. Map of the regions
with past and ongoing data
collection. Data collection
was ended in the Banff
region in 2006, in order to
establish the more
southerly Latir Peaks
region.
of either species is ~300 meters. Detailed mapping of moss campion seedlings has
shown that very few seedlings are found >10cm from the edge of parent plants. Bistort
bulbils are even larger than moss campion seeds and like them have no dispersal
mechanisms other than gravity. Second, in each region we sought to place populations
in areas with the full range of typical local growing conditions. In particular, we
deliberately placed half the populations in each region in more mesic and the other half
in more xeric conditions (analyses have shown no significant effects of these microsite
conditions on vital rates). Finally, logistical constraints (between- population travel
times and the availability of secure research sites) led us to cluster populations at each
latitude into relatively narrow regions. In some regions, the placement of our study
populations makes them truly distinct, with few or no conspecifics in intervening areas.
However, for other regions, plants of both species occur extremely widely, such that
some of our study populations are not discrete population units.
Field Methods
In our field censuses, we assessed the demographic fate of marked individuals
every year. Every plant encountered along randomly located transects in each
population was mapped and marked with a permanent metal tag (large moss campion
plants) or a color-coded plastic toothpick (small moss campion and all bistort). We
relocated marked plants each year, and recorded survival, size, and reproductive
output. We also quantified recruitment of new individuals and added these new
individuals to our set of annually monitored plants. Transect ends were marked with
long metal spikes driven into the ground, allowing us to accurately replace the transect
tape each year and to relocate all plants. Transects were typically 0.5 m wide, although
at some moss campion sites with low plant densities we used transects up to 5 m wide
to obtain an adequate number of plants for a demographic study. High density bistort
sites are sometimes narrower (0.20-0.30 m). At some populations of both species,
transects were double sided (i.e., we included plants on both sides of the transect
tape).
At one extremely dense bistort population in the Banff region (population BC2),
now discontinued, it was not feasible to mark all plants in even very narrow transects,
so we used a different sampling strategy. Here, we choose coordinates on a 5 x 5 cm
grid within the transect. At each set of coordinates, we searched for the nearest bistort.
If the nearest plant was within 2 cm of the starting coordinates, we mapped, marked,
and followed this individual.
Moss campion cushions extend by the addition of new branch tips that appear at
the surface of the cushion. We measured plant size by counting branch tips or (for
plants with 20 or more branch tips) by determining the two-dimensional area of the
cushion. From 2001 to 2006, we measured cushion area by photographing plants in the
field with digital cameras and then applying image analysis software to determine area.
Before and after this period, we determined cushion area by measuring the major and
minor axes of each cushion and visually estimating the percent of the hypothetical
ellipse defined by those axes that was “missing” (e.g., dead moss campion tissue,
rocks, or other vegetation). Areas determined by the two methods were highly
correlated.
We measured reproductive output for moss campion by counting the number of
fruits (which are retained to the end of the growing season). Each year we also
searched for and mapped new recruits within a 10cm radius of 10-20 randomly chosen
focal plants large enough to reproduce in each population.
For every bistort plant, we counted the number of leaves, measured the size of
the longest leaf, and measured the length of the inflorescence that bore flower and the
length that bore flowers. Leaf number includes all basal leaves, of whatever size, as
well as all cauline leaves of greater than 1 cm length. From 2001 to 2006, we measured
the length and the width of the longest leaf in each year. The product of the estimated
area of the largest leaf and leaf number then provides an excellent prediction of total
leaf area (linear regression of total leaf area on the product of predicted largest leaf
area (pi*length*width/4) and the number of leaves and with zero intercept: total area
= 0.570*(largest leaf area*leaf number); r2 = 0.965, n=51). From 2007 onwards, we
measured only the length of the longest leaf, but not its width, as we can still obtain
excellent estimates of total plant leaf area with only the length measure and the leaf
number (linear regression of total leaf area on the product of longest leaf length and
the number of leaves and with zero intercept: total area = 4.388*(longest leaf length
*leaf number);, r2 = 0.953, n=51).
We estimated the number of bulbils on bistort plants by measuring the length of
the bulbil-producing portion of each inflorescence and then used a regression of bulbil
number on length (bulbil number = 5.487 + 0.983*Length; r2 = 0.49, n=415). To
quantify the translation from bulbils to new recruits, each year we searched for,
marked, and followed new bulblings (newly recruited plants arising from bulbils) in
subsections of the transects. Estimates of recruitment rates come from regressions of
new bulbling numbers on the total bulbils produced the previous year in these searched
areas.
iButton data loggers were deployed at each population starting in 2008. From
two to seven iButtons are left at each population over each year: the loggers are
retrieved and re-deployed while visiting the sites for demographic data collection, from
late July to mid-August. Each iButton is placed in a small, sealed plastic jar that also
contains desiccant, and buried so that the jar’s surface is from 1 to 3 cm below the soil
surface. The locations of the loggers is kept constant from year to year to increase
comparability of data across years.
Table 1A: Population names, locations, and years of data collection for moss campion (Silene acaulis)
Population
Name
ST1
ST2
ST3
ST4
AB
BV
GC
PA
RI
SC1
SC2
SC3
SC4
SN1
SN2
SN3
SN4
SL1
SL2
Location
Toolik Lake LTER Site,
Alaska, USA
Toolik Lake LTER Site,
Alaska, USA
Toolik Lake LTER Site,
Alaska, USA
Toolik Lake LTER Site,
Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Banff National Park,
Alberta, Canada
Banff National Park,
Alberta, Canada
Banff National Park,
Alberta, Canada
Banff National Park,
Alberta, Canada
Niwot Ridge LTER Site,
Colorado, USA
Niwot Ridge LTER Site,
Colorado, USA
Niwot Ridge LTER Site,
Colorado, USA
Niwot Ridge LTER Site,
Colorado, USA
Latir Peaks Wilderness,
New Mexico, USA
Latir Peaks Wilderness,
New Mexico, USA
Latitude (N)
Longitude (W)
Year of first
census1
Year of last
census2
68.72102
149.04736
2001
2011
68.61435
149.65048
2001
2011
68.61825
149.68735
2001
2011
68.71893
149.05435
2001
2011
61.52666
142.86337
1998
2011
61.48848
142.81171
1998
2011
61.51342
142.84445
1998
2011
61.48917
142.82150
1995
2011
61.49036
142.81453
1995
2011
52.18089
117.12188
2001
2006
52.18243
117.13224
2001
2006
52.19353
117.15560
2001
2006
52.19466
117.15340
2001
2006
40.05523
105.58654
2001
2011
40.05648
105.59731
2001
2011
40.05514
105.59736
2001
2011
40.05638
105.58373
2001
2011
36.78601
105.46595
2007
2011
36.79594
105.48281
2008
2011
1
Data for years prior to 2001 available from the authors by request.
2
Demography censuses are continuing for all populations last censused in 2011.
Table 1B: Population names, locations, and years of data collection for bistort (Polygonum viviparum)
Population
Name
BT1
BT2
BT3
BT4
BW1
BW2
BW3
BW4
BC1
BC2
BC3
BC4
BN1
BN2
BN3
BN4
BL1
BL2
Location
Toolik Lake LTER Site,
Alaska, USA
Toolik Lake LTER Site,
Alaska, USA
Toolik Lake LTER Site,
Alaska, USA
Toolik Lake LTER Site,
Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Wrangell St. Elias National
Park, Alaska, USA
Banff National Park,
Alberta, Canada
Banff National Park,
Alberta, Canada
Banff National Park,
Alberta, Canada
Banff National Park,
Alberta, Canada
Niwot Ridge LTER Site,
Colorado, USA
Niwot Ridge LTER Site,
Colorado, USA
Niwot Ridge LTER Site,
Colorado, USA
Niwot Ridge LTER Site,
Colorado, USA
Latir Peaks Wilderness,
New Mexico, USA
Latir Peaks Wilderness,
New Mexico, USA
Latitude (N)
Longitude (W)
Year of first
census
Year of last
census1
68.61678
149.66879
2001
2011
68.61838
149.68799
2001
2011
68.71906
149.03471
2001
2011
68.71729
149.04411
2001
2011
61.48942
142.82079
2001
2011
61.48875
142.81323
2001
2011
61.49247
142.81970
2001
2011
61.49082
142.82068
2001
2011
52.18492
117.12016
2001
2006
52.18444
117.12016
2001
2006
52.19413
117.15423
2001
2006
52.19361
117.15556
2001
2006
40.05674
105.59755
2001
2011
40.0562
105.60034
2001
2011
40.05450
105.58354
2001
2011
40.05542
105.58720
2001
2011
36.79633
105.47019
2007
2011
36.79708
105.47570
2008
2011
Description of the moss campion transect files:
A separate file for each population contains the data for plants located along the transects that were
laid out when the population was initially censused. Rows are individual plants (only 1 row per plant)
and sets of columns correspond to successive annual data. A typical file has the following columns (in
order):
trans
Plt
X
Y
The transect on which the plant was found
Plant ID: an unique alphanumeric indicator for each plant
The position of the plant along the transect tape (in cm)
Perpendicular distance of the plant from the transect tape (in cm); can be negative for
two-sided transects
The following 10 columns are for 2001, and are repeated for 2002 to 2006:
flr01
Number of flowers on the plant that did not produce fruits
frt01
Number of mature fruits
ros01
Number of “rosettes” (branch tips) on the plant
notes01
Notes about permanent features of the plant
comm01
Comments about temporary features of the plant (such as that it had died back since
the previous year
photo01
The photograph number of the plant (photos available upon request)
totarea01
The total area encompassed by the photograph
areafract01
The percent of the total photograph area that represents the plant
area01
The area of the plant (in square centimeters) [ = totarea x areafraction /100 ]
alive01
= 1 if the plant was alive in that year, 0 if the plant died that year, and blank for all years
after the plant died (and for years – if any – before the plant entered the study)
The following 10 columns are for 2007, and are repeated for 2008 to 2011:
Trans07
Transect (same as first column of the file)
Plt07
Plant ID (same as second column of the file)
X07
The position of the plant along the transect tape (in cm) [could be different than the
number in the 3rd column of the file if the plant was poorly mapped initially]
Y07
The distance of the plant from the transect tape (in cm) [could be different than the
number in the 4th column of the file if the plant was poorly mapped initially]
Ros07
Number of “rosettes” (branch tips) on the plant
Frt07
Number of mature fruits
A1-07
Length of the longest (major) axis of the cushion (in mm)
A2-07
Length of the minor axis of the cushion (in mm); minor axis is the longest axis
perpendicular to the major axis
PM-07
Percent of the ellipse defined by the major and minor axes that is “missing”
Area07
Plant area (in cm2); = Pi*A1*A2*(100 – PM)/40000
Notes07
Notes about permanent features of the plant
Comm07
Comments about temporary features of the plant
Alive07
= 1 if the plant was alive in that year, 0 if the plant died that year, and blank for all years
after the plant died (and for years – if any – before the plant entered the study)
After 2006, plants that were composed of separate parts (rather than a single compact cushion) were
measured as multiple pieces, each of which was treated as an ellipse and the total area of the plant was
the sum of the areas of the elliptical pieces. In these cases, A1, A2, and PM will include separate
numbers for each piece, delimited by commas. Note that the major and minor axes are measured in
mm but area is in cm2. Typically a plant will have either an entry in the Ros column or entries in the
A1/A2/PM columns, but not both, because we employed the measurement rule that any plant with
fewer than 20 rosettes would have its rosettes counted only, while any plant with 20 or more rosettes
would have its major and minor axes and percent missing measured. Occasionally plants with close to
20 rosettes will have both measures. Plants with fewer than 20 rosettes rarely produce fruits. Blanks in
the Frt columns mean that the plant produced no fruits that year.
For two populations, the files contain additional columns. The RI population has two doublesided transects (with sides labeled L for left and R for right), but some plant numbers (Plt) were used for
different plants on the two transects. Columns labeled ID are unique plant identifiers (e.g., “3-1R” and
“3-2R”) constructed by combining the plant number with the transect. In the SL2 population, all plants
are marked with colored plastic toothpicks instead of numbered metal tags. Additional columns indicate
the type of toothpick marking each plant, using a two letter code [ the first letter indicates the color of
toothpick: (r)ed, (b)lue, (g)reen, (w)hite, (o)range, or (y)ellow; the second letter indicates the marker on
the toothpick from suits of playing cards: (c)lub, (h)eart, (s)pade, or (d)iamond ]
Description of the moss campion focal plant files
We used a method separate from the transects to quantify moss campion recruitment: we searched for
and followed small plants that were the offspring of a set of “focal” plants in each population, so that we
could quantify the number of seedlings in subsequent years resulting from the fruits produced by the
focal plant. These studies also provided information about the survival of seedlings and of plants in the
next older life stage (which we call “one-rosette” plants in reference to their single branch tip with its
whorl of leaves).
Beginning in 2002 in all moss campion populations that had been initiated in 2001 or earlier and that
were still being censused, we haphazardly chose 10 to 20 focal plants in each population that had
produced fruits in 2001 or 2002. At the two Latir populations, focal plants were chosen in the year each
population was initiated, from among the plants with fruits that year. Each year, we searched for new
seedlings and one-rosette plants within a 10 cm radius from the edge of the focal plant. Seedlings
(plants in their first year of life above ground) are easily distinguished from one-rosette plants by the
presence of cotyledons on the former and the presence of dead leaves from previous years on the
latter. We mapped each small plant in relation to the center of the focal plant, measured its distance
from the focal plant’s edge, and marked it with a plastic toothpick.
A separate file for each population contains the data for the small plants (seedlings and one-rosette
plants) found around each focal plant. All files have the following columns:
Focal
X
Y
Dist
Ros
Tp
Notes
Unique identifier of the focal plant, corresponding to that plant’s entries in the transect files
X coordinate (in cm) of the small plant in relation to the center of the focal plant (at X=0)
Y coordinate (in cm) of the small plant in relation to the center of the focal plant (at Y=0)
Distance (in mm) of the small plant from the edge of the focal plant
Size of the small plant
Type of toothpick marking the small plant (see codes in transect file descriptions)
Notes about permanent features of the small plant(s)
Comm
Plt
Trans
Year
Comments about temporary features of the small plant(s)
A unique alphanumeric identifier for each small plant
The transect on which the focal plant is found
Year of the census
X and Y coordinates were used to make maps of the small plants around focal plants with many
offspring, to make it easier to relocate them and in case the toothpick was missing. Plant size recorded
in the Ros column was typically either “Sd” or “sd” for a seedling or “1” for a one-rosette plant. When
multiple small plants were too close to one another to me marked by separate toothpicks, they were
included as a group of plants marked by a single toothpick and recorded on a single row of the data file
in each year. In these cases, the Tp column indicates both the toothpick type and the number of small
plants (e.g., “Rh3” indicates three small plants marked with a single red heart toothpick), and the rosette
column contains a character string indicating the types of plants present (e.g., “2 1ros 1 sd” would
indicate that the single red heart toothpick is marking two one-rosette plants and one seedling)
When a small plant that had been marked in a previous year was found to have died, the death is
indicated by “Dead” or “D” or “Dd” or “dd” in the Ros column in the year of death. Data file rows
representing a group of multiple small plants might include a character string that indicates some or all
of the plants in that group had died (e.g., “3Dd” indicates that the three plants from the previous census
had died in the intervening year, and “2 1ros 1 dd 1sd” indicates that of 3 plants in that group in the
previous census, 2 were now one-rosette plants, one had died, and a new seedling had appeared at that
location. MATLAB programs to extract from the focal plant files information about seedling recruitment
and survival of seedlings and one-rosette plants are available from the authors upon request.
In the focal plant files, each small plant is represented by a series of rows for the years it was still alive.
Thus unlike in the transect files, in which each plant has a single row and subsequent sets of columns
represent successive years, in the focal plant files each small plant can have multiple rows (but only 1
row per year).
Description of the bistort transect files:
A separate file for each region contains separate sheets of data for each population in that region. Rows
are individual plants (only 1 row per plant) and sets of columns correspond to successive annual data. A
typical file has the following columns (in order):
Tr
X
Y
TP
The transect on which the plant was found. Many bistort populations only have a single
transect, and for these there is no transect column.
The position of the plant along the transect tape (in cm)
Perpendicular distance of the plant from the transect tape (in cm); can be negative for
two-sided transects
The color and suite of the toothpick that marks each plant. Unlike our methods for moss
campion, we do not give unique numbers or tags to bistorts, and identify them only by
location and the toothpick marking each.
The following 10 columns are for 2001 (or 2007 or 2008, the first years for the two Latir Peaks
populations), and are repeated for 2002 through the last census, with exceptions as noted below:
L01
Length of the longest leaf
W01
Greatest width of the longest leaf. This measurement was discontinued in 2006 at all
sites but Niwot. For these populations, width was recorded up to 2006, and then again
in 2009 (but not in 2007, 2008, or thereafter).
N01
Number of leaves
inf01
Number of inflorescences
stlk01
The length of the inflorescence stalk below the zone bearing bulbils or flowers. This
measurement was discontinued after 2006.
blb01
The length of the inflorescence stalk bearing bulbils.
flr01
The length of the inflorescence stalk bearing flowers.
herb01
Whether there was significant herbivore damage to leaves or the inflorescences of the
plant.
Missing data in the primary data columns are indicated by two different codes: -100 indicates a plant
that either didn’t exist or was not found in a given year – that is, that is was missing and not locatable.
This code is used both for years before a plant was ‘born’ or before it was first censused, and also for
plants that were assumed to have died after multiple years of not being found. Some plants that were
simply missed in previous years are added each year, so that not all new plants are new bulblings.
Because bistorts occasionally seem to remain dormant through a year, and also sometimes have missing
or dead leaves at the time of our censuses, we generally only conclude that a bistort has died if we can’t
find it three years in a row. The second code used to denote missing data is zero: this is used in a year
when the marker for a plant was found, but the plant itself was not seen. In these cases, 0 in the leaf
number column indicates that there were no leaves, while 0 in other columns indicates that there were
no measurements possible.
Description of the bistort recruitment file:
A single file (bistortbulblings2001_2011.xls) contains the summarized recruitment data for each
population and year. As described above, defined areas of each population are searched for new
recruits (“bulblings”) each year. We summarize the bulblings found, along with the bulbils produced on
plants within these areas in both the current and previous year. This file has the following columns (in
order):
Region
Population
Year
A code for the study region (BL = Latir, BN = Niwot, BC = Canada, BW = Wrangells, BT =
Toolik).
A number indicating the population number within this region. Excect for Latir, where
we have only 2 populations, there are four populations per region.
The year, coded as 1=2001 to 11=2011.
Bulbils,
previous year This column contains the estimated number of bulbils produced on plants within in the
previous year, within the areas of the transects of a population searched for new
bulblings.
Bulbils,
current year This column contains the estimated number of bulbils produced on plants in the current
year, within the areas of the transects of a population searched for new bulblings.
Summed
bulbils
As implied, the sum of the bulbils produced in the two years.
New Bulblings The total number of bulblings found within the searched area of a population in a given
year.
Note that we show data up until the last year each population was surveyed (2011 except for the
Canadian populations), and starting with the year after each population was surveyed, when we could
first search for new recruits.
Description of the iButton temperature data files:
A separate file is given for each iButton in each year. In addition, a master excel file that shows the
correspondence of different file names (for the same iButton location in different years) is also given.
The file names all have a standard format: First, the population name, corresponding to the codes given
in Tables 1A and 1b above; second, an indication of the position of the iButton location in the
population; and, third, the year in which the iButton was collected and downloaded. The codes for
location include the transect (A, B, C, etc) for populations with more than one transect and either the
position on the transect (Start, End, or the meter along the transect) or the number of a mapped plant
that the iButton was placed next to.
The file filenames2009_2011.xls gives the names for each iButton location and the number of
observations taken in each annual deployment. The code of NA in observation number columns
indicates that the iButton was not deployed or was lost.
Each iButton was set to record temperatures at 255 minute intervals. Each data file is a comma
delimited text file with the following columns (in order):
date
time
AM/PM
Temperature
Units
Temperature
Date as month/day/year, where year is a two number code (e.g., 10 = 2010)
A 12-hour time code wt hours: minutes: seconds
A code for morning or afternoon time periods
Always equal to C for Celsius
Degrees Celsius
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