Great Basin Naturalist
Volume 53 | Number 1
Article 9
4-2-1993
Effects of rangefire on soil algal crusts in semiarid
shrub-steppe of the Lower Columbia Basin and
their subsequent recovery
Jeffrey R. Johansen
John Carroll University, University Heights, Ohio
John Ashley
Pennsylvania State University, Ogontz, Abington, Pannsylvania
William R. Rayburn
Washington State University, Pullman, Washington
Follow this and additional works at: http://scholarsarchive.byu.edu/gbn
Recommended Citation
Johansen, Jeffrey R.; Ashley, John; and Rayburn, William R. (1993) "Effects of rangefire on soil algal crusts in semiarid shrub-steppe of
the Lower Columbia Basin and their subsequent recovery," Great Basin Naturalist: Vol. 53: No. 1, Article 9.
Available at: http://scholarsarchive.byu.edu/gbn/vol53/iss1/9
This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been
accepted for inclusion in Great Basin Naturalist by an authorized administrator of BYU ScholarsArchive. For more information, please contact
[email protected].
· Great Basin Naturalist 53(1), pp. 73-88
EFFECTS OF RANGEFIRE ON SOIL ALGAL CRUSTS IN SEMIARID
SHRUB-STEPPE OF THE LOWER COLUMBIA BASIN
AND THEIR SUBSEQUENT RECOVERY
Jeffrey R. Johansen l , John Ashlel, and William R. Raybum3
ABSTHACf.-Effects of rangefire on soil algae in sagebrush steppe in the Lower Columbia Basin were studied, Dynamics
of recovery of the soil algal community in the first two years following the fire were also docwnented. The study site was
on the Arid LtUlds Ecology Reserve managed by Battelle Pacific Northwest Laboratory. Fire decreased the numbers of
algae by more than an order of magnitude. Species composition in burned plots was similar to that in unburned plots,
although some cyanophyte algae, particuhrrly No8toc commune, were decimated by the fire. Algal recovery took place in
the winter months of the second year. Ninety taxa of algae were identified during the course of the study, over half ofwhich
were chlorophytes. Seasonal changes in the algal flora were also noted.
Key words: algae, soil; cryptogamic crusts; microbiotic crusts; rangefire; seasonality; Microcoleus vaginatus; Nostoc
commune; A'id L(l1l(L~ Ecology Reserve.
Several researchers have claimed that cryptogamic soil crusts are critically important components of the arid and semiarid lands in which
they occur (Harper and Marble 1988, Metting
1991). Cryptogamic crusts, or microbiotic
crusts, are thought to stabilize the soil surface
and thus reduce erosion due to wind and thunderstorms. They may also contribute to soil fertility through nitrogen fixation, organic carbon
contributions, and accumulation of soil fines.
Some evidence indicates the crusts may increase vascular seedling establishment (St. Clair
et al. 1984). Water relations of the soil are also
affected in a complex way, and the crusts mayor
may not improve water relations for vascular
plants. Many of those who consider crusts valuable are particularly concerned about the destruction of crusts by grazing livestock, off-road
vehicles, foot traffic, and rangefire.
However, some workers have challenged the
majority opinion that cryptogamic crusts are
important in the ecosystems in which they occur
(West 1990, Gutknecht 1991). West has been
particularly critical of those claiming crusts are
of utmost importance, questioning the methodology of other workers and calling for more
research before conclusions are made as to their
relative value. Other workers, such as Savory
(1988), are of the opinion that soil crusts are
actually undesirable elements of the ecosystem
and advocate range management practices that
disrupt the continuity of the crust.
To resolve the controversy over the potential
roles that cryptogamiC crusts play in their environment, more research is needed on their longterm effects on stabilization of soil surfaces,
contribution to soil fertility, and interaction with
the vascular plant communities in which they
occur. We also need to know more about the
effects of various fonns of disturbance on the
crusts and the details oftheir recovery follOwing
such disturbance.
This paper reports the effects ofrangefire on
the soil algal communities ofa sagebrush steppe
and documents the first two years of recovery
follOwing the fire. The work was undertaken to
fill two major gaps in our understanding ofcryptogamiC crusts. First, past studies (Johansen et
.al. 1982,1984) have lookedat recovery 3-5 years
after the fire rather than immediately follOwing
the event. Initial effects of rangefire and early
recovery stages have to tlllS point been unknown. Second, most studies of cryptogamiC
crusts in the United States have been conducted
in the Great Basin and Colorado Plateau provinces (see Harper and Marble 1988, Metting
~Dep<lrbnent of Biology. Jolm Carroll University. University Heights. Ohio 44118.
~Deparbl1ent of Biology. Pennsylv<Ulia State University. OgOIlt'E.. Abington. PellusylV<Ulia 19(Xn.
State University. Pullman, ,Vnshington 99164-4233.
:3 Department of Microbiology. \V<lshington
73
74
GHEAT BASIN NATURALIST
1991, and West 1990 for extensive reviews of
these studies). Although other studies of soil
algae have been conducted in the Northwest
(Fairchild and Willson 1967, Metting 1980,
Metting and Rayburn 1979, Rayburn et al. 1982,
Zimmerman et al. 1980), this study represents
the first quantitative investigation of soil algae
from crusted soils of the shrub~stepperegion: of
the Columbia Basin.
SITE DESCRIPTION
The Arid Lands Ecology (ALE) Reserve is
located on the Hanford Reservation in the
Lower Columbia Basin near Richland, Washington. The Hanford Reservation, set aside in
1943, was closed to agriculture, grazing, and
off~road vehicles at that time (Thorp and Hinds
1971). This protected status has allowed the
development of a cryptogamic crust consisting
primalily of mosses and algae. Although soil
lichens are present elsewhere in the reserve,
they were fairly scarce in our study plots. The
ALE Reserve is classified as semiarid shrubsteppe (Franklin and Dyrness 1969). Several
shrub communities can be found on the reserve,
including those dominated by Artemisia tridentata Nutt., Atriplex spinosa (Hook.) Collotzi,
Ceratoides lanata (Pursh) Howell, and Sarco~
batus venniculatus (Hook.) Torr. Much of the
A. triclentata (sagebrush) shrubland has been
converted to grassland as a result of rangefires
and is now dominated by Elymus spicatus
[Volume 53
(Pursh) Gould, Festuca ovina L., and Poa
secunda Pres!' Without grazing pressure, sagebrush has been slow to reestablish itselfin these
burned areas.
On 10 August 1984 a major rangefire burned
an area of over 200,000 acres (most of the ALE
Reserve). The fire burned both shrubland and
grassland. In an area near ALE headquarters a
sagebrush locality was burned unevenly; leaving
several unburned sagebrush islands. A pair of
transects was established in one of these unburned sagebrush islands, with a similar pair
established in the burned field nearby. The
study area has an aspect of about 4(), with drainage to the northeast into Cold Creek Valley. Soil
at the study site is a Ritzville Silt Loam (Thorp
and Hinds 1977).
MATERIALS AND METHODS
A pair of parallel transects 1 m apart with a
total of 15 permanent points, each 1 m distant
from adjacent points, was placed in one of the
sagebrush islands. A similar pair of'transects,
also with a total of 15 permanent points, was
established in an adjacent burned area about 6
m from the sagebrush island. The points were
marked with red surveyor's tape tied to large
nails. On each sample date two shallowsoil cores
were taken from each point. Since sampling was
destll.lctive, samples were taken from previously
unsampled soil as close to the point as pOSSible.
Soil moisture for each site was determined on
evelY sample date by colleCting soil samples in
1993]
EFFECTS OF RANGEFlHE ON SOIL ALGAE
cans from the middle ofeach pair oftransects (3
replicates/site until 17 June 1985, 10 replicates
thereafter). Samples were taken 15 times in two
years on the following dates: 9/28/84, 11/26/84,
2/25/85, 4/14/85, 6/17/85, 8/22/85, 9/28/85,
11/8/85, 1/23/86, 2127/86, 3/28/86, 5/8/86,
5/30/86,7/31/86, and 9/12186.
Samples were taken using 1.9-cm-diameter
sterile stainless steel cylinders with removable
steel caps (Rayburn et al. 1982). In the field the
cores were pushed into the ground to remove a
relatively undisturbed core ofsoil. One set of30
cores was used to make dilution plate cultures;
the other set was processed using a technique
we call the moistened soil method.
To make dilution plate cultures, the cores
were returned to the laboratory; the caps removed, and the soil pushed up through the core
with a wooden dowel. The top few millimeters
were removed with an alcohol-sterilized razor
blade and placed in tared, sterile flasks. An
attempt was made to remove 1.0-1.5 g of soil in
tlns faslnon from each of the 30 cores. Then
sterile distilled water was added to each flask to
bring the soil/water weight to 100 g. The flasks
were placed in a Burrell wrist-action shaker for
30 minutes to loosen the crust.
Tenfold dilutions were made and O.l-ml
aliquots were plated, three plates per dilution,
on soil extract agar (Starr 1978). Incubation
conditions were 21°C and 115 J.1Km-2. s-1 irradiance from cool-wlnte fluorescent lamps regulated on a 16:8 h L:D cycle. Viable counts of
algae were made after 10-20 days ofincubation.
Generally 103 dilution plates were used, but in
instances in wInch tllere were more than 300
colonies per plate, 104 dilution plates were used
instead.
Following enumeration, algal isolations were
made from the agar dilution platesinto Bold's
basal medium (Bold 1949) modified by the addition of 40 ml soil water extract/liter. On each
sampling date about 100 isolations were made.
Many of these isolations were found to be multiple isolations of the same species, but by isolating such a large number ofalgae, many of the
more rare forms were also collected. Algal isolates were identified using a number of taxonomic references, of which the most valuable
were Desikachary (1959), Ettl (1978), Ettl and
Gaertner (1988), Geitler (1930-1932), Komarek and Fott (1983), and Starmach (1972). We
were able to identify most isolates at least to the
generic level, but on every sampling date there
75
were some isolates for which no determination
could be made. These few representatives were
omitted from the analyses reported in tllis paper. Isolations were made only during the first
year of the study.
The other 30 cores were processed using the
moistened soil method. TIns method is described in detail in Johansen et al. (1984), but
we will briefly review it here. For each sample,
2.5-3.0 g of soil were placed in a sterile petri
dish and flooded with sterile distilled water. The
petri dishes were incubated under controlled
conditions at 22°C on a 16:8 h L:D cycle for 8
days. Frequency and relative abundance of living algae were estimated by subsampling the
center of each petri dish and examining tllis
subsample under the light microscope. A total
of50 microscope fields were examined for each
subsample, and the presence or absence ofeach
species in each field was noted. The moistened
soil method was used because in past instances
we found it more effective for enumeration of
cyanobacteria than the dilution plate method.
This method was employed only during the first
year of the study.
On each sample date a kodachrome slide of
each sample point was taken to chronicle the
recovery of tlle vascular plant flora. Cover of
grasses, forbs, shrubs, and cryptogamic crusts
was estimated for all sample plots in tlle months
ofApril (spring) and September (late summer).
Six months into the study we realized that
patterns of algal abundance in the burned plots
were apparently relatedto patterns offire inten~
sity in the bum. Using the photograplnc record
of the sites, we calculated a burn intensity index
(BI) by calculating the sum of scores for each of
the following five characteristics: (1) blackening
of the soil (0 = none, 1 = ~30% of plot, 2 =
>30%), (2) grass sprouting from crowns (0 =
> 10,1 = 1-10,2 = none), (3) living moss cover
(0 = >5%, 1 = 1-4%,2 = <1%), (4) crust cover
in February 1985 (0 = >50%, 1 = 20..50%, 2 =
<20%, and (5) crust cover in June 1985 (0 =
>50%, 1 = 20..50%, 2 = <20%). The index
ranged from 0 (very lightly burned) to 10 (intensely burned). The variation in intensity was
apparently due to tlle fact that grasses and forbs
did not burn as hotly as shrubs. The scores for
the bum index are given in Table 1.
Nitrate nitrogen, ammOlnum nitrogen, sulphate, phosphate, potassium, percent organic
carbon (Walkley-Black method), and percent
organic matter were determined for samples
76
[Volume 53
GREAT BASIN NATURALIST
900
800
...J
g 700
I"
;;::
>
0:
600
Cl
~
<: 500
0:
~
'"j
400
w
()
g
o
300
200
lOa
Sept
Nov
Feb
.001
.001
.001 .001
1984
Apr
June
Aug Sept
Nov
Jan Feb Mar May
.001
.001 .001
.001
.001 .05 ns .05 ns
1985
July Sept
ns ns
1986
Fig. 1. Mean algal densities for burned and unburned transects as determined using the dilution plate technique. Error
bars represent ± standard error. ANOVA was performed to compare the burned and unburned means on each sample date;
probability levels for the F -tests are listed below sample month desigoations.
collected on 28 September 1984 by the Soil
Testing Laboratory, University ofIdaho in Moscow; Idaho. Soil texture (gravimetric method),
soil pH, electrical conductivity, and bulk density
were determined by the authors follOwing
standard methods (Soil Conservation Service
1972, Soil Survey Staff 1962). For all analyses,
three replicate samples were analyzed from
each study plot. Results of these analyses are
given in Table 2.
Several different biometric methods were
used to analyze the data. Analysis ofvariance was
used to compare mean algal abundance for each
. sample date (Snedecor and Cochran 1980). This
was done for both plate count data (algal density) and the moistened soil method (algal frequency). Centered, unstandardized principal
components analysis (Pielou 1984) was conducted using algal frequency ofselected species
enumerated in the moistened soil method. To
avoid the undue influence of rare species, only
spe,?ies occurring more than once were used in
the analysis. Similarity indices between the 14
samples analyzed with the moistened soil
method were calculated follOwing the methods
of Ruzicka (1958). These samples were then
clustered using the unweighted group average
method (Pielou 1984). Since we had only presence/absence data for species isolated from the
dilution plates, we were unable to conduct PCA
on that data set. However, we were able to
cluster the samples using Sorenson's similarity
index and the unweighted group average
method (Pielou 1984, Sorensen 1948).
Data from both methods did not appear to
form a normal distribution. Datafrom the moistened soil method were particularly suspect because of the high number of zero frequencies in
the samples. Thus, Pearson's l' (based on the
normal distribution) was deemed inappropriate.
Where measurement of correlation between
samples was needed, the nonparametric Kendall rank correlation test was used (Sokal and
Rohlf 1981).
All analyses were conducted using either the
Statgraphics statistical package or the Ecology
Program Library developed by Bill Evenson and
Jack Brotherson at Brigham Young University
(unpublished).
RESULTS
Pronounced differences existedbetween the
burned and unburned sites throughout the first
year of the study. Algal density as determined
using the dilution plate teclmique revealed pro"
nounced seasonal changes in unburned plots
both years ofthe study, with a major peak in late
1993]
77
EFFECTS OF RANGEFIRE ON SOIL ALGAE
winter and a minor peak in the fall (Fig. 1).
Mean algal density for unburned plots ranged
over 1-7 x 105 cells/g dry weight soil. Considerable variability among samples within unburned
transects was evident. The range for algal density for all samples taken from the unburned
area was 103-2.7 x 106 cells/g. Algal density in
the burned area did not show seasonal changes
or recovery for the first 16 months after the fire
(Fig. 1). Mean algal density dUring this period
had a range of 2-3.5 x 104 cells/g, with individual sample ranges of 103-1.3 x 105 cells/g. Recovery of the algal community in the burned
plots occurred during the winter months of the
second year in a very short time frame (January
to March). Analysis of variance for each sample
period showed significant (p < .05) differences
between burned and unburned transects
through Febmary 1986, after which the burned
area had similar or greater numbers of algae
than the unburned area (Fig. 1).
No statistically significant differences in algal
density using the moistened soil method were
found between burned and unburned transects,
although both blue-green algae and diatoms had
higher mean frequencies in unburned plots
(Fig. 2). Some ofthe samples in the burneda~ea
had algal frequencies of zero, while others had
frequencies similar to those in unburned plots.
Considerable variability was observed in unburned plots as welL It is likely that this heterogeneity in both burned and unbumed plots
contributed to the non-normality ofthe data and
is thus responsible for the lack of power of the
statistical procedure used. When the data were
transformed using aloglO(x + 1) transformation,
significant (p < .05) differences were detected
for some dates (9/84,2185,6/85,9/85). Because
of the lack of significant differences, the moistened soil method was discontinued after the
first year. It is interesting to note that the
method did locate seasonal differences in the
burned area comparable to those seen in the
unburned area (Fig. 2).
When first visiting the site, we were stmck
by the fact that the algal/moss cmst, though
blackened and dead, was still very much intact.
If this phenomenon occurs elsewhere, we surmise that crusts may be important in stabilizing
soils of burned areas during the clitical period
when all vascular vegetation is absent and soil is
exposed to the full erosive forces of wind and
water. The blackened cmst slowly broke down
over the first 6-8 months after the rangefire, at
50
. c c_ - -
~
Cyanophyta
- Bacillariophyceae
40
>-
Q
Z
w
~
ow
30
a:
"'-
IZ
w
Q
a:
w
20
Q.
10
Burnec:l
,,
Unburned,,"
-::-.;:-:::::;:~"",
__.Burned
Sept
1984
U
.... ,
,-:BU
,
Nov - -Feb' Apr- June
_. B
Aug
Sept
1985
Fig. 2. Mean percent frequencies of blue-green algae
(Cyanophyta) and diatoms (Bacillariophyceae) as determined using the moistened soil method. Standard error bars
are not included because in all cases they overlapped.
ANOVA did not reveal any significant differences.
which time visible vascular recovery had occUlTed.
Some areas in the burned transects seemed
to be less damaged than others. This was especially noticeable after fall rains in 1984 stimulated some of the bumt grasses to sprout back
from the crowns. There were areas where
grasses had sprouted back profusely and cmsts
were intact and unblackened, areas where fewer
grasses sprouted and the cmst appeared damaged but not excessively blackened, and areas
where no grasses sprouted and blackened cmsts
already had begun eroding. Upon investigating
the transects closely, we found burnt remnants
of sagebrush stems in the heavily burned plots.
It was evident that any place a sagebmsh
burned, the fire was much hotter in intensity,
causing destmction ofboth grasses and crusts in
close proximity
.
With such evident differences in fire intensity, we checked to see whether algal numbers
reflected these differences. We found a striking
correspondence. Kendall's rank correlation of
the burn intensity index (BI) "vith algal density
(dilution platA method) was consistently negative
78
[Volume 53
GREAT BASIN NATURALIST
TABLE 3. Kendall rank correlation analysis ofburned sites for all sample dates. Correlation values with the bum intensity
index (BI) are also given for each sample date.
Sample
date
9/84 11184. 2/85
9/28/84
6/85
8/85
9/85 11/85 1/86
3/86
5/86
5/86
7/86
9/86
BI
.35
049°
.23
.33
.39°
040°
047° -.02
.27
-.28
.44°
.33
-.03
_.50°
1.00
043°
.39°
.59°
.74°
.10
.21
.20
.12
.29
-.18
.28
.06
-.24
-.66°
.61"
.39°
.35
.03
042°
.18
.11
.20
-.29
.14
.05
-.08
_.37°
.34
.23,
.18
.28
.39°
.16
.16
_.56°
040° -.03
-.04
-.36
.49°
.12
.39°
.27
.08
.13
-.32
.22
.04
-.20
-.48·
.04
.20
.14
.15
.42
-.14
.22
.10
-.24
-.59·
AI·
.57·
.05
.n
-.06
043°
.30
.10
-.43·
.54·
.11
.28 -.12
.33
.24
.12
-.36·
.16
.20
-.17
.62·
.41·
.23
-045·
1.00
-.03
-.06
.10
.01
1.00
.02
.31
-.07
.08
-.44·
1.00
-.18
.10
.13
.10
2/25/85
1.00
1.00
4/14/85'
6/17/85
1.00
8/22/85
1.00
1.00
9/28/85
1.00
1118/85
1.00
1/23/86
2/27/86
3/28/86
5/8/86
5/30/86
1.00
.21
,1.00
7/31/86
9/12/86
°Sigl1ificant at a.
2/86
.29
1.00
11126/84
4/85
-.31
-.02
.39· -.54°
.21
-.28
1.00
-.04
< .05.
and Significant (p < .05) during the first 16
months ofthe study (Table 3), indicating that the
more intense the fire (higher BI), the lower the
algal density Especially surprising was the persistence of patterns of algal abundance through
the full two-year study. When contour plots
based on algal density were constructed, it was
evident that areas ofhigh algal density remained
high throughout the study (Fig. 3). On most
sample dates there is an area of higher abundance in the upper middle ofthe left-hand transect that corresponds to sample plots 27-29
(Fig. 3). These plots had the lowest BI values
(Table 1). Areas with high BI values (plots 16-17
and 23-25, lower right and lower left,. respectively) consistently had lower algal densities
(Fig. 3). Results from the moistened soil
method illustrate similar trends (Fig. 4).
Further evidence that spatial patterns in algal density persisted over time was sought by
determining Kendall's rank correlation coefficients between all sample dates (Table 3). A
positive correlation between two sample dates
indicates that relative abundances observed for
the 15 plots were similar on the two dates; i.e.,
plots with high densities on the first date had
high densities on the second date and plots with
low densities on the first date had low densities
on the, second date. In the first year's data (9/848/85) all sample dates were pOSitively correlated
with all other dates, with 8 of 15 (53%) of these
correlation coefficients being statistically significant (Table 3). The plots were shifted the
second year to avoid the area that had been
destructively sampled the first year. During the
second year (9/85-9/86), 78% of the correlation
coefficients were pOSitive, with only 25% of
these being statistically Significant. These results indicate that the pattern caused by initial
fire intensity was strong throughout the first
year but began to break down when algal recov~
elY took place in the winter of the second year
(from 2/86 to the end of the study).
Similar patterns in algal density were sought
in the unburned transects. However, the heterogeneity of the unburned area was so great that
no such patterns could be detected in contour
plots. Kendall rank correlation coefficients between all sample dates for unburned plots
showed much less correlation than that seen in
the burned plots. Although most of the coefficients for the first year's data were pOSitive, only
1993]
79
EFFECTS OF RANGEFIRE ON SOIL ALGAE
30
2?
?9
28
21
27
20
26
19
?5
18
?4
17
23
16
Fig. 3. Algal densities for the burned transect as determined usin,? the dilution plate technique. Last box shows plot
positions during the frrstyear (~ee Table 1). White represents <2 x 10 cells/g, light shading represents 2-10 x 104 cells/g,
medium shading represents 10°-lOG cells/g, dark shading represents> lOG cells/g.
30
o
Si8S
8/85
22
29
28
21
27
20
26
19
25
18
?4
17
, 23
16
9/85
Fig. 4. Blue-green algal percent frequencies as determined using the moistened soil method. Last box shows plot
positions (see Table 1). White represents 0--4%, light shading represents 5-29%, dark shading represents 30-100%.
3 of 15 (20%) were Significant (Table 4). During
the second year only 69% of the coefficients
were positive, with 3 ofthe 36 (8%) being statistically Significant. With an alpha level of 0.05,
one would expect "significant" coefficients 5%
ofthe time simply by random chance. The ratio
of 7 of 105 correlation coefficients in Table 4 is
very close to this hypothetical 5%, and we suspect this may mean that no meaningful patterns
were detectible with our sampling deSign. This
suggests that extensive microscale heterogeneity is present in the microbial distribution of
undisturbed arid soils, a topic that has been
subsequently pursued by others (Grondin and
80
[Volume 53
GREAT BASIN NATURALIST
TABLE 4. Kendall rank correlation analysis of unburned sites for all sample dates.
Sample
9/84 11/84 2/85
date
6/85
8/85
9/85 11/85 1/86
2/86
3/86
5/86
5/86
7/86
9/86
.31
.10
.17
.08
.25
.06
-.06
.23
-.16
-.07
-.10
.03
-.07
-.09
l.00
.19
.07
-.01
.24
-.24
-.19
-.09
-.17
-.25
-.17
-.21
-.08
-.04
9/28/84 1.00
11/26/84
4/85
2/25/85
4/14/85
6/17/85
8/22/85
l.00
.17
.42°
.29
-.10
-.16
-.15
-.22
.33
.14
.12
-.12
.05
1.00
.46°
.26
-.07
.17
-.05
.14
.06
.10
.15
-.04
-.20
.45° -.32
.02
.09
.15
.33
.06
.27
.08
.10
-.28
,
.10
.16
-.06
.19
-.15
.15
.30
l.00
.08
-.03
-.13
-.15
.08
.11
-.11
-.14
l.00
.19
.16
.20
.22
.05
.07
.29
-.10
-.06
.10
.00
.14
l.00
.18
-.01
.01
-.05
-.01
l.00
.35
.37
-.03
.14
.18
.16
.14
l.00
.26
.43°
l.00
.47°
1.00
l.00
9/28/85
ll/8/85
l.00
1/23/86
2/27/86
.45°
3/28/86
5/8/86
l.00
5/30/86
.38°
7/31/86
9/12186
l.00
°Si b'l1i6<'<Ult at a < .OOS.
TABLE 5. Species present in ALE plots based on cultures obtained from agar plates. B = burned, U
combined. Other letters in heading stand for months from September 1984 to September 1985.
Species
CYANOPHITA
Anabaena doliollUn Bharadw.
Lyngbya scotti Fritsch
Lyngbya subtilis West
Microcoleus vaginatus (Vauch.) Gom.
Nostoc commune Vaucher
NoSf:oc )Jaludosll1n Kuetz.
NoSf:oc )Jruniforme (L.) Ag.
Oscillatoria agardhii Gomont
Phormidiwnfragile (Menegh.) Gom.
Phormidillm tenue (Menegh.) Gom.
Scytonema schmidtii Gomont
TolY)Jothrix bouteillei (Breb. & Desm.) Forti
Tolypothrix tenuis (Kuetz.) J. Schmidt
=
unburned, C
=
SIC NIB NIU FIB FlU AlB AIU JIB JIU AlB AIU SIB S/U
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
CULOHOPIlYTA
A)Jatococcus vulgaris Brand
BraeteacOCCllS sp. 1
Braeteacoccussp.2
X
Centro.ll1'wem sp. 2
CentroS)J1Ulera sp. 3
Chlorella minutissinUl Fott & Novak.
X
Chiorella )Jrotothecoides Krueg.
X
Chiorella vulgaris
var. autotro)Jhica (Shih & Krauss) Fott & Novak.
Chiorella sp. 5
Chlorlumnidiumflaccidum (Kuetz.) Fott
ChlorllOnnidiumflaccidum
f. typica (Kuetz.) Fott sensu Starmach
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1993]
EFFECTS OF RANGEFIRE ON SOIL ALGAE
81
TABLE 5. Continued.
Species
Chlorococcum arenOSll1n Archib. & Bold
Chlorococcum infusionum (Schrank) Menegh.
ChlorococCllm minlltum Starr
Chlorosarcina sp. 1
Chlorosarcina sp. 2
Chlorosarcinopsis sp.
Chlorozebra colulerens Vinatzer
Fasciclllochioris sp.
Follicularia sp. (?)
Fottea sp.
Friedmannia israelensis Chant. & Bold
Gloeocystis polydermatica (Kuetz.) Hind.
Leptosira polychloris
Leptosira sp.
Lobococcus inci.~us (Reisigl) Reisigl
Lobococcus macronucleatus (Deason) Bourr.
Mynnecia biseeta Reisigl
Neochloris sp. 1
Neochloris sp. 2
Neospongiococcum ovatum Deason
Neospongiococcum sp. 1
Neospongiococcum sp. 3
Palmella miniata var. aequalis Naeg. sensu Smith
Palmella texensis Groover & Bold
Pleurasfrum sp. 1
Pleurastrum sp. 2
Protosiphon sp.
Radiosphaera minuta Herndon
Spongiochloris sp.
Stichococcus bacillaris Naeg.
Stichococcus minlltlls Grintzesco & Peterfi
Tetracystis sarcinalis Schwartz
Tetracystis sp.
Trebollxia sp.
Trichosarcina sp.
Chlorosarcinoideae sp.
SIC NIB NIU FIB FlU AlB NO JIB JIU AlB NO SIB SID
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
XANTHOPHYCEAE
Ellipsoidion anlllatum Pascher
Ellipsoidion oocystoides Pascher
Ellipsoidion penninimum Pascher
Gloeobotrys ovalis Reisigl
HeteroCOCCllS granulatus Pitschmann
Heterothrix debilis Vischer
Nephrodiella phaseolus Pascher
Plellrochloris commutata Pascher
Plellrochloris meiringensis Vischer
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
BACllURIOPHYCF..AE
Hantzschia amphioxys (Ehr.) Grunow
Navicula mutica Kuetzing
Pinnlllaria borealis Ehrenberg
X
X
Johansen 1993, Wheeler et al. 1993). Correla~
tions of algal density with vascular cover were
also attempted without success.
A total of 72 algal taxa were isolated from the
soils at ALE over the course of the two-year
study (Table 5). Over half the isolations were
green algae (47 taxa), with blue~green algae (13
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
taxa) being next in importance. Additional bluegreen and diatom taxa were observed by using
the moistened soil method (Table 6). In all, 41
Chlorophyta, 26 Cyanophyta, 9 Xanthophyceae,
and 8 Bacillariophyceae were observed, for a
total of90 taxa. This maybe the highest diversity
of algal species ever reported from soils of a
[Volume 53
CHEAT BASIN NATURALIST
82
TABLE 6. Average percent frequency of rugae observed in ALE plots using the moistened soil method. B = burned, U
= unburned. Other letters in heading stand for months from September 1984 to September 1985.
Species
SIB S/U NIB NIU FIB FlU AlB AlU JIB JIU AlB AlU SIB S/U
CYANOPHYTA
Anabaena variabilis Kuetz.
Arthrospira gomontiana Setch.
Chroococcus ineZicus Zeller
Chroococcus rninimus (Keissl.) Lemm.
Chroococcus pal/idus Naeg.
Chroococcus turgidus (Kuetz.) Naeg.
Chroococcus varius A. Br.
Gloeothece palea (Kuetz.) Habenh.
Lyngbya limnetica Lemm.
Microcoleus vaginatus (Vauch.) Gom.
Nostoc commune Vaucher
Nostoc paluclos1l1n Kuetz.
Oscillatoria agardhii Gomont
Oscillatoria angu~ta Koppe
Oscillatoria clzalybea (Mertens) Gom.
Oscil/at01ia sp. 1
PlumnieZium tenue (Menegh.) Gom.
SyneclwcocClls aeruginosus Naeg.
Tolypothri.-.: boutellei (Breb. & Desm.) Forti
Tolypothrix tenuis (Kuer.!:.) J. Schmidt
Total blue-green rugae
0.7
1.1
1.2
0.3
0.1 0.3
2.7
0.'1
0.1
0.7
1.1 0.5 0.9
0.1
0.3
0.1
0.3
0.1
1.5 2.9
1.9 3.5
0.1 21.2
0.1
0.3
2.9
0.1
0.1
1.3
0.1
204 0.3
0.8 1.1
2.8
0.5
5.2 3.9
0.8 304 2.0 4.5 0.3
604 1.6 9.7 10.9 0.3
1.2
0.3
0.5
7.1
0.1
0.3
8.9
0.3
5.1 004 2.3
0.1 0.5 004
0.1
0.9
1.3
0.1
004
0.8
0.1
0.7
3.7
0.'1
1.2
0.1
0.1
0.1
0.1
1.2
5.6 0.1
004
0.1
0.1
0.8
0.1
0.5
2.0
0.1
4.0
204
1.7
0.8 1.7 1.1
'1.6 0.5 504
0.3 0.2
0.1
0.3
0.1 0.1
3.7 1.2 1.6
1.1 0.2 004 0.1
0.2
0.1
004
5.3
1.6
0.1
0.3
004
0.7
0.1
7.6 41.5 8.0 1604 9.9 24.3 14.0 29.7 3.8 17.3 2.6 704 004 9.5
BACILLAHIOPHYCEAE
Achnanthes coarctata Brebisson
Achnanthes sp.
Hantzschia mnphioxys (Elll:) Grunow
Navicula cohnii (Rilse) Grun.
Navicula mutica Kuetzing
Navicula mutica var. undulata (Hilse) Gron.
Navicula nivalis Ehrenberg
Pinnlllaria borealis Ehrenberg
Totru diatoms
Totru chlorophytes
and xanthophytes
0.1
004
0.5
1.1 0.3
0.9 2.3 7.1
0.3
0.6
004 0.1
0.8
0.3
0.3
2.3
1.6 0.9
1.1 0.9 2.6
3.5
3.1 1.2
2.0 4.0 10.7
1.0
004
0.5 0.1
0.3 0.9 0.3
0.1
0.9
2.1 0.5
0.1
0.5 0.1
004 0.3
4.7
1.2
0.1
1.3
7.7 0.7
2.0 0.8
0.4
1.6 2.7
0.2
0.2
0.7
78.7 26.8 11.1 32.794.5 62.0 70.7 62.4.17.6 26.5 22.0 '1804 105 85.5
single site. One likely explanation for the number of species observed is the extended period
over which samples were taken and the sheer
number of isolations perfonned. The fact that
two different methods were employed also con~
tributed to the high species richness.
There did Ilot appear to be major differences
in species richness between burned and unburned plots. A total of 82 taxa were observed
in the unburned area, while 74 taxa were found
in the burned area. The difference was due
plimarily to a higher number of'blue-green algaeand xanthophytes in the unburned plots.
Seasonal patterns were not clear, although the
highest species riclmess was observed in February 1985 (Table 5), the month in which the
highest algal densities were also observed (Fig.
1). Because of time constraints, algal isolations
were not made after the first year.
The results of both the dilution plate technique and moistened soil method indicate that
significant differences existed between the algal
communities until the winter months of the
second year, when rapid recovery occurred. We
were interested in documenting floristic patterns of recovery as well. Using data from the
moistened soil method, we computed Ruzicka's
similmity coefficients and produced a dendrogram describing the cluster of the communities
(Fig. 5). Four cluster groups were identified.
Only unburned communities are in the first
cluster. Based on the results in Table 6, all of
these communities are characterized by having
high numbers of Nostoc commune Vaucher and
1993]
83
EFFECTS OF RANGEFIRE ON SOIL ALGAE
PERCENT SIMILARITY
19°
9,0
8,0
7,0
6,0
5,0
3,0
4,0
2,0
1,0
9
.ApU
June 85 U
Aug .85 U
Sep 85..U
Sep 84 U
Feb 85U
Nov 84 B
Nov 84 U
Sep 84 B
June 85_8
~
--
~-
.ApB
.FB
.FU
PG1
SB.
I--
Aug 85__ B
AuB
SeB'
I
JB'
·SU
SeU
.NB.
'JU
AuU NU
Feb 858
3
Apr ~5 B
Apr 85 U
I
4)se0 858
Fig. 5. Cluster dendrogram based on Ruzicka's similarity
index using qmmtitative data from the moistened soil
method. The first cluster contains unburned communities,
the second burned communities, the third represents a
seasonal spring flora, and the last cluster is an outlier due to
the near absence of species observed in September 1985.
See text for furtller explanation.
low numbers of Microcoleus vaginatus (Vauch.)
Gomont. The second cluster contains mostly
burned communities, although the November
unburned community is present because of its
similarity to the November burned community.
This cluster is characterized by low numbers of
both N. commune and M. vaginatus. Thus, it
appears that Nostoc species were damaged by
the fire and did not recover during the first year.
The third cluster represents seasonal changes in
M. vaginatus, which had elevated numbers in
the early spring samples. The last cluster consists of a single outlier, the September 1985
burned community. This sample is distinct in
that both N. commune and M. vaginatus are
absent (Table 6).
Principal components analysis (PCA) of the
same data set corroborates and further clarifies
the cluster analysis. Principal component 1 re~
flects the differences due to bUrning. Collec"
tively; the unburned floras have higher scores on
PC axis 1 than allburnedfloras (Fig. 6), although
some unburned floras are close to the relatively
tight cluster of burned floras. ¥lhen each date
pair is examined, the unburned flora has a distinctly higher score on PC axis 1 than its corresponding burned flora. The second PCA axis
seems to reflect seasonal influences, with late
winter/early spring floras having higher scores.
Fig. 6. Plot of ilie first and second components from an
unstandardized, centered principal compop.ents analysis of
data collected using tlle moistened soil method. Codes
represent date (S = 9/84, N = 11/84, F = 2/85, Ap = 4/85,
J = 6/85, Au = 8/85, Se = 9/85) and transect (B = burned,
U = unburned); Le., ApU = 4/85 unburned transect.
When the component weights are plotted., it
is evident that PC axis 1 is most heavilyweighted
. by numbers of N. commune, indicating tllat this
species is the primary contributor to the separation of burned and unburned floras (Fig. 1).
Nearly all species are weighted positively because average algal densities for all species
tended to be higher in unburned plots. PC axis
2 is most heavilyweighted by M. vaginatus (Fig.
7), the taxon that separates late winter/early
spring communities from the rest of the year's
samples. Principal components 1 and 2 explain
56% and 24% of the variability in the data,
respectively
Since we do not have quantitative information for individual species identified from isolations, we could not perform PCA or cluster
analysis based on Ruzicka's similarity index.
However, Sorenson's similarity index could be
calculated, and cluster analysis based upon this
similarity coefficient was performed (Fig. 8).
The first cluster consists of communities with
high numbers oftaxa and comprises late winterlate spring unburned samples, as well as the
February burned community. The second cluster is not separate from the first but is hierarchical to it. This part of the cluster consists of the
communities that had slightly lower species
richness and hence lower similarity. The late
summer community from unburned transects
also was in tllis group, indicating that some
species diversity maybe lost in the summer even
in undisturbed areas. The third cluster consists
84
[Volume 53
GREAT BASIN NATURALIST
PERCENT SIMILARITY
100
'MIVA
I
aD
90
I
J
70
I
60
J
40
50
J
I
30
I
A p, 85 U
Feb 85 U
Feb 85 B
-
June 85 U
Apr 85 B
Aug 65 B
TOTE
• ·PIBO
·HAAM
·OSAN
Aug 85 U
PC1
-
~
j~
June 85 B
Noco
INova4"
3
·OSSp
Fig. 7. Plot of component weights for first two components from an unstandarclized, centered principal components analysis of data collected using the moistened soil
method. Taxa codes consist of first two letters of the genus
tmd first two letters of the species (Table 6).
Nov" 84 U
Fig. 8. Cluster dendrogram based on Sorenson's similarity quotient using presence/absence data of taxa isolated
from the dilution plate cultures. The first cluster contains
early-late spring sample dates (mostly unburned). The second cluster is hierarchical to the first group and contains
months of depressed species richness. The tllird cluster
consists of the November floras, which clustered togetller
in all analyses.
of the November samples and reflects seasonal
distinctiveness of the flora at that time. The
November samples clustered tightly using the standing of cryptogamic recovery follOwing fire
moistened soil data as well (Fig. 5). .
• is still too sketchy to make generalizations. More
study is warranted.
In classical studies ofprimary and secondary
DISCUSSION
succession of terrestrial plant communities, the
first step in succession is colonization by
Recovery of the soil algal community follow~ Nelected pioneer species that establish early
ing the rangefire at the Arid Lands Ecology and take advantage of readily available reReserve was more rapid than any other soil algal sources. Colonization by green algae and xanrecovery repOlted in the literature. Johansen et thophytes has been observed in primary
al. (1982,1984) observed that algal communities succession on volcanic ash (Rayburn et al. 1982).
in two separate Utah shrub-steppe soils had not A similar phenomenon in the secondary succesrecovered three years follOwing rangefire, al- sion of tlle soil algal community follOwing fire
though in one study recoverywas complete after was hypothesized. However, succession was
five years. Callison et al. (1985) reported that fundamentally different. Even in the most incryptogamic crusts had not recovered in some tensely bumed plots, an average of 1000-5000
blackbrush communities even 30 years after algal cells/g dry weight of soil were present
fire. It has been suggested that recovery of the within a month after the fire. Furthermore,
algal community is tied to the specific climatic except for Nostoc commune, there was no subhistory ofthe bumed area (Johansen et al. 1984). stantial difference between species present in
It could be surmised thatWashington state sage- unbumed and bumed transects, although heavbrush steppe is cooler and wetter than the Utah ily bumed plots seemed to have fewer species
shrub-steppe communities studied in the past, by virtue of the fact tllat fewer colonies were
and thus recovery was quicker. However, other evident on agar plates. Migration and colonizafactors could also have played a role. For exam- tion by pioneer species were unnecessary beple, soil pH at ALE was slightly acidic, while pH cause algal propagules were still in place after
OfUtall and Arizona steppe soils is almost always the fire.
What is equally fascinating about the algal
alkaline. Green algae were much more abun~
dant in Washington than in study sites in the recovery following fire is that algal numbers did
Great Basin and Colorado Plateau, and perhaps not increase for nearly 16 months. No seasonal
tlns group of algae recovers more quickly than fluctuations were observed, nor was a general
blue-green algae dominating crusts of the latter increase observed during tlns time (Fig. 1). It
regions. What seems clear is that our under- appears that some environmental factor or com-
1993]
85
EFFECTS OF RANGEFIRE ON SOIL ALGAE
TABLE 7. Vascular plant cover observed in the burned lmd unburned h'ansects at the ALE study site. Percent cover in
late summer lmd spring for each year of the study is presented.
9/84
Cover class
Artemisia tridentata Nutt.
Poa secunda Presl
Other grasses
Lupinus leucophyllus Doug!.
Otherforbs
Total vascular cover
Total crust cover
Bare ground
Litter
B
4/85
U
0.2
22.7
B
8.6
9/85
U
TO
38.1
004
0,0
80.3
19.1
T
22.9
71.9
5.4
5,6
0.3
0.7
10.0
52.6
37.7
0.9
0.9
39.0
63.5
1.9
3.8
B
7.9
0.2
0.7
0.9
9.7
64.5
25.6
0.7
4/86
U
5.1
49.3
B
15.3
1.0
lOA
54.4
50.9
T
1.8
16.6
43.3
38.5
20.4
0.2
9/86
U
4.8
50.9
0.9
2.3
1.5
60.4
41.3
2.3
3.1
B
U
23.0
5.2
47.0
3.1
2.3
28.4
44.1
27.7
0.1
0.3
0.9
53.4
49.0
1.0
2.5
GT = trace.
bination of factors limited growth during the
first year.
Three factors are most likely responsible for
this phenomenon. While physical soil characteristics and chemistry were not Significantly
(p < .05) different between sites (Table 2), it is
possible that hydrophobic organic compounds
released by the fire sealed tlle soil surface, causing greater runoff and less water availability
Light burning on dry soils has been demonstrated to produce a thick and highly waterrepellent soil layer in California chaparral soils
(DeBano et al. 1970, 1976). the pH did not
change follOwing burning, which was unusual
since in most instances pH increases follOwing
fire (Groeschletal.1991, McKee 1991). Nitrate
nitrogen increased immediately follOwing the
fire (Table 2), but it may have subsequently
decreased. Soil nitrogen dynamics associated
with fire are poorly understood and a topic of
vigorous debate by others (Klopatek et al. 1991,
McKee 1991). However, itis unlikely that nitrogen availability explains tlle failure of algal
populations to grow the first year.
A second possibility is that algae require a
vascular plant canopyfor development. Vascular
plant cover in the burned area was completely
destroyed by the fire (Table '7). Some grasses
sprouted from crowns in late fall of1984, and by
spring of 1985 grass cover in the burned area
was about one-sixth of that in the unburned
area. Upright forbs did not appear until the
summer of 1985 and were more abundant in
burned transects than in tlle unburned island
(Table 7). It seems plausible that vascular cover
would ameliorate harsh conditions of sun and
wind on tlle soil surface, thus promoting algal
growth. Standing vegetation in the winter, even
if dead, could prolong periods of optimal soil
moisture at the soil surface and could have contributed to recovery during tlle second winter.
A third possibility is that the wetter winter of
1985--86 was partly responsible for algal recovery. Johansen et al. (1984) surnlised that unusuallywet weatherwas largely responsible for algal
recovery in a burned site studied in Utall. A
comparison of precipitation for the two winters
shows that over twice as much precipitation fell
the second winter (Fig. 9). For the months of
December to March, 12.0 cm precipitation fell
the second year, compared witl15.3 cm precipitation tlle first year. Furthermore, air temperatures were above freezing between January and
March when recovery occurred, whereas 198485 temperatures had been consistently below
freezing (Fig. 9).
We are unable to say which of tlle three
factors discussed above played the most Significant role in algal recovery. It is likely that some
combination of tllese and possibly other factors
is responsible. More research on cryptogamic
recovelY follOwing disturbance is needed. At the
same time, it should be recognized that recovery
follOwing fire is likelyvery different from recov~
ery follOwing trampling disturbance (livestock,
off-road vehicles) because of the differences of
impacts on soils and vascular communities.
We observed clear evidence of seasonality in
algal abundance at the ALE site. A repeating
pattern of winter and fall peaks was observed
using the dilution plate metllOd. Seasonalitywas
not limited to density differences; floristic
changes also occurred. When algae identified
from isolations were clustered using Sorenson's
similarity quotient, November floras of burned
and unburned transects clustered together (Fig.
8). August floras also formed a distinct cluster.
The two February floras clustered together
86
[Volume 53
GREAT BASIN NATURALIST
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;::
"tl
~
h~
~ ~~) V
goe
2
>
X
l- ·10C
~
"- \
A
1'\
1/23 2/27 3/28 51 5130
1986
/\
7/31
912
Fig. 9. Climate data at the ALE site for the duration of the study. The temperature range represents the mean minimum
to maximum temperature based on two-week periods. Precipitation represents the total precipitation over the same
two-week periods. Vertical lines represent sample dates.
along with the unburned April community The
tendency for floras to cluster by season rather
than treatment reflects the importance of seasonality even when a crude measure such as
presence/absence of taxa is considered. The
data obtained using the moistened soil method
gave a clearer indication of seasonal change.
Specifically, Microcoleus vaginatus and diatoms
showed high abundance in the early spring
months ofFebruary and April (Table 6), Chroococcus spp. were absent during the early spring
months, and Nostoc commune was highest in
September 1984 in the unburned transect
(Table 6).
Seasonality in algae of arid soils was studied
by Johansen and Rushforth (1985). Theirresults
were not as easily explained as the results in this
study.They found peaks in NovemberandJune,
with M. vaginatus having its greatest abundance
in May; June, and August. Unfortunately, they
did not sample between January and May; the
time of peak activity in the ALE site. Furthermore, the climate ofthe site in the Tintic Mountains of Utah was considerably wetter, with over
twice the precipitation (cf. Fig. 9 with Johansen
and Rushforth 1985, Fig. 5). These two studies
demonstrate that seasonal changes do occur in
desert soils and that presently this seasonality is
poorly understood.
Seasonal changes in algal communities of
temperate soils are much less pronounced, a
result of dense tree canopy and shading by leaf
litter (Grondin 1991). The presence of seasonality in desert soils rwses concerns about the
metllods of study employed by past workers. In
a number of studies samples have been collected only once during tlle year, based on the
assumption that a single collection is repre~
sentative of the site in terms of numbers and
species present (Anderson and Rushforth 1976,
Ashley et al. 1985, Cameron 1960, Fairchilp' and
Willson 1967, Johansen and St. Clair 1986, Johansen et al. 1981, 1982, 1984). Our data show
this assumption is erroneous. Finally, although
difficult to study, seasonality requires closer examination ifan understanding oflong-term succession is eventually to be gained.
The aJgal flora of the ALE site in the Lower
Columbia Basin is distinctively different from
floras reported from shrub-steppe communities
of the Great Basin and Colorado Plateau. The
major difference is the high diversity and abundance of green algae and xanthophytes in tlle
ALE soils. A total of 47 chlorophytes and 9
xantllOphytes were observed at a single site. In
most previous studies tllese algae have not been
identified even to generic level (Anderson and
Rushfordl 1976, Ashley et al. 1985, Johansen
and St. Clair 1986, Johansen et al. 1981, 1982,
1984). In a study of over 450 specimens of soil
algae from seven counties in Arizona, Cameron
(1960) reported onlY.12 chlorophytes and 1
1993]
EFFECTS OJ; RANGEFIRE ON SOIL ALGAE
xanthophyte. One possible explanation for the
abundance of these algae at ALE is that the soil
pH is slightly acidic, whereas almost all arid
shrub"steppe soils studied in the Great Basin,
Colorado Plateau, and Sonoran Desert are
slightly to strongly alkaline. In studies of tlle
relationship of soil pH to algal floras, both Jolm'
(1942) and Lund (1947) found that acid soils
support more green than blue-green algae.
Other studies ofWashington soils have had high
numbers of chlorophytes compared to cyano~
phytes (Metting and Rayburn 1979, Rayburn et
al. 1982, Zimmerman et al. 1980). Fairchild and
Willson (1967) found a pronounced effect ofsoil
pH in their study ofsoil algae in aridWashington
soils, with a higher chlorophyte/cyanophyte ratio in neutral soil than in the alkaline soil tlley
studied. More study of chlorophytes and xanthophytes in alkaline soils ofthe Great Basin and
Colorado Plateau is warranted.
Although by comparison blue"green algae
seemed scarce, the diversity of cyanophytes observed was also higher than in most previous
studies. For example, the maximum number of
cyanophyte species reported from studies of
Great Basin and Colorado Plateau soils is 17
(Anderson and Rushforth 1976, Ashley et al.
1985, Johansen and St. Clair 1986, Johansen et
al. 1981, 1982, 1984), comparedwith the 26 taxa
observed in the present study. In a study of arid
soils of neutral to alkaline pH in the Lower
Columbia Basin, Fairchild and Willson (1967)
found 20 species of blue-green algae, which is
comparable to the number observed in this
study when one considers tllat tlley sampled
only in the spring months.
Results of this study have raised as many
questions as they have answered. Algal recovery
time, density, and species composition observed
at the ALE Reserve suggest much greater regional differences in cryptogamic crust biology
than previously assumed. Because of the constancy in macroscopic appearance and the presence of some ubiquitous taxa, such as M.
vaginatus, N. commune, and Hantzschia amphioxys (Ehr.) Grunow; some workers may have
considered soil algal communities of arid lands
fairly similm: This perception is flawed, and
more study of diverse arid localities is needed.
Furthermore, the lack of standard methodologies for the study of soil algae and cryptogamic
crusts has made comparison between studies
very difficult. Further study oftlle chlorophytes
and xanthophytes is probably warranted, as is
87
continued study of seasonality Sampling once a
year should be considered insufficient in future
studies. And, finally, although recovery from fire
requires (in many cases) two to five years, more
study is needed regarding the dynamics of recovery in different types of shrubland and in
different climatic regimes. The complexity of
soil algal communities emerging as a result of
numerous unrelated studies should continue to
confuse and delight researchers for years to
come.
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