IARC-JAXA Workshop 2006 (March), Fairbanks
http://www.ijis.iarc.uaf.edu/en/news/0603_workshop2006_program.htm

p. 1

The effects of intensive forest fire on revegetation in interior Alaska(mid-term report, February 2006)

TSUYUZAKI Shiro, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo
060-0810 Japan
NARITA Kenji, Faculty of Education and Human Studies, Akita University, Akita 010-8502 Japan

Abstract: To detect the effects of large-scaled fire on the revegetation of Picea mariana forest,
we set up 16 10 m × 10 m plots at Poker Flat near Fairbanks, Alaska, USA, in the spring of2005. Forest fire occurred in this region in the summer of 2004. Owing to the fire, stem
density declined 9%-100% and canopy openness increased in the plots surveyed. The groundcover mostly consisting of Sphagnum was burned by the fire, and remained patchily. Burned
ground surface in the plots ranged from 3% to 100%. The relationship between the height ofsurvived trees and age determined by tree core samples was positively and linearly correlated.
The frequency of tree stems gradually decreased with increasing tree height. Those results
suggested that tree recruitment had gradually occurred so far. We set up six 1 m × 1 m
quadrats in each plot, and recorded plant cover on each species and marked all seedlings ineach quadrat. Of vascular plants, small shrubs, such as Betula nana and Ledum
groenlandicum, and sedges (Carex spp.), that recovered vegetatively, were common on the
unburned ground surface, while Epilobium angustifolium were common on burned surface.
In addition, even on the burned ground surface, shrubs, e.g., Betula nana and Ledum
groenlandicum, and perennial sedges, such as Carex bigelowii, could survive vegetatively
throughout the fire with low cover. We found out the safe sites for seedling emergence varied
greatly between tree species. Picea mariana germinated on Sphangum mat while Betula
papyrifera and Populus tremuloides emerged on bare ground where the aboveground coverincluding duff was completely removed by the fire. The surveys on the relationships between
revegetation patterns and its related environmental factors will be continued.
Key words: forest fire, Picea mariana forest, plant cover, seedling emergence, Sphagnum

Introduction
Natural forest fires with different interval,
intensity and scale operate plant community
structures and functions in various regions, since
the above-and below-ground environments, i.e.,light and nutrient, alter greatly by fire (Johnson
1992; Kenae et al. 2004). In particular, fires
take place frequently in taiga regions, e.g.,
Siberia and Alaska, due to lightning (van Cleve

et al. 1986; Engelmark 1999). In these regions,the distribution pattern of permafrost is
consistent roughly with the distribution of
ecosystems.
Picea mariana is adapted toestablish wet and nutrient-poor habitats that are
distributed more in north slopes of mountains(van Cleve et al. 1986).
On forest regeneration, the initial stages are
particularly important to determine the patterns
and dynamics. In Alaska, ordinary forest fire isp. 2

categorized into crown fire (Bonan & Shugart
1989). That means that the ground surface
cover is not greatly declined by fire.
In
discontinuous permafrost region, the scenarios of
succession differ greatly between north and south
slopes, due partly to the presence of permafrost
on north slope and the absence on south slope(van Cleve et al. 1986). Soil properties are also
different between south and north slopes in aninterior Alaska (Ping et al. 2005). In total,
Picea mariana forest develops more on northslopes, while mixed white spruce forest
establishes on south slopes.
The frequency, intensity and scale of fire
will be altered by global warming (Dale et al.
2001; Hinzman et al. 2005). Furthermore,permafrost thaw accelerates in boreal peatlandsin the last century (Camill 2005). Therefore,
we have mentioned the effects of large-scaled
fire on the regeneration of Picea mariana forest
on north slope. The major objectives of thisresearch are: 1) Detecting the characteristics ofplant community recovery after large-scaled
wildfire, 2) Characterizing the characteristics ofplant community dynamics, including succession
and revegetation, after the wildfire in a
discontinuous permafrost zone, and 3) The final
goal is generalizing the patterns by comparing
with the other references. This mid-term report
is situated in a comprehensive research on forest
community dynamics after large-scaled fire(Team Leader, M. Fukuda, ILTS, HU). For the
progress of this project, we summarize ourresearches in 2005, although we have to say
every study has been ongoing.
Study area and methods
Study area

Poker Flat, approximately 50 km north of
Fairbanks, interior Alaska, USA, was selected
for the present survey, because of large-scaled
and intensive fire, north slope, and highaccessibility and convenience. The forest fire
was recorded in the summer of 2004.
In this region, there are three types of
upland taiga forests: Picea mariana, Picea
glauca, and Betula-Populus (Kielland 1998).
Of these forest types, Picea mariana forest is
characterized by the predominance of Picea
mariana on nutrient-poor habitats (Bonan &Shugart 1989).
On the north slope of Poker Flat, monospecific dominant tree was Picea mariana.
This forest is situated in the northern part of the
Alaskan boreal forest, above the boundary
betweencontinuousanddiscontinuous
permafrost zones. On the forest floor excluding
vascular plants, peat moss (Sphagnum spp.),feather moss (Thuidium abietinum) and lichens(mostly Cladina spp.) were common.
Field methods
On a north-faced slope at Poker Flat, 16 10 m ×
10 m plots were established in the spring of 2005.
The location of each plot was recorded onlatitude, longitude and altitude by a portable GPS
receiver (PokeNavi-Mini, Empex, Tokyo).
Slope aspect and gradient were measured in eachplot by a transit compass (Electronic Total
Station ET2, Topcon, Tokyo).
On each plot, we measured tree height anddiameter at breast height (= 1.3 m) for stems !
1.3 m in height. The diameter was measured bya tape or a pair of calipers. On this survey, allstems including alive and dead stems were
measured to reconstruct forest structure before
the fire. The fallen trees with 1.3 m in heightp. 3

were included in the measurement. Crosssectional area at breast height was calculated
based on diameter at breast height. Stemvolume was calculated by the assumption ofconical-shaped stem.
The burned area on the ground surface wasvisually estimated in each plot. In addition, toclarify seed immigration patterns, we set up twoseed traps made of plastic on each plot in thesummer of 2005. The design of trap is illustratedby Terry’s Lab.
In each plot, six 1 m × 1 m quadrats wererandomly set up. Of the six quadrats, fivequadrats are used for non-destructive monitoringon plant communities, and the remainder is forthe measurements on belowground properties bydestructive measurements.
On the fivemonitoring plots at every census, the vegetatedarea was measured to evaluate plant cover
recovery. Then, cover on each species wasrecorded separately between burned andunburned areas on each quadrat. Duff (or mossorganic layer) thickness was measured by a steel
stake. When the stake hit parental rock or

frozen soil layer, the length of stake penetrated
into duff was recorded. In each quadrat, three
replicates of the thickness measurement weremade on burned and unburned areas.
Two photos were taken on each quadrat by afish-eye lens at cloudy day to estimate canopy
openness. The position of camera was adjusted
to 1.3 m in height. Canopy openness wasmeasured from the photos, using a freeware Gap
Light Analyzer ver. 2.0 (Frazer et al. 1999).
When tree annual seedling was observed in
the quadrats, each seedling was marked by anumbered flag and was recorded on height,
crown diameter and location.
From the outside of the plots, 22 tree cores
were collected at 10-30 cm above the groundsurface by an increment borer or by clippers.
Tree ring width was measured under astereomicroscope at 0.01-mm intervals.

Photo 1. An example of a 10 m × 10 m plot established
for the long-term monitoring. The ground surface
was burned patchily, and all Picea mariana trees weredead in this plot, while moss cover remained patchily.
This plot is categorized into moderately-burned site.

Fig. 1. Relationship between burned area and tree
survival rate in the 16 plots. Plot codes assigned byfire intensities and/or the other remarks: H = heavilyburned, M: moderately, L = less, K = Kodama, S =Sawada.

Statistical analysis
The relationships between dependent factors(e.g., tree height) and independent factors (e.g.,DBH) were preliminarily examined by linear

p. 4

Duff thickness (cm)regressions (Zar 1999).
The difference inseedling density between unburned and burned
areas was examined by "2-test. More robust
analyses will be performed finally.
Resultsy = -0.23x + 52.81, r2 = 0.263

Environments and fire intensities
The altitudes on the plots were between 244 m to437 m. The slopes on all the plots faced 7.0o43.5o from north to west. The slope gradient
ranged from 4.8o to 19.0o. Frozen soil layer was
detected in two plots located on the bottom of theslope at the summer survey, while the frost layer
was indefinite in the other plots.
Even though the stems of Picea mariana
were killed by the fire in 2004, the most of stem
were standing because the fire burned stem
surface layers up to a few centimeters deep inmost cases. While, a few stems on the othertree species might be lost due to the fire.
Therefore, we were able to reconstruct pre-fireforest structure well.
Table 1. The forest structures before and after the2004 fire on the north slope of Poker Flat. Pre-fireforest structure is estimated by the sum of alive anddead stems, and post-fire one is determined by alive
stems. Each numeral shows mean with standard error
per plot. Ranges (minimum to maximum) are shownin parentheses.
Picea mariana
Stem density
Total cross-sectional areaat breast height (cm2)
Total stem volume (m3)OthersStem density
Total cross-sectional areaat breast height (cm2)
Total stem volume (m3)Pre-fire

Post-fire

24.3 ± 3.9(5-54)
439 ± 74
(95-1090)
9.2 ± 2.0
(1.0-28.0)

5.3 ± 2.7
(0-30)
112 ± 58
(0-665)2.3 ± 1.4
(0.0-16.9)

0.8 ± 0.6
(0-7)
7±6
(0-77)
0.0 ± 0.1
(0.0-0.6)

0.2 ± 0.2
(0-2)
2±3(0-32)
0.1 ± 0.1
(0.0-1.4).
Burned area on the ground surface (%)

Fig. 2. Relationship between burned area and mean duff
thickness in 80 1 m × 1 m quadrats.

Picea mariana was predominated in all theplots before the fire (Table 1), although the stem
density and volume varied greatly. Namely,
there were 5-54 Picea mariana tree stems ! 1.3
m in height on the plots, of which averaged
density was equivalent to ca. 2400 stems/ha.
On Picea mariana, total cross-sectional area atbreast height and stem volume were 439 ± 74
cm2 (mean ± standard error) and 9.2 ± 2.0 m3,
respectively. Three other tree species, Alnus
crispa, Betula papyriferea1 and Salix sp., wererecorded with low frequency. Total number ofalive and dead stem with ! 1.3 m in height on
Picea mariana was 389, and that of the other tree
species was only 13. Therefore, 96.8% of treestems were Picea mariana before the fire. The
maximum tree height was 13.0 m by Picea
mariana.
Owing to the fire, 81.3% of Picea mariana
stems were burned and dead, and the total stem
volume declined about 77.9%. The groundsurface was mostly covered by Sphagnum spp.
By the fire, the plant cover on the forest floor, inparticular, the cover of moss represented by
Sphagnum, declined variously, i.e., 0%-100%
1This may be incorrect, and may be Betula neoalaskana
Sarg. B. neoalaskana is similar to, but smaller (< 13 m
in height) than, Betula papyrifera. B. neoalaskana twigs
are densely covered with resin-glands.

p. 5

Fig 3. Relationship between averaged burned area ofsix 1 m × 1 m quadrats and whole burned area in the 10
m × 10 m plot. Error bars indicate standard error. Plotcodes in the figure, refer to Fig. 1.

(Fig. 1). This result indicated that the forest
floor was patchily burned with various scales.
The thickness of duff layer ranged from 2.6 cm
to 73.3 cm, and was negatively related to burned
area (Fig. 2). Although the linear regression
was statistically significant, the variation and/or

Fig. 4. Relationships between diameter at breast
height (DBH) and tree height. Closed and open circles
indicate alive and dead Picea mariana trees,
respectively. Closed and open triangles indicate theother alive and dead trees, respectively. Solid andinterrupted lines indicate linear regression lines on aliveand dead Picea mariana, respectively. The regressions
are obtained from Picea mariana.

range of duff thickness varied greatly.
For the further studies, we classified into
three intensities of forest damages by the fire, i.e.,
less-, moderately-, and heavily-disturbed areas,
based on burned area and ratio of alive trees (Fig.
3). Less-disturbed plot (hereafter, i.e., L) is
characterized by high Sphagnum cover retaining
on the ground surface and higher tree stem
survival (Fig. 1). Moderately-disturbed plot(M) is situated between less-disturbed andheavily-disturbed areas, i.e., most trees were
killed (Fig. 1) but the ground surface plant coverremained somewhat (Fig. 3). The burned area
in plot was linearly correlated to mean burned
area in quadrats on each plot. However, thevariance of mean of burned area in quadrats
fluctuated greatly, in particular, in moderately
burned plots. Heavily-disturbed plot (H) iscompletely burned by the fire, i.e., all stems were
killed and the more than 80% of ground surface
was burned. Based on those investigations, weassigned L1, L2, L3, and L4 to category L, M1,
M2, M3, M4, S1 and K2 to M, and H1, H2, H3,
H4, K1 and S2 to H.
Canopy openness ranged from 57% to 95%
on the 80 quadrats. The control forest, i.e.,
unburned in 2004, where the forest height was
similar with the examined burned-area showed
the canopy openness was less than 54%. Evenon L plots, plant cover on forest floor declined
up to 40% by fire (Fig. 3) and 5-40% of treestems were killed (Fig. 1).
Those results
indicated that the surveyed area received firedamage, to some extent even on the lessdisturbed area, that increased canopy openness.
Therefore, changes in the effects of solar
radiation will be able to be monitored along fireintensity gradient.

p. 6Tree age and size
Of 22 tree cores sampled, the maximum age was
174 with the height of 9.1 m. The relationshipbetween tree height (m, independent variable x)
and age (yr, dependent variable y) was explained
well by a linear regression (y = +0.049x + 0.050,
r2 = 0.78, significant at P < 0.01). Stem heighton Picea mariana was linearly related todiameter at breast height (Fig. 4). In addition,
various sizes of stems were observed in the forest(Fig. 1). Not only large stems but also small
ones were killed haphazardly by the last fire.
Those indicated that the forest regeneration
pattern before the 2004 fire was not
simultaneously, and/or the previous forest fires
killed randomly the established stems.
The stem-diameter growth has a peak at 4060 years before 2005 on a few stems (Fig. 5),
suggesting that drastic events, such as fire,occurred around 60 years before the present date.
Plant communities in herb layer
We have collected 96 quadrat data in the spring

Photo 2. An example of 1 m × 1 m quadrat formonitoring temporal changes in plant cover andseedling establishment. Picea mariana stem, that
produced numerous cones, overlaid on the quadrat.
Ledum groenlandicum recovered vegetatively on
burned surface.

and summer of 2005, because quadrats used for
destructive measurements had not been utilized.
By the field observations and measurements, wehave confirmed that a few shrub species could
survive throughout the latest fire even on burned
surface, e.g., Betula nana and Ledum
groenlandicum2. The data will be analyzed byordination techniques and others to extract
significant environmental factors on plantcommunity structures and to predict revegetation
patterns. All voucher specimen will be kept inthe Hokkaido University Museum (SAP).
Seedling establishment patterns
In the spring of 2005, we marked 109 seedlingsin the quadrats surveyed. Most seedlings were
Epilobium angustifolium. The minorities were
Populus
tremuloides
andCalamagrostis
cadandensis. The seedling survival rate was ca
40% by the summer, while an individual of
Epilobium angustifolium flowered in thesummer.
In the summer, we marked 575 tree
seedlings in the quadrats (Table 2). The firstleading species was Picea mariana.
The
seedlings of this species appeared on both burned
and unburned ground surfaces, but the density
was significantly higher on unburned surface.
In contrast, Populus tremuloides and Betula
papyrifera established only on burned surface,although there was only 1 stem ! 1.3 m high on
Betula papyrifera and no stems ! 1.3 m high on
Populus tremuloides in the 16 plots surveyed.
The relationship between micro-topography andseedling emergence will be determined, using
fine scale photos taken by Sawada JJ (see his MS
in this report).
2

Note: The synonym of this species is Ledum palustre L.
var. groenlandicum (Oeder.) Hulten.

p. 7

Table 2. Numbers of seedlings recorded in burned andunburned areas. Density (/m2) is shown in parentheses.
Significant differences in seedling densities between
burned and unburned areas are examined by "2-test for
Picea mariana (P < 0.01). The significance test was
not conducted for the other three species.

remains on the ground surface after fire, soil
temperature keeps low. However, the complete
removal of moss mat should promote soil
temperature increase and/or melting permafrost

HabitatPicea mariana
Betula papyrifera
Populus tremuloides
Salix sp.
Total

(Yoshikawa et al. 2002). In permafrost-freeareas, surface soils become dry because
infiltration is not restricted (Hinzman et al. 2005).
Those suggest that the patterns of removal andrecovery of ground surface cover by fire are
prerequisite to predict the fates of seedlingemergence and growth.
Since global warming has modified climate
and its related factors, including frozen layer insoils (Dale et al. 2001; Camill 2005), fire may
become larger and more intense. Initial treecomposition after fire had little effects onunderstory composition in the coniferous forestsof eastern Canada, while soil burn severity
significantly affected temporal changes inunderstory species (Lecomte et al. 2005).
Those suggest that forest regeneration patterns
after large-scaled fire differs from fires that haveusually occurred so far.
Tree ring growth suggested that a fire mightoccur on Poker Flat approximately 60 years
before the latest 2004 fire, although the intensity
was not severe. We may confirm if changes inannual tree ring growth are related to the

Unburned
353 (13.7)000353 (13.7)

Burned105 (1.9)
20 (0.4)
96 (1.8)
1 (0.0)222 (4.1)

Discussion

Tree ring width (mm)Fire patterns and forest structure
In the plots surveyed, the forest fire intensities
were diverse from mild to severe. Mean annual
biomass increment is higher in dry sites than inwet sites along a chronosequence on Picea
mariana forests in Manitoba, Canada, but carbon
pools in bryophyte, understory and forest floor
are less for the dry than for wet sites (Wang et al.
2003). In Picea mariana forest, the groundsurface is mostly covered by mosses, representedby Sphagnum spp., that may explain 80-90% of
the aboveground biomass (Bonan & Shugart
1989). Forest fire, in particular, on north slopes
in interior Alaska, usually occurs as crown fire
and thus moss mat is removed incompletely(Bonan & Shugart 1989). When moss mat

0

20

40

60

80

100

120

140

160

Fig. 5. An example of annual growth of tree ring on Picea mariana. The tree core was sampled from a treewith 8 m in height and 10.1 cm in diameter at breast height. The peak of growth is observed 40-60 years before
2005.

p. 8

previous fire(s). In addition, based on the
yearly fluctuation patterns of tree ring growth,
we will examine if the estimation of fire intensity
is possible on the forest level.
Canopyopenness influences the distribution pattern andproductivity of herbaceous plants in the forest
floor (Reich et al. 2001; Whigham 2004). We
are monitoring canopy openness and its related
factors, such as leaf area index and direct solar
radiation.
The safe sites for seed germination differed
between Picea mariana and broad-leaved tree
species.
Seedling recruitment on Picea
mariana is highest in the first five years after
fires, while additional establishment is notobserved after 10 years (Johnstone et al. 2004).
Picea mariana is well-known as producing
serotinous or semi-serotious cones (Bonan &Shugart 1989), while the most of all broadleaved tree species, i.e., Betula, Populus, Salix
and Alnus, produce a great amount of longdistance, wind-dispersed seeds in the most ofyears. Therefore, the yearly fluctuation of
seedling emergence should be monitored on
those tree species.
The age structure of Picea mariana was nothomogenous in the present study area. To
clarify the determinants on the forest
development, we have a plan to monitor the
relationships between seedling establishment andvarious environmental factors. The most ofenvironmental factors that are possible
determinants on plant community recovery havebeen measured by the members in this project,e.g., soil temperature, albedo, microtopography,
micro-climate, soil profile and ground surface
stability. Those environmental factors, such as
direct solar radiation, albedo and snow-coverperiod, interact with the plant communities (Liuet al. 2005).
Future plans
Based on the present results, we have a plan tomonitor the following five subjects in 2006 and2007. 1) plant community structures in theplots and quadrats, 2) safe sites for seedlingestablishment, 3) the effects of Sphagnum mat on
the growth of seedling and sapling, and 4)
canopy development, by fish-eye photos, 5)
temporal changes in seed immigration, andseedling establishment. The other measurements
described above well be conducted, pro re nata.
We believe that those investigations canclarify plant community-climate interactions
with micro-and macro-scaled, spatio-temporalchanges not only in boreal forests but also invarious ecosystems after disturbances.
Acknowledgements
We thank all members of this research projectand IARC, UAF, who served us various supports,
Terry Chapin and his collaborators for usefuladvice and help, and Shu-ko Nishiyama for her
kindness.
References
Bonan, G.B. & Shugart, H.H. 1989. Environmental
factors and ecological processes in boreal forests.
Annual Review of Ecology and Systematics 20: 1-28.
Camill, P. 2005. Permasfrost thaw accelerates in boreal
peatlands during late-20th century climate warming.
Climatic Change 68: 135-152.
Dale, V.H., Joyce, L.A., McNulty, S., Neilson, R.P.,
Ayres, M.P., Flannigan, M.D., Hanson, P.J., Irland,
L.C., Lugo, A.E., Peterson, C.J., Simberloff, D.,
Swanson, F.J., Stocks, B.J. & Wotton, B.M. 2001.
Climatechange and forest disturbances. BioScience
51: 723-734.
Engelmark, O. 1999. Boreal forest disturbances. In:
Walker, L.R. (ed.). Ecosystems of the world 16:

p. 9

Ecosystems of disturbed
Amsterdam. pp. 161-186.

ground.

Elsevier,

Frazer, G.W., Canham, C.D. & Lertzman, K.P. 1999.
Gap Light Analyzer (GLA), version 2.0: Imaging
software to extract canopy structure and gap lighttransmission from true-colour fisheye photographs,
users manual and program documentation. Simon
Fraser University, Burnaby, British Columbia, andthe Institute of Ecosystem Studies, Millbrook, NewYork.
Hinzman, L.D., Bettez, N.D., Bolton, W.R., Chapin, F.S.,
Dyurgerov, M.B. Fastie, C.L., Griffith, B., Hollister,R.D., Hope, A., Huntington, H.P., Jensen, A.M., Jia,
G.J., Jorgenson, T., Kane, D.L., Klein, ,D.R., Kofinas,
G., Lynch, A.H., Lloyd, A.H., McGuire, A.D., Nelson,
F.E., Oechel, W.C., Osterkamp, T.E., Racine, C.H.,
Romanovsky, V.E., Stone, R.S., Stow, D.A., Sturum,M., Tweedie, C.E., Vourlitis, G.L., Walker, M.D.,
Walker, D.A., Webber, P.J., Welker, J.M., Winker,
K.S. & Yoshikawa, K. 2005. Evidence andimplications of recent climate change in northern
Alaska and other arctic regions. Climatic Chagne 72:
251-298.
Johnson, E.A. 1992. Fire and vegetation dynamics:
Studies from the North American boreal forest.
Cambridge University Press, New York.
Johnstone, J.F., Chapin III, F.S., Foote, J., Kemmett, S.,
Price, K. & Viereck, L. 2004. Decadal observationsof tree regeneration following fire in boreal forest.
Canadian Journal of Forest Research 34: 267-273.
Kielland, K., Barnett, B. & Schell, D. 1998.
Intraseasonal variation in the #15N signature of taiga
trees and shrubs. Canadian Journal of Forest
Research 28: 485-488.
Keane, R.E, Gary, G.J., Davies, I.D., Flannigan, M.D.,
Gardner, R.H., Lavorel, S.L., Lenihan, J.M., Li, C, &Rupp, T.S. 2004. A classification of landscape firesuccession models: spatial simulations of fire andvegetation dynamics. Ecological Modelling 179: 327.
Kushida, K., Kim Y., Tanaka, N. & Fukuda, M. 2004.
Remote sensing of net ecosystem productivity basedon component spectrum and soil respiration
observation in a boreal forest, interior Alaska. Journalof Geographical Research D 109: doi 10.
1029/2003JD 003858.
Lecomte, N., Simard, M., Bergeron, Y., Larouche, A.,
Asnong, H. & Richard, P.J.H. 2005. Effects of fireseverity and initial tree composition on understorey
vegetation dynamics in a boreal landscape inferredfrom chronosequence and paleoecological data.
Journal of Vegetation Science 16: 665-674.
Liu, H., Randerson, J.T., Lindfors, J. & Chapin III, F.S.

2005. Changes in the surface energy budget after firein boreal ecosystems of interior Alaska: An annual
perspective. Journal of Geophysical Research 110:doi 10.1029/2004JD005158.
Ping, C.L., Michaelson, G.J., Packee, E.C., Stiles, C.A.,
Swanson, D.K. & Yoshikawa, K. 2005. Soil catena
sequences and fire ecology in the boreal forest of
Alaska. Soil Science Society of America Journal 69:
1761-1772.
Reich, P.B., Peterson, W., Wedin, D.A. & Wrage, K.
2001. Fire and vegetation effects on productivity andnitrogen cycling across a forest-grassland continuum.
Ecology 82: 1703-1719.
van Cleve, K., Chapin III, F.S., Flanagan, P.W., Viereck,
L.A. & Dyrness, C.T. 1986. Forest ecosystems in the
Alaskan taiga. Springer-Verlag, New York.
Wang, C., Bond-Lamberty, B. & Gower, S.T. 2003.
Carbon distribution of a wel-and poorly-drained
black spruce fire chronosequence. Global Change
Biology 9: 1066-1079.
Whigham, D.F. 2004. Ecology of woodland herbs intemperate deciduous forests. Annual Review of
Ecology, Evolution and Systematics 35: 583-621.
Yoshikawa, K., Bolton, W.R., Romanovsky, V.E.,
Fukuda, M. & Hinzman, L.D. 2002. Impacts ofwildfire on the permafrost in the boreal forests ofInterior Alaska. Journal of Geophysical Research 107,
8148, doi:10.1029/2001JD000438.
Zar, J.H. 1999. Biostatistical analysis (4th ed.). PrenticeHall, Englewood Cliffs, NJ.