Forest Ecology and Management 250 (2007) 89–95
www.elsevier.com/locate/foreco
Fire history and tree species composition in managed Picea abies
stands in southern Finland: Implications for restoration
Tuomo Henrik Wallenius a,*, Saara Lilja b, Timo Kuuluvainen b
a
Finnish Forest Research Institute, Kolari Research Unit, Muoniontie 21, FI-95900 Kolari, Finland
b
Department of Forest Ecology, PL 27, FIN-00014 University of Helsinki, Finland
Abstract
We studied the fire history of 24 managed Picea abies-dominated stands in southern Finland using dendrochronological dating of fire scars in
old stumps. Forests in the study area have been heavily utilized in many ways for centuries for swidden cultivation, tar burning, forest pasturage and
pasture burning. Old charred stumps of Pinus sylvestris were found in every stand although in nine of them the stumps were too decayed to provide
a sample that could be dated. In the 17th and 18th centuries, forests burned at intervals of ca. 50 years on average. The last fires in the study plots
occurred in the latter half of the 19th century. Based on the presence of the old Pinus stumps, past frequent fires and historical documents, it can be
judged that forests were Pinus-dominated in the 17th and 18th centuries. Around the middle of the 19th century a gap occurred in the annual tree
ring chronologies of all study plots. This suggests that large coniferous trees were absent at that time. The currently dominating Picea populations
regenerated at the beginning of the 20th century. Our results demonstrate that in an area where human impact on forests has been variable, pervasive
and long-lasting, the goal of forest restoration can be very different depending on the choice of reference period. We conclude that for defining
restoration goals, knowledge of local forest history is needed.
# 2007 Elsevier B.V. All rights reserved.
Keywords: Charred stumps; Forest fire; Human influence; Forest structure; Norway spruce; Prescribed burning
1. Introduction
As a response to the quest for multi-purpose use of forests
and conservation of biodiversity, several approaches for
restoration and more ecological forest management have been
proposed (Lindenmayer and Franklin, 2002; Stanturf and
Madsen, 2005). The principle behind many of these approaches
is that in order to prevent losses of biodiversity, human actions
in forests should mimic natural disturbances (Bergeron et al.,
2002; Kuuluvainen, 2002). Since in the boreal forest, fires are
suggested to be the most important natural disturbance, one
popular idea is to use the past occurrence and effects of forest
fires as a natural range of variability template for forest
management and restoration (Angelstam, 1998; Landres et al.,
1999; Granström, 2001; Bergeron et al., 2002; Kuuluvainen
et al., 2005).
In the past, forest fires have been frequent over most of
Fennoscandia, and stands have usually burned at intervals from
* Corresponding author. Tel.: +358 10 211 35 38.
E-mail address: Tuomo.Wallenius@Metla.fi (T.H. Wallenius).
0378-1127/$ – see front matter # 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.foreco.2007.03.016
ca. 50 to 100 years (Zackrisson, 1977; Niklasson and
Granström, 2000; Wallenius et al., 2004). The shortest fire
intervals have been recorded in southern Sweden, where before
the 1770s forests burned every 20 years on average (Niklasson
and Drakenberg, 2001). However, in P. abies (L.) Karst.dominated forests, and in northern areas in general, fires have
been rare and fire cycles can range up to a few hundred years
(Engelmark, 1984; Wallenius et al., 2005).
In southern and central Fennoscandia, human activity has
strongly affected past fire frequencies and forest structures
(Wallenius et al., 2004; Groven and Niklasson, 2005). During
the most intensive swidden cultivation period (ca. 1500–1850),
frequent forest fires increased the proportion of fire tolerant P.
sylvestris L. and decreased the fire intolerant Picea (Pitkänen
et al., 1999). At present fires are very rare in Fennoscandia
because of more than a century of pervasive forest management
and related efficient fire prevention. Due to the lack of fires, late
successional species, such as Picea, have again gained ground
from early successional Pinus, Betula and Populus (Niklasson
and Drakenberg, 2001; Kouki et al., 2004). This change in tree
species composition has also been observed in nature
conservation areas (Haapanen and Siitonen, 1978; Bradshaw,
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T.H. Wallenius et al. / Forest Ecology and Management 250 (2007) 89–95
1993; Lilja and Kuuluvainen, 2005). Similar species compositional shifts in the absence of fire have been reported from
unmanaged forests in North America (Minnich et al., 1995;
Lesieur et al., 2002).
Another important reason for changes in tree species
composition was past selective cutting, which concentrated on
large-diameter Pinus trees (Sarvas, 1944). Thus, particularly
managed forests lacked large-diameter trees, which are a
characteristic feature of near-natural forests (Linder and
Östlund, 1998; Lilja and Kuuluvainen, 2005).
An understanding of historical or natural fire regimes and
stand structure is needed for the use of fire in restoration and
ecologically sustainable forest management. Because fire
frequencies have considerably varied in time and space
between different landscapes and forest types, it is necessary
to acquire local knowledge of the historical fires of each area to
be restored (Angelstam, 1998). In addition, it is important to
estimate the past human influence on fire regimes (Wallenius
et al., 2004, 2005; Groven and Niklasson, 2005).
The first aim of the study was to reconstruct the fire history
of managed P. abies-dominated stands in southern Finland in
the Lammi and Padasjoki municipalities. Secondly, based on
this information and historical records, we make deductions
about the likely past tree species composition and structure of
the stands. Finally, we discuss the implications of our findings
for forest restoration in southern Finland.
2. Material and methods
2.1. Study area
The study was carried out in the Lammi and Padasjoki
municipalities (618190 N, 25860 E) in southern Finland. The
region is located in the southern boreal vegetation zone (Ahti
et al., 1968). The average temperature is about 17 8C in July and
8 8C in January (National Board of Survey, 1987). Yearly
rainfall totals 650 mm on average, most of which precipitates
during summer and autumn. Soils are mostly podzolic soils on
basal tills (National Board of Survey, 1990).
P. abies is the dominating tree species in the landscape,
although mixed forests and P. sylvestris forests are also common.
According to forestry statistics for the Häme-Uusimaa district,
Picea makes about 54%, Pinus 27% and Betula spp. 14% of the
volume of the growing stock (Finnish Forest Research Institute,
2003). In the study area, the proportion of the stands older than 80
years is about 1:4 in the forested area (Korhonen et al., 2000). In
the past, peatlands covered a bit more than 10% of the land area of
the districts, but most of the mires have been drained over the last
50 years (Finnish Forest Research Institute, 2003). At present,
less than 5% of the original peatlands is untouched (National
Board of Survey, 1990).
Since WWII the landscape has been shaped by intensive
forestry characterized by standwise clear cutting and even-aged
stands. The forest land is mostly privately owned, and the mean
stand size is only a few hectares. This makes a fragmented
landscape dominated by small even-aged stands of different
ages but younger than 100 years (Kuuluvainen et al., 2005).
The stands used in this study were originally selected for an
experimental study of forest restoration (Lilja et al., 2005).
The samples for the fire history study were collected before
forest restoration treatments (Lilja et al., 2005). Altogether 24
stands were found in forestry databases and selected using the
following criteria: mature managed Picea-dominated stands,
area 1–3 ha, and Vaccinium myrtillus site type (Cajander,
1926). Before acceptance, the stands were visited in the field
to check whether they fulfilled the above criteria. The average
age of the stands was 83 years (range 61–101 years). All the
stands had been managed, but their origin and exact
management history is unknown. All the stands were of the
V. myrtillus site type (MT), but five stands had other
characteristics, for example, a small patch of the more fertile
Oxalis myrtillus site type (OMT) (Cajander, 1926). Although
Picea-dominated the stands, other tree species were present,
including Betula spp., Populus tremula L., and Pinus. In
addition, Sorbus aucuparia L. and Juniperus communis L.
occurred in the sapling layer.
2.2. Past human influence in the region
Southern Finland was inhabited 9000 years ago, soon after
the retreat of ice shields (Huurre, 2001). The first people were
nomadic tribes who survived by hunting, fishing and gathering
berries and mushrooms. The oldest signs of agriculture in
Koski, the neighboring municipality of Lammi, date back to
3400 BP (Tolonen, 1978). In Lammi, swidden cultivation
appears to have started about 1800 BP (Huttunen, 1980). Along
with the increasing human population, agriculture escalated in
the 15th century, and gradually the majority of crops were
cultivated on permanent fields (Tolonen, 1978; Huttunen,
1980). Nevertheless, in the mid 19th century, swidden
cultivation was still very common in Lammi and Padasjoki,
and about half of the forest soils were considered as ‘‘burn
beaten land’’ (Heikinheimo, 1915). After the 1860s swidden
cultivation steeply decreased (Tasanen, 2004).
Other traditional forest uses in the area consisted of forest
pasturage, pasture burning and tar burning (Kaila, 1931a;
Tasanen, 2004). Between 1752 and 1772 a sawmill was
founded in Nystölä (Kaila, 1931b) (Fig. 1). In 1798 a new
sawmill were founded nearby in Arrakoski (Kantonen, 1996).
These sawmills situated only 5–20 km from our study plots.
The timber for the mills was supplied by selective cutting,
which was a widespread method in Finland until the middle of
the 20th century. In the 1850s, due to the intensive use of the
forests, large areas in southern Finland including the Lammi
and Padasjoki municipalities suffered from a lack of timber
(Gyldén, 1850).
2.3. Stand structure and fire history
In the summer of 2001, tree species composition and stand
structure were measured in a randomly located rectangular
(20 m 40 m) plot in each 1–3 ha study stand. The height of
the trees and the diameter at breast height (for trees with height
>2 m) were recorded. In addition, from a 5-m buffer zone
T.H. Wallenius et al. / Forest Ecology and Management 250 (2007) 89–95
91
Fig. 1. The study area was located in the southern boreal zone in the Lammi and Padasjoki municipalities. The right-hand figure shows the study plots and dated fire
years. The locations of the old sawmills in the 18th century in Arrakoski and Nyystölä are also marked.
surrounding the subplots, we measured the height and diameter
of the living trees (dbh > 10 cm). The average age of the
dominant tree cohort was acquired from the forestry databases
of different landowners.
The examination of past fires was based on finding firescarred trees from the study plots and their immediate
neighborhoods. The aim of the sampling was to reconstruct
a fire chronology that is as long as possible. Fire scars were only
found in old partly decayed stumps; fire scars were also sought
in living trees, but none were found. All fire-scarred stumps, if
they were not too decayed, were sampled. In addition, a few
stumps without fire scars were sampled in order to get longer
tree ring chronologies.
Altogether 39 tree stumps were sampled in 18 study plots.
Samples were dated by dendrochronological methods. These
included the polishing of the tree disks and the final preparation
of the surface with a scalpel. Zinc paste was used for better
visibility of the annual rings. The widths of the annual rings
were measured, and the acquired annual ring sequence was
dated using COFECHA software and the master chronology of
Helama et al. (2005).
For the examination of the fire history, the proportion of
burnt areas (computed as a percentage of the study area) and fire
cycle (number of years needed to burn an area equal to the study
area) were reconstructed for the 17th and 18th centuries, which
was the period with good sample coverage. We determined that
a stand was burned if it had at least one charred stump with one
or more fire scars. For each fire event, the burnt area was
determined as the ratio of the number of burnt study plots to the
number of unburnt plots. Only those study plots where the
annual ring chronology of the plot extended to the year in
question were considered.
3. Results
The average age of the dominating Picea cohorts in the study
stands was 83 years, but as the two samples taken from living
Pinus show, the oldest trees could be considerably older
(Fig. 3). Nonetheless, there seems to be a gap in the year ring
chronologies of at least a few decades between the dated old
stumps of Pinus and the present day Picea forest. The volume
of the Picea-dominated stands was on average 220 m3/ha
(range 171–293 m3/ha). The proportion of deciduous was on
average 3.2 m3 (1.5%; range 0–14 m3/ha).
Although the forests in the region as well as the selected
stands are currently dominated by Picea (Fig. 2), it appears that
in the past the tree species composition has been more Pinusdominated. This can be deduced from the fact that there were
Fig. 2. Average volume (m3/ha) of different tree species in the study plots
before experimental burning and cutting in 2001. Error bars are standard
deviations.
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T.H. Wallenius et al. / Forest Ecology and Management 250 (2007) 89–95
Fig. 3. Tree ring and fire chronologies of different study plots sorted by the first year ring. Black squares denote dated fires on Pinus stumps. The figure is produced
with the help of the FHX2 program (Grissino-Mayer, 1995).
old charred stumps of Pinus in every study plot, although most
of the stumps were too decayed and fragmented to allow
dendrochronological dating. In some of the stands with charred
Pinus stumps, no living Pinus were present. Datable wood
samples from old stumps could be found only in 15 plots
(Fig. 3). It was inferred from cut marks and the level end of the
stumps that many of them were from the period of selective
cutting.
Cross-dated year ring chronologies extended from the year
1439 to the present (Fig. 3). The first dated fire occurred in 1468
and the last in 1838. Altogether 48 different fire years were
dated. Relatively good coverage of samples only stretched from
the beginning of the 17th century to the end of the 18th century.
Although many of the plots were close to each other, there were
only a few common fire years (Fig. 1). This indicates that fires
have been mostly relatively small in the area during the last
400–500 years.
The last year rings of most of the dated stumps were charred
indicating that there had been fires after the death of the trees. It
appears that the last fires in the study plots occurred in the latter
half of the 19th century (Fig. 3). During the period 1600–1800
the study plots burned on average four times (Fig. 4),
corresponding to a fire cycle of 50 years. However, between
1650 and 1700 the studied forests burned at intervals of about
30 years on average.
4. Discussion
Fig. 4. Cumulative area burnt as a percentage of the total study area in the
period 1600–1800.
In the intensively managed forests of southern Finland,
forest restoration has been suggested as a means to protect
biodiversity and improve the sustainability of forest management (Kuuluvainen et al., 2005; Lilja et al., 2005). The studied
mature Picea-dominated stands were typical managed forests,
with low structural complexity, scarcity of dead wood and
almost monodominant species composition (Lilja et al., 2005).
The rather short fire cycles that we found (Fig. 4) are similar
to documented past fire cycles in Pinus-dominated forests in
central Finland and northern Sweden, where fires have occurred
at intervals of 30–60 years during the period 1600–1800
(Zackrisson, 1977; Lehtonen et al., 1996). Our study stands
T.H. Wallenius et al. / Forest Ecology and Management 250 (2007) 89–95
were currently dominated by Picea. However, it can be deduced
from the short fire cycles in the 17th and 18th centuries, and
from the presence of old Pinus stumps, that at that time the
studied stands were not dominated by Picea but rather by Pinus
and deciduous trees.
Picea is known to usually die in fires, and thus short fire cycles
favored thick-barked Pinus and fast-growing, well-dispersing
deciduous trees over Pinus (Cajander, 1916; Pitkänen et al.,
1999). The short fire cycles in the past also promoted the
regeneration and spread of Pinus-dominated forests to more
fertile stands previously dominated by Picea (Cajander, 1916).
After the cessation of fires in the latter half of the 19th century,
Picea thrived better than Pinus because Picea is a stronger
competitor, especially in nutrient rich habitats. In addition, the
widespread industrial selective cutting of big Pinus at the turn of
the 19th and 20th centuries probably contributed to the increase
in the proportion of Picea (Sarvas, 1944).
Other evidence also supports this change in forest
composition. Forest and vegetation inventories carried out in
the latter half of the 19th century confirm that the forests of the
Lammi–Padasjoki region were Pinus-dominated (Leopold,
1879; Montell, 1879). In addition, palaeoecological pollen
studies from lake sediments 20 km to the south of our study
sites have shown that Picea populations increased at the
beginning of the 20th century (Tolonen, 1978; Huttunen, 1980).
Before that the abundance of Picea was low for centuries
because of frequent fires. The increase of Picea was made
possible by the decrease in the number of fires as well as in
annually burnt areas since the mid 19th century (Fig. 3).
The decrease in fires is a common and well-documented
phenomenon in Fennoscandia and in large areas in central
North America. Over most of Finland and Sweden, this
decrease occurred between 1860 and 1890 (Kohh, 1975;
Zackrisson, 1977; Lehtonen et al., 1996). However, in southern
Scandinavia and in southwestern Finland, fires had already
obviously stopped a century earlier, between 1750 and 1770
(Tolonen, 1985; Niklasson and Drakenberg, 2001; Groven and
Niklasson, 2005).
In the 19th century, foresters considered the most important
reasons for forest fires to be people who burned the forest on
purpose, e.g. pasture burning, or by accident when fires escaped
from swidden cultivation, smoldering campfires, etc. (Gyldén,
1853; von Berg, 1859; Sargent, 1884; Blomqvist, 1888). An
important reason for the decrease in fires was probably that with
the onset of the sawmill industry, timber became a valuable
resource (Kohh, 1975; Massa, 1994), and fire was therefore
handled more carefully than before. This took place
concomitantly with the establishment of forest administration
and the forest ranger institution, which started to control the use
of forests in the middle of the 19th century (Heikinheimo, 1915;
Zackrisson, 1977; Ruuttula-Vasari, 2004).
Almost all annual ring chronologies of the sampled Pinus
ended by the middle of the 19th century, and many of the last
rings were dated before the end of the 18th century (Fig. 3). The
present Picea forests regenerated at the beginning of the 20th
century. This suggests that there were only a few large
coniferous trees in the stands in the middle of the 19th century.
93
Accordingly, the forestry map of Gyldén (1850) indicates that
the Lammi and Padasjoki communalities suffered from a lack
of large timber, and in some areas even small diameter fire
wood was limited. Moreover, the pollen analyses from nearby
lakes suggest that the landscape in Lammi and Koski was
almost treeless at the turn of the 18th and 19th centuries
(Tolonen, 1978; Huttunen, 1980). This situation was also
reported by some contemporaries, who were horrified by the
devastation of forests in southern Finland (von Berg, 1859).
It is obvious that in past centuries the forests of the region
were heavily utilized by people, often with little or no
consideration of sustainability. Swidden cultivation, tar
burning, forest pasturage and pasture burning have directly,
or indirectly by increasing the number of fires, drastically
affected the forests, structure and composition. Finally, it is
likely that since the end of the 18th century the two small
sawmills, within 10 km of the nearest study plots, have
consumed large quantities of good quality timber from the area.
These human actions in concert apparently are the reason for
the observed decrease in the coniferous forest cover.
5. Implications for forest restoration
In Finland, the goal of forest restoration is traditionally
defined as the rehabilitation of natural structures, processes and
species of forest ecosystems that have been biologically
impoverished by human utilization (Working Group, 2003;
Kuuluvainen et al., 2005). This definition is clear, but what is
natural can be problematic to define in areas of long-lasting
human influence (Lilja and Kuuluvainen, 2005). In our study
area, the current managed forest dominated by Picea differed
considerably from the more open forest dominated by Pinus
and the deciduous trees that prevailed in the area in the 17th–
19th centuries (Leopold, 1879; Montell, 1879; Huttunen,
1980). However, at that time the forest was also far from any
natural state because forest fires ignited by humans were
frequent and forests were heavily utilized in many ways. Thus,
it was a culturally modified forest. Furthermore, it is known
from previous studies that some thousands of years back into
the past, the forest had very different characteristics, with less
human impact and fires, and mixed Picea–Pinus–Betula forests
characterized by old trees (Tolonen, 1978; Huttunen, 1980;
Kuuluvainen, 2002; Pennanen, 2002).
The high variation in past fire cycles and forest structures
through time, reflecting different types of human impact, makes
it difficult to apply the often suggested natural range of variability
approach in restoration and management (Landres et al., 1999).
For example, if we take the forest structures and fire regimes that
prevailed in southern Finland in the 17th and 18th centuries as a
reference for restoration, our goal is a forest state that was
strongly culturally modified. However, recreating a historical
forest would be difficult as this would require prescribed burn
intervals of 30–50 years. Moreover, prescribed burning alone
would probably not be enough to restore the culturally modified
forests of the 17th and 18th centuries, because widespread forest
pasturage also affected the structure and species composition of
the forests in the past (Helander, 1949).
94
T.H. Wallenius et al. / Forest Ecology and Management 250 (2007) 89–95
We conclude that for defining restoration goals, knowledge
of local forest history is necessary, although setting restoration
goals is finally a question of values and policy. However, there
is no single true reference point in the past that should be
selected as a goal for restoration, but a pragmatic goal could be
to rehabilitate important historical and natural structures that
sustain biodiversity, including important landscape characteristics such as forest age structure (Pennanen, 2002). Restoration
can include rehabilitating both cultural features, familiar to the
conservation of habitats related to traditional agriculture, and
more natural forest states.
Acknowledgements
We would like to thank Hanna Karttunen for her assistance
in the field. The Emil Aaltonen Foundation, the Maj and Tor
Nestling Foundation and the Academy of Finland financed the
study.
References
Ahti, T., Hämet-Ahti, L., Jalas, J., 1968. Vegetation zones and their sections in
northwestern Europe. Annu. Bot. Fenn. 5, 169–211.
Angelstam, P., 1998. Maintaining and restoring biodiversity in European boreal
forests by developing natural disturbance regimes. J. Veg. Sci. 9, 593–602.
Bergeron, Y., Leduc, A., Harvey, B.D., Gauthier, S., 2002. Natural fire regime: a
guide for sustainable management of the Canadian boreal forest. Silva Fenn.
36, 81–95.
Blomqvist, A.G., 1888. Kulowalkeasta. Simeliuksen perillisten osakeyhtiön
kirjapaino, Helsinki (in Finnish).
Bradshaw, R.H.W., 1993. Tree species dynamics and disturbance in three
Swedish boreal forest stands during the last two thousand years. J. Veg.
Sci. 4, 759–764.
Cajander, A.K., 1916. Metsänhoidon perusteet I. Kasvibiologian ja kasvimaantieteen pääpiirteet. Porvoo (in Finnish).
Cajander, A.K., 1926. The theory of forest types. Acta For. Fenn. 29, 1–108.
Engelmark, O., 1984. Forest fires in the Muddus National Park (northern
Sweden) during the past 600 years. Can. J. Bot. 62, 893–898.
Finnish Forest Research Institute, 2003. Finnish Statistical Yearbook of Forestry 2003. Vammalen kirjapaino Oy, Vammala (in Finnish with English
summary).
Granström, A., 2001. Fire management for biodiversity in the European boreal
forest. Scand. J. For. Res. 16 (Suppl. 3), 62–69.
Grissino-Mayer, H.D., 1995. Tree-ring reconstructions of climate and fire
history at El Malpais National Monument, New Mexico. Ph.D. Dissertation.
University of Arizona, Tucson.
Groven, R., Niklasson, M., 2005. Anthropogenic impact on past and present fire
regimes in a boreal forest landscape of southeastern Norway. Can. J. For.
Res. 35, 2719–2726.
Gyldén, C.W., 1850. Karta öfver Finland utvisande skogstillgångarna i landets
särskilda delar år 1850. Available on line at: http://www.tiedekirjasto.
helsinki.fi/digi/1850Gylden.html (in Swedish).
Gyldén, C.W., 1853. Handledning för skogshushållare i Finland: med tabeller,
en planch och en skogskarta. H. C. Friis, Helsinki. Available on line at:
http://www.tiedekirjasto.helsinki.fi:70/dspace/bitstream/1975/414/1/
handledning.pdf (in Swedish).
Haapanen, A., Siitonen, P., 1978. Kulojen esiintyminen Ulvinsalon luonnonpuistossa. Silva Fenn. 12 (3), 187–200.
Heikinheimo, O., 1915. Kaskiviljelyksen vaikutus Suomen metsiin. Acta For.
Fenn. 4, 1–264. (in Finnish).
Helama, S., Lindholm, M., Merilainen, J., Timonen, M., Eronen, M., 2005.
Multicentennial ring-width chronologies of Scots pine along a north-south
gradient across Finland. Tree-ring Res. 61 (1), 21–32.
Helander, B., 1949. Suomen metsätalouden historia. WSOY, Helsinki (in
Finnish).
Huttunen, P., 1980. Early land use, especially the slash-and-burn cultivation in
the commune of Lammi, southern Finland, interpreted mainly using pollen
and charcoal analyses. Acta Bot. Fenn. 113, 1–45.
Huurre, M., 2001. Kivikauden Suomi. Otavan Kirjapaino, Keuruu (in Finnish).
Kaila, E.E., 1931a. Tervanpolton leviäminen Suomessa 1700-luvun puolimaissa. Silva Fenn. 21, 1–38 (in Finnish with English summary).
Kaila, E.E., 1931b. Pohjanmaa ja meri 1600-ja 1700-luvuilla: talousmaantieteellis-historiallinen tutkimus. Suomalaisen kirjallisuuden seuran kirjapaino, Helsinki (in Finnish with German summary).
Kantonen, T., 1996. Satakunta sahaa Suomessa: kulttuurihistoriallisesti merkittäviä saharakennuksia ja -ympäristöjä. Museovirasto, Helsinki (in Finnish).
Kohh, E., 1975. Studier över skogsbränder och skenhälla i älvdalsskogarna.
Sveriges skogsvårdsförbunds tidskrift 73, 299–336 (in Swedish with English summary).
Korhonen, K.T., Tomppo, E., Henttonen, H., Ihalainen, A., Tonteri, T., 2000.
Hämeen- Uudenmaan metsäkeskuksen alueen metsävarat 1965–99. Metsätieteen aikakausikirja 3B, 489–566 (in Finnish).
Kouki, J., Arnold, K., Martikainen, P., 2004. Long-term persistence of aspen – a
key host for many threatened species – is endangered in old-growth
conservation areas in Finland. J. Nat. Conserv. 12, 41–52.
Kuuluvainen, T., 2002. Natural variability of forests as a reference for restoring
and managing biological diversity in boreal Fennoscandia. Silva Fenn. 36,
97–125.
Kuuluvainen, T., Tukia, H., Aapala, K., 2005. Ecological restoration of forested
ecosystems in Finland. In: Stanturf, J.A., Madsen, P. (Eds.), Restoration of
Boreal and Temperate Forests. CRC Press, Boca Raton, pp. 285–298.
Landres, P.B., Morgan, P., Swanson, F.J., 1999. Overview of the use of natural
variability concepts in managing ecological systems. Ecol. Appl. 9, 1179–
1188.
Lehtonen, H., Huttunen, P., Zetterbreg, P., 1996. Influence of man on forest fire
frequency in North Karelia, Finland, as evidenced by fire scars on Scots
pines. Annu. Bot. Fenn. 33, 257–263.
Leopold, C., 1879. Anteckningar öfver vegetationen i Sahalahti, Kuhmalahti
och Luopiois kapeller af Södra Tavastland. Meddelanden af Societatis Pro
Fauna et Flora Fennica 5, 81–130. (in Swedish).
Lesieur, D., Gauthier, S., Bergeron, Y., 2002. Fire frequency and vegetation
dynamics for the south-central boreal forest of Quebec, Canada. Can. J. For.
Res. 32, 1996–2009.
Lilja, S., Kuuluvainen, T., 2005. Stand structural characteristics of old Pinus
sylvestris-dominated forests along a geographic and human influence
gradient in boreal Fennoscandia. Silva Fenn. 39, 407–428.
Lilja, S., de Chantal, M., Kuuluvainen, T., Vanha-majamaa, I., Puttonen, P.,
2005. Restoring natural characteristics in managed Norway spruce [Picea
abies (L.) Karst.] stands with partial cutting, dead wood creation and fire:
immediate treatment effects. Scand. J. For. Res. 20 (Suppl. 6), 68–78.
Lindenmayer, D.B., Franklin, J.F., 2002. Conserving Forest Biodiversity. A
Comprehensive Multiscaled Approach. Island Press, Washington.
Linder, P., Östlund, L., 1998. Structural changes in three mid-boreal Swedish
forest landscapes, 1885–1996. Biol. Conserv. 85, 9–19.
Massa, I., 1994. Pohjoinen luonnon valloitus. Gaudeamus Kirja, Tammer-Paino
OY, Tampere (in Finnish).
Minnich, R.A., Barbour, M.G., Burk, J.H., Fernau, R.F., 1995. Sixty years of
change in Californian conifer forests of the San Bernardino mountains.
Conserv. Biol. 9, 902–914.
Montell, R. (Ed.), 1879. Talouskirjoja Hokajärven metsälohosta Evon kruununpuistossa. Finska Forstföreningens Meddelanden 1, 99–139 (in Finnish).
National Board of Survey, Geographical Society of Finland, 1987. Atlas of
Finland, Climate. Folio 131, pp. 1–32 (in Finnish).
National Board of Survey, Geographical Society of Finland, 1990. Atlas of
Finland, Geology. Folio 123, pp. 1–8 (in Finnish).
Niklasson, M., Drakenberg, B., 2001. A 600-year tree-ring fire history from
Norra Kvills National Park, southern Sweden: implications for conservation
strategies in the hemiboreal zone. Biol. Conserv. 101, 63–71.
Niklasson, M., Granström, A., 2000. Numbers and sizes of fires: long-term
spatially explicit fire history in a Swedish boreal landscape. Ecology 81,
1484–1499.
T.H. Wallenius et al. / Forest Ecology and Management 250 (2007) 89–95
Pennanen, J., 2002. Forest age distribution under mixed-severity fire regimes—
a simulation-based analysis for middle boreal Fennoscandia. Silva Fenn. 36,
213–231.
Pitkänen, A., Lehtonen, H., Huttunen, P., 1999. Comparison of sedimentary
microscopic charcoal particle records in a small lake with dendrochronological data: evidence for the local origin of microscopic charcoal produced by forest fires of low intensity in eastern Finland. Holocene 9, 559–
567.
Ruuttula-Vasari, A., 2004. Herroja on epäiltävä aina—metsäherroja yli kaiken,
Metsähallituksen ja pohjoissuomalaisten kanssakäyminen kruununmetsissä
vuosina 1850–1900. Ph.D. Thesis. University of Oulu, Oulu (in Finnish with
English summary).
Sargent, C., 1884. Report on the Forests of North America (Exclusive of
Mexico). Government Printing Office, Washington.
Sarvas, R., 1944. Tukkipuun harsintojen vaikutus Etelä-Suomen yksityismetsiin. Valtioneuvoston kirjapaino, Helsinki (in Finnish).
Stanturf, J.A., Madsen, P. (Eds.), 2005. Restoration of Boreal and Temperate
Forests. CRC Press, Boca Raton.
Tasanen, T., 2004. Läksi puut ylenemähän Metsien hoidon historia
Suomessa keskiajalta metsäteollisuuden läpimurtoon1870-luvulla. Met-
95
säntutkimus-laitoksen tiedonantoja 920, 1–443 (in Finnish with English
summary).
Tolonen, M., 1978. Palaeoecology of annually laminated sediments in Lake
Ahvenainen, S. Finland. I. Pollen and charcoal analyses and their relation to
human impact. Annu. Bot. Fenn. 15, 177–208.
Tolonen, M., 1985. Palaeoecological record of local fire history from a peat
deposit in SW Finland. Annu. Bot. Fenn. 22, 15–29.
von Berg, E., 1995 (1859). Kertomus Suomenmaan metsistä. Kustannusosakeyhtiö Metsälehti, Helsinki, Finland (in Finnish).
Wallenius, T., Kuuluvainen, T., Vanha-Majamaa, I., 2004. Fire history in
relation to site type and vegetation in Vienansalo wilderness in eastern
Fennoscandia. Russ. Can. J. For. Res. 34, 1400–1409.
Wallenius, T.H., Pitkänen, A., Kuuluvainen, T., Pennanen, J., Karttunen, H.,
2005. Fire history and forest age distribution of an unmanaged Picea abies
dominated landscape. Can. J. For. Res. 35, 1540–1552.
Working Group on Restoration, 2003. Restoration in protected areas: report by
the working group on restoration 2003. Finn. Environ. 618, 1–220 (in
Finnish with English abstract).
Zackrisson, O., 1977. The influence of forest fires in the North Swedish boreal
forest. Oikos 29, 22–32.