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RES E AR C H A R T I C L E Open Access
Buffer strips can pre-empt extinction debt in
boreal streamside habitats
Ville A O Selonen
*
and Janne S Kotiaho
Abstract
Background: Conservation of biological diversity and economical utilization of natural resources form an almost
inevitable confrontation between the two. In practice, however, a balance between the two ought to be found,
and in managed boreal forests, preservation of woodland key habitats is increasingly used strategy to safeguard
biological diversity. According to the Finnish Forests Act, certain Forest Act habitat (FAH) types must be
safeguarded, provided they are clearly distinguishable from their surroundings. Furthermore, once the habitat has
been identified as a FAH, its special characteristics must not be altered. Both of these aspects contain ambiguities
that potentially undermine the practical application of the Act. We designed a replicated sampling study to address
these ambiguities at the most common FAH type, riparian habitat of small boreal streams. As response variables we
used vascular plants and mosses. We asked i) how wide is the FAH around small streams that is distinguishable
from its surrounding and ii) how wide buffe r strip around the FAH is sufficient for long term to preserve the natural
species community composition of the FAH.
Results: We found that an average three meters wide strip around the stream constitutes the distinguishable FAH
and that a minimum of 45 meters wide buffers on both sides of the stream are needed for the species community
composition to remain unaltered.
Conclusions: We conclude that 45 meters wide buffers appear sufficient to safeguard vascular plant and moss
species communities within the FAH, prevent local populations from extinctions and thus pre-empt extinction debt
that would be realised with more narrow buffers. While 45 meters may seem intolerable from the commercial
forestry point of view, anything less than that may be intolerable from the point of view of conservation, and thus
against the idea of sustainable use of natural resources.
Keywords: Conservation, Extinction debt, Forest management, Legislation, Valuable habitat, Woodland key habitat
Background
Conser vation of biological diversity and economical
utilization of natural resources form an almost inevit-
able confrontation between the two. In boreal forests ,
biodiversity and commercial forestry are the key players.
Today, the negative effects of forestry on forest bio-
diversity are axiomatic [1,2], and in many countries
practical mea sures have been initiated to remedy and
overcome these effe ct s. In Fennoscandia and Baltic
countries, one measure that has been taken is to pre-
ser ve the so called woodland key habitats (WKH) in the
commercial forests [3]. WKHs are small habitat patches
with presumably high conser vation value [3] and they
are generally perceived to be a cost-effective tool in con-
ser vation of commercial forest biodiversity. Although
the ecology behind the concept is questioned and criti-
cized [2,4,5], in practice WKHs are widely applied in
Fennoscandia and Baltic countries. There is some vari-
ation among the countries in the details of the defini-
tions and in protection of the WKHs [3], but the
underlying idea in all is to preser ve habitat patches that
are thought to be of value from the standpoint of forest
ecosystems and biodiversity.
In Finland, a Forest Act was passed in 1996, the main
aim of which is to allow sustainable management and
utilization of forests, while simultaneously safeguarding
biodiversity [6]. In the Finnish Forest Act, the concept of
WKH was applied and some habitat types were defined
as Forest Act Habitats (FAH) where demanding, rare
* Correspondence: ville.selonen@jyu.fi
Department of Biological and Environmental Science, University of Jyväskylä,
PO Box 35, 40014, Finland
© 2013 Selonen and Kotiaho; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the
Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Selonen and Kotiaho BMC Ecology 2013, 13:24
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and threatened species are likely to occur [6]. All of these
habitats are terrestrial and the most numerous FAH type
is the riparian habitat of the boreal brooks or rivulets
(small streams) [7]. Riparian habitats are a heterogeneous
mosaic of terrestrial and aquatic habitats, therefore often
harbouring a rich biodiversity [8-10]. Small streams them-
selves and the adjacent riparian habitats appear to be vul-
nerable and their biodiversity is often adversely influenced
by forests management [11,12].
Two important practical details in the Finnish Forest
Act are that first, to qualify as a FAH that must be
protected, the habitat must be clearly distinguishable from
its surroundings [6], and second, once the habitat has been
identified as a FAH, its special characteristics must not be
altered. Both of these details contain ambiguity that poten-
tially undermines the practical application of the Act: what
constitutes clearly distinguishable or special characteristics
and how to ensure that the special characteristics are not
altered. Moreover, no clear guidelines for the delineation
and demarcation exist. The decision about the distinguish-
ability, the definition of special characteristics and the
overall demarcation of the FAH depends on the forest au-
thorities on site, e.g. during the management planning.
The most likely biological aspect that can make a habi-
tat clearly distinguishable from its surroundings for a
human observer is variation in the plant community
composition. In similar line of thought, the special char-
acteristics that must not be altered are the characteris-
tics of the plant community. It is well established that
forest management influences plant community com-
position [13-15]. Therefore, since FAH’s special charac-
teristics must not be altered, unmanaged buffer strips
around the FAHs are of fundamental importance for the
spirit of the Act. Research on edge effects has provided
robust e vidence that communities of the target habitat
will be altered if the buffer strips are not sufficient
[16,17]. More specifically, studies that have focussed on
plant communities of boreal forests emphasize the im-
portance of the width of the buffer strips [18,19], and it
has been stated that if the plant communities of the
streams and the streamside riparian habitats are to be
preserved, sufficient buffer strips are ne cessary [20-22].
Unfortunately, from the practical point of view it is not
enough to state that sufficient buffer strips are needed.
Rather, we need to provide clear guidelines based on
solid empirical evidence for the widths of buffer strips
that constitute sufficient and are likely to be enough to
protect the community composition in the long run.
However, what should be born in mind is that from
society’s p erspective, over buffering may be as undesir-
able a s under buffering since in commercial forests
the management must be e conomically as well a s eco-
logically sustainable and the apparent trade-off is ra-
ther challenging.
From these grounds we designed a study to address
two concrete and practical issues: i) how wide is the For-
est Act Habitat around small streams that is distinguish-
able from its surr ounding and ii) how wide buffer strip
around the stre am is sufficient to preserve the natural
species community composition of the FAH.
Methods
Study sites and sampling design
We established 39 study sites (out of 213 candidate sites)
on riparian FAHs located in mature managed spruce
dominated coniferous forests, in Central Finland within
a 100 kilometre radius of the city of Jyväskylä (62.23°N,
25.74°E). Our design uses space-for-time-substitution.
This method has the advantage that it provides us with
the opportunity to analyse patterns based on a single
field season. At the same time, the disadvantage of the
method is that it relies on the assumption that the sites
are similar to begin with, and that for any given manage-
ment combination the successional trajectories of the
sites would be similar. While the latter is not possible to
control for in a study design, a violation of this assump-
tion would make any patterns due to management more
difficult to observe. As we do observe patterns (see
Results) it is likely tha t this assumption is not badly vio-
lated. The former assumption is easier to control in the
study design and to this end we applied selection criteria
to the study sites to make them as similar as possible:
All selected sites belong to the southern boreal vegeta-
tion zone, and in all sites the forests were mature,
managed and spruce dominated coniferous forests, char-
acterized by deciduous undergrowth. Due to the previ-
ous management history large deciduous trees are rare
and we included in the study only sites in which they
were completely absent. According to the Finnish forest
site type classification [23], the vegetation on the stream-
side was mainly the Oxalis-myrtillus type (OMT, herb-
rich heath forest) with occa sional patches of Myrtillus
(MT) and Ox alis Maianthemum (OMaT) types. In
addition, some peatland vegetation type occurred occa-
sionally, thus the parent mate rial in the soil w a s va ry ing
between the peat and till. All sites were selected to be
non-flooding and topographically homogenous. In
addition, all other habitat factors (e.g. boulders , stand
characteristics and deadwood) were taken into account
and sites were preselected to be as similar as possible
(see Additional file 1: Appendix 1). The edge orientation
was observed and north facing edges were not selected
(see Additional file 1: Appendix 1 and 2). All water
channels were small and narrow (on average of one
meter) streams or rivulet s with regular, year-round flow.
Seven sites were considered a s unmanaged reference
sites, where the nearest clear-cut was located at lea st 80
meters from the focal site. Although these seven sites
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are considered here as unmanaged, their forest mana ge-
ment history apart from the location of the nearest
clear-cut is similar to all other sites. The unmanaged
and managed sites did not differ from e ach othe r in any
of the mea sured habitat characteristics except that the
diameter and height of the trees at unmanaged refer-
ence sites were on average slightly less (differences
were <5cm and <4 meters respe ctively) than those at
the managed sites (Additional file 1: Appendix 1 and 2).
Differences are a result of that unmanaged sites had
higher amount of smaller trees that was n ot been
thinned out yet. Given that the stand ages and in par-
ticular total volumes did not differ, we consider these
statistically significant differences biologically trivial. It
is worth noting that our unmanaged reference sites w ill
be more disturbed than would be pristine sites, had
therebeenanyavailableforthestudy.Thusourresults
pointing to impacts of har vesting on FAH species com-
munities should be considered as minimum estimates.
Among the 32 managed study sites, the distance from
the stream to the clear-cut (i.e. width of the FAH plus
the buffer strip) varied from 0 to 50 meters. The time
since the forest behind the buffer strip was harvested by
clear-cutting varied from 1 to 50 years. All buffer strips
were one-sided and the other side of the stream was
equivalent to unmanaged sites (minimum of 80 meters
to the closest clear-cut). All of the sites were inventoried
during 2003-2004. Each study site consisted of three par-
allel species sampling lines orthogonally from the stream
shoreline, the distance of which were between 10-15 meters
from the other. Each sampling line was divided into
one square meter sampling units. From the shoreline
up to 15 metres each of the sampling units were inven-
toried. After the first 15 meters , the sampling was
conducted every 5 meters to the clear-cut. In each sam-
pling unit, ground layer’s vascular plants (excl. arbores-
cent species) and ground layer ’s mosses (Bryophyta)
were identified to the species and the coverage deter-
mined as percentages. Spe cies crowing distinctly above
the ground layer (e.g. on a boulder or dead wood) were
excluded from the sampling.
How wide is the FAH around small streams that is
distinguishable from its surrounding
The immediate stream side is by Forest Act definition
part of the FAH. Therefore, to empirically determine the
extent or width of the riparian FAH that is distinguish-
able for the surrounding forests, we rearranged our spe-
cies community data of the seven unmanaged site s by
the distance from the stre am and ran an analysis of simi-
larities (ANOSIM) between the distances [24]. ANOSIM
is a non-metric analysis based on dissimilarity measures
and it uses the rank order of dissimilarity values , thus
being analogous to non-metric multidimensional scaling
(NMDS). We performed ANOSIM with vascular plant
and moss species data separately and with a pooled vas-
cular plant and moss species data. This ensures compre-
hensive interpretation of the delineation. In ANOSIM
Bray-Curtis similarity index was used. Bray-Curtis simi-
larity index takes into account the relative abunda nce of
species and, in addition to changes in species identities,
reveals also changes in species community composition
that are due to changes in the relative abundances of
species. Prior to analysis, species data was log
10
-
transformed to downweight the dominant taxa. Species
that occurred only once were excluded from the an alysis.
Significances of similarities between groups were derived
from 10000 permutations. We compared the community
composition of our focal sampling unit bordering the
stream (sampling unit one) to each of the community
compositions of the other sampling units 2-15 meters
from the stream. ANOSIM was performed with PAST
(version 2.08) [25].
How wide buffer strip around the stream is sufficient to
preserve the natural species community composition of
the FAH
The value obtained from the above analysis on the un-
managed sites was used to determine the extent of the
FAH on the managed sites. Sites with a buffer strip less
than the extent of the FAH (3 meters, see Results) were
excluded from the forthcoming analyses. Thus, the final
number of managed sites used in the analyses is 20.
Regression analysis was conduc ted to determine differ-
ences in species richness (i.e. number of species) and
taxonomic diversities [26] between different manage-
ment histories (i.e. width of the buffer strip and time
since harvested). Suitability of variables for analysis was
verified and required transformations conducted. Taxo-
nomic diversity was determined to obtain a variable to
reflect the changes in species composition. Taxonomic
diversity is an index describing distribu tion of abun-
dances and ta xonomic relatedness of species in each of
the studied sites. It is a combination of standard diver-
sity indices and an average relatedness between any two
species chosen at random from the site [26]. Taxonomic
diversity in one sample is Δ ¼
∑∑
i<J
ω
ijx
i
x
j
∑∑
i<j
x
i
x
j
þ∑
i
x
i
x
i
−1
ðÞ
2
, where
the ω
ij
is weight (ω
ij
=0ifi and j are the same species,
ω
ij
= 1 if they are the same genus, ω
ij
= 2 if they are the
same family, etc. accord ing to the des ired taxonomic cat-
egories). The x denotes the abundances of species i and j.
In other words , the mea sure weights species depend-
ing on t heir affinity (i.e. near kinship spe cies are
weighted less). The higher the taxonomic diversity is ,
the more different taxonomic categories sample encom-
passes and more diverse the species assemblage is. The
Selonen and Kotiaho BMC Ecology 2013, 13:24 Page 3 of 10
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suggested advantage of this mea sure is that it attempts
to capture phylogenetic diversity and is more closely
linked to f unctional diversity than the more traditional
diversity indices [26,27]. It is suggested that such phylo-
genetic diversity indices should be used as a biodiversity
metric for predicting and monitoring of biodiversity
changes and threats [28].
To intensify the taxonomic information, vascular plant
and moss species data was specified with family data
according to Hämet-Ahti et al.1998 [29] and Ulvinen
et al. 2002 [30], respectively. In this analysis, the abun-
dance of a certain species is the number of occupied
sampling units in a site. The buffer strip width and time
since harvested were log-transformed (log
10
(1+x)). Spe-
cies richness and the taxonomic diversity were deter-
mined with PAST (version 2.08) [25] and all statistical
analyses were carried out with PASW 18 (SPSS Inc.).
Analysis of similarities (ANOSIM) was used to deter-
mine the minimum buffer width for no change in com-
munity composition in the FAH. First we divided
managed sites into six groups (every fifth meter 1-5,
6-10 etc.), and then compared the species community
composition of each of the managed groups to unman-
aged sites. The buffer width from where the species
community composition in the managed sites no longer
differed from that of the unmanaged sites indicates the
minimum buffer strip width for maintaining the com-
munity composition.
It can be considered that the environment in which a
species is most abundant is close to the species environ-
mental optimum [31,32]. The estimate of the optimum
environment can be calculated a s a weighted average of
the environmental variable values of the sites in which
the species is present [32]. The weighted average esti-
mate of the optimum is
~
u
k
¼
∑
n
i¼1
x
ik
y
i
∑
n
i¼1
x
ik
, where x is the
abundance of species k in sample i and y is the empirical
environmental value in sample i (e.g. buffer width or
time since harvested). In the present study, this method
was used to estimate the optimum buffer width and the
optimum time since harvested for species in the FAH.
Estimate was calculated for species observed in five or
more sites. In addit ion, we used the method in the un-
managed sites to estimate the “natural” optimum dis-
tance of the species from the stream. Optimum values
were determined with PAST (version 2.08) [25].
Results
How wide is the FAH around small streams that is
distinguishable from its surrounding
In vascular plants, the community compositions of the
sampling units 5-15 were significantly different from our
focal sampling unit (Table 1). This means that the habi-
tat strip of about 0-4 meters from the stream is
distinguishable from the surrounding forest. In mosses
the corresponding distinguishable habitat strip was 0-2
meters and in the combined data of vascular plants and
mosses it was 0-3 meters from the stream (Table 1). Nat-
urally, each species has its own characteristic ecological
requirements. Therefore, based on species specific abun-
dance, we have tabulated the natural optimal distance of
vascular plant and moss species from the stream in
Additional file 1: Appendix 3 and 4 respectively.
How wide buffer strip around the stream is sufficient to
preserve the natural species community composition of
the FAH
In the previous analysis, the distinguishable habitat strip
was determined to extend 3 meters from the stream.
From now on, we only analyse diversity in this distin-
guishable habitat strip and call it the FAH, the special
characteristics of which must not be altered by forest
management. After excluding sites with the buffer strip
less than the width of the FAH, the final number of
managed sites included into the analysis was 20. Total
number of vascular plant and moss species found in the
whole study area were 130 and 85, respectively. The
total number of vascular plant and moss species found
in the FAH were 108 and 69, respectively and the num-
ber of unique vascular plant and moss species for FAH
were 19 and 21 respectively. The total number of vascu-
lar plant and moss species found outside the FAH were
Table 1 Analysis of community similarities (ANOSIM)
between the first sampling unit (1 meter from the
stream) and the other sampling units 2–15 meters from
the stream
Vascular plants Mosses Pooled data
Comparison R p R p R p
1 - 2 -0.069 0.778 0.050 0.275 -0.066 0.751
1 - 3 0.064 0.244 0.272 0.012 0.086 0.166
1 - 4 0.122 0.072 0.474 0.000 0.271 0.008
1 - 5 0.317 0.002 0.621 0.001 0.460 0.001
1 - 6 0.402 0.001 0.632 0.000 0.518 0.000
1 - 7 0.469 0.002 0.608 0.000 0.502 0.001
1 - 8 0.507 0.001 0.658 0.001 0.528 0.001
1 - 9 0.563 0.001 0.689 0.001 0.559 0.001
1 - 10 0.599 0.001 0.703 0.001 0.583 0.001
1 - 11 0.610 0.001 0.693 0.001 0.600 0.001
1 - 12 0.655 0.001 0.739 0.000 0.631 0.001
1 - 13 0.645 0.001 0.772 0.001 0.640 0.001
1 - 14 0.656 0.001 0.708 0.001 0.635 0.000
1 - 15 0.661 0.000 0.770 0.001 0.651 0.000
Data is from the unmanaged reference sites. R values are effect sizes based on
the difference of mean ranks between and within groups [32]. N for all groups
is 7.
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92 and 56, respectively and the number of unique vascu-
lar plant and moss species for outside the FAH were 19
and 9 respectively.
There was an interaction between the width of the
buffer strip and the time since harvested by clear-cutting
on both, the vascular plant species richness and taxo-
nomic divers ity of FAH (Table 2). We have depicted the
interactions in Fig ures 1 and 2, from which one can see
that on a narrow buffer strips both species richness and
taxonomic diversity of vascular plants decline with time,
while on wider buffer strips similar decline does not
occur.
To estimate the minimum buffer width needed to safe-
guard the FAH vascular plant community composition,
we divided the buffer widths into six classes and com-
pared the vascular plant species community of each with
the corresponding communities of unmanaged reference
sites with ANOSIM. FAH community composition dif-
fered from the unmanaged references still with 36 me-
ters wide buffers and the communities were unaltered
only after the buffer strip widths exceeded 45 meters
(Table 3). It is noteworthy that although the sample size
and thus power to observe a signi ficant difference for
the last comparison was small, the effect size R also
decreases ten-fold indicating a real change towards
more similar communities. Vascular plant species bene-
fiting from anthropogenic disturbance were found in
FAHs with narrow buffer strips (see Additional file 1:
Appendix 5). In these species, the smallest weighted
average of buffer widths was 0 meters, i.e. not at all FAH
external buffer (Additional file 1: Appendix 5).
For moss species richness or taxonomic diversity there
were no interaction between the width of the buffer strip
and the time since harvested (Table 2). However, moss
species richness declined with time since harvested,
whereas the taxonomic diversity of mosses increased
with the buffer width (see Table 2 and Figures 3 and 4).
Similar to vascular plants, also moss community compo-
sitions of the FAH differed from the unmanaged refer-
ences still with 36 meters wide buffers and the moss
communities appeared unaltered only after the buffer
strip widths exceeded 45 meters (Table 3). However, in
mosses the effect size does not change much for the last
comparison suggesting that the change in the signifi-
cance is related to the decreased sample size and even
with 45 meters wide buffers the communities may still
have been altered. As with vascular plants, moss species
benefiting from anthropogenic disturbance were found
in the FAH with narrow buffer (see Additional file 1:
Appendix 6). However, in mosses, the smallest weighted
average of buffer widths was 12 meters (Additional file 1:
Appendix 6).
Discussion
Our first objective was to determine how wide is the
Forest Act Habitat (FAH) around small streams that is
distinguishable from its surrounding. Although defining
an average width of streamside riparian habitat or FAH
may be ecologically questionable and undesirable, from
the management point of view such a generalisation is
essential. Despite the importance of the generalization
for management, it may not be stressed too much that
care is needed when such a generalization is executed,
and in practise every delineation has to be done indi-
vidually depending on forests stand structure, vegetation
type and topography of the site. Thus, even if our result
that the FAH was on average 3 meters wide strip along
the small stream is correct, the actual metric value
should be decided on site.
Buffer strips are not mentioned in the Forest Act, but
what is important, is that the Forest Act states that the
characteristics of the FAH may not be altered. Therefore,
to fulfil the statutes of the Act, it is ne cessary that a buf-
fer strip around the 3 meters wide FAH must be left.
From these premises, our second objective was to deter-
mine how wide buffer strip around the stream is needed
to preserve the natural species community composition
of the FAH. We found that vascular plant species rich-
ness and taxonomic diversity were affected by an inter-
action between buffer strip width and time since the
formation of the buffer strip. At narrow buffer strips,
species richness and diversity declined with time but
similar decline did not occur in the wider buffer strips.
In mosses there were no interactions, but the moss spe-
cies richness declined with time since harvested by
clear-cutting and the taxonomic diversity declined with
the declining width of the buffer strip.
The interaction between buffer strip width and time
since harvested on vascular plant species richness and
taxonomic diversity provides an indication of extinction
Table 2 Regression analyses for vascular plant and moss
species richness and taxonomic diversity
R
2
F Sig. Partial η
2
Buffer*Time Plant species 0.489 5.822 0.024 0.202
Plant diversity 0.270 4.427 0.047 0.161
Moss species 0.220 0.918 0.348 0.038
Moss diversity 0.301 2.889 0.103 0.112
Buffer Moss species 0.189 0.598 0.447 0.024
Moss diversity 0.213 6.220 0.020 0.206
Time Moss species 0.189 5.568 0.027 0.188
Moss diversity 0.213 0.051 0.823 0.002
Buffer*Time is the interaction term, i.e. the product term of variables. Buffer
and Time denotes variables buffer width and the time since harvested,
respectively. Plant and moss species denotes species richness (number of
species) and diversities are taxonomic diversities. Values are calculated from
log
10
-transformed data. Species data is from the FAH. Degrees of freedom for
the models are 1, 24.
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Figure 1 Interaction between the width of the buffer strip and time since harvested on vascular plant species richness. Bold line across
the surface represents the 45-meters wide buffer. Vascular plant species data is from the FAH. Buffer strip width and time since harvested are
at log
10
-scale.
Figure 2 Interaction between the width of the buffer strip and time since harvested on taxonomic diversity of vascular plants. Bold line
across the surface represents the 45-meters wide buffer. Vascular plant species data is from the FAH. Buffer strip width and time since harvested
are at log
10
-scale.
Selonen and Kotiaho BMC Ecology 2013, 13:24 Page 6 of 10
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debt [33-35] due to forest management. Although the ef-
fect sizes were at most medium (Table 2), the implica-
tion for the local risk of extinction due to forest
management are not trivial. In our study, the FAH itself
was not directly disturbed by the management, but still,
extinction debt was accrued in the FAH depending on
the distance (i.e. buffer strip width) from the disturb-
ance. Based on figure 1, it appears that with narrow buf-
fer strips it takes approximately 10 years to lose 20% of
vascular plant species and 30 years for a third of the spe-
cies to be lost while similar decline in species richness is
not evident with wider buffers. With taxonomic diversity
(Figure 2) it appears that the decline in FAHs with
narrow buffers may be slower and a clear decline is
observed only 20-30 years after the disturbance. Decline
in taxonomic diversity due to forest management is
distressing because taxonomic diversity inflect the
ecosystem functioning [28,36], and may be as significant
threat to ecosystem services as the much worried cli-
mate change [37].
When we are considering the effects of anthropogenic
disturbance, it must be remembered that ultimately from
the nature conservation perspective, any change on the
species community, a loss or a gain of a species, is un-
desirable. Thus, since the legislation states that character-
istics of the valuable habitats may not be altered, any
alteration due to forest management that can be detected
in the community composition should be considered to
violate the act. Based on our analyses, the sufficient width
for a buffer strip that pre-empts the creation of extinction
debt seems to be around 45 metres. Our sample size for
this particular comparison is small, but it is worth noting
that from the point of view of conservation, the value of
45 meters can be considered a conservative minimum es-
timate. This is because all comparisons with less than 45
meter buffer width resulted in a significant difference be-
tween the communities.
There are obvious economical costs associated with
leaving buffers and thus from the economical point of
view one needs to be careful not to over buffer. Above
we stated that the 45 meters was a conservative mini-
mum estimate from the point of view of conservation.
Thus from the perspective of sustainable forest manage-
ment it should be clear that this is indeed the minimum
that must be left in order to avoid altering the commu-
nity compositions, while it is not clear that buffering
more than 45 meters would not benefit the biodiversity
even more. Ours is not the first study to suggest that at
Table 3 Analysis of community similarity (ANOSIM) of
different buffer width categories between unmanaged
(N
1
) and managed sites (N
2
)
Vascular plants Mosses
Buffer width (metres) N
1
,N
2
RpRp
0 - 5 7, 3 0.758 0.009 0.677 0.008
6 - 10 7, 3 0.651 0.010 0.544 0.008
11 - 15 7, 5 0.488 0.001 0.390 0.008
21 - 25 7, 4 0.442 0.019 0.454 0.011
32 - 36 7, 3 0.540 0.025 0.482 0.009
45 - 50 7, 2 0.058 0.410 0.451 0.084
Species communities are from the FAH.
Figure 3 The effect of time since harvested on moss species richness. Moss species data is from the FAH. Circles and squares denote
managed and unmanaged sites, respectively. Time axis is at log
10
-scale.
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least 45 meters wide buffers should be left but earlier
values of similar magnitude have been suggested [38-41].
The interesting and somewhat natural result of mosses,
the increasing diversity with increasing buffer width, is re-
sult of functional buffering. The wider buffers are able to
safeguard the species diversity of the FAH. Moreover, the
result of decreasing species richness with time is indicat-
ing that due to management actions there are a loss of
species that will occur with a time lag. Species that have
short optimum time since harvesting and wide optimum
buffer strip width are species that are still present just after
the management, but soon disappear in spite of relatively
wide buffers.
We did not observe a clear increase in the vascular plant
species richness after the disturbance, although based on
earlier research such an increase could have been expected
[14,15]. However, some indication of such an effect may
be seen in the figure 1 and 2 if we concentrate on the cor-
ner of the matrix where the buffer strip width is small and
time since harvested short: in both graphs this corner
tends towards higher richness. Moreover, at the FAH we
observed a few pioneer plant species typically found in
clear-cuts (e.g. Epilobium angustifolium) (see Additional
file 1: Appendixes 5 and 6). For example, E. angustifolium
was not present in any of the unmanaged reference sites
but was present on the managed sites. On managed sites,
weighted averages of the buffer width and time since
harvested for occurrences of E. angustifolium in the FAH
was 0 meters and 5 years, respectively.
The smallest average optimum buffer width for moss
species was 9 meters. This species is a pioneer species
Ceratodon purpureus and it is typically found in clear-
cuts. The other common pioneer species Pohlia nutans
is still found from FAH with up to on average 14 meters
wide buffers (Additional file 1: Appendix 6). Overall, oc-
currence of these kinds of pioneer species in the FAH is
evidence for the adjacent disturbance breaking through
the narrow buffer strips. Moreover, although species
richness of mosses did not rise after clear-cutting, it was
the initially species rich stream side habitat that was the
main interest, not the typical forests habitat. This leads
to already higher richness at the outset compared to the
former inland forest orientated studies. Note that the
gradual chan ge from stream side species to clear-cut
species does not necessarily increase species richness,
and ultimately the changes in species community com-
position in time reveals the effects of the disturbance.
In general the species specific responses to buffer width
and time since harvested suggest that some microclimatic
changes have taken place in the FAH. In vascular plants,
Moneses uniflora, typical in moist forests, is found in
FAHs with on average 34 meters wide buffers, but only on
average one year after the harvesting (see Additional file 1:
Appendix 5). Moreover, the moss Sphagnum riparium,a
species which is known to suffer from drainage, is found
on average just one year after harvesting, indicating that it
may really suffer from forest management. The average
buffer width for S. riparium is as much as 34 meters.
Figure 4 The effect of width of buffer strip on the taxonomic diversity of mosses. Moss species data is from the FAH. Circles and squares
denote managed and unmanaged sites, respectively. Buffer width axis is reverse and at log
10
-scale.
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Similarly another moss species, Ptilium crista-castrensis,
which is typically found in moist and shady habitat, is found
only few years after harvesting (see Additional file 1:
Appendix 6). These examples suggest considerable change
in moisture conditions and alteration in run-off properties
in streamside F AH even with relatively wide buffers. Simi-
larly also exposure to sun and wind is likely to increase
evaporation, thus changing ground level moisture and cli-
mate conditions. Thus it is clear that the effects of forest
management can travel far and buffers of at least 45 meters
are needed if we really want to adhere to the statement
(andspirit)oftheForestActthatthecharacteristicsofthe
F AH may not be altered.
Conclusions
Trying to find a one-size-fits-all –buffer strip width as
we did here, is not sensible in ecological sense, simply
because organisms with different ecology will respond
differently. However, at the same time in reality we very
much need to be able to make every day decisions in
our commercial forests about how wide buffe rs to leave.
Therefore, we need to work out practicable guidelines
for forests managers and authorities that unavoidably
overlook some of the ecological detail in the landscape.
Based on our analyses the width of the FAH along the
boreal forest streams (sensu Finnish forest Act) is on
average 3 meters wide. In practice, it will be safer to use
4-meter FAHs based on vascular plant species. However,
as the forest act also demands that the characteristics of
these habitats may not be altered, it should immediately
be obvious that a buffer is needed. Our results indicate
that even if the valuable habitat itself is only a narrow
strip along the stream, to conserve this strip unal tered it
is imperative to leave a minimum of 45 meters wide buf-
fer strip of forest on both sides of the streams. If we
really mean what we have written into the legislation,
anything less than 45 meters buffers around the valuable
habitats will be against the spirit of the act, and against
the idea of sustainable use of natural resources.
Additional file
Additional file 1: Appendix 1. Stand characteristics of studied sites.
Appendix 2. Test statistics between managed and unmanaged reference
sites: i) T-test for equality of habitat and stand characteristic means;
ii) Mardia-Watson-Wheeler test for equal directional distribution (i.e.
direction of edge in managed sites and direction of sample lines in
unmanaged reference sites); iii) Pearson correlation between
independent variables used in regression analysis. Appendix 3. Optimum
distance (meters) of vascular plant species from the stream. Optimum
distances are based on weighted averaging. Data is from the unmanaged
reference sites. Appendix 4. Optimum distance (meters) of moss species
from the stream. Optimum distances are based on weighted averaging.
Data is from the unmanaged reference sites. Appendix 5. Optimum
buffer width (meters) and time from harvesting (years) for vascular plant
species. Optimums are based on weighted averaging. Species are from
the FAH. Appendix 6. Optimum buffer width (meters) and time from
harvesting (years) for moss species. Optimums are based on weighted
averaging. Species are from the FAH.
Abbreviations
ANOSIM: Analysis of similarities; FAH: Forest Act habitat; WKH: Woodland key
habitat.
Competing interests
Neither of the authors has competing interests.
Authors’ contributions
Authors conceived the study and the design together. VS conducted and
coordinated the field work and the species identification. Together the
authors conducted the statistical analysis and wrote the manuscript. Both
authors read and approved the final manuscript.
Acknowledgements
We thank Jyrki Ilves, Kovanen Miina and Salla Selonen for the help in the
field. Also we thank the Finnish Forest and Park Service and Forestia Oy for
providing study areas. The study was funded by the Ministry of Agriculture
and Forestry, Kone Foundat ion, The Emil Aaltonen Foundation and The
Finnish Cultural Foundation.
Received: 29 January 2013 Accepted: 4 July 2013
Published: 10 July 2013
References
1. Rassi P: Suomen lajien uhanalaisuus 2000. Edita: Helsinki; 2001.
2. Hanski I: The shrinking world: ecological consequences of habitat loss.
Oldendorf/Luhe: International Ecological Institute; 2005.
3. Timonen J, Siitonen J, Gustafsson L, Kotiaho JS, Stokland JN, Sverdrup-
Thygeson A, Monkkonen M: Woodland key habitats in northern Europe:
concepts, inventory and protection. Scand J For Res 2010, 25(4):309–324.
4. Hanski I: In the midst of ecology, conservation, and competing interests
in the society. Ann Zool Fenn 2002, 39(3):183–186.
5. Pykälä J: Implementation of Forest Act habitats in Finland: does it protect
the right habitats for threatened species? For Ecol Manage 2007,
242(2–3):281–287.
6. Savolainen J: Metsälaki perusteluineen. Helsinki: Edita; 1997.
7. Kotiaho JS, Selonen VAO: Metsälain erityisen tärkeiden elinympäristöjen
kartoituksen laadun ja luotettavuuden analyysi. Helsinki: Suomen
ympäristökeskus; 2006.
8. Selonen VAO, Mussaari M, Toivanen T, Kotiaho JS: The Conservation
Potential of Brook-side Key Habitats in Managed Boreal Forests.
Silva Fenn 2011, 45(5):1041–1052.
9. Gregory SV, Swanson FJ, Mckee WA, Cummins KW: An Ecosystem
Perspective of Riparian Zones. BioScience 1991, 41(8):540–551.
10. Nilsson C, Svedmark M: Basic principles and ecological consequences of
changing water regimes: Riparian plant communities. Environ Manage
2002, 30(4):468–480.
11. Naiman RJ, Decamps H: The ecology of interfaces: Riparian zones.
Annu Rev Ecol Syst 1997, 28:621–658.
12. Hylander K, Dynesius M, Jonsson BG, Nilsson C: Substrate form determines
the fate of bryophytes in riparian buffer strips. Ecol Appl 2005,
15(2):674–688.
13. Esseen P, Ehnström B, Ericson L, Sjöberg K: Boreal Forests. Ecol Bull 1997,
46:16–47.
14. Pykälä J: Immediate increase in plant species richness after clear-cutting
of boreal herb-rich forests. Appl Veg Sci 2004, 7
(1):29–34.
15. Widenfalk O, Weslien J: Plant species richness in managed boreal forests–
Effects of stand succession and thinning. For Ecol Manage 2009,
257(5):1386–1394.
16. Brosofske KD, Chen JQ, Naiman RJ, Franklin JF: Harvesting effects on
microclimatic gradients from small streams to uplands in western
Washington. Ecol Appl 1997, 7(4):1188–1200.
17. Harper K, Macdonald S, Burton P, Chen J, Brosofske K, Saunders S,
Euskirchen E, Roberts D, Jaiteh M, Esseen P: Edge influence on forest
structure and composition in fragmented landscapes. Conserv Biol 2005,
19(3):768–782.
Selonen and Kotiaho BMC Ecology 2013, 13:24 Page 9 of 10
http://www.biomedcentral.com/1472-6785/13/24
18. Hylander K, Jonsson BG, Nilsson C: Evaluating buffer strips along boreal
streams using bryophytes as indicators. Ecol Appl 2002, 12(3):797–806.
19. Stewart KJ, Mallik AU: Bryophyte responses to microclimatic edge effects
across riparian buffers. Ecol Appl 2006, 16(4):1474–1486.
20. Hylander K, Nilsson C, Güthner T: Effects of Buffer-Strip Retention and
Clearcutting on Land Snails in Boreal Riparian Forests. Conserv Biol 2004,
18(4):1052–1062.
21. Dynesius M, Hylander K: Resilience of bryophyte communities to clear-
cutting of boreal stream-side forests. Biol Conserv 2007, 135(3):423–434.
22. Ström L, Hylander K, Dynesius M: Different long-term and short-term
responses of land snails to clear-cutting of boreal stream-side forests.
Biol Conserv 2009, 142(8):1580–1587.
23. Cajander AK: The theory of forest types. Acta For Fenn 1926, 29(3):1–108.
24. Clarke KR: Non-parametric multivariate analyses of changes in
community structure. Austral Ecol 1993, 18(1):117–143.
25. Hammer Ø, Harper DAT, Ryan PD: PAST: Paleontological Statistics
Software Package for Education and Data Analysis. Palaeontol Electron
2001, 4(1):1–9.
26. Clarke KR, Warwick RM: A taxonomic distinctness index and its statistical
properties. J Appl Ecol 1998, 35(4):523–531.
27. Magurran AE: Measuring Biological Diversity. Oxford: Blackwell Publishing;
2004.
28. Cadotte MW, Cardinale BJ, Oakley TH: Evolutionary history and the effect
of biodiversity on plant productivity. Proc Natl Acad Sci USA 2008,
105(44):17012–17017.
29. Hämet-Ahti L, Suominen J, Uotila P, Lampinen R, Koistinen M: Retkeilykasvio.
Helsinki: Luonnontieteellinen keskusmuseo; 1998.
30. Ulvinen T, Syrjänen K, Anttila S: Suomen sammalet - levinneisyys, ekologia,
uhanalaisuus. Helsinki: Suomen ympäristökeskus; 2002.
31. Macarthur R, Levins R: Limiting Similarity Convergence and Divergence of
Coexisting Species. Am Nat 1967, 101(921):377–385.
32. Jongman RHG, ter Braak CJF, van Tongeren OFR: Data Analysis in
Community and Landscape Ecology. Cambridge: Cambridge University Press;
1995.
33. Tilman D, May RM, Lehman CL, Nowak MA: Habitat Destruction and the
Extinction Debt. Nature 1994, 371(6492):65–66.
34. Hanski I: Extinction debt and species credit in boreal forests: modelling
the consequences of different approaches to biodiversity conservation.
Ann Zoo Fenn 2000, 37(4):271–280.
35. Kuussaari M, Bommarco R, Heikkinen RK, Helm A, Krauss J, Lindborg R,
Öckinger E, Pärtel M, Pino J, Rodà F, Stefanescu C, Teder T, Zobel M, Steffan-
Dewenter I: Extinction debt: a challenge for biodiversity conservation.
Trends Ecol Evol 2009, 24(10):564–571.
36. Flynn DFB, Mirotchnick N, Jain M, Palmer MI, Naeem S: Functional and
phylogenetic diversity as predictors of biodiversity-ecosystem-function
relationships. Ecology 2011, 92(8):1573–1581.
37. Cardinale BJ, Duffy JE, Gonzalez A, Hooper DU, Perrings C, Venail P, Narwani
A, Mace GM, Tilman D, Wardle DA, Kinzig AP, Daily GC, Loreau M, Grace JB,
Larigauderie A, Srivastava DS, Naeem S: Biodiversity loss and its impact on
humanity. Nature 2012, 486(7401):59–67.
38. Young A, Mitchell N: Microclimate and Vegetation Edge Effects in a
Fragmented Podocarp-Broadleaf Forest in New-Zealand. Biol Conserv
1994, 67(1):63– 72.
39. Murcia C: Edge Effects in Fragmented Forests - Implications for
Conservation. Trends Ecol Evol 1995, 10(2):58–62.
40. Wenger S: A review of the scientific literature on riparian buffer width, extent
and vegetation. Athens: University of Georgia. Institute of Ecology. Office of
Public Service & Outreach; 1999.
41. Spittlehouse DL, Adams RS, Winkler RD: Forest, edge, and opening
microclimate at Sicamous Creek. Research Report. British Columbia: Ministry of
Forests; 2004.
doi:10.1186/1472-6785-13-24
Cite this article as: Selonen and Kotiaho: Buffer strips can pre-empt
extinction debt in boreal streamside habitats. BMC Ecology 2013 13:24.
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