Dead wood in semi-natural temperate broadleaved woodland:contribution of coarse and fine dead wood,

attached dead wood and stumps

Bjorn Nordena,*, Frank Gotmarkb, Marie Tonnberga, Martin Ryberga

aBotanical Institute, Goteborg University, P.O. Box 461, SE-405 30 Goteborg, SwedenbZoological Institute, Goteborg University, P.O. Box 463, SE-405 30 Goteborg, Sweden

Received 27 May 2003; received in revised form 27 October 2003; accepted 20 February 2004

Abstract

Dead wood is essential for biodiversity in forests and is therefore often surveyed in conservation inventories. Usually only

coarse downed trees (logs) and standing dead trees (snags) are surveyed, but dead wood also occurs on living trees, in stumps,

and in fallen branches. Attached, standing (including stumps) and downed dead wood with a diameter of more than 1 cm was

surveyed in 25 semi-natural stands of temperate broadleaved woodland dominated by oak in southern Sweden (most trees

younger than 70 years but with an older generation of Quercus, and often Corylus scrub). This study is primarily motivated by

the rising interest in biofuel harvesting by thinning which will affect dead wood structure in forests, especially the finer dead

wood fractions. The sites in this study contained on average 14.3 m3/ha coarse dead wood (defined as wood with a diameter

>10 cm), which is more than twice as much as in production woodland. Fine dead wood (diameter 1–10 cm) made up another

12.2 m3/ha (45% of the total dead wood volume). Of the fine dead wood, on average 20% was oak wood and 71% was wood from

other broadleaved trees. The coarse dead wood fraction consisted equally of oak wood (46%) and wood from other broadleaved

species (47%). Coniferous wood amounted to 7% (coarse dead wood) or 8% (fine dead wood). The total dead wood volume was

dominated by downed (66%) and standing dead wood (22%), while attached dead wood and stumps amounted to smaller

fractions (6% each). The total volume of fine dead wood did not correlate with the total volume of coarse dead wood. These

results therefore suggest that fine dead wood cannot be predicted from conservation surveys of coarse dead wood. The value for

biodiversity of fine dead wood is discussed, and should not be overlooked in conservation work due to the fact that for example,

many fungi and insects are associated with it.

# 2004 Elsevier B.V. All rights reserved.

Keywords: Temperate broadleaved woodland; Biofuel; Coarse dead wood; Fine dead wood; Biodiversity

1. Introduction

Temperate broadleaved woodland is one of the most

severely disturbed and endangered biomes world-wide

(Hannah et al., 1995; Peterken, 1996). In Europe, such

woodland has declined dramatically, especially during

the last few centuries, and few natural or semi-natural

stands remain (Peterken, 1996; Lofgren and Anders-

son, 2000; Nilsson et al., 2001). The focus of this study

is on temperate broadleaved woodland and one habitat

component that is now rare; dead wood. Dead and

dying trees are crucial for biodiversity and for

Forest Ecology and Management 194 (2004) 235–248

* Corresponding author. Tel.: þ46-31-7732656;

fax: þ46-31-7732677.

E-mail address: bjorn.norden@botany.gu.se (B. Norden).

0378-1127/$ – see front matter # 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.foreco.2004.02.043

ecosystem functions, such as nutrient recycling in

forests (Harmon et al., 1986; McComb and

Lindenmayer, 1999). In many temperate broadleaved

woodlands, dead wood is a depleted resource, and the

situation is more severe in temperate forests than in

boreal forests, both within and outside reserves

(Fridman, 2000). As a part of ongoing conservation

and restoration programmes in this temperate biome,

knowledge of dead wood and its biology is essential.

Most of the existing literature on dead wood concerns

the boreal forest zone, where productivity is lower and

where coniferous trees predominate (but see Nilsson

et al., 2002).

Most of the land presently covered by temperate

broadleaved forest in Europe was once part of the

agricultural landscape, and often used as pasture

woodland (Harding and Rose, 1986; Vera, 2000). In

many areas of northern Europe pasture woodland was

dominated by oak trees (Quercus robur L.) with wide

canopies. Most pasture woodlands were abandoned

during the 19th century. Succession after the cessation

of grazing may potentially lead to habitats that are rich

in dead wood, created e.g. through self-thinning of

pioneer trees and branch-shedding in an increasingly

dense forest. Subsequently, large snags and logs may

also be created by the death of oak trees.

Current research on dead wood biology focuses on

large standing dead trees (referred to as snags below)

and large downed dead trees (referred to as logs

below) (Fridman and Walheim, 2000; Nilsson et al.,

2002). These two components of dead wood (pooled)

are often referred to as coarse woody debris (CWD).

Thinner fractions of the dead wood have rarely been

studied (but see Kruys and Jonsson, 1999). The focus

on CWD is often motivated by the depletion of large

snags and logs due to modern forestry practices.

The amount of CWD has decreased drastically since

the middle of the 19th century, following intense for-

estry (Linder and Ostlund, 1998; Siitonen et al., 2000;

Nilsson et al., 2001). As a result, the conditions for

many saproxylic organisms have deteriorated resulting

in a large number of them being threatened (Berg et al.,

1994; Jonsell et al., 1998; Gardenfors, 2000).

In recent times, the use of tops and branches from

trees for biofuel has increased (Lundborg, 1998;

Johansson, 2000; Malinen et al., 2001; Skogsstyrel-

sen, 2001; Fung et al., 2002). In addition whole-tree

harvesting of smaller trees occurs; for instance,

thinning of younger trees around old oak trees, a

recommended conservation management method in

overgrown oak-pastures (Butler et al., 2001; Dagley

et al., 2001), is a potential source of biofuel subject to a

current surge of interest in Sweden. The reason for this

current interest in forest biofuel is that it is a renewable

energy source that gives no net contribution of the

green-house gas CO2 to the atmosphere, in contrast to

fossil fuels. It is therefore often viewed as a sustain-

able alternative, but there are potential hazards for

biodiversity as a result of its harvesting. The removal

of biofuel material may strongly reduce the amount of

fine dead wood in forests with energy-rich hardwoods

and thus the current levels of fine dead wood and its

importance for biodiversity needs to be evaluated.

Increased harvesting may also have negative effects

on the carbon budget and nutrient status in forest soils

and thus also on tree growth (Olsson et al., 1993;

Jacobson et al., 2000; Agren and Hyvonen, 2003;

Egnell and Valinger, 2003).

Dead wood attached to live trees (Christenssen,

1977) and cut stumps (Siitonen et al., 2000) are two

commonly overlooked above-ground dead wood com-

ponents. In closed semi-natural forest, attached dead

wood (e.g. on oaks) may be important, and stumps

might be common, depending on the level of historical

human impact. This study provides a nearly total

estimation of the above-ground dead wood in 25 forest

stands and attempts to quantify the contributions made

by four dead wood components (attached, standing,

downed and stumps) in closed and mixed temperate

broadleaved woodland with oak; a common succes-

sional habitat in Sweden. The relative volumetric

contribution of fine dead wood and coarse dead wood

(more inclusive than the term CWD since some of the

coarse dead wood recorded is not debris, but still

attached to living trees, or in stumps) is also quanti-

fied. For coarse dead wood, densities of snags and logs

are quantified, to allow comparisons with earlier

studies. In addition to above-ground dead wood,

20–30% of the dead wood may exist in roots (Thomas,

2001), but this dead wood component is not studied

by us.

CWD is increasingly used for monitoring of

wildlife and biodiversity values (Keddy and

Drummond, 1996; McComb and Lindenmayer,

1999; Skogsstyrelsen, 2001). Fine dead wood and

components other than logs and snags may also be

236 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248

valuable for biodiversity. Thus, this study investigates

whether levels of coarse logs and snags (CWD) are

reflected in the quantity of fine dead wood, and in the

components of coarse dead wood that are often over-

looked. This study also tests, for semi-natural stands,

if the density of stumps (i.e. logging intensity) is

negatively correlated to the CWD volume and the

volume of attached wood, which would indicate lin-

gering effects of cutting and a former degree of open-

ness on the present dead wood structure.

Several authors (Harmon et al., 1986; Sippola et al.,

1998; Nilsson et al., 2002) suggest that the volume of

dead wood is directly proportional to the living timber

volume (and hence to the productivity of the forest).

This study tests this hypothesis using the estimates of

dead wood volume (fine and coarse dead wood com-

bined) and total basal area of live trees. In addition the

differences between the contributions from different

woody species to attached and fine dead wood is

studied and analysed. Finally, the biodiversity values

of the four dead wood components (and fine and

coarse dead wood) for wood-living species, particu-

larly cryptogams and beetles is discussed.

2. Study sites

Closed temperate broadleaved woodland (mixed

oak woodland, with formerly open or semi-open stand

structure) was studied due to the fact that it potentially

has an interesting dead wood structure, and oak trees

have been reported to play key roles for biodiversity

(Berg et al., 1994; Ranius and Jansson, 2000; Nilsson

et al., 2001; Butler et al., 2001). The stands were semi-

natural in the sense that they were not planted, had a

tree species composition typical of the boreo-nemoral

zone (Table 1), and were old enough to accumulate

relatively high levels of dead wood without being

ancient forest (similar to the definition given by

Peterken, 1996). Twenty-five woodland sites were

surveyed, located in five counties in southern Sweden

(Fig. 1). The 25 sites were once open or semi-open, but

grazing was abandoned between about 1930 and 1960.

Most of the trees (except the oldest generation; which

were mainly oaks and Corylus) were therefore

between 40 and 70 years old. Historical maps from

the late 1800s (‘Generalstabens karta’) indicate that

the study sites were pasture woodlands with deciduous

trees (in one case, also coniferous trees). Only four of

the 25 sites lacked markings indicating the presence of

trees on these maps, Table 1. One of these sites (no.

18) apparently had some big oaks, judged from stumps

found in the area, although no trees were indicated on

the maps.

The sites were selected mainly on the basis of the

presence of Q. robur (on average 50 � 17% of the

basal area of living trees >5 cm diameter at breast

height (dbh), some Q. petraea Liebl. and intermediate

forms also occurred). The majority of oaks were 120–

160 years old, but at a few sites older oak trees were

also present. Stands of this kind are very small (usually

0.5–3 ha) but common in the landscape (5000–10 000

stands in southern Sweden, based on files from for-

estry boards studied by the authors). Younger trees of

many species, mainly Betula pendula Roth, B. pub-

escens Ehrh., Populus tremula L., Fraxinus excelsior

L., Acer platanoides L., Tilia cordata Mill. and Sorbus

aucuparia L. have invaded and now form a dense

canopy around the oaks. At seven sites, Picea abies

(L.)H. Karst. had invaded and forms a part of the

canopy (basal area of Picea at these sites, 10–35%;

>5 cm dbh). A common understorey shrub at almost

all sites was Corylus avellana L. All of the sites had

mesic and relatively rich soil, level ground (no steep

slopes), and closed or almost closed canopy; on

average 14% (S.D. 3.5%) of the sky was visible from

the ground (n ¼ 25, based on photographs).

All sites share the characteristics of woodland key

habitats (i.e. forest sites identified as potentially

important for Red Data Book plant species, see

Gustafsson, 2002), and eight of them are protected

as nature reserves. The sites thus had quite high

conservation values and relatively high concentra-

tions of coarse dead wood compared to production

forests in southern Sweden was expected. Due to the

fact that relatively young, abandoned pasture wood-

lands were used, no stands with extremely high con-

servation values were included (e.g. with many very old

trees,studiedbyRaniusandJansson,2000;Nilssonetal.,

2001).

3. Methods

Fieldwork was conducted during the autumn of

2000, the spring of 2001, and in late summer and

B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248 237

autumn of 2002. Each site consisted of two juxtaposed

squares (assigned for other purposes), each covering

1 ha (usually 100 m � 100 m). All surveys followed

the same base-line transects in the squares, but the

number of transects and size of the area inventoried

varied between surveys of different dead wood com-

ponents. The transects were separated by at least 10 m,

and placed systematically in each square (Fig. 2). Only

dead wood occurring inside the limits of the area

defined by the transects was included; thus, parts of

dead branches or logs extending outside of the transect

area were excluded.

A lower diameter limit of 10 cm was chosen for

coarse dead wood, thus excluding most branches from

this category, and instead recording them as fine dead

wood. The most commonly used lower limit for CWD

seems to be 10 cm (Kruys and Jonsson, 1999; Fridman

and Walheim, 2000; Nilsson et al., 2002), although

some authors include wood down to 5 cm (Siitonen

et al., 2000) or even 2.5 cm in diameter (Peterken,

1996). All dead wood with a diameter of more than

10 cm was defined as coarse dead wood in this study,

including standing, attached (to live trees) and downed

wood, as well as wood in stumps. Coarse dead wood

was surveyed in four 10 m � 100 m transects

(4000 m2) running across each square (two squares

per site; Fig. 2).

The length of logs was measured up to the point

where they became less than 10 cm in diameter, and

the diameter at the centre of the measured part (half

Table 1

Characteristics of the studied sites

Sitea Protection statusb Stand agec (years) Cutting intensityd Basal area of living trees (m2/ha)

Coniferous Oak Other broadleaved trees

1 WKH >124 40.0 1.2 18.2 9.0

2 WKH >124 38.8 0.3 13.1 6.7

3 WKH >111 78.8 1.6 15.1 14.4

4 WKH >111 5.0 15.1 10.2 5.5

5 NR >121 27.5 1.3 22.8 7.9

6 WKH >125 20.0 5.5 4.2 19.9

7 NR >124 31.2 1.1 11.6 0.0

8 WKH <141 37.5 0.2 11.8 15.8

9 NR >141 72.5 5.7 16.2 12.3

10 WKH >138 70.0 2.3 20.3 13.3

11 NR >126 13.8 0.0 6.0 15.6

12 WKH >128 22.5 4.5 17.2 16.5

13 WKH >127 21.2 3.5 7.2 16.1

14 WKH >127 7.5 2.6 14.0 13.0

15 WKH <125 23.8 4.9 18.8 5.9

16 WKH >125 27.5 11.0 15.8 7.5

17 WKH >128 88.8 1.4 10.1 13.0

18 WKH <126 77.5 0.5 18.3 7.1

19 WKH >132 17.5 3.5 14.4 5.5

20 WKH >132 32.5 8.7 17.1 5.4

21 WKH >134 42.5 0.3 10.6 15.8

22 NR >134 27.5 10.2 16.8 7.1

23 NR >162 32.5 2.7 8.5 10.4

24 NR >164 7.5 0.0 26.5 4.3

25 NR <164 5.0 0.0 11.9 17.2

Mean 34.8 3.5 14.3 10.6

S.D. 24.4 4.0 5.3 5.1

a Numbers refer to Fig. 1.b WKH: Woodland Key Habitat, NR: Nature Reserve.c Number of years of forest cover according to available historical maps. Oldest tree generation usually oaks.d Number of cut stumps with a diameter of more than 20 cm/ha.

238 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248

length). The volume of logs was estimated as

V ¼ ðLpD2Þ=4 (Patterson et al., 1993), where V is

the volume, L the length, and D the diameter. This

formula gives estimates roughly similar to the formula

for volume of a cut cone (frustum). The volume of

standing dead trees was calculated from estimated

height and diameter measured at breast height, by

using the tables presented in Hagberg and Matern

(1975) for oak and beech (Fagus sylvatica L.), and

Naslund (1947) for other broadleaved trees and con-

ifers. The density of coarse logs and snags (CWD)

were calculated from the same transects. Cut trees had

on occasions been sawn up into pieces after felling.

These pieces (left by cutters, and subsequently noted

in our survey) were not counted separately. Instead the

pieces were pooled up to a given summed length and

the density of such ‘standard logs’ was calculated. The

length of standard logs was set at 8 m when the

diameter of the logs exceeded 15 cm. For pieces with

a diameter of 10–15 cm, the length of a standard log

was set at 6 m.

The stumps were either natural (formed by e.g.

wind-throw) or due to cutting. The diameter of natural

stumps was measured at the top if they were short,

otherwise at breast height, and their maximum height

was set at 2 m (otherwise recorded as snags). Most

stumps were lower than 0.4 m. The height of cut

stumps and the diameter at the cutting height and at

ground level was measured, but only cut stumps that

were more than 20 cm in diameter at the cutting height

were included. The volume of stumps was calculated

from the formula for a cut cone.

Fine dead wood (defined in this study as wood with

diameter between 1 and 10 cm) measurements are

more time-consuming to collect, so a smaller area

in each coarse dead wood transect was surveyed for

this fraction. Each transect was divided into four 25 m

sections. The fine dead wood was surveyed in

Fig. 1. Locations of the forest stands investigated in southern Sweden: 1, Skolvene; 2, Karla; 3, Ostadkulle; 4, Sandviksas; 5, Rya asar; 6,

Strakaskogen; 7, Bondberget; 8, Langhult; 9, Bokhultet; 10, Kraksjoby; 11, Stavsater; 12, Atvidaberg; 13, Fagerhult; 14, Aspenas; 15, Norra

Vi; 16, Froasa; 17, Ulvsdal; 18, Hallingeberg; 19, Ytterhult; 20, Farbo; 21, Emsfors; 22, Getebro; 23, Lindo; 24, Vickleby; 25, Albrunna.

B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248 239

2 m � 2:5 m squares, placed randomly within each

section, along the central axis of each coarse dead

wood transect (Fig. 2; in total thirty-two 2 m � 2:5 m

squares, or 160 m2 of each of the 25 sites).

To calculate dead wood volume, the diameters of

branches were measured at the top and bottom. The

volumes were then calculated from the formulas for a

cylinder, or cut cone (if the top and bottom diameters

differed). Attached dead wood was defined as

branches and other dead wood attached to live trees

2 m above the ground (branches—always thinner than

10 cm—attached below 2 m were counted as fine dead

wood and recorded only in that survey). Standing dead

wood was defined as snags and smaller standing dead

trees and bushes. Attached dead wood (above 1 cm in

diameter) was surveyed in 2000 m2 in each square,

and two representative transects of the four

10 m � 100 m transects were followed. Firstly the

height above the ground for each attached dead branch

was determined, and then its diameter where it met the

trunk was visually estimated (using a ‘diameter ruler’,

calibrated by the authors from dead branches of a

known diameter on the ground observed at known

distances). Finally the length of each branch was

visually estimated. In the volume calculations, uni-

formly thick branches (or parts of) and cone branches

were separated, using the standard formulas.

Diameter at breast height (considered to be 1.3 m

above the ground) was measured for the calculation of

basal area in a representative area of 3000 m2 in each

square, excluding stems less than 5 cm dbh (and

higher than 1.3 m) which were surveyed along two

transects (50–200 m2 per square, depending on stem

density). The volume of dead wood per hectare, and

basal area per hectare, was extrapolated from the

respective measurements, and a mean value for the

two squares was used for the analyses. Sites (n ¼ 25,

Fig. 1) were sample units in the statistical analyses.

Spearman’s rank test was used for all correlation

analyses, since the data did not conform to normality

and other assumptions needed for parametric tests

even after transformation. Bonferroni correction

(Rice, 1989) was used to adjust significance levels

whenever the same data was used for multiple tests.

The volume of CWD (coarse logs and snags) was

tested against the volume of fine dead wood, stumps

and attached wood. To investigate if the proportion of

attached dead wood and fine dead wood differed

between tree species, indices were produced based

on the relative contribution made by the six most

important woody taxa, viz. B. pendula and B. pub-

escens (pooled in the field), C. avellana, P. tremula, Q.

petraea and Q. robur (pooled), P. abies and S. aucu-

paria. The indices were calculated by dividing the

proportion of attached wood and fine dead wood by

the proportion of basal area for each woody species at

each site. The values were log transformed and tested

by ANOVA. The Tukey’s HSD test for unequal N

(Spjotvoll/Stoline test) for post-hoc comparisons was

then used.

4. Results

4.1. Dead wood volume and structure

Based on mean values for the 25 sites, the total dead

wood volume was dominated by downed (66%) and

standing dead wood (22%), while attached dead wood

and stumps amounted to smaller fractions (6% each;

Table 2). Of the stump volume, 84% consisted of cut

stumps and 16% of natural stumps (mean volumes

1.42 and 0.27 m3/ha, respectively). Standing dead

20 m

Fig. 2. The transects sampled for dead wood. Coarse dead wood

was sampled in four 10 m broad transects, each divided into four

sections, in each square. The transects were separated by at least

10 m. Fine dead wood was sampled in 2 m � 2:5 m squares

randomly placed in each section along the central axis of the four

transects.

240 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248

wood and stumps had the highest coefficients of

variation, attached was intermediate and downed dead

wood varied least of the components over the sites

(Table 2).

The volumes of dead wood of the four components

were not significantly correlated to each other except

for the volume of attached wood which was negatively

correlated with the volume of stumps (Table 3),

although this correlation did not hold at the 5% level

after Bonferroni correction.

In contrast to what one might expect, the total dead

wood volume was dominated by broadleaved species

other than oak (on average 57%, Table 2); the average

contribution of dead oak wood was 33% (basal area

50 � 17%), whereas conifers (mainly Picea abies)

were of minor importance (on average 9%), which

was expected since the study focused on broadleaved

stands. Compared with conifers and other broadleaved

trees and shrubs however, dead oak dominated in

attached dead wood (on average 67%) and in stumps

(63%). In absolute volumes, oak had the most even

distribution of dead wood over the four components

(Table 2), implying that it has the highest dead wood

diversity (in terms of wood components) in this type of

forest. Dead wood of other broadleaved species

mainly occurred as downed wood.

Fine dead wood on average made up almost half

(46%) of the total dead wood volume (Table 4), of

which 18% (4.9 m3/ha) had a diameter between 1 and

5 cm and 27% (7.2 m3/ha) had a diameter between 5

and 10 cm. Twenty-two percent (5.9 m3/ha) of the

dead wood had a diameter between 10 and 20 cm,

Table 2

Volumes of attached dead wood, downed dead wood, standing dead wood, and stumps (m3/ha; mean and S.D.) for coniferous trees (Picea

abies, Pinus sylvestris and Juniperus communis), oaks (Q. robur and Q. petraea), and other broadleaved species (pooled) (n ¼ 25 sites)

Dead wood component Attached Standing Downed Stumpsa Total CVb

Coniferous 0.07 � 0.09 0.30 � 0.69 1.74 � 2.77 0.17 � 0.11 2.28 � 3.25 1.43

Oak 1.06 � 0.74 2.76 � 3.00 3.87 � 3.32 1.08 � 0.68 8.76 � 4.75 0.54

Other broadleaved 0.47 � 0.39 2.62 � 2.23 11.8 � 6.12 0.45 � 0.29 15.4 � 7.21 0.47

Total 1.59 � 0.88 5.69 � 4.18 17.4 � 6.78 1.70 � 1.08 26.4 � 8.69 0.33

CVb 0.56 0.73 0.39 0.64 0.33

a Only stumps broader than 20 cm are included.b Coefficient of variation (S.D./mean), based on total values for each component and site.

Table 3

Spearman’s rank correlation between the different components of dead wood (n ¼ 25 sites)

Dead wood component Attached Standing Downed

rs P rs P rs P

Standing �0.062 0.770

Downed 0.375 0.065 0.259 0.211

Stumps �0.458 0.021a �0.169 0.419 �0.209 0.315

a Not significant after Bonferroni correction.

Table 4

Amounts of coarse (diameter >10 cm) and fine (diameter 1–10 cm)

dead wood at 25 sites (m3/ha; mean and S.D., n ¼ 25 sites) for

coniferous trees (Picea abies and Pinus sylvestris), oaks (Q. robur

and Q. petraea), and other broadleaved species (pooled)

Dead wood

component

Fine dead

wood

Coarse dead

wood

Coniferous 0.98 � 1.23 1.03 � 1.97

Oak 2.44 � 1.24 6.60 � 4.48

Other broadleaved 8.67 � 5.89 6.69 � 4.79

Total 12.2 � 5.09 14.3 � 7.95

CVa 0.42 0.56

a Coefficient of variation (S.D./mean), based on total values for

each component and site.

B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248 241

and 32% (8.4 m3/ha) had a diameter of more than

20 cm. Coarse dead wood volume varied more than

fine dead wood volume between sites (Table 4). The

coarse dead wood volume at the sites did not correlate

with the fine dead wood volume (rs ¼ �0:04,

P ¼ 0:86, n ¼ 25), and the sum of coarse logs and

snags (CWD) did not correlate with the sum of the

other components i.e., fine dead wood, stumps, and

attached dead wood (rs ¼ 0:00, P ¼ 1:00, n ¼ 25).

Together these on average amounted to a slightly

lower volume than did CWD (12.2 m3/ha as opposed

to 14.3 m3/ha or 46% versus 54%).

4.2. Dead wood density

Broadleaved trees other than oaks had the highest

densities of coarse dead wood (in spite of the basal

area of oak being 50 � 17%). The total average den-

sity was 115 coarse dead wood objects per hectare

(Table 5). Table 6 shows the summed numbers of

coarse dead wood objects belonging to different tree

species; the dominating trees were Quercus, Betula

and Picea.

The number of cut stumps per hectare (logging

intensity) was significantly negatively correlated to

Table 5

Densities of coarse dead wood objects (numbers per hectare; mean and S.D., n ¼ 25 sites) in the categories snags, downed and stumps for

coniferous trees (Picea abies and Pinus sylvestris), oaks (Q. robur and Q. petraea), and other broadleaved species (pooled)

Coarse dead wood Snags Downed Stumps Total CVa

Coniferous 1.15 � 2.34 4.00 � 8.97 4.95 � 9.12 10.1 � 14.8 1.47

Oaks 12.6 � 11.4 16.4 � 17.0 20.3 � 14.7 49.2 � 31.5 0.64

Other broadleaved 10.5 � 9.07 32.7 � 22.5 12.6 � 9.95 55.8 � 33.9 0.61

Total 24.2 � 13.6 53.1 � 30.1 37.8 � 24.4 115 � 46.6 0.40

CVa 0.56 0.57 0.65 0.40

a Coefficient of variation (S.D./mean), based on total values.

Table 6

The total numbers of coarse dead wood objects belonging to different tree species summed over all sites

Tree species Logs Snags Stumps, cut Stumps, natural Total

Acer platanoides 8 0 2 1 11

Alnus glutinosa/incana 78 15 44 17 154

B. pendula/pubescens 235 78 64 20 397

Corylus avellana 42 28 3 8 81

Crataegus spp. 5 7 0 2 14

Fagus sylvatica 7 3 10 0 20

Fraxinus excelsior 38 14 11 1 64

Juniperus communis 17 0 1 1 19

Malus domestica 2 5 0 0 7

Picea abies 80 17 78 11 186

Pinus sylvestris 16 6 11 2 35

Populus tremula 84 24 12 5 125

Prunus avium 2 0 1 1 4

Prunus padus 3 0 1 0 4

Q. robur/petraea 323 252 400 17 992

Salix caprea 35 7 6 1 49

Sorbus aucuparia 19 10 4 1 34

Sorbus intermedia 15 5 0 3 23

T. cordata 33 12 16 5 66

Ulmus glabra 1 0 0 0 1

Unknown 24 2 31 4 61

Total 1067 485 695 100 2347

242 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248

Fig. 3. Correlations between basal area and dead wood volume: (A) coniferous trees (rs ¼ 0:32;P ¼ 0:004; n ¼ 25); (B) oak trees

(rs ¼ 0:13;P ¼ 0:07; n ¼ 25); (C) other broadleaved trees and shrubs (excluding oak) (rs ¼ 0:38;P < 0:001; n ¼ 25); (D) total

(rs ¼ 0:006;P ¼ 0:72; n ¼ 25).

Tree species

Inde

x of

atta

ched

woo

d

0

0.5

1

1.5

2

2.5

3

Betula Corylus Picea Populus Quercus Sorbus

Fig. 4. Proportion of attached dead wood for the six most common woody species (B. pendula and B. pubescens (treated together, n ¼ 18);

Corylus avellana, n ¼ 22; Picea abies, n ¼ 19; Populus tremula, n ¼ 18; Q. robur and Q. petraea (treated together, n ¼ 25) and Sorbus

aucuparia, n ¼ 24). Each bar shows the proportion of attached wood for one tree group divided by the proportion of basal area (of the total

basal area) for the same species. Given are mean values and S.E. (n ¼ 25).

B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248 243

the volume of attached dead wood (rs ¼ �0:50;P ¼0:01; n ¼ 25; also significant at the 5% level after

Bonferroni correction), but not to the total dead wood

volumeexceptstumps(rs ¼ �0:25;P ¼ 0:23; n ¼ 25).

4.3. Correlations between basal area and dead wood

The forest stands studied were closed and dense, but

the basal area for the tree species groups varied among

Fig. 5. Proportion of fine dead wood for the six most common woody species (B. pendula and B. pubescens (treated together, n ¼ 13); Corylus

avellana, n ¼ 16; Picea abies, n ¼ 12; Populus tremula, n ¼ 12; Q. robur and Q. petraea (treated together, n ¼ 15) and Sorbus aucuparia,

n ¼ 16). Each column shows the proportion of fine dead wood for one woody species divided by the proportion of basal area to the total basal

area for the same species. Given are mean values and S.E. (n ¼ 25).

Table 7

Results of post-hoc ANOVA tests (Tukey’s HSD test for unequal N) of differences between fine dead wood indices

P-value Betula, n ¼ 13 Corylus, n ¼ 16 Picea, n ¼ 12 Populus, n ¼ 12 Quercus, n ¼ 15 Sorbus, n ¼ 16

Betula <0.001* 0.999 0.564 0.999 0.015*

Corylus <0.001* 0.112 <0.001* 0.862

Picea 0.316 0.999 0.007*

Populus 0.388 0.621

Quercus 0.003*

To produce the indices, the proportion of fine dead wood per tree or tree group was divided by the proportion of basal area for the same tree or

tree group.* Denotes significance at the 5% level, n is the number of sites used in statistical analysis.

Table 8

Results of post-hoc ANOVA tests (Tukey’s HSD test for unequal N) of differences between attached dead wood indices

P-value Betula, n ¼ 18 Corylus, n ¼ 22 Picea, n ¼ 19 Populus, n ¼ 18 Quercus, n ¼ 25 Sorbus, n ¼ 24

Betula 0.188 0.993 0.981 0.070 0.641

Corylus 0.039* 0.579 0.997 0.950

Picea 0.796 0.011* 0.260

Populus 0.315 0.961

Quercus 0.716

To produce the indices, the proportion of attached dead wood per tree or tree group was divided by the proportion of basal area for the same

tree or tree group.* Denotes significance at the 5% level, n is the number of sites used in statistical analysis.

244 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248

the sites. There was a positive trend between oak basal

area and oak dead wood volume (rs ¼ 0:13;P ¼ 0:07;n ¼ 25) and strong positive correlations for conifers

(rs ¼ 0:32;P ¼ 0:004; n ¼ 25) and broadleaved trees

excluding oaks (rs ¼ 0:38;P < 0:001; n ¼ 25). On

the contrary however, the total basal area did not

correlate with the total volume of dead wood

(rs ¼ 0:006;P ¼ 0:72; n ¼ 25). These four relation-

ships are shown in Fig. 3.

The quotient of attached dead wood (Fig. 4) and fine

dead wood (Fig. 5), in relation to basal area, was

highest for Corylus avellana. This study highlighted a

strong effect of tree species on the fine dead wood

index (one-way ANOVA, F ¼ 9:54; d:f: ¼ 5;P <0:001). Post-hoc comparisons with Tukey’s HSD test

showed that Corylus and Sorbus both had significantly

higher fine dead wood indices than Betula, Picea and

Quercus (Table 7). For attached dead wood, the

Tukey’s HSD test showed that Corylus and Quercus

both had significantly higher indices than Picea

(Table 8).

5. Discussion

Dead wood components other than coarse woody

debris (CWD; coarse logs and snags) can apparently

form a major part of the total volume of dead wood in

semi-natural temperate broadleaved woodland. The

total volume of fine dead wood, attached dead wood

and stumps did not correlate to that of CWD at the site

(stand) level. Large logs and snags are easy to survey

and if they had given an indication of the total volume

of dead wood, it would be sufficient to survey only

these components. The results of this study however,

suggest that fine dead wood, attached dead wood and

stumps also need to be surveyed. In particular, if the

aim is to quantify the total volume of dead wood or the

major components of dead wood in forests. The

amount and relative importance of coarse dead wood

probably increases as the forest matures and finally

reaches old-growth stage (Nilsson et al., 2002). Whilst

the amount of coarse dead wood is considerably less in

young stands than in old-growth stands, the amount of

fine dead wood may be as high or higher in the former

due to copious self-thinning and branch-shedding.

This remains however, conjecture, since no studies

have been carried out on the amount and relative

importance of fine dead wood in comparable forest

stands of varying ages. Another factor influencing the

type of dead wood produced is the openness of the

forest. For instance, oaks change architecture accord-

ing to light regime and may develop very wide cano-

pies with coarse limbs in copious light. At the study

sites, which share a similar history and used to be more

open, such coarse branches have now largely been

shed.

At the 25 study sites, the coarse dead wood

volume was on average 14.3 m3/ha. In comparison,

managed woodlands in southern Sweden contain on

average less then half of this amount (Fridman and

Walheim, 2000), whilst natural old-growth forest

may contain much higher amounts of CWD than

was found in this study (Nilsson et al., 2002). The

density of downed coarse dead wood at the study

sites was also lower than in old-growth woodland.

The mean density of logs and snags with a minimum

diameter of 10 cm at the study sites was 38% of the

average for old-growth forests in Europe (see

Nilsson et al., 2002).

According to Peterken (1996), dead wood input in

temperate broadleaved woodland is generally lower

than in boreal coniferous forests, decay rates are faster

and accumulation of dead wood therefore lower (due

to climatic and other differences between the biomes).

Differences between dead wood structure of broad-

leaved and coniferous trees in mixed forest has, to the

authors’ knowledge, not been studied before. The

quotients of attached and fine dead wood to basal

area differed between tree species. The factors which

are likely to be responsible for this are varying tree age

and density between sites, and differences in canopy

architecture between species. In relatively dense and

closed forest, such as those studied, trees successively

shed lower branches due to low or decreasing light

levels (Addicott, 1991), a process often associated

with specialised fungi (von Butin and Kowalski,

1983). Most of the broadleaved trees at the study sites

had higher quotients compared to the conifer Picea

abies. Broadleaved trees generally have more complex

branching patterns than coniferous trees (Niklas,

1997), which may lead to a higher production of fine

dead wood. The shrub hazel Corylus avellana had the

highest quotients. It differs from the other tree species

studied, by the fact that it is lower in height (usually

less than 6 m) and multi-stemmed, with individual

B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248 245

stems rarely exceeding 10–15 cm dbh. Hazel is an

early colonising light-demanding species, often dis-

favoured by continued succession towards high forest

(Vera, 2000). It is likely that dead wood production by

hazel reaches its peak in an intermediate phase of

succession.

In general it is clear that the more there is of a tree

species in a forest, the more dead wood is produced

from that tree species. When tested separately for tree

species groups, there were significant correlations and

in one case a strong positive trend, between basal area

and dead wood volume. A correlation between site

productivity and volume of CWD was predicted by

Nilsson et al. (2002) for natural old-growth wood-

lands. The authors’ tested if there was an analogous

correlation between total basal area of living trees

(strongly correlated to productivity as noted by Nils-

son et al. (2002)) and total volume of dead wood, but

found no such pattern. This indicates that basal area

(pooled) should not be used to predict dead wood

volumes, at least not in the type of forest studied here,

where total basal area is not only a measure of site

productivity, but is probably also related to stand age

and past management. In the stands included in this

study, succession to natural forest is currently taking

place; they are not natural in the sense that they have

lingering effects of former land-use influencing tree

demography and dead wood structure.

Tree species, diameter of the dead wood and com-

ponent of dead wood (attached, standing, downed or

stump) are likely to be important determinants of

species diversity of saproxylic organisms. Among

the 6000 or so saproxylic species in Sweden, 50%

are associated with broadleaved trees, 27% with con-

iferous trees, 11% with both types of trees, and for an

additional 11%, information on their associations is

lacking (Dahlberg, 2003). Betula and Pinus are the

two tree species supporting the highest numbers of

saproxylic species (around 1100–1200 species each),

closely followed by Picea, Populus and Quercus with

around 1000 species each (Dahlberg, 2003). Propor-

tionately, Quercus supports a higher number of species

than any of the other mentioned tree species, since

Quercus constitutes only 1% of the volume of living

trees in Sweden (Stener, 1998), a country dominated

by boreal forests and conifers. Oak also supports a

higher proportion of Red Data Book species than any

other tree species in Sweden; approximately 300 Red

Data Book species are dependent on dead oak wood

(Dahlberg, 2003).

A very large number of cryptogams, invertebrates,

birds and mammals are dependant upon CWD (coarse

dead trees, including those which are broken and

fallen; Berg et al., 1994; Samuelsson et al., 1994;

Jonsell et al., 1998), but the potential values of fine

dead wood are rarely discussed in the literature.

Dahlberg (2003) found that more than 50% of all

saproxylic species in Sweden occur mainly in dead

wood with a diameter of less than 20 cm, and 10%

occur mainly on wood with a diameter of less than

5 cm. Many saproxylic beetles, several of which are

listed in the Red Data Book in Sweden, occur exclu-

sively or predominantly in such wood (Ehnstrom and

Axelsson, 2002). It is also known that fine dead wood

is important for saproxylic bryophytes, fungi and

lichens in boreal coniferous forest (Kruys and Jonsson,

1999). The authors’ own recent studies indicate that

fungi form very species-rich communities on fine dead

wood (Norden and Paltto, 2001), and that 75% of the

saproxylic ascomycetes in temperate broadleaved

woodland may occur exclusively on fine dead wood

(Norden et al., 2004).

The value of attached dead wood and stumps for

biodiversity needs further investigation. Stumps may

be very old in the types of stands studied here, as dead

oak wood persists for long time. Both stumps and

attached wood supply specialist niches for saproxylic

species. A survey of the 25 study sites showed that

stumps of oak supported an interesting flora of cryp-

togamic species, with for instance the Red Data Book

lichen Cladonia parasitica (Hoffm.) Hoffm. and the

Red Data Book fungus Perenniporia medulla-panis

(Jacq.: Fr.) Donk. In addition, stumps generally had

higher species density (number of species per surface

area) of bryophytes and lichens than logs and snags

(Lindholm, 2001). Dead oak branches still attached

support a specialised fungal flora (for instance the Red

Data Book species Pachykytospora tuberculosa (DC.:

Fr.) Kotl. & Pouzar; see also Boddy and Rayner, 1983)

and several beetles (Ehnstrom and Axelsson, 2002).

In conclusion, the role of fine dead wood and

other components of dead wood often overlooked,

can be greater than commonly assumed. This needs

further investigation given that fine dead wood can

contribute substantially to the total dead wood volume

in semi-natural successional forests. Self-thinning

246 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248

broadleaved stands in particular, such as those studied

here may be interesting habitats that are important for

biodiversity. Biofuel production from forests, if per-

formed on a large proportion of the forest land, must

take this into consideration.

Acknowledgements

We are grateful to Camilla Niklasson and Julia

Svenker for help with the field work, and to Thomas

Appelqvist who read and critically commented on an

early draft of the manuscript. The following forest

owners kindly provided study sites: Sven-Gunnar and

Dan Ekblad; Anders Heidesjo; Gote, Gullan and

Mikael Isaksson; Anette Karlsson; Bo Karlsson;

Nils-Olof and Jan-Ake Lennartsson; the County

Administration Boards of Kalmar and Ostergotland;

the Municipalities of Boras, Jonkoping, Oskarshamn

and Vaxjo; the Dioceses of Linkoping and Skara; and

the forest companies Boxholms Skogar, Holmen

Skog, and Sveaskog. We thank all involved in this

work, and gratefully acknowledge that the Swedish

Energy Agency, the Swedish Research Council, and

the foundations of Anna and Gunnar Vidfelt, Magnus

Bergvall, and Carl Stenholm provided financial sup-

port.

References

Addicott, F.T., 1991. Abscission: shedding of parts. In: Raghaven-

dra, A.S. (Ed.), Physiology of Trees. Wiley, New York,

pp. 273–300.

Agren, G.I., Hyvonen, R., 2003. Changes in carbon stores in

Swedish forest soils due to increased biomass harvest and

increased temperatures analysed with a semi-empirical model.

For. Ecol. Manage. 174, 25–37.

Berg, A., Ehnstrom, B., Gustafsson, L., Hallingback, T., Jonsell,

M., Weslien, J., 1994. Threatened plant, animal, and fungus

species in Swedish forests. Distribution and habitat associa-

tions. Conserv. Biol. 8, 718–731.

Boddy, L., Rayner, A.D.M., 1983. Ecological roles of

Basidiomycetes in attached oak branches. New Phytol. 93,

77–88.

Butler, J.E., Rose, F., Green, T.E., 2001. Ancient trees, icons of our

most important wooded landscapes in Europe. In: Read, H.,

Forfang, A.S., Marciau, R., Paltto, H., Andersson, L., Tardy, B.

(Eds.), 2001. Tools for Preserving Woodland Biodiversity.

NACONEX Textbook 2. Toreboda Tryckeri AB, Sweden,

pp. 20–26.

Christenssen, O., 1977. Estimation of standing crop and turnover of

dead wood in a Danish oak forest. Oikos 28, 177–186.

Dagley, J., Warnock, B., Read, H., 2001. Managing veteran trees in

historic open places. the Corporation of London’s perspective.

In: Read, H., Forfang, A.S., Marciau, R., Paltto, H., Andersson,

L., Tardy, B. (Eds.), 2001. Tools for Preserving Woodland

Biodiversity. NACONEX Textbook 2. Toreboda Tryckeri AB,

Sweden.

Dahlberg, A., 2003. Vedlevande arters krav pa kvaliteer av dod ved

[Substrate requirements of saproxylic species in Sweden].

Swedish Threatened Species Unit, Uppsala (in Swedish with

English summary).

Egnell, G., Valinger, E., 2003. Survival, growth, and growth

allocation of planted Scots pine trees after different levels

of biomass removal in clear-felling. For. Ecol. Manage. 177,

65–74.

Ehnstrom, B., Axelsson, R., 2002. Insektsgnag i bark och ved.

Artdatabanken SLU, Uppsala (in Swedish with English

summary).

Fridman, J., 2000. Conservation of Forest in Sweden: a strategic

ecological analysis. Biol. Conserv. 96, 95–103.

Fridman, J., Walheim, M., 2000. Amount, structure and dynamics

of dead wood on managed forestland in Sweden. For. Ecol.

Manage. 132, 23–36.

Fung, P.Y.H., Kirschbaum, M.U.F., Raison, R.J., Stucley, C., 2002.

The potential for bioenergy production from Australian forests,

its contribution to national greenhouse targets and recent

developments in conversion processes. Biomass Bioenergy 22,

223–236.

Gardenfors, U. (Ed.), 2000. Rodlistade arter i Sverige 2000 [The

2000 Red List of Swedish Species]. ArtDatabanken, Swedish

University of Agricultural Science, Uppsala.

Gustafsson, L., 2002. Presence and abundance of red-listed plant

species in Swedish Forests. Conserv. Biol. 16, 377–388.

Hagberg, E., Matern, B., 1975. Volume Tables for Oak and Beech.

Research Notes 14. Department of Forest Biometry, Royal

College of Forestry, Stockholm.

Hannah, L., Carr, J.L., Lankerani, A., 1995. Human disturbance

and natural habitat. a biome level analysis of a global data set.

Biodivers. Conserv. 4, 128–155.

Harding, P.T., Rose, F., 1986. Pasture-Woodlands in Lowland

Britain. Natural Environment Research Council, UK.

Harmon, M.E., Franklin, J.F., Swanson, F.J., Sollins, P., Gregory,

S.V., Lattin, J.D., Anderson, N.H., Cline, S.P., Aumen, N.G.,

Sedell, J.R., Lienkaemper, G.W., Cromack, K., Cummins,

K.W., 1986. The ecology of coarse woody debris in temperate

ecosystems. Adv. Ecol. Res. 15, 133–302.

Jacobson, S., Kukkola, M., Malkonen, E., Tveite, B., 2000. Impact

of whole-tree harvesting and compensatory fertilization on

growth of coniferous thinning stands. For. Ecol. Manage. 129,

41–51.

Johansson, T., 2000. Regenerating Norway spruce under the shelter

of birch on good sites might increase the biofuel supply in

Sweden. NZ J. For. Sci. 30, 16–28.

Jonsell, M., Weslien, J., Ehnstrom, B., 1998. Substrate require-

ments of red-listed saproxylic invertebrates in Sweden.

Biodivers. Conserv. 7, 749–764.

B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248 247

Keddy, P.A., Drummond, C.G., 1996. Ecological properties for the

evaluation, management and restoration of temperate deciduous

forest ecosystems. Ecol. Appl. 6, 748–762.

Kruys, N., Jonsson, B.G., 1999. Fine woody debris is important for

species richness on logs in managed boreal spruce forests of

northern Sweden. Can. J. For. Res. 29, 1295–1299.

Linder, P., Ostlund, L., 1998. Structural changes in three mid-

boreal Swedish forest landscapes, 1885–1996. Biol. Conserv.

85, 9–19.

Lindholm, M., 2001. Epixyla lavar och mossor—mangfald i

relation till habitatets variation. Master Thesis. Goteborg

University (in Swedish).

Lofgren, R., Andersson, L. (Eds.), 2000. Sydsvenska lovskogar och

andra lovbarande marker. kriterier for naturvardering, skydd

och skotsel. Rapport 5081. Naturvardsverket, Stockholm,

Sweden (in Swedish).

Lundborg, A., 1998. A sustainable forest fuel system in Sweden.

Biomass Bioenergy 15, 399–406.

Malinen, J., Pesonen, M., Maatta, T., Kajanus, M., 2001. Potential

harvest for wood fuels (energy wood) from logging residues

and first thinnings in Southern Finland. Biomass Bioenergy 20,

189–196.

McComb, W., Lindenmayer, J., 1999. Dying, dead, and down trees.

In: Hunter, M.L. (Ed.), Maintaining Biodiversity in Forest

Ecosystems. Cambridge University Press, Cambridge, UK,

pp. 335–372.

Naslund, M., 1947. Funktioner och tabeller for kubering av staende

trad. Meddelanden fran Statens Skogsforskningsinstitut 36 (in

Swedish).

Niklas, K.J., 1997. The Evolutionary Biology of Plants. The

University of Chicago Press, Chicago.

Nilsson, S.G., Hedin, J., Niklasson, M., 2001. Biodiversity and its

assessment in boreal and nemoral forests. Scand. J. For. Res.

(Supplement 3), 10–26.

Nilsson, S.G., Niklasson, M., Hedin, J., Aronsson, G., Gutowski,

J.M., Linder, P., Ljungberg, H., Mikusinski, G., Ranius, T.,

2002. Densities of large living and dead trees in old-growth

temperate and boreal forests. For. Ecol. Manage. 161, 189–204.

Norden, B., Paltto, H., 2001. Wood-decay fungi in hazel wood.

species richness correlated to stand age and dead wood

features. Biol. Conserv. 101, 1–8.

Norden, B., Ryberg, M., Gotmark, F., Olausson, B., 2004. The

relative importance of coarse and fine woody debris for the

diversity of wood-inhabiting fungi in temperate broadleaved

forest. Biol. Conserv. 117, 1–10.

Olsson, M., Rosen, K., Melkerud, P.A., 1993. Regional modelling

of base cation losses from Swedish forest soils due to whole-

tree harvesting. Appl. Geochem. 8 (Supplement 2), 189–194.

Patterson, D.W., Wiant, H.V., Wood, G.B., 1993. Log volume

estimations. The centroid method and standard formulas. J. For.

91, 39–41.

Peterken, G.F., 1996. Natural Woodland—Ecology and Conserva-

tion in Northern Temperate Regions. Cambridge University

Press, Cambridge.

Ranius, T., Jansson, N., 2000. The influence of forest regrowth,

original canopy cover and tree size on saproxylic beetles

associated with old oaks. Biol. Conserv. 95, 85–94.

Rice, W.R., 1989. Analyzing tables of statistical tests. Evolution

43, 223–225.

Samuelsson, J., Gustafsson, L., Ingelog, T., 1994. Dying and Dead

Trees, A Review of their Importance for Biodiversity. Swedish

Threatened Species Unit, Uppsala.

Siitonen, J., Martikainen, P., Punttila, P., Rauh, J., 2000. Coarse

woody debris and stand characteristics in mature, managed and

boreal mesic forests in southern Finland. For. Ecol. Manage.

128, 211–225.

Sippola, A.L., Siitonen, J., Kallio, R., 1998. The amount and

quality of coarse woody debris in natural and managed

coniferous forests near the timberline in Finnish Lapland.

Scand. J. For. Res. 13, 204–214.

Skogsstyrelsen, 2001. Skogsbransle, hot eller mojlighet?—vagle-

dning till miljovanligt skogsbransleuttag. Skogsstyrelsens

forlag, Kristianstad, Sweden (in Swedish).

Stener, L.G., 1998. Lansvisa uppgifter om areal och virkesforrad

for lovtrad. SkogForsk Redogorelse 4, 1998 (in Swedish).

Thomas, P., 2001. Trees: Their Natural History. Cambridge

University Press, Cambridge.

Vera, F.W.M., 2000. Grazing Ecology and Forest History. CABI

Publishing, Oxon, UK.

von Butin, H., Kowalski, T., 1983. Die naturliche Astreinigung und

ihre biologischen Voraussetzungen. I. Die Pilzflora der Buche

(Fagus sylvatica L.). Eur. J. For. Pathol. 13, 322–334.

248 B. Norden et al. / Forest Ecology and Management 194 (2004) 235–248