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Natural Regeneration of Beech Forests in Europe - Netherlands: Approaches,
Problems, Recent Advances and Recommendations
S.M.J. Wijdeven; Haar, Barbro
Publication date:
2003
Document Version
Early version, also known as pre-print
Citation for published version (APA):
S.M.J. Wijdeven, & Haar, B. (2003). Natural Regeneration of Beech Forests in Europe - Netherlands:
Approaches, Problems, Recent Advances and Recommendations.
Download date: 29. Oct. 2016
NAT-MAN
Working Report 41
Natural Regeneration of
Beech Forests in Europe Netherlands: Approaches,
Problems, Recent Advances
and Recommendations
S.M.J. Wijdeven
Deliverable 22 of the Nat-Man Project
Produced under Work-Package 3
2003
The report is produced by the Nat-Man Project (Nature-based Management of Beech in Europe) co-ordinated
by Forest & Landscape Denmark, and funded by the European Community 5th Framework Programme.
Contact: Co-ordinator Jens Emborg, [email protected] - The report is available at www.flec.kvl.dk/natman
NATURAL REGENERATION OF BEECH FORESTS IN EUROPE NETHERLANDS: APPROACHES, PROBLEMS, RECENT ADVANCES
AND RECOMMENDATIONS
Report from research on approaches to naturally regenerate beech managed forests
- Netherlands (NAT-MAN, D22)
S.M.J. Wijdeven, Alterra, 2003
An overview of management of beech forests in the Netherlands
4.1 Introduction
4.2 Overview of beech in the Netherlands
4.2.1 Beech forest types
4.2.2 Beech characteristics
4.3 Beech management
4.3.1 Main management systems
4.3.2 Beech management practices
4.4 Future developments
4.5 References
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4.1 Introduction
This working document presents an overview of beech forest management in the Netherlands,
with emphasis on regeneration. Information from unpublished and published documents has
been combined. Potentially beech woods will be the dominating forest type in the Northwest
of the European continent (see Map of Potential Natural Vegetation of Europe; Bohn 2000).
Beech forests will dominate on a wide range of soils (from sandy to loamy and from acid to
alkaline), with a medium soil water availability (not too wet and not too dry). Fagus sylvatica
is one of the potential prominent tree species in the Netherlands.
4.2 Overview of beech forests in the Netherlands
The current extent of beech forests in the Northwest of the European continent is restricted to
approximately 7,750 hectares in The Netherlands, 50,000 hectares in Flanders and the west of
Walloon and 140.000 ha (110,000 ha high forest and 30,000 coppice or coppice with
standards) in the northwest and centre-west of France (source EFI-data base, Dirkse 2003). In
the Netherlands the area of beech forests is currently 3% of the total forests area (EC-LNV
2003). The greatest part is pure beech forest (40%), 30% is mixed with deciduous species and
25% ha with conifers (Dirkse 2003). Beech is often found in stands dominated by other
species; in 29% of the stands beech individuals were encountered (Dirkse 1987). The area if
beech is expanding from 7,150 ha in 1984 to 7,750 in 2002, mainly as a result of the
spontaneous invasion by beech. In potential, beech is one of the main species in 35% of the
total forest area of the Netherlands (van der Werf 1995). Three major beech forest types can
be discerned (Nat-man WP2, see below). Beech forests on calcareous soils, beech forests on
acid substrates and beech forests on mesotrophic substrates. In the beech forests types, beech
is the dominant tree species, but co-occurring species are: Quercus robur and Q. patraea,
Carpinus betulus, Fraxinus excelsior, Acer pseudoplatanus, Betula pendula and Pinus
sylvestris.
4.2.1 Beech forest types
Fago-Quercetum
The Fago-Quercetum forest is the most dominant forest type in the Netherlands. Stortelder et
al. (1999) distinguish next to the Fago-Quercetum also the Deschampsia-Fagetum. They
occur also in Belgium and Northern France (van der Werf 1991, Stortelder et al. 1999, Koop
& Hilgen 1987). The Fago-Quercetum and Deschampsia-Fagetum consist of calcareous poor,
(light) loamy (10-50% loam), fairly acid soils (pH of 4), relatively poor and dry, often
developed into podsols. Co-occurring tree species are Quercus patraea, Q. robur and Betula
pendula (all in low numbers) They are relatively homogeneous forests due to shading,
extensive root system and thick humus layer. There is a poorly developed shrub layer with
Ilex aquifolium and Sorbus aucuparia as the most prominent species. The herb layer is open
and consists of species as Deschampsia flexuosa, Maianthemum bifolium, Carex pilulifera,
Lonicera periclymenum and Pteridium aquilum in gaps. In less dry places species such as
Populus tremula, Betula pubescens, Rhamnus frangula and Molinia caerulea can be found.
From pollen records it can be concluded that 80-90% was beech and 10-20% oak (Trautmann
1969 in van der Werf 1991), while Noirfalise (1984 in van der Werf 1991) in Belgium
currently finds 55-80% and 10-35% respectively.
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Milio-Fagetum
These forest types occur on relatively rich, loamy, moistures soils. Beech forests are classified
as Stellario-Carpinetum (Stortelder et al. 1999) and as potential vegetation type as MilioFagetum (van der Werf 1991). They occur in the Netherlands as in Belgium (Berge et al.
1990) and Germany (Koop 1981) and parts are comparable to the Fago-Quercetum. The
dominant tree is Fagus sylvatica, with some Quercus robur or Q. patreae, Fraxinus excelsior
and Carpinus betulus. The shrub and herb layer is in general poorly developed and may
consist of Corylus avellana, Sorbus aucuparia, Crataegus monogyna, Ilex aquifolium,
Anemone nemorosa, Viola riviniana, Milium effusum and Poa nemoralis. Due to frequent
harvesting and coppice these forest types are now mainly dominated by Carpinus betulus and
Quercus robur.
Melico-Fagetum
In the Netherlands two main potential vegetation types are distinguished; Melico-Fagetum
and Carici (albae)-Fagetum (van der Werf 1991). Melico-Fagetum also occurs Northern
France (Koop & Hilgen 1987) and parts may also be attributed to the Stellario-Carpinetum.
The soils are calcareous with loam or clay in the topsoil, moistures, with humus type mull,
and pH 5.5-7. It forms a closed beech forest, with a shrub layer only in canopy gaps but with
a fairly developed herb layer. Co-occurring species are Quercus robur and Q. patreae,
Carpinus betulus, Fraxinus excelsior, Acer pseudoplatanus and Prunus avium. The most
prominent shrub is Corylus avellana. The herb layer consists of Melica uniflora, Galium
odoratum, Mercurialis perennis, Hedera helix and Sanicula europaea.
4.2.2 Beech characteristics
Beech occurs on a wide range of mesic soils, with a pH of 3.5 – 7 and a texture of clay-loam
to loamy sands (%50µm > 10%). On poor soils beech is possibly present but lower in height
(van den Burg 1997). Presently beech predominantly on acid, nutrient poor soils in the
Netherlands (Fanta 1995). Humus form may vary from mull to moder and litter can have acid
or podzolization effect on soil (Peters 1992). Water availability is very important since beech
is sensitive to drought or (periodic) wet soils, especially if summer precipitation is irregular or
insufficient (Peters 1992). Furthermore, beech is sensitive to late spring frost which causes
seed production and seedling survival to fail.
Beech architecture follows Troll’s model; plagiotrophic differentiation in all aerial axes. This
plagiotrophic growth model forms, compared to orthotrophic models, a flattened and highly
organised leaf layers, capable of intercepting light over large surfaces with less investment.
Orthotropic species invest more in height growth. Beech is relatively flexible in growth
strategy, capable of forming short and long shoots in relation to environmental conditions
(Peters 1992), and has a leaf area index higher than of most other species (4-6 m2/m2; oak 3-4
m2/m2; pine 1-3 m2/m2; Oosterbaan & Bartelink 1995). This is a means of responding to a
variable environment (Peters 1992). Maximum age for beech varies between 200 and 400
years.
4
Beech flowers in April/May and is wind pollinated. Seed production starts at an age of 40 to
60 years (Fanta 1995, van der Werf 1995). It produces seeds in mast years. A frequency of
every 5-7 years is reported, although this is variable and seed production in between these
mast years is not uncommon (Bastide & Vredenburch 1970, Oosterbaan & Bartelink 1995,
Fanta 1995). High temperatures, sunny with low precipitation, have a positive effect, while
rain and night frost during flowering and seed set negatively affect seed production (van Tol
1979, Fanta 1995). Topoliantz & Ponge report that seed production is age related and the
main influencing environmental variables are water and light (Topoliantz & Ponge 2000).
Seeds may be affected by insects, fungy and birds. In low to moderate seed years, most seeds
are affected. Only in mast years sufficient viable seeds remain (van Tol 1979). The viability
of seeds varies; in tests viability ranged between 56% and 80% (Oosterbaan & van Hees
1991, Oosterbaan 1987). Seed fall is in October-November, and viability last up to 6 months
(Oosterbaan 1999). Seeds are relatively heavy, ranging from 20-40mg. In mast years, 400-600
seeds may fall under adult trees per m2 (Oosterbaan 1999). Jay (Garrulus glandarius) is the
most important long range seed vectors, capable of dispersing (few) seeds several 100s meters
to kilometres (Fanta 1995, Koppe 1998). Nevertheless, the majority of the seeds are dispersed
within the vicinity of the mother trees (van der Werf 1995; Alterra unpublished data). Van der
Werf (1995) observed that most seedlings occurred within 20m and that the furthest seedling
was encountered at 60m. Voles, mice and squirrels are the main dispersers over short
distances, carrying and cache seeds away from the mother tree (Fanta 1995, Oosterbaan
1999). Fallen and dispersed seeds may be affected by insects, fungi and consumed by rodents,
birds, deer and wild boar (Koppe 1998).
In the Netherlands, the growth of beech, expressed as potential top height at infinite age (Svalue), is mainly related to a few environmental factors (van den Burg 1997). From 92 beech
stands across the Netherlands, it was concluded that the S-value (r2=0.79) could for a large
part be related to moisture availability (38%) and temperature (35%). Soil nutrient content
and acidity did not have a decisive influence. It is remarkable that the wind resistance is
relatively large, as concluded from high S-values on nutrient rich, moistures soil in the
western part of the country (van den Burg 1997). In this study the maximum age varied
between 150 to 200 years, with heights ranging from 23 to 38m. The S-value of beech varied
between 35.2 and 49.1 m (see also Jansen et al. 1996).
Although beech was not used extensively in the past, it is now regarded as a potentially
prominent species, given the environmental conditions and due to its characteristics in height
growth and shade tolerance. Beech has a relative slow height growth in its youth.
Nevertheless, due to the shade tolerance can beech survive and grow in combination with
several other species (oak, larch, Scots pine, birch). Beech timber has various uses, from
furniture to fire wood. A whitish colour is valued important. Chances on red colouring of the
stem increase with age, and harvesting before 100yrs has therefore been advised (Oosterbaan
& Bartelink 1995). Beech is flexible in growth, capable of occupying open spaces. However,
occupying open spaces can cause less straight stems. In contrast, variation in annual growth
ring width does not have a great influence on wood quality (van Goor et al. 1974).
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4.3 Beech management
Beech is a relatively young tree species, which reached the far north of the NorthwestEuropean lowlands approximately 2000 years ago. Beech expanded from 3000-1000 BC due
to higher temperatures, changing competition and human influences. Around 0c deforestation
increased, also on higher sand soils. The resulting fragmented (oak) forests were difficult to
reach for the animal dispersed beech seeds. Together with cattle grazing in forests, beech
regeneration was hampered. Therefore beech could never develop fully as a dominant forest
species in climax forest communities (Fanta 1995). On the potential beech areas, open areas
due to heavy grazing in combination with other species were favoured (e.g. oak). In the late
19th century, when grazing became less profitable, reforestation and forest conversion started
towards more economic interesting species, amongst others with Scots pine, but also with
larch and Douglas fir. Nowadays, due to the less intensive clearing, cutting and grazing, and
due to more available seed sources (e.g. planted beech lanes), beech (slowly) expands in the
Dutch forests.
4.3.1 Main management systems
This section presents an overview of the different management systems of beech forests in
Europe, and consists of an unpublished document of van Hees & Joustra (unpublished 2003).
The management systems are characterised by the scale and techniques of regeneration, as
these are the most important determinants for the variety of beech management systems in
Europe.
Beech coppice
Beech coppice was a traditional management system concentrated in the mountainous areas of
Central and South Europe (France, Italy and Spain). Beech wood has been used primarily as
firewood or for the production of charcoal. In most areas coppice as a management system
has ended. If not converted, neglected beech coppice has developed into a multiple stemmed
high forests. Locally, this is presumably also the case in the Netherlands.
Clear cut system
Under the clear-cut system the old stand is harvested in one cut, generally followed by
planting. There is a clearly defined rotation period, which for beech stands varies between
100 and 140 years. Clear cut leads to the development of large even-aged stands. Generally
the area of a clear cut is larger then 0.5 ha. After the clear cut the area is planted with young
beech trees in a density of 4,000 to 10,000 trees per ha. In the early phase of development the
young beech plantation will be tended by removing ill shaped fast growing and dominant
individuals. From the age of 20 to 30 years the plantation will be thinned with a regular
interval. Clear cut (is and) has been a common management system for beech in Northwest
Europe (UK, NL, B, DK, S, D, F)
Shelter wood system
In the shelterwood system the old beech stand is harvested while leaving a limited number of
old trees as seed trees and as shelter for the new generation. The remaining old beech trees
will be cut in a period of 15 to 20 years, depending on the development of the new beech
generation. The shelterwood system has similarities with the clear-cut system. It also leads to
the development of large even-aged young stands in which tending and thinning is similar to
6
beech plantations. The shelterwood system is the most common management system for
beech stands in Europe. In spatial and temporal context it is a rather easy and clearly
structured management system.
Strip cut system
Essentially a strip cut is a long and small clear cut facilitating natural regeneration. Under this
system strips with a width of 1 to 1.5 times the dominant tree height are cut on the Southeast
side of the stands. In these strips trees beech will regenerate naturally and depending on the
width of the strips successful regeneration of light demanding species is possible. If the
density of the regeneration is insufficient additional planting is possible. By cutting new strips
with an interval of 5 to 10 years the old stand will replaced in a few decades. The strip cut
system leads to a mixed forest with beech and light demanding species as birch (Betula
pendula and others deciduous species like oak, ash, aspen) and larch (Larix decidua). The
strip cut system is a common management system in beech forests in central and Eastern
Europe.
Group selection system
In the group selection system regeneration starts with the cut of gaps in the old stand with an
area of 0.1 to 0.3 ha. Depending on the size of the gaps light demanding and/or shade tolerant
species will regenerate. If natural regeneration is insufficient additional planting is possible.
In time the area in regeneration will expand by harvesting trees in the border of the gaps
and/or creating new gaps. Eventually the gaps will merge and in a period of 30 to 60 years the
old stand will be replaced by the next forest generation. The group selection system leads to
the development of a semi even-aged or uneven aged mixed stand. The group selection
system is common in the mixed beech forests of central and Eastern Europe. Especially in
central Europe combinations between Strip cut system and Group selection system has been
developed (saumfemelschlag, blendersaumschlag).
Single tree selection system
A stand under a single tree selection system has a heterogeneous stand structure, due to the
small-scale variation in age and diameter of the trees. Advanced regeneration is continuously
present. Dominant individual trees are harvested, which gives young trees the opportunity to
grow into the dominant tree stratum. Stands under this management system are mixed beech
forests (beech, fir and spruce) and don’t have a clear rotation period or a clear regeneration
period. Generally the group selection system is restricted to the moist and more nutrient rich
sites in the mountainous areas of central and east Europe.
Nature oriented forestry
The previous described management systems all have been developed with the primary
objective of wood production. Nowadays there is a clear trend to combine wood production
and biodiversity conservation explicitly. Clear management systems has not yet evolved.
However there seems to be a common basis for the development of a nature based forestry
system. Such a system should be based on a group selection system with a variable group
size, should lead to an uneven-aged mixed forest with a limited number of over-mature trees
which may die of old age and in which a substantial amount of dead wood (standing and
lying) is present.
7
In the Netherlands, the main beech management systems were and/or are clear cut, group
selection en nature oriented forestry.
4.3.2 Beech management practices
Information on beech management practices in this section come from (Schütz & van Tol
1981, Peters 1995, Fanta 1995, Oosterbaan & Bartelink 1995, van der Jagt et al. 2000, van
Goor et al. 1974, SBB 1996). In the past, beech was not used extensively as one of the main
forestry species, and therefore specific management systems were not developed.
Nevertheless, it is now regarded as a potentially prominent species. As mentioned, there is a
general shift in management systems from mainly planted monocultures in the past towards
mixed naturally regenerated stands at present. Four main types of management interventions
strategies are recognized here; the regeneration strategy, the tending strategy, the thinning
strategy and the harvesting strategy.
Regeneration strategy
In the past, stands were generally planted with 3yr old seedlings, with 4000-6500 individuals
per ha. New stands were initiated in relatively small or sheltered locations; in large clear cuts
frost damage was a serious risk. In some occasions, sowing of 2 to 3hl of seeds was used
below a tree shelter, after which a shallow soil cultivation was applied. More recently, natural
regeneration has become the main strategy. This regeneration is partially stochastic and is
highly influenced by night frost, moisture availability, seed dispersal and predation, herbivory
and establishment, survival and growth in combination with the environmental conditions of
the regeneration niche (see also Nat-Man WP3, D3,D21). These conditions are often initiated
by tree fall gaps. In managed forests, foresters influence these processes actively by altering
light conditions, preparing soil or excluding browsing animals, to ensure an optimal
establishment. Generally, small gaps (1 to 1.5 times tree height) or a heavy thinning is
applied. Soil cultivation can have a positive effect. In the absence of seed sources, planting
(preferably in groups) in combination with natural regeneration with other species can be
applied. The gap size may vary in order to influence tree species abundances. After successful
establishment, the remaining shelter can slowly be removed.
Tending, thinning and harvesting strategy
In the early phase, the main emphasis is on the removal of ill shaped stems and/or controlling
the species abundances. Due to the shade tolerance, beech can be used below other tree
species in layered stands. After this, with regular thinning the stands remain closed to ensure
branch-free stems. Between 14-20m height, Future-trees are selected, based on stem
straightness, h/d ratio (<100) and branch-free bole height. After that, generally a thinning
interval of 5yrs is applied, where in each intervention 50% of a Future trees crown is
liberated, in order to promote radial growth. Mentioned basal areas vary between 26 and
30m2/ha. Depending on the soil types, a target diameter harvesting is applied, varying
between 40-70cm dbh and 70-100cm dbh.
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4.4 Future developments
Virtually all forests in the Netherlands are influenced by human activities. Most forests were
planted and/or actively managed (as high beech forests) for timber production. However,
recently forest and nature organisations realise that a small-scale, nature oriented,
management can serve multiple goals, from wood production to nature conservation and
recreation. Aspects highly valued in this densely populated country. This shift in management
also encompasses a main shift from planting (in clear-cut areas) to natural regeneration in
(small) gaps, coupled with a shift from monocultures to mixtures.
Beech is becoming a more prominent species in the Dutch forests, mainly due to invading
natural regeneration. Forest management in the Netherlands is generally focused on multiple
goals. It is assumed that natural processes (e.g. regeneration) on a relative small scale with the
use of mixtures is most advantageous. Both native and non-native species can be used in these
mixed forests. Two main forest types have been identified and are now promoted as
interesting species combinations. The types are: (a) beech, birch, larch and Douglas fir and (b)
beech, ash and maple on more richer soil types. Beech in combination with oak (and other
species) is sometimes promoted, but will possibly induce frequent interventions to ensure
sufficient oak abundance. Species abundances can be influenced by gap size, in combination
with seed source availability. With these species combinations, the group selection system
will be applied. At present, experience with these types of management systems and species
combinations is slowly building up.
As indicated before (Nat-Man D3 and D21) regeneration is often hampered. More insight is
needed on the whole trajectory from seed production, seed dispersal, seedling establishment,
humus, light and moisture availability and predation and browsing. Moreover, research
focused on competition and developments in the (young) mixtures of species is needed in
combination with field experience.
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4.5 References
Bastide, J.G.A. la & C.L.H. van Vredenbuch, 1970. Factoren die de zaadproduktie van bomen
beinvloeden: analyse, prognose en consequenties voor de praktijk. Nederlands
Bosbouw Tijdschrift 41, 88-93.
Berge, K. van den, P. Roskams, A. Verlinden, P. Quataert, B. Muys, D. Maddelin & J.
Zwaenenpoel, 1990. Structure and dynamics of a 215-years old broadleaved forest
stand recently installed as a total forest reserve. Silva Gandavensis, 55: 113-152.
Burg, J. van den, 1997. Groei en groeiplaats van de beuk in Nederland. IBN-DLO, rapport
303. The Netherlands.
Dirkse, G.M., 1987. De natuur van het Nederlandse bos. RIN-rapport 87/28. Leersum, the
Netherlands. 217 p.
Dirkse, G.M., 2003. Meetnet functievervulling bos: het Nederlandse bos 2001-2002. EC-LNV
nr 2003/231. Ede, the Netherlands. 62 p.
Fanta, J., 1995. Beuk (Fagus sylvatica L.) in het Nederlandse deel van het nw-Europees
diluvium. Nederlands Bosbouw Tijdschrift 67, 225-0234.
Goor, C.P. van, K.R. van Lynden & H.A. van der Meiden, 1974. Bomen voor nieuwe bossen.
StiBoKa, De Dorschkamp, St. Industrie hout, Wageningen, the Netherlands. 118 p.
Jagt, J.L., J.M. Paasman, L.A.S. Klingen, M.R. Houtzagers & C.J.F Konings, 2000.
Geïntegreerd bosbeheer. EC-LNV, Wageningen, the Netherlands. 214 p.
Jansen, J.J., J. Sevenster & P.J. Faber, 1996. Opbrengsttabellen voor belangrijke boomsoorten
in Nederland. LUW & IBN-DLO, IBN-rapport 221. 202 p.
Koppe, J.A., 1998. Natuurlijke verjonging in de boscomplexen van Nationaal Park ‘De Hoge
Veluwe’. MSc. dissertation, Wageningen Agricultural University. Wageningen, the
Netherlands. 35p.
Koop, H. 1981. Vegetatiestructuur en dynamiek van twee natuurlijke bossen: het
Neuenburger en Hasbrucher Urwald. Verslagen van Landbouwkundige
Onderzoekingen 904. Pudoc, Wageningen, the Netherlands. p. 112.
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Koop, H. & P. Hilgen, 1987. Forest dynamics and regeneration mosaic shifts in unexploited
beech (Fagus sylvatica) stands at Fontainebleau (France). Forest Ecology and
Management, 20: 135-150.
Oosterbaan, A., 1987. Een onderzoek naar de invloed van bekalking en opperlvakkige
grondbewerking op natuurlijke verjonging van beuk (Fagus sylvatica). De
Dorschkamp, rapport 488. De Dorschkamp, Wageningen, the Netherlands. 29 p.
Oosterbaan, A. & A.F.M. van Hees, 1991. Natuurlijke verjonging van beuk; een
lichtingsproef op rijke holtpodzolgrond. De Dorschkamp, rapport 636. De
Dorschkamp, Wageningen, the Netherlands. 34 p.
Oosterbaan, A. & H.H. Bartelink, 1995. Teeltkundige mogelijkheden van beuk in gemengd
bos. Nederlands Bosbouw Tijdschrift 67, 246-252.
Peters, R. 1992. Ecology of beech forests in the northern hemisphere. PhD. dissertation,
Wageningen Agricultural University. Pudoc, Wageningen, the Netherlands. 122 p.
Peters, R., 1995. Toekomst van het Nederlandse beukenbos. Nederlands Bosbouw Tijdschrift
67, 218-224.
Schütz, P.R. & G. van Tol, 1981. Aanleg en beheer van bos en beplantingen. Pudoc,
Wageningen, the Netherlands. 504 p.
Staatsbosbeheer, 1996. Regionaal
Driebergen, the Netherlands.
beheersschema
Veluwe-Achterhoek
1995-2004.
Stortelder, A.H.F., J.H.J Schaminée & P.W.F.M. Hommel, 1999. De vegetatie van Nederland.
Deel 5; ruigten, struwelen en bossen. Opulus Press, Uppsala, Leiden. The Netherlands.
Tol, G. van, 1979. Natuurlijke verjonging van beuk op de Veluwe. Nederlands Bosbouw
Tijdschrift 51, 106-112.
Topoliantz, S. & J.-F. Ponge, 2000. Influence of site conditions on the survival and growth of
Fagus sylvatica seedlings in an old-growth beech forest. Journal of Vegetation Science
11, 396-374.
Werf, S. van der, 1991. Natuurbeheer in Nederland, deel 5; Bosgemeenschappen. Pudoc,
Wageningen.
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Werf, S. van der, 1995. Komst en uitbreiding van beuk in Nederland. Nederlands Bosbouw
Tijdschrift 67, 235-240.
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