CLOSE TO NATURE MANAGEMENT IN FORESTS WITH
PREVAILING ECOLOGICAL AND ENVIRONMENTAL FUNCTIONS
Martin MORAVČÍK, Bohdan KONÔPKA
Forest Research Institute Zvolen, T. G. Masaryka 22, SK – 960 92 Zvolen, SLOVAK REPUBLIC, moravcik@fris.sk,
bkonopka@fris.sk
Abstract
MORAVČÍK, M., KONÔPKA, B.: Close to Nature Management in Forests with Prevailing Ecological and
Environmental Functions.
The article deals with objectivisation of forest management planning in forests with prevailing ecological
and environmental functions on the example mountain forests of Norway spruce vegetation altitudinal
zone. The target is to enforce a new, close to nature approach, at planning and care about these forests in
dependence on degree of deviation of structure of particular forest stands from the structure of primeval
forests eventually natural forests. Article submits a proposal of management models as well as procedure
in decision making about need and urgency of measures.
Key words: management models, management targets, basic decisions, management principles
Introduction
The Slovak Republic represents rather small area (49,034 km2) but belongs to the most forested
countries in Europe. The forests cover about 20 thousand km2, i. e. about 41% of the total area of the
country. The substantial part of the country is occupied by the mountains of the Carpathians Arch with
the highest point of the Gerlachovsky Pick (2,655 m above see level). The forests have not only
wood–producing, but also public–beneficial functions. For instance, a lot of rivers, important also for
neighboring countries, spring just on the Slovak territory. Because of the mountainous nature and the
above–mentioned water supply significance, Slovakia is sometimes called “the roof of the Central
Europe”.
The Slovak forests are classified according to dominating tree species into eight vegetation zones:
1. Oak (located on altitudes below approximately 300 m), 2. Beech–oak (about 200–500 m), 3. Oak–
beech (300–700 m), 4. Beech (400–800 m), 5. Fir–beech (500–1,000 m), 6. Spruce–beech–fir (900–
1,300 m), 7. Spruce (1,250–1,550 m) and 8. Mountain pine (over 1,500 m). From public–beneficial
point of view, the most important forest ecosystems are those located in the seventh, i.e. spruce
vegetation zone (SVZ). All these forest ecosystems belong to the category of protective forests.
Particularly, there are important mainly from water management, soil erosion control, avalanche
control, nature conservation, tourism and aesthetic aspects.
In this vegetation zone, the sum of annual precipitation is between 1,000–1,300 mm, mean annual
temperature 2.0–4.0ºC, vegetation period lasts 70–100 days. The area of the forests of the SVZ is
about 40 thousand ha, that is 2% of the total forest area in Slovakia. The forests of the SVZ are located
in the central and northern parts of Slovakia. In fact, the SVZ conforms to the potential forest
vegetation of mountain spruce.
The original forests of the SVZ were made up mostly of sparse stands or groups of trees with a
Norway spruce as a dominant species. Except this species, some forests are composed also by
European larches, European beech, mountain ash and even–species fragments of dense mountain pine
stands. Also, silver fir, cembra pine, and sycamore maple can be found there.
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The large area of forests of the SVZ spreads on the territories of the national parks. The most
frequent forest type groups are Sorbeto–Piceetum (Mountain ash–spruce) and Lariceto–Picetum
(Larch–spruce). The forest type groups express original tree species composition, i.e. how should look
like in the case of no man influence. This phytocenological units reflect also site and climatic
conditions.
The main problems in the spruce vegetation zone
In Slovakia, attention of scientists has been focused on forest ecosystems growing in the SVZ (the
term “high–mountain forests” is often used for them as well) usually in term of worsening health
conditions of trees. Decline of forests on some areas located in the SVZ was demonstrated through
monitoring of forest health, which showed that about 90% of the forest area in the SVZ could be
considered as effected by air pollution of different intensities (the A, B, and C zones with high, middle
and low concentrations of air pollution, particularly). The C zone, typical with a low air pollution load,
i.e. existing growth conditions allow spruce trees to survive further about 60 years, is the most
frequent in the SVZ. In this SVZ, a rise of ozone concentration with altitude was proved.
Also, the significant decrease of pH values was recorded in the soils of the high–mountain forests.
Particularly, since 60’s the pH values decreased by 0.5 – 1.0 unit in the forest soils. In the last decade,
the emissions of sulphur and nitrogen matters were considerably cut down but still are accumulated in
the soils.
Another negative ecological factor influencing significantly health of the Slovak high–mountain
forests, especially in the last two decades, are unfavourable climatic conditions. It concerns a lack or
unsuitable distribution of annual precipitation and temperature extremes. Formerly, the Slovak high–
mountain forests were considered as ecosystems with sufficient amount of precipitation and having
favourable soil moisture. However, resent studies showed dramatic changes of water regime in
mountain forest soils. This is the most evident in sparse spruce stands. Soil acidification and lack of
soil moisture are considered as the most negative factors worsening, or on some sites even disabling
the natural regeneration in the high–mountain forests.
In addition, windstorm damages to mountain forests are serious. Trees damaged by wind as well as
those physiologically weakened by climatic extremes create favourable conditions for bark beetle
outbreaks. While in the past bark beetles outbreaks occurred up to altitude of about 1,000 m above see
level, presently this limit is in 1, 300 m, on certain areas even on the timberline.
High ozone concentration, nitrogen and sulphur depositions accumulated in the soil, climatic
extremes and some other harmful agents, individually or in combination, cause weakening of forest
ecosystems or even their collapse. Consequently forest stands become sparse and fragmented. This
phenomenon is the most evident on mountain ridges in altitudes of 1,300 – 1,600 m a.s.l. Previously,
mainly in the Low Tatra National Park, the issues of restoration (reforestation) of mountain pine
stands, reduced due to livestock grazing in the previous centuries, were figured out by researchers.
Also, reclamation measures, e.g. liming and fertilizing in spruce forests of the SVZ weakened by air
pollution or other agents have been studied.
The forest stands of the SVZ have changed, vertically and horizontally little differentiated stand
structure on a large part of them. Remoteness, technological inaccessibility and economic non–
profitability of management caused neglect of care about these forests in the last decades. A great part
of these forests had been gradually grown old. Further neglect of care would necessarily lead to
reduction eventually loss of their utility. Therefore with the aim of intensifying the care, improvement
stability, health condition and securing of required utility objectivized methods and procedures of
forest management planning in these forests were elaborated.
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Material and Methods
Elaboration of objectivised methods and procedures of framework and detailed forest management
planning goes out the principles formulated by GREGUŠ (1989) according to which management of
forests should lead to achievement of maximal benefits of forest and their permanent and effective
providing. Forests fulfil their ecological and mostly also social functions the best in such status that
responds to the status of primeval forests, untouched by man (permanent existence of forest with
suitable spatial, age and tree species structure, preserved self–regulating abilities, good health
condition). These principles represent starting points and recommendations for elaboration of
management models for the forests with prevailing ecological and social functions.
From these reasons we proposed to elaborate management models for the SVZ differentiated by
level of retaining / conservation of natural structure (naturalness class). Another criteria for
differentiation of the management models are site and stand conditions and altitude (altitudinal zone:
below 1400 m and above 1400 m). The main part of empirical material came from field measurement
and observations designed in a two–level scheme. The higher level was made up by five research
areas, the lower level by 122 research plots. The research areas represented a size from 20 to 135
hectares, a size of research plots was from 2 to 10 are (set of at least 25 trees). Research plots were
distributed so that they represented variety of types of stand structure and different levels of man
influence of forests and comprehended all important typological units particularly the forest type
groups.
Table 1. Frequency and distribution of the research plots by site, naturalness and height above see
level
Forest type groups, n /%
AcP (Acereto–
CP (Cembreto–
FP (Fageto–Piceetum)
Piceetum)
Piceetum)
22 / 18,0
9 / 7,4
7 / 5,7
Naturalness class, n /%
A/B
B
B/C
C
D
E
16 / 13,1
49 / 40,2
25 / 20,5
20 / 16,4
7 / 5,7
4 / 3,3
Height above see level, n /%
1351 – 1400
1401 – 1450
1451 – 1500
1501 – 1550
nad 1551
21 / 17,2
29 / 23,8
32 / 26,2
19 / 15,6
7 / 5,7
SP (Sorbeto–Piceetum)
LP (Lariceto–Piceetum)
84 / 68,9
A
1 / 0,8
do 1350
14 / 11,5
Status of forest on the research plots was complexly analyzed. There were done also
comprehensive studies all parts forest ecosystems, particularly bedrock, soil, water, herb layer, woody
plants, bioclimate and air quality. Mainly results of these analyses were used as a background material
on elaboration of management models.
Classification of the naturalness was performed on the research plots through the visual signs left
by human activities that caused changes in age, spatial and tree species structure. For practical needs
these three kind of aggregated naturalness class were specified:
Table 2. Aggregated naturalness classes and their development stages
1 – Primeval forests
11 – In stage of growing up
12 – In stage of optimum
13 – In stage of destruction
2 – Natural forests
21 – In stage of growing up
22 – In stage of optimum
23 – In stage of destruction
3 – Man–made forests
31 – In period of tending
32 – In period of regeneration
–
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The empirical material of the research plots was processed and evaluated through the specifically
formed database system in the scope of programme MS Access 2000 which enable:
–
archiving of all values and parameters,
–
immediate threedimensionatial visualization of the research plots,
–
primary data processing of individual research plots (computation of basic characteristics,
indicators of spatial structure and indexes of horizontal and vertical structure),
–
interactive classification of data with consecutive calculations of average values and basic
statistical characteristics for defined sets of data.
Evaluated empirical material together with knowledge obtained from literary sources were used for
elaboration management models in following classification:
Management models
Management targets
Basic decisions
Management principles
– outlook
– available
Target tree species
composition
Target stand structure
Target stocking
Target production
Forest category
Management system
Rotation
Regeneration period
Period of securing
consecutive stand
Especially principles:
Tending, silvidulture
Regeneration
Formation of forest
Results achieved
Management targets
Target tree species composition
In tree species composition of the original high–mountain forests, the Norway spruce represented
absolute prevalence. It is the tree species, which tolerates harsh living conditions of the SVZ the best.
Therefore, also at present, Norway spruce stands are dominant on these sites. The other premixing
species were proposed according to site and climatic conditions with the main aim of ensuring public–
beneficial functions and stability of forests.
Target stand structure
The limit values for selected indicators of target stand structure were derived from data collected
on the research plots classified in the first naturalness class (primeval forests). These characterize the
most original forest stands of the SVZ. Therefore, they were considered as a model of target stand
structure. Naturally, the primeval forests have three development stages growing up, optimum, and
declination.
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Table 3. Criteria for target stand structure
1st natural– Development stage (adjusted average values)
ness class
Growing up
Optimum
Declination
50 ± 15
60
45
50
Tree diameter variability (Sx%)
3
3
2–3
3
Degree of diameter dispersion
40 ± 20
50
30
40
Tree height variability (Sx%)
55 ± 15
45
65
60
Upper
25 ± 15
30
25
20
Share of canopy level (%) Middle
20 ± 15
25
15
20
Downer
75 ± 10
80
75
75
Crown length / tree height (%)
60 ± 10
55
60
55
Tree height / tree diameter
Texture:
Mosaic of stand clumps and clusters with the maximal size by 0.5 hectare
Indicator
Because of large area of man–made forest stands with neglected management in the past it will not
be possible to reach desired stand structure even in the next generation. Therefore, available target
stand structure was derived too, from the data representing the second degree of naturalness (natural
forest).
Outlook target stand
structure (Primeval forest)
Available target stand
structure (Natural forest)
Man–made forest
Fig. 1. Demonstration of the target stand structure.
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Table 4. General characteristic of target stand structure according to forest type groups and altitudinal
zone
SFT
SP
LP
AcP
FP upper d.
PiL upper d.
Target Stand Structure
The target is strongly age, diameter and height (horizontally and vertically)
differentiated structure that secure fulfilment important ecological functions of forests
of SVZ. First–rate is also static stability and adequate stocking of these forests.
Permanent, continual effect of stand structure to forest functions is desirable. The target
is irregular stair–step stand structure where trees and their clusters of various age,
differentiated diameter and height alternate in mosaics. Trees have favourable
indicators of static stability with deeply and lively branched crowns. Their height
gradually declines with growing above–Sea altitude. In upper zone (above 1 400 m) the
trees grow mostly in squad set–up.
Target stocking
Target stocking was derived on the basis of original procedure respecting requirements of soil and
water protection, stability and natural regeneration. Relationships between stocking, indicators of
stability and complex of preconditions for natural regeneration were analysed. Combining these
aspects, the value of 0.7 (0.6 at the upper forest limit) proved to be optimal for the stand stocking.
Basic decisions
The basic decisions in the Slovak forest management practice are mainly: category of forest
(commercial, protective, special purposes), silvicultural system (clear cutting, shelterwood, selective),
rotation and regeneration period. The baisc decisions were elaborated for the three classes of
naturalness (primeval, natural, and man–made forests), which reflect intensity of man effects on the
forest ecosystems.
Table 5. Basic decisions differentiated according to naturalness class
Naturalness class
Category of
forest
Silvicultural system
Rotation
(years)
Regeneration
period
1–Primeval forest
Protective
Retain for self–regulating
processes without interventions
250 – 300
Continual
2–Natural forest
Protective
Shelterwood system but mostly
retain for self–regulating
processes without interventions
200
Continual
3–Man–made forest
Protective
Shelterwood system – gradual
reconstruction for close to
nature forests
150
Continual
Management principles
On a large area of the forests of the SVZ the management target is aimed at restoration,
improvement or maintenance their self–regulating abilities. To achieve this target it is necessary to
form functionally effective stand structure. The more the stand structure approaches to the status of
primeval or natural forests the more are forests able to develop themselves through the internal self–
regulating processes. The restoration or improvement of self–regulating abilities of these forests has
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also a great economic significance because by achievement the forests close to nature the interventions
of the manager will be decreased to the minimum and so the providing public beneficial functions by
this forests is getting very effective.
Respecting these starting–points we propose to plan and carry out any measures in these forests on
the basis of actual naturalness class, which has to be decisive criterion for substantiation of need and
urgency of proposed measures. For identification and expression of the naturalness class were chosen
indicators listed in the Table 3: degree of diameter dispersion (for assessment of the tree diameter
variability), share of canopy level (for assessment of the tree height variability), ratio between crown
length and tree height and mosaic of stand clumps and clusters. For specification of need and urgency
of measures is necessary to carry out also assessment of the static stability, natural regeneration, health
condition and stocking as an indicator of fulfilment of ecological functions mainly soil– and water–
protective ones.
Basically it can be stated that the forest stands classified by the 1st naturalness class could be left
without any measures. Such stands generally meet also another criteria, i.e. natural regeneration is
fully corresponding to actual stand structure and static stability as well as health condition are
excellent. If the forest stand does not meet above mentioned criteria it requires performing the
concrete measures that can be, regarding its actual status, differentiated into three degrees of urgency
(high, medium, low). Such forests are mostly man–made, even–aged, vertically and horizontally little
differentiated, but also natural forests in various development stage with insufficient natural
regeneration belong among them.
Table 6. Criteria for determination of the need and urgency of the measures
Forest stand or its part doesn´t require any
measures
1st naturalness class
Static stability – excellent
Health condition – excellent
Natural regeneration – fully corresponding
Forest stand or its part requires measures in
the 2nd degree of urgency (within 10 years)
3rd or 2nd naturalness class
Static stability – satisfactory
Health condition – mediumly declined
Natural regeneration – slight or minimal at the
age of forest less than 50 years under rotation
Forest stand or its part requires measures in the
1st degree of urgency (within 3 years)
3rd (2nd) naturalness class
Static stability – unsatisfactory
Health condition – caduceus or died forest
Natural regeneration – slight or minimal
Forest stand or its part requires measures in the
3rd degree of urgency (postponable)
2nd (3rd) naturalness class
Static stability – good
Health condition – slightly declined
Natural regeneration – slight or minimal at the age
of forest more than 50 years under rotation
Conclusions
Further perspectives of the spruce vegetation zone
Better high–mountain forest management will request built up comprehensive net of forestry roads
ecologically designed in the terrain. It will be necessary to perform ecologization of all forestry
activities in the high–mountain forests, especially by means of introducing the newest techniques and
technologies. Clear cutting system is forbidden in the SVZ. It was fully replaced by the shelterwood
and selection systems. Implementation of recovery measures on the sites with deteriorated soils will
create suitable growth conditions for subsequent forest stands. Generally, the natural regeneration is
preferred. However, on certain sites, tree species diversity will be enhanced by planting desired tree
species. The monitoring of health status of forests and occurrence of harmful agents will necessary
continue. Preventive methods will be preferred to suppressive methods in the field of forest protection.
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Decreasing volume of emitted pollutants will influence health status of high–mountain forests
positively. On the other hand, harmful effect of climatic changes will have growing tendency and
might be a further threat for existence of the forest ecosystems. Thus, the newest findings achieved in
forestry research would be largely implemented. One of the possibilities will be applying knowledge
from population genetics, especially issues concerning individual resistance of trees to climatic
extremes and others harmful agents.
References
MORAVCIK, M. et al., 2002: Research of method of management of mountain forests on the principle
of sustainable development. Final research report. Forest Research Institute Zvolen, 350 p.
MORAVCIK, M., 2003: Management models for stable forests of spruce vegetation zone. Topical
problems in forest protection 2003. Forest research Institute Zvolen, p. 81–88.
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