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Volume 16(2), 131-138, 2012
JOURNAL of Horticulture, Forestry and Biotechnology
www.journal-hfb.usab-tm.ro
131
The structure of a natural mixed beech – sessile oak forest in
Runcu Grosi Natural Reserve
Merce O.1*, Turcu D.1, Cantar I.1
1Forest Research and Management Institute – Timisoara Branch
*Corresponding author. E-mail: oliver_merce@yahoo.com
Abstract Sustainable forest management can be developed and
implemented only based on scientific information regarding the natural
structure and functioning of the forest ecosystems. The Runcu Grosi Natural
Reserve, a mixed sessile oak – beech forest, was chosen to study the
structural characteristics of the natural forest. 134 sample plots were
established within a systematic sample grid, from which 34 plots were
measured. The stand structure was expressed by the following features: the
number of trees by species, the diameters’ distribution, the heights’
distribution, the diamter-height relationship, the trees’ volumes distribution,
the state of vegetation of the trees, the characteristics of natural regeneration,
the state of vegetation of the trees, the structural diversity expressed by
specific indexes.
Key words
Runcu – Groşi, natural
forest, structure, diversity
Natural forests are valuable depositories for the
scientific information regarding the structure and
functioning of forest ecosystems. Studies conducted in
natural forests are able to observe how these
ecosystems are constituted (ecosystem structure) and
the ongoing processes (ecosystem functioning), both
developed naturally under the laws of biological
evolution. Only few natural forest ecosystems
remained in Europe, most of them in isolated locations
of the mountain areas. A natural forest, having
experienced low human impact, in the hill zone is rare.
This study focuses on the structure of a natural mixed
beech – sessile oak forest ecosystem from the Runcu
Grosi Natural Reserve, a remnant of the natural forests
which covered Romania in the past.
Study site and research method
The study site is represented by the Runcu Groşi
Natural Reserve, Arad County, Western Romania. This
Reserve is part of the 4th Management Unit „Groşi”
from the Bârzava Forest District, Arad Forestry
Directorate, being located in the lower basin of the
Mures river, on the right slope, in the basin of Grosi
River. The total surface of the Reserve is 262,6 ha, the
geographical coordinates being 46011’ Northern
Latitude and 22007’ Eastern Longitude (Giurgiu, V., et
al, 2001) (Fig.1).
Fig. 1 – Map of Romania. Position of Runcu Groşi Natural Reserve
Runcu – Groşi
Natural Reserve
CORINE Land
Cover 2000
132
The Reserve was sampled using a network of sample
plots having circular shape and the surface of 1000 m2
each in order to highlight the aspects concerning the
vertical and the horizontal structure of the stand (Fig.
2). The network of sample plots uses a rectangular grid
of 200 m by 150 m.
A total number of 134 sample plots were set up in the
Reserve. Measurements were carried out on 34 of these
sample plots, 2068 standing trees and 674 seedlings
were sampled. The recorded information consisted of
the following:
Information about the plot’s location –
altitude, slope orientation, inclination;
Precise positioning of the trees insidde the
circular plot – x, y, z coordinates
measured using the FieldMap technology;
Tree species;
Diameter at breast height (DBH) – mean
of 2 perpendicular dimaters measured by
forest calliper;
Total height, dead crown base height (up
to the first dead branch) and living crown
base (up to the first living branch) –
measurements carried out for each tree
using FieldMap or VERTEX;
State of vegetation (vigor);
Dammages (defects) of the tree;
Other observations regarding individual
characteristics of the trees.
In each sample plot, data were also recorded
concerning the regeneration. Four sub-plots of circular
shape having an area of 3,14m2 were set up at 9 m
distance from the plot center, following the 4 cardinal
directions (North, East, South, West). The data
recorded for regeneration consist of the number of
seedlings counted by species and by height category.
The stand structure was analysed in trems of
distribution of the trees by species, diameter categories,
height classes, state of vegetation. Regarding the
heights and diameters, they were studied the
relationships between these two elements by
computing the correlation coefficient and by
expressing the bi-dimensional distribution in relation to
the elements mentionned above.
Fig. 2 – Network of systematic sample plots in Runcu Grosi Natural Reserve
- Measured sample plots
- Sample plots network
133
Processing of inventory data by methods
specific to the structure analysis (statisticl
methods, indexes) and interpretation
The stand structure expressed by the number
of trees by species
Within the 34 sample plots they were inventoried 2068
standing trees. 12 tree species were encountered: the
European beech (Fagus sylvatica L.), the sessile oak
(Quercus petraea Liebl.), the hornbeam (Carpinus
betulus L.), the wild cherry tree (Prunus avium L.), the
Turkey oak (Quercus cerris L.), the Hungarian oak
(Quercus frainetto Ten.), the field maple (Acer
campestre L.), the sycamore (Acer pseudoplatanus L.),
the wild pear tree (Pyrus pyraster (L.) Burgsd.), the
wild service tree (Sorbus torminalis L. Cr.), the silver
lime (Tilia tomentosa Moench.), the mountain elm
(Ulmus glabra Huds.). The distribution of the number
of trees by species within the sample plots is expressed
in Table 1. The beech is the most frequent species,
having a percentage of participation of 74 % and being
the only species present in all 34 sample plots. The
next species by frequency os the sessile oak, with a
percenatge of participation of 13 % and presence in 22
plots, followed by the horbeam (9 %, respectively
presence in 21 plots). The other tree species have a
much smaller frequency (Fig. 3).
176
23
1522
7
275
17
20
11
1
5
10
1
Turkey oak
Hornbeam
Wild cherry
Beech
Hungarian oak
Sessile oak
Field maple
Sycamore
Wild service tree
Lime tree
Wild pear
Elm
Fig. 3 - The stand structure expressed by the number of trees by species
Regarding the analysed parameter – the mean number
of trees per sample plot – a large amplitude of variation
was observed; therefore, the analysis was performed on
number of trees per hectare. For the area covered, the
mean number of trees is 608, having an extremely
uneven distribution (coefficient of variation of 37.5
%). The species with the highest spatial constancy is
the beech, 448 trees/ha and a coefficient of variation
46.6 %, unlike the sessil oak which has a more modest
representation (81 exemplars/ha) and a very uneven
distribution (coefficient of variation of 99.8 %) and the
hornbeam with 52 trees/ha and coefficient of variation
163.3 %. The other species have only sporadic
occurrence (between 3 and 7 trees/ha) and coefficient
of variation between 213.9 % and 479.01 %.
The stand structure expressed by the trees’
diameter
The particularities of the natural stands require the use
of different distribution types than the ones used in
modelling the even-aged stands. Within natural stands,
the distribution of trees by diamter categories is
characterized generally by a progressive decrease of
the number of trees from smaller to larger diameter
categories. This distribution can be expressed either by
a geometrical progression (Assman, 1970; Liocurt,
1898) or a hyperbolic equation (Meyer, 1952), or by
one of the density functions Pearson-type. In all of the
cases when the population of trees was represented by
134
a sufficent number of trees, excepting the sessile oak,
we observed this natural tendency known from the
natural forests, unafected by human intervention, of
decreasing the number of trees towards the large
diameter categories. In the case of the sessile oak, the
distribution is rather atypical, close to a bimodal
distribution.
0
100
200
300
400
500
600
700
Diameter class (cm)
Number of trees
< 6
6-10
10-14
14-18
18-22
22-26
26-30
30-34
34-38
38-42
42-46
46-50
50-54
54-58
58-62
62-66
66-70
70-74
74-78
78-82
82-86
86-90
90-94
94-98
98-102
Fig. 4 - The stand structure expressed by the trees’ diameter
The stand structure expressed by the trees’
height
The distribution of the trees’ heights provide a better
picture about the relationships established within the
stand. For each of the species and also for the whole
stand a specific distribution is observed, characterised
by decreasing of the number of trees as the height
increases. The exception is the sessile oak, as it was in
the diamters’ distribution, this species showing a
bimodal distribution. The beech trees’ heights
distribution shows, as in the diameters’ distribution, the
largest tree dimensions (total heights of 50 m), this
species having the most important structural
varaibility.
135
0
50
100
150
200
250
300
350
400
450
Number of trees
0-4 4-8 8-12 12-
16 16-
20 20-
24 24-
28 28-
32 32-
36 36-
40 40-
44 44-
48 48-
50
Height class (m)
Hornbeam
Turkey oak
Wild cherry
Beech
Hungarian oak
Sessile oak
Field maple
Sycamore
Wild pear
Wild service tree
Lime tree
Elm
Fig. 5 - The stand structure expressed by the trees’ height
The relationship between diameters and
heights
The relationship between diameters and heights offers
new perspectives on the relationships within the stand
which can be observed using the heights distribution.
Therefore, the distribution of heights was expressed for
all trees (all species) and for each species in particular,
the regression equation and the coefficient of corelation
being shown. There were used polynomial functions –
both for the height distribution of all trees (Fig. 6) and
respectively for each species; the values for the
coefficient of correlation R vary between 0.948 for the
sycamore and 0.582 for the sessile oak. This (last) very
small value is explainde by the fact that many old
exemplars of sessile oak are standing dead, having
broken the trunk at different heights from a large
variety of abiotic causes.
y = 5E-05x3 - 0.0119x2 + 1.0414x + 2.6566
R2 = 0.803
0
10
20
30
40
50
60
020 40 60 80 100 120
Diameters (cm)
Heights (m)
Fig. 6 - The relationship between diameters and heights
136
The stand structure expressed by the trees’
volume
Regarding the volume of the trees, the beech is the
most significant presence (376,62 m3/ha), being
followed by the sessile oak (194,99 m3/ha), the Turkey
oak (21,43 m3/ha) and the hornbeam (13 m3/ha),
although the proportion of participation of the tree
species by number of trees within the stand
composition is significantly different. Thus, altough the
beech has a share of participation of 74 % by number
of trees compared to only 13 % sessile oak, it can be
observed that the volumes don’t follow the same
tendency – the beech partcipates with 62 % and the oak
with 32 %. This situation is caused by the fact that
within the stand the number of the oak trees started to
reduce, but the ones remained have large and very
large dimensions. Another significant difference is
oberved in the case of the participation of Turkey oak
(1 % by number of trees) and the hornbeam (9 %), still
the volume participation for these two species are
different – the Turkey oak sheres 3 % of the total
volume and the hornbeam 2 %).
1280.52
13.83
662.98
3.23
0.02
1.35
44.53
0.10
8.93
5.92
72.86
7.52
Hornbeam
Turkey oak
Wild cherry
Beech
Hungarian oak
Sessile oak
Field maple
Sycamore
Wild pear
Wild service tree
Lime tree
Elm
Fig. 7 - The stand structure expressed by the trees’ volume
The stand structure expressed by the state of
vegetation
The methodology of data assessment in the field
included the recording of the state of vegetation (vigor
of vegetation) for all trees. A scale having 3 categories
was used:
- state of vegetation 1 – healthy tree
- state of vegetation 2 – dammaged tree
- state of vegetation 3 – dead tree
The vast majority of trees (82 %) were recorded as
healthy trees – state of vegetation 1 (fig. 8), but more
interesting is this distribution of trees by state of
vegetation for each of the encountered species. For the
beech (83% healthy trees, 13% dammaged trees, 4%
dead trees), the situation is almost similar to the one
observed al the level of the entire stand. The sessile oak
has a relative good vigor of vegetation in this area, 72
% of the trees being cathegorised as healthy. Still, in
the case of sessile oak the highest rate of dead trees
was recorded – 16 %, the process of dying on feet of
the large trees being the most frequent for this species.
The hornbeam’s situation is close to the species
mentionned above – 85 % of the trees were described
as heathy, state of vegetation 1. the other participating
species within the stand (having a lower frequency)
show also good and very good vigor of vegetation.
137
1697
261
110
0
200
400
600
800
1000
1200
1400
1600
1800
Number of trees
1
State of vegetation
Healthy
Dammaged
Dead
Fig. 8 - The stand structure expressed by the state of vegetation
Characteristics of regeneration of the tree
species
Within the 34 sample plots stated in the Runcu Grosi
Natural Reserve, a number of 674 seedlings were
inventoried, most of them beech, sessile oak and
hornbeam. Other species found within the natural
regeneration (represented by 1-2 seedlings): wild
cherry, Turkey oak, wild service tree, elm, lime and
Hungarian oak. Beech is the species most represented
at the regeneration level – 79 %, being characterisred
also by a very good uniformity in space, this species
having a larger biological potential compared to the
sessile oak and the hornbeam. Due to it’s adaptative
strategies and it’s strong installation strategy, beech is
the most important species within the regeneration
layer. Most of the seedlings are smaller than 1.3 m, but
the species is well represented in other categories of
height also. This species –the beech– is present from
the young stages to the disintegration stages of the
phytocoenosis, through the maturity and oldgrowh
stages. The sessile oak is the most uneven distributed
species within the regeneration layer, compared to the
beech. Even if within the first stage of development of
the seedlings they grow relatively fast, later the number
of seedlings reduces, thus the species cannot be found
in the superior categories of height (96 % of the
seedlings are smaller than 1.3 m). the hornbeam is
present also within the regeneration layer of the forest,
but the number of seedlings is small and the
distribution very uneven. A direct and significant
correlation was observed between the proportion of
participation of species within the mature stand and the
proportion of species within the regeneration layer.
Structural diversity
A number of specific indexes of diversity were
computed in order to express the structural
characteristics of the studied tree population. Values
were claculated for the most used diversity indexes–
Simpson, Shannon-Weaver, Berger-Parker, McIntosh,
Margalef, Menhinick, Glisson. Due to it’s logarithmic
expression, the Shannon-Weaver index is the most
sensitive to the unusual structures, being more
appreciated the presence and not the abundance of a
certain structural category. The Simpson index, being
non-logarithmic, expresses better the changes in
dominance of certain categories. Therefore, it is
recommended the use of a large variety of indexes
which express the most the structural diversity of a
population. The results obtained are shown in Table 1 .
The value of these indexes can be interpreted by
comparing to the values obtained in other locations
and/or experiments.
138
Table 1
Structural diversity
Index of richness
12,000
Simpson Index(D)
0,566
Simpson Index (1-D)
0,433
Simpson Index (1/D)
1,763
Shannon-Weaver Index
0,933
Equity
0,375
McIntosh Index
0,252
Margalef Index
1,441
Menhinick Index
0,264
Conclusions
After analysing the collected data, the following
conclusions can be drawn:
A decreasing of participation of sessile oak in
expense of beech at the stand composition level was
found; this conclusion is mainly sustained by the poor
regeneration of the sessile oak (seedlings are
completely absent in the superior height classes),
corelated with high mortality recorded for this species
(sessile oak represents the largest amount of dead
wood, both total and standing dead wood);
There is a very large number of development
stages, each of them having a specific function, which
gives a very high integrality degree to the Runcu Grosi
Natural Reserve, fact that generates a high capacity of
reaction to external disturbances;
The Reserve has well defined structural
mechanisms naturally developed to assure a dynamic
equilibrium as the main result of adaption of the
biocoenosis to the site conditions and the regime of
disturbances;
The Reserve has a complex structural mosaic
which carries out simultaneously, bot on small and
large scale, all forest ecosystem functions;
Within the Runcu Grosi Natural Reserve it was
observed a large « waste » of biomass geared in the
bio-geo-chemical cycles which can’t be economically
sustainable within the managed forest, this biomass
being a cathalist element of the forest, representing
regeneration points on one side and microhabitats for
many plant and animal organisms on the other side;
The occurence of disturbances is characterised, in
the case of the managed (cultivated) forests, as
cathastrophic events. Within this Natural Reserve, this
kind of events are part of a normal cycle, meant to
assure the dynamic equilibrium which aims to self-
perpetuate the forest.
References
1. Casella, G.; Berger, R., 2001: Statistical Inference,
Second Edition, Duxbury Advanced Series, 660 pp.
2. Donita, N., 1998 – Ecologie generala si forestiera,
Academia Universitara “Atheneum”, Bucuresti;
3. Doniţă, N.; Borlea, F.; Turcu, D., 2006: Cultura
pădurilor (silvicultura în sens restrâns). Note de curs,
Ed. EUROBIT Timişoara, 367 pp.
4. Gilg, O., 2005: Old-growth forests: characteristics,
conservation and monitoring, Technical Report 74 bis,
ATEN, Montpellier, 96 pp.
5. Gotelli, N. J.; Ellison, A. M., 2004: A Primer of
Ecological Statistics, Sinauer Associates Inc., 510 pp.
6. Oliver, C.; Larson, B., 1996: Forest stand dynamics,
Update edition, John Wiley and Sons, Inc., 520 pp.
7. Merce, O., Cantar, I., Turcu, D. O., 2009: Evaluarea
biodiversităţii în ariile forestiere protejate
reprezentative pentru gestionarea durabilă a pădurii
cultivate, Institutul de Cercetări şi Amenajări Silvice,
Raport Ştiinţific, 46 pp;
8. Shugart, H. H., 1984: A Theory of Forest Dynamics:
The Ecological Implications of Forest Succesion
Models,The Blackburn Press, 278 pp.
9. xxx – Amenajamentul unitatii de productie IV Grosi
