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International Journal of Forestry and Wood Science
Vol. 1(2), pp. 010-026, December, 2014. © www.premierpublishers.org. ISSN: 2167-0465x
IJFWS
Research Article
Continuous cover forestry and harvest event analysis
Adrien N. Djomo
Department of Geography, Queen’s University, Kingston, Canada.
Corresponding author: Department of Geography, Mackintosh Corry Hall, 68 University Avenue, Queen’s University,
Kingston, ON, Canada K7L 3N6. Tel: 613 533-6000, Fax: 613 533-6122, Email: [email protected]
Continuous cover forest management system is gaining popularity to clear-felling and the rotation
management system associated. Very few researches have been done to assess this management
system. A harvest event was analysed in a Reinhausen forest compartment of 2ha, belonging to
the state forest of Göttingen; Göttingen is situated in the state of Lower Saxony in Germany. The
harvest has modified the stem number per hectare mostly in bigger class of diameter. The
diameter class the most affected was between 14 and 23 cm. The harvest affected 11% of the stem
in the stand and was constituted only by Fagus silvatica (7.5%) and Fraxinus excelsior (3.5%)
which are the main species of this forest. The thinning removed 15% of the basal area and 16% of
the volume of the forest stand. The type of thinning was thinning from above (high thinning).
Apart from Fagus silvatica that the average height of trees reduces of 45cm after harvest, there
was no difference on average height after harvest for other species. The harvest event has
induced changes on the spatial distribution of the forest stand. The impact of this modification on
environment has not been analyzed by this study.
Keywords: Thinning, harvest event analysis, continuous cover forestry, clear-cutting, rotation forest management.
INTRODUCTION
Continuous cover forestry (CCF) is a silvicultural system
in which forest stands always maintain trees alive
throughout the entire life span (Mason et al., 1999). The
system is mainly characterized with a selection system
and a shelterwood system. Thinning operations are
therefore operated in the forest for improved
management or for timber supply. This may cause
changes to soil physical, chemical, and biological
properties that reduce site productivity (Osman, 2013). A
harvest modifies stand structure, species composition,
forest density which results to a change on micro-climate,
ground vegetation and nutrient cycle (Gadow, 2004). The
soil compaction through this operation has effects on the
cation exchange capacity, soil respiration, buffer capacity
of the soil. The modifications caused by a harvest are
abrupt and often drastic and it has been observed that
foresters, when given the same set of silvicultural
instructions, are not always unanimous in their judgments
when marking trees for survival (Zucchini and Gadow,
1995). Harvest event analysis helps to evaluate the
changes, to assess the thinning weight, to monitor
management activities. The concept requires that before
effective thinning operation or harvest, unwanted trees
which are competing with target trees and commercial
trees are marked. Target trees will remain on site as seed
bearers or to ensure continuous cover vegetation in the
stand. Prior or post-harvest analysis is done to evaluate
the effect of thinning on the remaining stand.
The concept of CCF is usually opposed to the rotation
forest management (RFM) which is usually used in
industrial timber plantations and consists of establishing
young stands by planting, thinning operations and final
harvest at a specified rotation age (Gadow et al., 2012;
Continuous cover forestry and harvest event analysis
Djomo
010
Figure 1. View of clear-felling for a rotation forest management system. Photo taken in Central Germany.
Schütz et al., 2012; Seydack, 2012). Despite the fact that
most of the world’s forests are dominated by mixed
species stands, the management practices in many
countries around the world are still dominated by
monocultures industrial timber plantations because the
popular belief is that this type of management is simple
and fibbers production can be maximized (Gerlach et al.,
2002). RFM presents several ecological disadvantages.
For example, when trees are clear cut in a forest stand
(Figure 1), they remove nutrients from the soil and this
contributes in the land degradation; therefore, soil may
rely in the near or long future on fertilizers to replenish
nutrients loss from this system. Adding further fertilizer
may improve short term growth of young trees but will
further decrease soil productivity as shown in a study in
South-eastern Ontario (Jaggard, 2012). Also, the
outgoing trees from the forest reduce or eliminate the
capacity of the original forest to sequester carbon from
the atmosphere. It is often argued that the newly planted
forest with fast growing tree species will grow with a
higher sequestration capacity (Carrow, 1993). Some
environmental groups such as (ARB, 2010) reconsider
support for clear-cutting in forestry and argue for GHGoffset of this sivilcultural system. The growing potential
with higher carbon uptake on a short term will not
compensate the other environmental damages on soil
and habitat loss for the biodiversity present in the original
forest (Pukkala et al., 2012). For instance, (de Blécourt et
al., 2013) show that conversion of forest to rubber
plantation resulted in losses of soil carbon stocks by an
average of 37.4 Mg C ha-1 in the entire 1.2 m depth over
a time period of 46 years, which was equal to 19.3 % of
the initial soil carbon stocks in the secondary forests. This
decline in soil carbon stocks was much larger than
differences between published aboveground carbon
stocks of rubber plantations and secondary forests, which
range from a loss of 18 Mg C ha-1 to an increase of 8 Mg
C ha-1. Despite the negative environmental impact of
RFM and the lack of old growth trees in this types of
forest stands the practice has been in used since the 19th
century. One of the reasons in favour to this silvicultural
system is that, in the Nordic countries, many foresters still
believe that the RFM follows quite well the natural
dynamics of the forest (Carrow, 1993;Keto-Tokoi and
Kuuluvainen, 2010) which may not likely be always the
case. Clear-cuttings are often replaced by monoculture
plantations which are more vulnerable, more sensitive to
forest fire, wind damage which create serious damages in
temperate and boreal ecosystems where this type of
silviculture system dominates (Carrow, 1993). Including
Alaska, Russia and Canada, the extend of forest fire in
boreal forests in these regions range annually between 5
to 20 million hectares (Martinez et al., 2006). Another
reason of preference of RFM was that the traditional
uneven-aged management with selective cuttings did not
provide enough cheap raw materials for the expanding
pulp and paper industry in the middle of the 1900s
(Pukkala et al., 2012). This situation lead forest
authorities in many countries to make declaration against
uneven-aged management and to promote RFM with low
thinning, clear felling, and planting (Pukkala et al., 2011).
Continuous cover forestry (CCF) represents a possibility
to convert the current RFM into a forest management
practise near-natural characterized by uneven stands
with different ages which are less vulnerable to
environmental hazards. The transformation of RFM to a
CCF can be achieved in a stepwise process by following
Continuous cover forestry and harvest event analysis
Int. J. Forestry Wood Sci.
011
Figure 2. Schematic representation of the structure of the forest before and after haverst. Selected trees marked
with an X sign (centre) will be removed to reduce the competition on crop trees to give the resulting stand shown
in the righ. (Source: modified from Gadow, unpublished)
Figure 3. Variation of stock in continuous cover forest system. Selective trees are felled from the forest stand which reduces the
stock in the forest. With time, trees will grow to reach more or less the initial stock and at that time a thinning operation will be
scheduled to lower again the stock. The process continues throughout the life cycle of the stand to produce a horizontal dental
curve of the stock. t1 and t2 are two times in the life cycle having equal stock (Source: modified from Gadow, unpublished)
these successional activities. First, the young stands
constituted by even-aged seedlings are subject to low
thinning that enhance the growth without favouring trees.
Subsequent thinning will consist of removing mainly
mature trees from above that may be used to achieve the
industrial requirements. As shown in Figure 2, some
other big trees will remain on the stand to serve as seed
bearers. The open canopy through harvest of mature
trees will help for the recruitment of regeneration that will
replenish the gaps in the forest stand. The intensity of
thinning also refer to in this paper as thinning weight is
the amount or the proportion of trees harvested in the
forest. The thinning weight may depend on the type of
species been promoted in the gap. Fast growing species
may need more gaps to grow and in this case, heavier
felling may be needed to promote their growth. For the
promotion of shade tolerant species, it is recommended
to do less intensive felling that will allow the growth of this
type of species under the shade of bigger trees. The
continuous management of the forest will be done
thereafter through a shelterwood system that will consist
of regular intervention in the forest for selection of big
trees, maintenance of mother trees (seed bearers) and
promotion of natural regeneration (Davies et al., 2008).
This continuous intervention in the forest at more or less
regular interval results to a stock which is more or less
constant between the interventions as shown in Figure 3.
This study was carried out to: 1) analyse the effect of the
harvest on the remaining stand; 2) determine the thinning
type; 3) predict the growth of the remaining stand after
the harvest 4) make recommendations for continuous
cover forestry.
MATERIALS AND METHODS
Study Site
The study was carried out in 2005 in a 2 ha forest
belonging (Reinhausen) to the state forest of Göttingen
which is situated in the state of Lower Saxony in
Continuous cover forestry and harvest event analysis
Djomo
013
Figure 4. Map of the study area. The study was carried out in Reinhausen close to
Goettingen. Goettingen is small city located in the state of Lower Saxony in Germany.
Germany (Figure 4). Reinhausen is located about 8 km
Southeast
of
Göttingen.
The
primarytreespeciesistheBeech
(Fagus
sylvatica),
accountingfor
57%
ofthetrees.
Other
significantspeciesincludeOak
(QuercusroburandQ.
petraea),
Norwayspruce
(Piceaabies),
andLarch
(Larixdecidua). The soils are shallow with a depth of
between 20 and 50 cm, pH (H2O) between 5.5–7.4 (0–20
cm), and are rich in base cations and carbonate content.
The soil parent material is calcareous bedrock with a
calcite content of about 95%. The biological activity in this
soil is very high and has caused the development of a
mull type litter layer and a humus-rich surface mineral soil
(Meesenburg and Brumme, 2009). For the observation
period 1990–2002, the annual mean air temperature was
7.4 ± 0.8 (5.5, 8.3)˚C; this value varied from 12.6 ± 0.63
(11.3, 13.4)˚C in May–October and 2.2 ± 1.18 (-0.4,
3.7)˚C in November–April. The annual precipitation in the
same period (1990–2002) was 709 ± 193 (537, 973) mm;
this value varied from 410 ± 156 (233, 596) mm in May–
October and 299 ± 143 (170, 453) mm in November–April
(Panferov et al., 2009). The values in brackets represent
the minimum and maximum of the observations. For the
observation period 1961–1990, the mean annual
sunshine duration varied between 1,400 – 1,450 hours;
the sum of the radiation per year in this period varied
between 960–980 kWh m-2 and the corresponding
-2
irradiance varied between 109.6–111.9 W m (Panferov
et al., 2009).
The studied area was constituted of uneven-aged mixed
species with diameter range between 7 and 38 cm and a
mean diameter of 16 cm. 35 plots located at equidistance
of 23.9 m were selected within the study area at a
sampling intensity of 70%. Plots were of circular form with
radius of 11.29 m, and subplots of 1 m 2 in each where
natural regeneration was assessed. All trees with
diameter more than 8 cm were measured in the entire
plot. A total of 1466 trees were recorded for analysis. The
parameters recorded were the species name, the dbh
(diameter at breast height), the diameter at 20 cm (d0.2),
the geographical coordinates, and total height. For trees
which were close to the edge of the plots the Relascopic
prism was used to check whether the tree was in or
outside the plot. All trees with diameter less than 8 cm
were assessed in the subplot of 1 m 2 located at the
centre of the plot. Strict regulation did not allow harvest of
trees for the research purpose and all trees selected for
harvest were just assumed for this study and were
marked accordingly.
Trees designed for harvest were marked with a red
colour ribbon and the target trees with yellow colour
ribbon. As illustrated in Figure 5, target trees were big
trees that remain on stand to provide seeds for natural
generation and also to ensure there will be enough
recruitment during the next intervention for timber supply.
During the inventory, trees designed for harvest were
recorded with the initial H and target trees with the initial
T.
Analysis of Thinning
The forest structure before and after harvest was
analyzed. For this study, it was assumed that all trees
marked with H will be effectively harvested; therefore,
harvest analysis was done under this assumption. The
forest composition before harvest was assessed by
analysing species distribution in the studied forest. The
Continuous cover forestry and harvest event analysis
Int. J. Forestry Wood Sci.
014
Figure 5: View of thinning operation associated with harvest event
analysis. Tree marked with red colour ribbon is selected for removal; tree
with yellow colour ribbon is a target tree for future harvest and seedbank.
diameter distribution was then plotted to assess how
thinning has affected each diameter class and also each
species. We also used the geographical coordinates of
trees in the plot to generate the map of the forest before
harvest. Then, all trees which were marked for harvest
were removed to generate another map representing the
feature of the forest after harvest. The diameter
distribution of the forest before and after harvest was
plotted to assess the impact of the thinning on the forest
structure. The thinning weight was analyzed by
evaluating the importance of the basal area removed
from the forest using the formula:
The future development of a forest is not only influenced
by the weight, but also by the type of thinning which is
defined by the selective removal of specific members of
the population. The thinning type is also reflected by the
change of the diameter distribution (Gadow and Hui,
1999). In this study, we evaluated the thinning type using
this formula:
Thinning weight
where NG represents the thinning type, rN the proportion
of stem number removed by thinning and rG the
corresponding proportion of basal area removed by
thinning. Relative spacing is another way of evaluating
thinning (Gadow and Bredenkamp, 1992). It is an index
rG 


removed basal area m 2 / ha
(i)
total basal area m 2 / ha


Thinning type
(NG ratio) NG

Continuous cover forestry and harvest event analysis
N removed / N total  rN

(ii)
Gremoved / Gtotal  rG
Djomo
015
Figure 6. Species distribution in the studied area. Ash:
Fraxinus excelsior; Beech: Fagus silvatica; Elm: Ulmusglabra;
Maple (Bah): Acerpseudoplatanus (SycamoreMaple); Maple
(Sah): Acerplatanoides (NorwayMaple); Spruce: Piceaomorika
which helps to understand how the density was affected
and to evaluate how the average distance between the
trees have changed after the harvest. It was evaluated in
this study using the two formulas (iii and iv) below:
values, used the values obtained after thinning as guide
curve and checked if the J-shaped was maintained
before and after thinning.
Height and Growth Analysis
average dis tan ce between trees
(iii)
RS 
do min ant s tan d height
Taking into consideration square spacing, formula iii
above can be rewritten
For the height - diameter relation different models were
tested for each species and we selected the model that
provided for a species the best coefficient of
determination. The models tested were (Schmidt, 1968):
h  a0  a1  d  a 2 d 2
h  ea a lnd a ln d 
2
RS 
10000/ N
Hd
0
(iv)
1
2
(v)
2
(vi)
h  a0  a1  lnd  (vii)
whereN is the number of stems per ha and Hd the
dominant stand height (m).
The sensibility of thinning to basal area and volume was
analysed by plotting per species for basal area and
volume the quantity removed and those remaining in the
stand. It was also analysed by estimating for each
species the proportion of basal area and volume which
was removed by thinning. The sensibility of thinning to
the stand height was analysed by assessing the average
height of each species before and after thinning and by
assessing the change in average height before and after
thinning in each diameter class.
Uneven-aged forests present usually a negative
exponential diameter distribution following a J-shaped
(Djomo, 2006; Djomo et al., 2012; Lamprecht, 1989).
Schütz et al. (2012) explained that in continuous cover
forestry, ideal target number should be defined for each
diameter class to compare the real value before thinning
and the ideal value after thinning and a J-shaped should
be maintained before and after thinning. For this study,
we plotted the diameter distribution before harvest as real
h  ea0 a1lnd a2 d  (viii)
The projection of the height growth after harvest was
done using the TREEGROSS Software developed by the
department of growth and yield of the Forest Research
Station of Lower Saxony in Germany (Nagel, 2003). This
software was developed based on the shift in silvicultural
policy in Lower Saxony in Germany. The silvicultural
system moved from stand RFM system to a CCF
management system. Therefore, this software focuses on
single tree information based on the experimental plots
which is scattered over north-west Germany (Nagel,
2003, Nagel et al., 2003). For the actual tree model a
simple approach by linear and non-linear regression
technique was used. The regression analysis was
performed for each species separately (Nagel, 2003).
RESULTS
The studied forest was constituted mostly by Fagus
silvatica (Beech) (65%), followed by Fraxinus excelsior
(Ash)
(28%).
Piceaomorika
(Spruce)
and
Continuous cover forestry and harvest event analysis
Int. J. Forestry Wood Sci.
016
Figure
6.Speciesdistribution
in
thestudiedarea.
Ash:
Fraxinusexcelsior; Beech: Fagus silvatica; Elm: Ulmusglabra;
Maple (Bah): Acerpseudoplatanus (SycamoreMaple); Maple
(Sah): Acerplatanoides (NorwayMaple); Spruce: Piceaomorika
Figure 7: Diameter distribution before and after thinning in the studied forest
Acer pseudoplatanus (Sycamore Maple) represent
respectively only 5% and 2 %. Only very few stems of
Acer platanoides (Norway Maple) and Ulmusglabra (Elm)
were found in the forest (Figure 6).
Change of Stand Density and Forest Structure
The stand density is an evaluation of the number of stem
on a given land (Gadow and Bredenkamp, 1992). The
harvest event has modified the stem number per hectare
mostly in bigger class of diameter (Figure 7). The class
the most affected was between 14 and 23 cm.
The harvest affected 11% of the stem in the stand and
was constituted by Fagus silvatica (7.5%) and Fraxinus
excelsior (3.5%) which are the main species of this forest.
The proportion of Fagus silvatica harvested within their
population was 11.5% while the one of Fraxinus excelsior
represented 12.3% (Figure 8).
The removal of a tree modifies the spatial distribution, the
radiation and influences a variety of biogeochemical
processes (Gadow and Kleinn, 2004). The harvest event
has induced changes on the spatial distribution of the
forest stand. This can be viewed on the sketch showing
the structure of the forest before and after the harvest
(Figure 9).
Change of Basal Area and of Volume
The thinning removed 15% of the basal area in the stand
and this was constituted only by Fagus silvatica (12%)
and Fraxinus excelsior (3%) (Figure 10). The proportion
of Fagus silvatica affected within their population was
16% while the one of Fraxinus excelsior represented
15%. The thinning removed 16% of the volume in the
Continuous cover forestry and harvest event analysis
Djomo
017
Figure 8. Species structure before and after harvest. Maple (Bah): Acer pseudoplatanus
(Sycamore Maple) ; Maple (Sah) : Acer platanoides (Norway Maple)
Figure 9. Spatial structure of the forest before and after harvest
Figure 10. Evaluation of thinning effects on volume (left) and basal area (right)
stand and this was constituted by Fagus silvatica (13%)
and Fraxinus excelsior (3%). The proportion of Fagus
silvatica affected within their population was 17% while
the one of Fraxinus excelsior represented 15% (Figure
10).
Change of Height
For evaluation of the effect of thinning on height, we
analysed the average height before and after the thinning
per diameter class and per species (Figure 11). The
average height of tree harvested (19.4 m) was bigger
than the average height of the trees before the harvest
(17.9 m) and after the harvest (17.6 m). The average
height of the forest reduces after the harvest of 32 cm
moving from 17.9 m to 17.6 m. In the diameter class of
29 cm and 35 cm, the average height of the trees
increases respectively of 17 cm and 90 cm after the
Continuous cover forestry and harvest event analysis
Int. J. Forestry Wood Sci.
018
Figure 11. Evaluation of thinning effects on the average height for each species (Left) and for diameter
distribution (Right)
Table 1. Structure of the forest (N/ha and basal area) before and after thinning, the proportion
of stems removed rN, the thinning weight rG and the thinning type NG
Species
N/ha
Before
harvest
N/ha
harvested
Basal area before Basal area
harvest
removed
(m 2/ha)
(m 2/ha)
rN
rG
NG
Beech
Ash
674
295
78
36
19.06
5.63
3.06
0.82
0.12
0.12
0.16
0.15
0.72
0.84
Total
1046
114
26.01
3.87
0.11
0.15
0.73
Figure 12. Relation between rG and NG. The lower proportion of basal area removed in Ash corresponding to a
higher proportion of stem number shows that there was a removal preference on Ash compared to Beech.
harvest. Apart from Fagus silvatica that the average
height of trees reduces of 45 cm after harvest, there was
no difference on average height after harvest for the
other species (Figure 11, left). This result confirms that
the average or dominant height is independent of stand
density and thus not much affected by thinning (Gadow
and Hui, 1999).
and the thinning type (NG). From this table, the value of
NG is for all the cases studied less than one showing that
the thinning was from above (high thinning). Figure 12
presents the relation between the thinning weight (rG)
and the thinning type (NG) for Fagus silvatica, Fraxinus
excelsior and for the whole forest (All).
Height Curve and Growth Modeling
Thinning Weight and Thinning Type
Table 1 summarizes for Fagus silvatica, Fraxinus
excelsior and the entire forest the thinning weight (rG)
Stand height is one of the key variables in most growth
models in commercial plantation today (Gadow and
Bredenkamp, 1992). The height regression equation of
Continuous cover forestry and harvest event analysis
Djomo
019
Figure 13. Height diameter relation for Ash, Beech, Maple and Spruce
Figure 14. Growth curve after each group of five year (2005 – 2020) for the entire forest and for Beech, Ash
and Spruce.
the forest stand Piceaomorika,Acer sp., Fraxinus
excelsior, Fagus silvatica has been evaluated (Figure
13). The regression equations and the related coefficient
of determination are the follow:
Forest standh = 3.402 + 7.61 In (d), R2=0.42
Fraxinusexcelsior h= 7.632 + 3.772 In (d), R2=0.14 (xii)
Fagus silvatica
h =5.563 + 8.376 In (d), R2=0.50 (xiii)
(ix)
DISCUSSION
2
2
Piceaomorikah = 6.763 + 0.108d + 0.019d , R =0.73 (x)
Acer s h =
7.525 + 2.484d0.055d2, R2=0.61
(xi)
Harvest modified the forest structure, the species
composition, the stand density, the basal area, the
volume of the forest. The change on forest structure may
Continuous cover forestry and harvest event analysis
Int. J. Forestry Wood Sci.
020
Figure 15. Guide curveforassessingthethinningregime
also modify the radiation which may influence
biogeochemical
processes
(Bartos
and
Booth,
1994;Gadow and Kleinn, 2004;Gadow, 2004). The
management system studied is continuous cover forestry
(CCF). This system was characterised by selective
harvesting of mature trees which resulted to low thinning
from above and the use of natural regeneration to fill the
gap opened in the forest through forest renewal and
enough retention of some older trees to ensure a good
balance between mature trees and regeneration during
the next intervention.
The relative spacing moved from 0.17 before harvesting
to 0.19 after the thinning. At similar density range, our
values were consistent with the findings of (Zhao et al.,
2012) who studied relative spacing relationships in pine
plantation in USA. Relative spacing is sometimes used as
a quantitative measure for comparing thinning regimes or
for constructing thinning guide curves (Gadow and
Bredenkamp, 1992). Harvest control is based on some
ideal diameter distribution (Guldin, 1991;Schütz,
1994;Virgilietti and Buongiorno, 1997). Figure 15 shows
the thinning guide curves for the forest stand. This guide
curve which compares before and after harvest may also
help to assess the intensity of the intervention and decide
whether or not additional tree removal may be needed to
ensure a smooth distribution of the trees in all the
diameter classes. Plotting this distribution may also help
during the next thinning operations by allowing to assess
the incoming regeneration and the growth of the trees in
all diameter classes (Gadow and Kleinn, 2004). Selective
harvesting also favours site-adapted tree species and
some kind of “natural forest management” (Gadow and
Kleinn, 2004). The studied forest was dominantly
constituted by Fagus silvatica (65%) and Fraxinus
excelsior (28%) and the harvest event analysis reveals
that these dominant species were the ones affected by
thinning. Gadow et al. (2012) explained that the removal
preference is another index to determine a pressure on
species trough thinning intervention. The removal
preference is the ratio of the proportion of trees removed
in a structural class to the proportion of trees before
harvest in that particular class. The removal preference of
Fraxinus excelsior was 44% while the one of Fagus
silvatica was 18%. This index shows that though the
proportion of Fagus silvatica removed was close to the
one of Fraxinus excelsior, there was a higher removal
preference on Fraxinus excelsior. The relation between
rG and NG (Figure 12) also show that there was harvest
preference on Fraxinus excelsior through a lower basal
area removed corresponding to a higher proportion of
stem number.The remaining species in the forest
Piceaomorika, Acer pseudoplatanus, Acer platanoides
andUlmusglabra represented only about 7 % of all trees
in the studied area. These species was not affected by
thinning. These species which were present in low
number in the forest may increase in the future through
natural regeneration favoured by the gaps opened in the
forest and the preservation of these species in the actual
conditions to serve as seed bank for the future.
The vertical and horizontal distributions of tree sizes may
determine the distribution of micro-climatic conditions, the
availability of resources and the formation of habitat
niches and thus, directly or indirectly, the biological
diversity within the forest community. Thus, the new
forest structure induces by the thinning will contribute to
improve the functions and future development potential of
Continuous cover forestry and harvest event analysis
Djomo
021
the forest ecosystem (Franklin et al., 2002; Harmon et al.,
1986; Ruggiero et al., 1991; Spies, 1997). Thinning
exclusively affects mature wood; the effect of thinning
becomes more similar to that of initial spacing since
thinning favors the development of longer and larger
crowns by reducing the rate of crown recession (Briggs
and Smith, 1986; Pape ,1999). The most important
effects of thinning are on growth rate in the lower half of
the stem within the mature wood. Thinning has been
found to shift increment downwards on the stem, which
results in increasing stem taper (Larson, 1963;Valinger,
1992). Knoke and Seifert (2008) evaluated the influence
of the tree species mixture on forest stand resistance
against natural hazards, productivity and timber quality
using Monte Carlo simulations in mixed forests of Norway
spruce and European beech. They found superior
financial returns of mixed stand variants, mainly due to
significantly reduced risks.
CONCLUSION
The thinning has modified forest structure, forest density,
species composition, basal area and volume of the forest.
It also reduces competition on target trees which are left
on site for the future interventions, and also for ecological
and financial return; this may lead to the fast grow of
these target trees and also of incoming regeneration in
the gap created. The modification of forest structure has
impact on radiation, light, soil and fauna population. The
impact of this modification on environment has not been
analyzed by this study. Harvest event analysis is a tool
for monitoring forest management. It has been used in
plantations and in the so called Near-Natural Forest
Management as now practiced in Germany. In many
countries including Canada, clear-cutting is still part of
the forest management system. This study may
contribute to the discussion to minimize the harmful
potential of clear-cutting in the environment through
continuous cover forestry.
ACKNOWLEDGMENTS
The contributions of Dr. Nils Tremer and Prof. Dr. Klaus
von Gadow, Georg-August-University, Goettingen, at the
early stage of this study are highly acknowledged. We
also acknowledge the contribution of the professional
foresters of the Reinhauser forest who marked the trees
for this study. The author acknowledged the contributions
of three anonymous reviewers which helped to improve
the quality of this paper.
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Accepted 15 September, 2014.
Citation: Djomo AN (2014). Continuous cover forestry
and harvest event analysis. Int. J. Forestry Wood Sci.
1(2): 010-022.
Copyright: © 2014 Djomo AN. This is an open-access
article distributed under the terms of the Creative
Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium,
provided the original author and source are cited.
Continuous cover forestry and harvest event analysis

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