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Land 2022, 11, 388. https://doi.org/10.3390/land11030388 www.mdpi.com/journal/land
Article
Variations of Soil Physico-Chemical and Biological Features
after Logging Using Two Different Ground-Based Extraction
Methods in a Beech High Forest—A Case Study
Rachele Venanzi
1
, Francesco Latterini
2,
*, Walter Stefanoni
2
,
Damiano Tocci
1
and Rodolfo Picchio
1
1
Department of Agricultural and Forest Sciences, University of Tuscia, Via San Camillo de Lellis,
01100 Viterbo, Italy; venanzi@unitus.it (R.V.); tocci@unitus.it (D.T.); r.picchio@unitus.it (R.P.)
2
Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria (CREA), Centro di Ricerca
Ingegneria e Trasformazioni Agroalimentari, Via della Pascolare 16, 00015 Monterotondo, Italy;
walter.stefanoni@crea.gov.it
* Correspondence: francesco.latterini@crea.gov.it
Abstract: Considering that forests are crucial in the ecosystem of our planet and that forests provide
timber products as well as several ecosystem services, it is evident that the application of sustainable
forest operations (SFOs) is of substantial importance to achieve sustainable forest management
(SFM). One of the most important issues to be evaluated when dealing with SFOs is limiting the
disturbance and impacts related to logging. Harvesting activities can indeed alter the conditions of
soil through compaction and litter removal which can also lead to modifications from the biological
point of view, for example, diminishing the presence of soil microarthropods. While keeping these
objectives in focus, the aim of the present study was to evaluate physico-chemical and biological
impacts on forest soil in Mediterranean beech forests after forest logging with two different extrac-
tion systems, which are forestry-fitted farm tractors equipped with winch and forwarder. Specifi-
cally, authors aimed to investigate: i) soil disturbance levels of ground-based extraction methods;
ii) soil disturbance levels of the applied forestry intervention; iii) soil disturbance levels between
winching-skidding and forwarding. Findings showed that the physical, chemical, and biological
soil features were slightly disturbed by the forestry itself. In addition, forest operations and machine
traffic showed clear soil disturbance, resulting in a substantial alteration of the characteristics. Be-
tween the two extraction techniques tested, winching caused less disturbance while forwarding had
stronger impacts. However, it should be noted that these impact levels are found only on approxi-
mately 28% of the surface where operations were carried out. From the evidence gathered in this
study, winching seems a less impactful extraction method in the studied context. On the other hand,
to decrease the impact of forwarding, some technical adjustments such as bogie-tracks, as well as
improved operator training, should be applied.
Keywords: sustainable forest operations; sustainable forest management; QBS-ar index; winching;
forwarder
1. Introduction
Forests are crucial in the ecosystem of our planet. In fact, they provide not only tim-
ber products but also several ecosystem services [1] such as carbon balance, hydrological
protection, recreational opportunities and habitat provision [2–4]. To allow forests to per-
form their fundamental services, it is crucial to manage them properly by applying sus-
tainable forest management (SFM) [5]. When speaking of SFM, it is intended that this type
of management allows forests to maintain and enhance their economic, social and envi-
ronmental value for the benefit of present and future generations [6].
Citation: Venanzi, R.; Latterini, F.;
Stefanoni, W.; Tocci, D.; Picchio, R.
Variations of Soil Physico-Chemical
and Biological Features after Log-
ging Using Two Different Ground-
Based Extraction Methods in a Beech
High Forest—A Case Study. Land
2022, 11, 388. https://
doi.org/10.3390/land11030388
Academic Editor: Cezary Kabala
Received: 15 February 2022
Accepted: 4 March 2022
Published: 5 March 2022
Publisher’s Note: MDPI stays
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Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license
(https://creativecommons.org/license
s/by/4.0/).
Land 2022, 11, 388 2 of 15
Several approaches and behaviors can be helpful to achieve SFM. Among these are
innovating silvicultural treatments [7], valorizing residues through the development of
innovative by-products [8] and adopting close-to-nature silviculture [9]. Another benefi-
cial and fundamental approach in this context is developing sustainable forest operations
(SFOs). This means practicing forest logging in a way that ensures high productivity and
low costs (economic pillar), reduced impact on the environment referred to as the envi-
ronmental pillar and safe working conditions for the operators that is the social pillar
[10,11].
The application of SFOs is particularly necessary to achieve SFM. Without sustaina-
ble forest utilization, it is impossible to guarantee the health of the forest ecosystem
[12,13].
One of the main issues when putting SFOs into practice is limiting the impact on
forest soil caused by logging [14]. Soil compaction because of forest operations that can
lead to hydrological issues of increased runoff and sediment yield [15,16], including the
improper development of natural regeneration with decreased seedling biomass and root
length [17].
Several studies have been conducted to evaluate such impacts, and there is a wide
range of literature on the topic [18,19]. The evaluation of the implications of different sil-
vicultural practices and harvesting methods on forest soil has been one of the most im-
portant research topics in the sector of forest engineering since the 1980s [20–23].
Nonetheless, there is still much to investigate regarding the issue of soil impacts re-
lated to forest logging. Indeed, the major part of the current literature is focused on conif-
erous stands, considering the generally higher economic importance of this type of forest.
Furthermore, while the implications of logging on physico-chemical soil properties have
been widely investigated, only a few studies focused on impacts to soil biological features
[24]. For example, using the QBS-ar index (soil biological quality index based on microar-
thropods) has shown very interesting features as an indicator of impacts on soil edaphic
fauna after logging [25,26].
Finally, few studies [27–29] have been reported in the literature regarding the com-
parison of different harvesting systems working in the same conditions (studying the
same intervention in the same area to evaluate soil impacts related to the different ma-
chineries).
Regarding this topic, Allmann et al. [27] compared the impacts to soil bulk density
after logging with different forwarders and skidders in several soil conditions, highlight-
ing that different machines led to similar kinds of impact on soil physical features. Eroğlu
et al. [28] studied the impacts of three different extraction systems (cable yarder, skidder
and chute system) in a spruce forest in Turkey. These reported higher impacts in the
ground-based extraction via skidder in comparison to the other systems. Some years later
Picchio et al. [29] evaluated three different extraction systems (cable yarder, forestry fitted
farm tractor, with winch and horse) concerning physico-chemical and biological impacts
after a strip clear cut in a pine stand, reporting the lowest impact for cable yarder and
tractor with winch.
Among the studies reported above [27–29], no one focused on hardwood species
managed as high forest and treated with the shelterwood system. This may be due to the
fact of the higher economic importance that softwood stands are currently showing. How-
ever, the climate change scenarios forecast for the following decades predict a substantial
impact of global warming on coniferous species. A consequent increased attention toward
the silviculture of hardwood species for silvicultural issues is expected, especially regard-
ing beech (Fagus sylvatica L.) [30,31].
On the other hand, there is still much to do regarding the deep understanding of
impacts related to logging in beech stands, mostly regarding biological issues in European
forests [18].
Land 2022, 11, 388 3 of 15
Indeed, several studies have been conducted to assess forest utilization impacts on
soil in beech forests, but the major part of these has been carried out outside Europe with-
out taking into consideration soil biological features [16,32,33]. Furthermore, very little
attention has been given to the evaluation of the impact on forest soil in beech stands of
cut-to-length (CTL) machineries, as forwarders, except for one study dated 2003 referring
to data from 1989–1991 [34].
This last mentioned is a very important aspect considering that in the last few years
CTL machineries have been introduced in hardwood stands. Until recently this system
was exclusively used in softwood stands, mostly in the Mediterranean context. Obviously,
there is still much to investigate in the application of CTL machineries in a sustainable
way in hardwood stands [35–38].
Considering all the literature, the objective of this study was to evaluate the physico-
chemical and biological impact on the forest soil in Mediterranean beech forests, because
of forest logging with two different extraction systems, which are forestry-fitted farm trac-
tors equipped with winch and forwarder.
There are several innovative aspects in this study. First, this is the first work that
considered the impact on soil fauna in beech forests. Second, this is the first comparative
study between the winching-skidding method and forwarding in this type of stand. Fi-
nally, this represents the first evaluation of soil impact after ground-based extraction to
beech stands carried out in the Mediterranean context. The research was developed fol-
lowing the methodology proposed in scientific studies on the same topic and highlighted
also by Picchio et al. [18].
The research hypothesis supported by the standardized experimental design can be
summarized as: i) the ground-based extraction system has a significant impact on soil
physico-chemical and biological properties with a short time perspective; ii) the impact
related to forestry is lower than the one triggered by forest logging. Moreover, a further
question for research is as follows: which is the most soil friendly ground-based logging
method in similar conditions, winching-skidding or forwarding?
2. Materials and Methods
2.1. Study Area
The study area is located on Mount Amiata in the region of Tuscany in Italy (coordi-
nate in WGS84UTM32T 713319 E; 4750291 N). It consists of two different subcompart-
ments of the forest management plan of the Forest Consortium of Amiata, a public entity
that manages all the public forests of the district of Grosseto, which includes Mount
Amiata and some private ones. Both subcompartments are even-aged beech stands man-
aged as high forest and treated as shelterwood systems (Figure 1). In both parcels the
intervention consisted of a late thinning from below carried out throughout the entire sur-
face of the subcompartment. Along with beech, there is the sporadic presence of silver fir
(Abies alba Mill.), sweet chestnut (Castanea sativa Mill.) and wild cherry (Prunus avium L.).
Soil texture is the same in both parcels, and the soil can be classified as sandy loam. Topo-
graphic features are also the same in the two subcompartments, with limited roughness
and medium slope (prevalent slope 28%).
Land 2022, 11, 388 4 of 15
Figure 1. Study area. The boundaries of the two subcompartments are reported in red. The parcel
extracted with a forwarder has yellow lines, while the one in which extraction was performed via
winching has light blue lines. In the figure the existing road network before harvesting is shown.
Blue line is for the main road, and the orange line is for the existing skid trails.
Both stands underwent the same type of intervention. The stands were also very close
in age: one stand was 102 years, and the other was 106 years. The preintervention average
dbh (diameter at breast height) was 45 cm, average height 26.6 m, stand density 149 n°
ha−1 and standing volume 311.010 m3 ha−1 in both parcels. Harvested volume was also very
similar, accounting for about 25% of the standing volume in both subcompartments.
The two subcompartments were both harvested in 2020 by forest operators with sim-
ilar working experience (> 15 years). Felling and processing were carried out in both sub-
compartments in a motor-manual way by chainsaw. Extraction operations were per-
formed with different systems. The CTL extraction system was performed by a forwarder
(FORW) in the subcompartment n. 3, while in the subcompartment n. 6 ,the tree length
system (TLS) was applied by a forestry-fitted farm tractor equipped with forest winch
(WINCH). These systems represent the most applied harvesting machineries for logging
activities in Mediterranean beech forests [36,39]. Indeed, while until some years ago
winching was practically the only option for forestry interventions in beech high forests,
in the last years there has been a growing application of forwarders [40]. Technical char-
acteristics of the applied machineries are reported in Table 1.
Table 1. Technical features of the applied machineries for WINCH and FORW experimental treat-
ments and main average operative data (±SD).
Parameter WINCH FORW
Machine type Forestry-fitted farm tractor Forwarder
Machine model Landini 135DT John Deere 1110D
Engine power 98 kW 120 kW
Land 2022, 11, 388 5 of 15
Equipment 60 kN Schwarz EGV 60 forest
winch n.a.
Empty weight 6
,
400 kg 15,370 kg
Average load for cycle 1,580.9±237.6 kg 10,411.7±729.4 kg
Average distance for cycle 195.8±7.7 m 273.9±10.1 m
Two different areas were identified in each subcompartment. The disturbed area
(DIST) consisted of all the forest surface directly affected by logging activities, which were
skid trails, strip roads and winching corridors. The undisturbed area (UND) was repre-
sented by the soil affected only by the silvicultural activity for instance the logging gaps
without winching corridors. Moreover, a third area used as control (CON) was identified.
This was a forest close to the two subcompartments, which in this case were properly
adjacent and with the same topography, soil and stand features. No harvesting operations
had not been carried out in this area in the last 30 years. This approach allowed us to
separately evaluate the impacts related to the silviculture treatment in itself (UND) with
the impacts caused by the proper forest operations (DIST). All the parameters mentioned
below were properly evaluated by considering this experimental design.
2.2. Investigated Variables
First, the assessment of the percentage of soil affected by the utilization was carried
out for both FORW and WINCH. To perform this evaluation six linear transects were es-
tablished in each subcompartment. Each transect was rectangular in shape (1 m × 200 m)
and defined using a compass and tape measure. Along the transect, visual inspection was
conducted for the presence or absence of bent understory, crushed litter, ruts, or soil mix-
ing and was applied to discriminate between disturbed soil and undisturbed soil. Data
were subsequently referred as the percentage of disturbed soil on the overall surface of
the transect.
The impact on the soil was evaluated on six randomly selected sample plots per treat-
ment (FORW-DIST; FORW-UND; WINCH-DIST; WINCH-UND; CON). Sample plots
consisted of circular areas of a 15 m radius, totaling a surface of 706.5 m2. The parameters
investigated of the soil physico-chemical properties were penetration resistance (PR),
shear resistance (SR), bulk density (BD) and organic matter (OM). Biological impacts were
assessed applying the QBS-ar index. The field survey was carried out in June 2021, about
one year after the end of the harvesting operations in both parcels.
2.3. Soil Physico-Chemical Properties
PR (MPa) and SR (Mg m−2) were evaluated by a handheld dedicated instrument in
the first 3-10 cm of soil. Obtained values for PR and SR were referred to the soil water-
holding capacity as suggested by Saxton et al. [41]. For both PR and SR 18, measurements
were taken in each experimental treatment and six measurements in the control zone.
BD (g cm−3) were assessed by sampling the soil with a dedicated corer (18 soil samples
in each experimental treatment and six samples in the control area). Then soil samples
were sealed in plastic bags and shipped to the laboratory for weighing after oven drying
at 105 °C to constant weight (dry weight). The dry weight divided by the volume of the
cylinder (100 cm3) gives the BD [42].
Organic matter (OM, %) evaluation was carried out by collecting 12 soil samples in
each experimental treatment and six in the control area. Each sample was collected with
the same corer applied for bulk density, put into a plastic bag and shipped to the labora-
tory. OM assessment was carried out with the incineration method in a mitten at 400 °C
for 4 h, after eliminating all the water with a pretreatment at 160 °C for 6 h [43].
2.4. QBS-ar Index Evaluation
Land 2022, 11, 388 6 of 15
Regarding biological impacts, the QBS-ar index was applied. This is a qualitative in-
dex that evaluates the complexity of the soil microarthropod community.
This index is based on the concept that the higher the soil quality, the higher the
number of microarthropod groups present as they are adapted to the soil environment.
Soil microarthropods are separated into several biological forms according to their mor-
phological adaptation to soil habitats. Each form is linked with a score named EMI (eco-
morphological index), that ranges from 1 to 20 in proportion to the degree of adaptation
[43]. The QBS-ar index value is the sum of the EMI of all found groups. To assess the QBS-
ar index, three soil cores 100 cm2 and 10 cm deep were sampled with a dedicated corer in
each area. Subsequently, microarthropods were extracted with a Berlese–Tüllgren funnel.
The various specimens were collected in a preserving solution (75% ethyl alcohol and 25%
glycerol by volume) and identified with different taxonomic levels (class for Myriapoda
and order for Insecta, Chelicerata and Crustacea) using a stereo microscope.
2.5. Statistical Analysis
After checking for data normality (Shapiro–Willk test) [44] and homoscedasticity
(Levene test) [45], the presence of statistically significant differences among the mean val-
ues of treatments was investigated with unpaired samples T-test (for the percentage of
impacted surface) [46] and one-way analysis of variance (ANOVA, for the other investi-
gated variables) [47]. An HSD Tukey test was applied post hoc [48]. Data which did not
show normal distribution, or which presented insufficient homogeneity of variance, were
statistically processed using the nonparametric ANOVA Kruskal–Wallis test [49] apply-
ing the Duncan test [50] post hoc. Furthermore, a principal component analysis (PCA)
[51] was performed to investigate any linear correlations between the treatments. To min-
imize the scaling effect because of different measurement units, the data of each independ-
ent variable were standardized using box-cox transformation.
Statistical analysis was carried out with Statsoft Statistica 7.0 (Statsoft, Tulsa, USA)
[52] and PAST software [53].
3. Results and Discussions
Both extraction systems led to a similar percentage of impacted surface (Figure 2). In
detail, ground-based operations via winching and forwarding impacted about 28% of the
overall surface, with values in line with similar systems applied in different conditions
[25,54,55]. The low tree density of the investigated stands did not lead to a lower percent-
age of impacted surface. This was rather expected for the forwarder, considering the short
working distance of this system, i.e., 10–12 m [36], forces the operator to extensively drive
the machine along the stand. On the contrary, winching in the presence of a stand with
low density (around 100 trees per hectare after the intervention) would assume a lower
impacted surface, considering the possibility of winching on longer distances. It is proba-
ble that the obtained results, which do not confirm this assertion, are related to the limited
application of snatch blocks which are effective solutions to reduce tree and soil damages
during winching [56]. These results therefore suggest the importance of the application of
best management practices during forest operations, considering that these are effective
solutions to mitigate the negative impact of logging [57–59].
Land 2022, 11, 388 7 of 15
Figure 2. Percentage of impacted surface with the two analyzed extraction systems. No statistically
significant difference was detected according unpaired samples T-test (p < 0.05). FORW: extraction
with forwarder; WINCH: extraction with forestry-fitted farm tractor equipped with winch.
Data on soil bulk density in the different treatments are given in Figure 3. Note that
BD is higher than CON for both disturbed and undisturbed soil for both extraction sys-
tems. Soil affected by forwarder passage (FORW-DIST) showed higher bulk density than
WINCH-DIST, suggesting a higher impact related to the CTL machinery on soil bulk den-
sity. On the other hand, as expected, no difference was revealed between the two UND
soil portions, considering that the silviculture treatment and the magnitude of interven-
tion and canopy removal was the same for the two investigated forest subcompartments.
Impact level in UND soil is indeed related to the degree of canopy cover removal [60,61].
Focusing on the comparison between the two applied extraction systems, it is possi-
ble to assert that obtained results are consistent with what was reported by Venanzi et al.
[62] concerning a comparison of soil impact related to winching and forwarding in a Med-
iterranean turkey oak (Quercus cerris L.) coppice. Authors of this publication revealed a
higher increase in soil bulk density triggered by forwarding operations compared to ex-
traction by winching-skidding. On the other hand, the obtained findings are not consistent
with the common assertion that an advanced mechanization level leads to decreased im-
pact on the soil. Therefore, it can be speculated that the lower impact reported in current
literature for machinery specifically dedicated to forestry [14] could be related more to the
correct application of specific tools to decrease soil damage that is caused by the tires of
the forwarders, for instance bogie tracks [12,26]. Without such specific adjustments, the
higher number of passages per volume unit needed to extract timber with the CTL system
in comparison to the TLS system seems to lead to higher soil disturbance.
Surprisingly, the magnitude of machinery-induced soil compaction found in this
study is three times higher than CON values for both WINCH and FORW, which is higher
than what was reported in current literature. Indeed, a recent meta-analysis on the topic
revealed an average increase in bulk density after forest utilization of 5–15% [63], while a
previous study carried out in Iran on oriental beech stands reported an average increase
of 19–39% [64]. This suggests a high sensitivity of the soil of the Mediterranean beech
forests to ground-based extraction, which should be evaluated carefully in future studies
along with an evaluation of the time needed for recovery.
Land 2022, 11, 388 8 of 15
Figure 3. BD for the different treatments. Different letters indicate different homogeneous group
according to an HSD Tukey test (p<0.05): CON: control area; WINCH: winching; FORW: forward-
ing; DIST: soil directly affected by machineries’ passage; UND: soil in the harvested parcels but not
directly affected by machineries’ passage.
Data on PR and SR are reported in Figure 4. The obtained results suggest a significant
impact related to forest utilisation for both variables, but not an influence because of sil-
vicultural activities. Indeed, regarding PR, FORW-DIST and WINCH-DIST were signifi-
cantly higher than CON with no difference between them. Concerning SR, FORW-DIST
was significantly higher than CON, while no difference was detected for WINCH-DIST.
From these results it can be speculated that there is a rather clear impact on both PR and
SR related to forest utilization, and the magnitude of this impact is not related to the ap-
plied machinery. Interestingly, no impact related to the silviculture in itself was detected
for both WINCH-UND and FORW-UND, which is consistent with what was reported in
a recent similar study carried out in a different kind of stand [62].
Figure 4. PR (a) and SR (b) for the different treatments. Different letters indicate different homoge-
neous group according to an HSD Tukey test (p < 0.05): CON: control area; WINCH: winching;
FORW: forwarding; DIST: soil directly affected by machineries’ passage; UND: soil in the harvested
parcels but not directly affected by machineries’ passage.
Land 2022, 11, 388 9 of 15
Interesting results were also obtained concerning OM (Figure 5). A significant impact
of forest utilization was revealed for both winching and forwarding. Furthermore, FORW-
DIST values were significantly lower than WINCH-DIST ones, suggesting that a higher
impact on soil OM occurred in the extraction via forwarder, as found by Venanzi et al.
[62], but different from what was reported by another similar study carried out on chest-
nut (Castanea sativa Mill.) coppice [26]. Regarding OM, silviculture in itself caused a sig-
nificant impact. Indeed, both WINCH-UND and FORW-UND showed lower values than
CON (with no differences between them as expected). From the obtained results it seems
that also the limited canopy gaps created by thinning interventions can lead to a decreased
soil OM in the first year after harvesting.
Figure 5. OM for the different treatments. Different letters indicate different homogeneous groups
according to an HSD Tukey test (p<0.05): CON: control area; WINCH: winching; FORW: forward-
ing; DIST: soil directly affected by machineries’ passage; UND: soil in the harvested parcels but not
directly affected by machineries’ passage.
Data on the impact on soil biological features are given in Figure 6. As is shown, only
WINCH-DIST had a significant impact in comparison to CON. A trend can therefore be
observed which is inverse to what is seen for the major part of the other parameters ana-
lyzed in the present study. Interestingly, and in contrast with similar studies carried out
with the same methodology but in different kinds of stands in the Mediterranean area
[25,26,62], silviculture in itself does not lead in the short-term to a decrease in the biodi-
versity of soil edaphic fauna, and WINCH-UND and FORW-UND values are not different
from CON. This could be related to the low litter decomposition rate typical of beech
[65,66], along with the fact that the studied stands were not affected by interventions at
least for 40 years before the harvesting intervention. This led to the creation of a thick layer
of litter, which acted as a sort of protective buffer, limiting the amount of light radiation
reaching the soil and thus decreasing the disturbance to soil edaphic fauna. Obviously,
further dedicated studies are needed to confirm this hypothesis and to assess its validity
with a longer time perspective.
Land 2022, 11, 388 10 of 15
Figure 6. QBS-ar index values for the different treatments. Different letters indicate different homo-
geneous group according to the Duncan test (p<0.05): CON: control area; WINCH: winching;
FORW: forwarding; DIST: soil directly affected by machineries’ passage; UND: soil in the harvested
parcels but not directly affected by machineries’ passage.
Focusing on an overview of the data found, Figure 7 shows the results of the principal
Ccmponents analysis (PCA) to summarize the findings obtained in a comprehensive
graphical framework. The two principal components PC1 and PC2 explained 48% and
26% of the total variance, respectively. It is evident how the undisturbed areas are close
to the control one, while disturbed zones are more distant, thus highlighting a higher im-
pact on the soil features. Moreover, the distance from the CON as compared to the
WINCH-DIST, showed that FORW-DIST had a greater impact.
Figure 7. Score plot of components PC1 and PC2 of the principal component analysis referred to the
investigated soil variables. Control area is reported in green; WINCH-UND in light blue; FORW-
Land 2022, 11, 388 11 of 15
UND in dark blue; WINCH-DIST in dark red and FORW-DIST in light red. Green lines indicate the
Biplot.
To summarize, this was the first study aimed at evaluating in the short-term the im-
pact triggered by two different harvesting systems in Mediterranean beech forests, focus-
ing on both physico-chemical and biological disturbances. The applied experimental de-
sign allowed for the separate assessment of the impact related to the applied machineries
(DIST soil) and of the ones related to forestry (UND soil). The first aspect which is worth
highlighting is that the impacts related to forestry are much lower than the ones related
to forest operations. The disturbance in UND soil was indeed evident for bulk density and
organic matter but not for penetration resistance, shear resistance and, interestingly, for
QBS-ar index. Focusing on the comparison between the two applied harvesting systems,
winching with a forestry-fitted farm tractor showed the ability to trigger lower disturb-
ance than forwarding. This statement is rather in contrast with current literature on the
topic [14], which suggests that machinery specifically developed for forest operations are
less impactful than adapted agriculture machinery. Instead, in the present study forward-
ing resulted in more impact than winching, particularly concerning increased bulk den-
sity and organic matter depletion. In this specific case, the difference can be attributed to
two factors. First, the CTL system applied with the forwarder needs more passages to
extract the same volume of material [67], thus triggering higher soil compaction [63]. Sec-
ond, the application of CTL machineries, such as forwarders, in Mediterranean forestry
has been growing extensively only in the last few years [36]. Therefore, operators could
be still not be fully skilled with the proper application of these machineries, as well as
with the technical adjustments which can decrease soil damages (such as, for example, the
application of bogie tracks or the placement of logging residues on the strip roads to de-
crease soil compaction) [12]. This highlights the need of increasing operators’ skills con-
cerning these modern machineries in Mediterranean context, suggesting the importance
of the collaboration between forest researchers, technicians and operators, in implement-
ing effective sustainable forest management [68,69].
4. Conclusions
Research conducted on this topic is of great interest. Findings give a precious insight
into the topic of “forest harvesting best practices”. The increase in knowledge for better
sustainable forest management supports the decision making of managers and stakehold-
ers. This is of particular importance when dealing with alterations to soil features that are
related to logging activities, which are defined as soil disturbances or soil impacts.
The data acquired from these case studies are important for updating meta-analysis
research, guidelines, criteria and indicators for SFOs applications.
As found in other studies, the physical, chemical, and biological soil features were
slightly disturbed by the forestry itself, as expected from continuous forest-cover silvicul-
ture. Forest operations and machine traffic showed clear disturbance through the mechan-
ical action on the soil structure, resulting in a substantial alteration to the soil characteris-
tics.
Between the two extraction techniques observed, winching caused lower disturbance
while forwarding had stronger impacts. This result is probably related to the different
applied harvesting systems, TLS and CTL, with the need for CTL to make more passages
per unit of volume. TLS application via winching seems therefore a solution able to trigger
lower disturbance to soil in the short-term. On the other hand, to increase the sustainabil-
ity of forwarding in Mediterranean beech forests, applying bogie-tracks and increasing
operator training could be possible solutions.
However, it should be noted that these impact levels are found, for both machineries,
on approximately 28% of the surface. Furthermore, although short-term impacts are sub-
stantial for both systems, data from the literature suggests a recovery time that should not
last longer than 5–8 years. However, further research is needed to test this hypothesis.
Land 2022, 11, 388 12 of 15
Abbreviations
BD: bulk density
CON: control area
CTL: cut-to-length harvesting system
DIST: disturbed soil (affected by machinery’s passage)
EMI: eco-morphological index
FORW: forwarder
OM: organic matter
PR: penetration resistance
QBS-ar: soil biological quality index based on microarthropods
SFM: sustainable forest management
SFOs: sustainable forest operations
SR: shear resistance
TLS: tree length harvesting system
UND: undisturbed soil (soil in the harvested parcel but not directly affected by the pas-
sage of machineries)
WINCH: forestry fitted farm tractor equipped with winch
Author Contributions: Conceptualization, F.L., R.V. and R.P.; methodology, F.L., R.V., D.T., W.S.
and R.P.; formal analysis, F.L. and R.P.; writing—original draft preparation, F.L., R.V., D.T. and
W.S.; writing—review and editing, F.L., R.V., W.S. and R.P.; supervision, R.P. All authors have read
and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Acknowledgments: The authors gratefully acknowledge Forest Consortium of Amiata, Arcidosso
– Italy. This research was in part carried out within the framework of the MIUR (Italian Ministry for
Education, University and Research) initiative “Departments of Excellence” (Law 232/2016), WP3,
which financed the Department of Agriculture and Forest Science at the University of Tuscia. This
research was in part carried out within the project PLANNING CHANGE (CAMBIO PIANO), PSR
2014-2020 Tuscany Region, met. Leader. Meas. 16.2 – Gal F.A.R. Maremma.
Data Availability Statement: Not applicable.
Informed Consent Statement: Not applicable。
Data Availability Statement: The data presented in this study are available on request from the
corresponding author.
Conflicts of Interest: The authors declare no conflict of interest.
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