ArticlePDF Available

Long-Term Climate Sensitivity of Resin-Tapped and Non-Resin-Tapped Scots Pine Trees Based on Tree Ring Width and Blue Intensity

MDPI
Forests
Authors:
Marcin Jakubowski at University of Life Sciences in Poznań
Marcin Jakubowski
Marek Dobroczyński
Marek Dobroczyński
Marek Dobroczyński
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

The resin tapping of pine trees in Poland ended in the early 1990s. However, we can still find individual trees, and sometimes larger groups of trees, that were tapped. This study focused on the effect of the mechanical wounding of trees during resin tapping on the growth and climatic sensitivity of pine trees. The study concerned a 160-year-old pine stand in northwestern Poland in which resin tapping was last performed in the 1970s. All the trees had remained standing because of their high quality, which had destined them for seed collection. The stand included both resin-tapped (RT) and non-RT (NRT) trees. Our study was based on a dendrochronological analysis of two signals—annual tree ring widths (TRWs) and their delta blue intensity (DBI). We observed a significant increase in annual TRW after resin tapping had ceased, alongside a decrease in the DBI. The temporal stability in growth response was examined using daily climatic correlations from 1921 to 2021. It was found that the climatic sensitivity of RT and NRT pines was similar. There were differences in only some of the years, most while resin tapping was occurring, and then approximately 20 years after the resin tapping had ceased. However, these were small differences that mainly related to the strength of the correlation. It was also discovered that we can obtain different types of information from the study of TRWs and DBI.
Figures - available from: Forests
This content is subject to copyright.
Access to this full-text is provided by MDPI.
Learn more
Content available from Forests 
This content is subject to copyright.
Citation: Jakubowski, M.;
Dobroczy´nski, M. Long-Term
Climate Sensitivity of Resin-Tapped
and Non-Resin-Tapped Scots Pine
Trees Based on Tree Ring Width and
Blue Intensity. Forests 2023,14, 593.
https://doi.org/10.3390/f14030593
Academic Editor: Stefan Arndt
Received: 15 February 2023
Revised: 10 March 2023
Accepted: 15 March 2023
Published: 16 March 2023
Copyright: © 2023 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/licenses/by/
4.0/).
Article
Long-Term Climate Sensitivity of Resin-Tapped and
Non-Resin-Tapped Scots Pine Trees Based on Tree Ring Width
and Blue Intensity
Marcin Jakubowski * and Marek Dobroczy ´nski
Department of Forest Utilisation, Faculty of Forestry and Wood Technology, Pozna ´n University of Life Sciences,
Wojska Polskiego 71 A, 60-625 Pozna´n, Poland
*Correspondence: marcin.jakubowski@up.poznan.pl
Abstract:
The resin tapping of pine trees in Poland ended in the early 1990s. However, we can still
find individual trees, and sometimes larger groups of trees, that were tapped. This study focused
on the effect of the mechanical wounding of trees during resin tapping on the growth and climatic
sensitivity of pine trees. The study concerned a 160-year-old pine stand in northwestern Poland in
which resin tapping was last performed in the 1970s. All the trees had remained standing because of
their high quality, which had destined them for seed collection. The stand included both resin-tapped
(RT) and non-RT (NRT) trees. Our study was based on a dendrochronological analysis of two signals—
annual tree ring widths (TRWs) and their delta blue intensity (DBI). We observed a significant increase
in annual TRW after resin tapping had ceased, alongside a decrease in the DBI. The temporal stability
in growth response was examined using daily climatic correlations from 1921 to 2021. It was found
that the climatic sensitivity of RT and NRT pines was similar. There were differences in only some of
the years, most while resin tapping was occurring, and then approximately 20 years after the resin
tapping had ceased. However, these were small differences that mainly related to the strength of the
correlation. It was also discovered that we can obtain different types of information from the study of
TRWs and DBI.
Keywords: resin tapping; tree response; dendrochronology; delta blue intensity
1. Introduction
Pine resin tapping in Poland was conducted intensively after World War II, reaching a
peak in the 1960s–1970s. About 15,000–20,000 tons of resin were tapped per year in Poland,
mostly from Scots pine (Pinus sylvestris L.), which was also commonly tapped for resin
in other European countries [
1
–
4
]. Over time, the mass cultivation of more productive
pines in other regions of the world caused resin-tapping activities to cease in the Central
European area, although in Western Europe, Pinus pinaster Aiton is still being resin-tapped
(RT) [
5
]. In Poland, resin has not been harvested since 1994 [
3
]. When regular resin tapping
was practiced in Poland, the main goal of forest management was to first produce raw
wood material, with resin production being an additional activity. Consequently, trees
approximately 90 years old, after accumulating raw wood material, were subject to resin
tapping, after which the stands were planned to be harvested. However, it is still possible
today to find individual trees or even groups of trees that were not felled. When the
wounds were made for resin tapping, the trees were subjected to a severe stress situation,
which continued throughout the resin-tapping period. In Poland, the wound exploitation
would have lasted for 2 to 6 years. After this, the wounds would rapidly overgrow; these
overgrowths are easily visible. According to current guidelines, 70% of the circumference of
the trunk would be injured, making the wounds large and unable to completely heal. The
uninjured part of the circumference—called the life band—was designed to keep the tree
alive during the resin-tapping period. This 30% was left in one, two, or three zones around
Forests 2023,14, 593. https://doi.org/10.3390/f14030593 https://www.mdpi.com/journal/forests
Forests 2023,14, 593 2 of 14
the circumference, depending on the diameter of the trunk. The regenerative abilities of
Scots pine are so strong that the trees remained for many years with no apparent further
damage [1,3,4].
Several researchers have addressed the climate sensitivity of Scots pine [
6
–
8
]. However,
little work has been performed on the effects of resin tapping on pine growth, especially
in an ecological context. A study by Zaluma et al. [
4
] suggested that RT pine trees in
Latvia had retained their health and vitality several decades after the resin tapping had
ceased. This is highly significant because those trees were so old (140–160 years). Van der
Mateen et al. [
1
] determined that there were no differences between the climatic responses
of RT versus non-RT (NRT) pines, the implication being that resin tapping is not associated
with a significant climatic response in pine trees, as measured by annual increment width.
A study by Magnuszewski et al. [
3
], conducted nearly 40 years after resin tapping had
ceased, found a similarity in the growth patterns of RT and NRT pines (despite differences
in their increment widths). By contrast, differences in the growth response of the two
groups after resin tapping were found to occur at a height of 3.30 m. The aforementioned
studies covered remote areas, and only in stands in Germany could the climatic sensitivity
of RT pines be determined.
Most studies on trees are based on a chronology built on the tree ring width (TRW).
This parameter is also historically the oldest and most widely used tool for studying climate
sensitivity. However, we can use different sources of signals, such as the TRW and basal area
increment (BAI), to determine different climatic information [
9
]. An important technique
used by dendrochronologists is X-ray-determined wood density, otherwise referred to as
maximum latewood density (MXD). Chronologies built on MXD can be used in temperature
reconstructions [
10
] because these MXD data show a strong correlation with temperature,
especially during summer [
11
,
12
]. Recent studies have also revealed that wood density
can be used to study drought [
13
,
14
], using not only maximum density but also minimum
density, which is more useful for obtaining a spring drought signal [
15
]. However, the
X-ray technique is expensive and difficult to access, so researchers have been pursuing
faster, cheaper, and more readily available methodologies [16].
One of these methods is blue intensity (BI), which is based on the reflection of blue light
from certain anatomical elements of wood, scanned at high resolution [
17
]. Studies suggesting
the utility of blue light reflectance in pine wood were first conducted quite a long time ago [
18
].
More recent studies have pointed to BI having a strong correlation with the X-ray-based
wood density [
19
–
22
], and finding that it can be used on the wood of coniferous species to
determine similar data. With the help of this technique, it has been possible to determine a
proxy for latewood and earlywood density, or the difference between the two values—that
is, delta BI (DBI) [
23
]. Previous applications of the BI technique have included dendro-
climatic responses [
24
–
26
], especially those related to summer temperature [
20
,
21
,
27
], climate
reconstructions [
27
–
29
], drought-related relationships [
30
–
32
], historic timber dating [
27
,
33
],
and dendro-provenancing [34].
The climatic sensitivity of RT Scots pine has been under-researched. This is probably
because resin tapping has not been conducted in this species for several decades. Such studies
have more often been conducted on other species that are being actively tapped [
6
,
35
–
38
].
However, in Central Europe, there are sporadic long-term climatic records that allow comparison
of the responses of RT and NRT pines to change [
1
]. Similar studies with slightly narrower
scopes, involving comparing annual TRWs, have also been presented [
2
–
4
]. The annual TRWs
of RT and NRT pines differ, but their sensitivity to climate has not been adequately examined.
Earlier analyses have involved the testing of correlations based on monthly climate data [
1
]. In
the present study, correlations with daily climatic data were used, with the scope of the study
being expanded to include tree responses measured by BI. This allowed more accurate analyses
to be conducted for specific time periods. The aim of this study was to determine the effect of
the mechanical wounding of pine trees on the incremental response and sensitivity of those
trees to climate over a 40-year period since resin tapping had ceased.
Forests 2023,14, 593 3 of 14
2. Materials and Methods
2.1. Research Area
A pine stand in the Trzcianka Forest District in the northern part of Poland (53
◦
04120 N,
16
◦
23564 E) was used in this study (Figure 1). The total area of the stand was 8.5 ha. Pine
(90%) and beech (10%) were the dominant species, both aged 160 years. After resin tapping,
the stand was earmarked for seed collection, so no felling was performed. The average
diameter at breast height (DBH) was 49 cm, the average height of the trees was 29 m, and
the stand was located at 95 m above sea level. The average annual temperature between
1921 and 2021 was 7.8
◦
C, and the annual precipitation was 575 mm, with the distribution
of monthly values being shown in Figure 2. Resin tapping was performed for several years,
beginning in 1976, with the last wound made in 1980. The average height of the wounds
was 150 cm. All the trees were healthy, showing no signs of disease either on the outside or
inside of the trunk when drilled.
Forests 2023, 14, x FOR PEER REVIEW 3 of 15
wounding of pine trees on the incremental response and sensitivity of those trees to cli-
mate over a 40-year period since resin tapping had ceased.
2. Materials and Methods
2.1. Research Area
A pine stand in the Trzcianka Forest District in the northern part of Poland (53°04120
N, 16°23564 E) was used in this study (Figure 1). The total area of the stand was 8.5 ha.
Pine (90%) and beech (10%) were the dominant species, both aged 160 years. After resin
tapping, the stand was earmarked for seed collection, so no felling was performed. The
average diameter at breast height (DBH) was 49 cm, the average height of the trees was 29
m, and the stand was located at 95 m above sea level. The average annual temperature
between 1921 and 2021 was 7.8 °C, and the annual precipitation was 575 mm, with the
distribution of monthly values being shown in Figure 2. Resin tapping was performed for
several years, beginning in 1976, with the last wound made in 1980. The average height of
the wounds was 150 cm. All the trees were healthy, showing no signs of disease either on
the outside or inside of the trunk when drilled.
Figure 1. Site location and sample collection: (a) RT Scots pine; (b) location of research area; (c)
wounded trunk; and (d) method of coring two-wound and three-wound trees.
Figure 1.
Site location and sample collection: (
a
) RT Scots pine; (
b
) location of research area;
(c) wounded trunk; and (d) method of coring two-wound and three-wound trees.
Forests 2023, 14, x FOR PEER REVIEW 3 of 15
wounding of pine trees on the incremental response and sensitivity of those trees to cli-
mate over a 40-year period since resin tapping had ceased.
2. Materials and Methods
2.1. Research Area
A pine stand in the Trzcianka Forest District in the northern part of Poland (53°04120
N, 16°23564 E) was used in this study (Figure 1). The total area of the stand was 8.5 ha.
Pine (90%) and beech (10%) were the dominant species, both aged 160 years. After resin
tapping, the stand was earmarked for seed collection, so no felling was performed. The
average diameter at breast height (DBH) was 49 cm, the average height of the trees was 29
m, and the stand was located at 95 m above sea level. The average annual temperature
between 1921 and 2021 was 7.8 °C, and the annual precipitation was 575 mm, with the
distribution of monthly values being shown in Figure 2. Resin tapping was performed for
several years, beginning in 1976, with the last wound made in 1980. The average height of
the wounds was 150 cm. All the trees were healthy, showing no signs of disease either on
the outside or inside of the trunk when drilled.
Figure 1. Site location and sample collection: (a) RT Scots pine; (b) location of research area; (c)
wounded trunk; and (d) method of coring two-wound and three-wound trees.
Figure 2.
Climatic data for Trzcianka. Orange line—mean temperature, circles—range of monthly
mean temperatures from 1921 to 2021. Data imported from the E-OBS database.
Forests 2023,14, 593 4 of 14
2.2. Tree Coring and Sample Preparation
We selected 23 healthy RT trees and 20 NRT trees as a reference. Two increment cores
were collected at a height of 1.3 m in two directions at an angle of 90
◦
from the NRT trees
and, in the RT trees, from the live area between wounds (Figure 1d). Resin extraction with
acetone was performed to enable the recording of the blue signal without the disruption
caused by resin. As suggested by Rydval et al. [
11
], 72 h is sufficient for the extraction;
however we processed it for slightly longer because of the resinous nature of the trees. The
process was conducted at room temperature for over 96 h. The samples were then subjected
to natural drying before being glued onto wooden sticks. The sample surfaces were sanded
using a belt sander with a successive grade of sandpaper (150, 240, 400, and 800).
After sanding, the samples were scanned on an EPSON V 600 scanner at a resolution
of 2400 dpi. Color calibration of the scanner was performed using a Fuji IT8.7/2 card
(http://www.silverfast.com, accessed on 10 March 2023). Measurements of annual TRW
and BI values were made using CoRecorder and Cdendro v.9.6 [
39
]. The reflectance of blue
light differs between sapwood and heartwood because of the darker color of the heartwood,
so we used the DBI index instead of the commonly used latewood BI [
23
]. Two series
were averaged and detrended using a cubic spline smoothing with a 50% frequency cut-off
at 30 years. To remove the autocorrelation, chronologies were developed by calculating
a bi-weighted robust mean. This resulted in four chronologies, two of which we used
for the annual TRW and two for the DBI values. The chronologies were built based on
the following numbers of trees: 17 TRW, NRT; 14 DBI, NRT; 22 TRW RT; and 16 DBI, RT
(Table 1). Standard statistics were used for quality assessment: Gleichläufigkeit (GLK),
first-order autocorrelation (AR1), mean series intercorrelation (RBAR), the signal-to-noise
ratio (SNR) and the expressed population signal (EPS). All statistics were calculated using
the dplR R package (R Core Team) (Table 1) [40].
Table 1. Characteristics of the tested trees.
Characteristic NRT RT
TRW DBI TRW DBI
No. of trees 17 14 22 16
DBH (cm) 47.4 49.7
Height (m) 30.7
GLK 0.659 0.645 0.664 0.626
AR1 0.747 0.628 0.762 0.691
RBAR 0.506 0.344 0.472 0.332
EPS 0.942 0.873 0.948 0.881
SNR 16.36 6.90 18.29 7.42
2.3. Climate–Signal Correlations
In order to illustrate the influence of climatic factors, non-stationary correlations
were used, which were determined for the years 1921–2021 in 20-year time windows. As
opposed to stationary correlations, changes in correlations over time can be observed with
this technique, which provide much more information than averaging stationary values for
the entire period. For this purpose, the dendroTools package [
41
,
42
] was used to correlate
the daily data. Monthly and daily climate data were obtained from the E-OBS [
43
] database
(v.25.0) at 0.1
◦
resolution (https://www.ecad.eu, accessed on 10 March 2023). Daily data
were obtained for air temperature (maximum, minimum, and average) and precipitation.
These values were correlated with both the TRW (indexed) and DBI data. To match the
optimal correlation pattern over time, different time windows (from 15 to 180 days) were
tested. Ultimately, a 45-day running window was used for precipitation and average
temperature, and a 30-day running window for minimum and maximum temperature.
Correlations were performed using the bootstrap method, with all calculations performed
Forests 2023,14, 593 5 of 14
to a significance level of
α≤
0.05 and also without a significance level being specified in
order to record weaker correlations throughout the study period.
3. Results
3.1. Comparison of the Chronologies
The indexed chronologies showed a similar pattern for the RT and NRT trees, which is
important for the pre-resin-tapping period, which did not indicate strong events from the
past for either group. Only a small difference was apparent in the wound-making period,
as indicated in Figure 3, where the red line (RT) dips deeper than the black line (NRT), as
highlighted by the grey field on the red line. The indexed DBI curves also appeared similar
for the RT and NRT trees prior to the resin-tapping period. In this case, we also observed a
large depression during the resin-tapping period (Figure 4, grey field on blue line).
Forests 2023, 14, x FOR PEER REVIEW 5 of 15
To match the optimal correlation paern over time, different time windows (from 15 to
180 days) were tested. Ultimately, a 45-day running window was used for precipitation
and average temperature, and a 30-day running window for minimum and maximum
temperature. Correlations were performed using the bootstrap method, with all calcula-
tions performed to a significance level of α ≤ 0.05 and also without a significance level
being specified in order to record weaker correlations throughout the study period.
3. Results
3.1. Comparison of the Chronologies
The indexed chronologies showed a similar paern for the RT and NRT trees, which
is important for the pre-resin-tapping period, which did not indicate strong events from
the past for either group. Only a small difference was apparent in the wound-making pe-
riod, as indicated in Figure 3, where the red line (RT) dips deeper than the black line
(NRT), as highlighted by the grey field on the red line. The indexed DBI curves also ap-
peared similar for the RT and NRT trees prior to the resin-tapping period. In this case, we
also observed a large depression during the resin-tapping period (Figure 4, grey field on
blue line).
Figure 3. Indexed ring width (RWI) chronologies. Black line—NRT, red—RT; grey rectangles indi-
cate the resin-tapping period.
Figure 4. Indexed delta blue intensity chronologies. Black line—NRT, blue line—RT; grey rectangles
indicate the resin-tapping period.
We found a strong signal in all the detrended series and high values for the GLK
(over the 0.60 threshold) and EPS (over 0.87) (Table 1). The AR1 value was also high (over
0.72), although it was slightly lower for DBI (over 0.62). There was a difference in the SNR
and RBAR between the TRW and DBI series; the SNR was much higher for TRW (16.4 and
18.3) and lower for DBI (6.9 and 7.4), whereas, correspondingly, the RBAR was higher for
TRW (0.51, 0.47) and lower for DBI (0.34, 0.33) (Table 1).
Figure 3.
Indexed ring width (RWI) chronologies. Black line—NRT, red—RT; grey rectangles indicate
the resin-tapping period.
Forests 2023, 14, x FOR PEER REVIEW 5 of 15
To match the optimal correlation paern over time, different time windows (from 15 to
180 days) were tested. Ultimately, a 45-day running window was used for precipitation
and average temperature, and a 30-day running window for minimum and maximum
temperature. Correlations were performed using the bootstrap method, with all calcula-
tions performed to a significance level of α ≤ 0.05 and also without a significance level
being specified in order to record weaker correlations throughout the study period.
3. Results
3.1. Comparison of the Chronologies
The indexed chronologies showed a similar paern for the RT and NRT trees, which
is important for the pre-resin-tapping period, which did not indicate strong events from
the past for either group. Only a small difference was apparent in the wound-making pe-
riod, as indicated in Figure 3, where the red line (RT) dips deeper than the black line
(NRT), as highlighted by the grey field on the red line. The indexed DBI curves also ap-
peared similar for the RT and NRT trees prior to the resin-tapping period. In this case, we
also observed a large depression during the resin-tapping period (Figure 4, grey field on
blue line).
Figure 3. Indexed ring width (RWI) chronologies. Black line—NRT, red—RT; grey rectangles indi-
cate the resin-tapping period.
Figure 4. Indexed delta blue intensity chronologies. Black line—NRT, blue line—RT; grey rectangles
indicate the resin-tapping period.
We found a strong signal in all the detrended series and high values for the GLK
(over the 0.60 threshold) and EPS (over 0.87) (Table 1). The AR1 value was also high (over
0.72), although it was slightly lower for DBI (over 0.62). There was a difference in the SNR
and RBAR between the TRW and DBI series; the SNR was much higher for TRW (16.4 and
18.3) and lower for DBI (6.9 and 7.4), whereas, correspondingly, the RBAR was higher for
TRW (0.51, 0.47) and lower for DBI (0.34, 0.33) (Table 1).
Figure 4.
Indexed delta blue intensity chronologies. Black line—NRT, blue line—RT; grey rectangles
indicate the resin-tapping period.
We found a strong signal in all the detrended series and high values for the GLK (over
the 0.60 threshold) and EPS (over 0.87) (Table 1). The AR1 value was also high (over 0.72),
although it was slightly lower for DBI (over 0.62). There was a difference in the SNR and
RBAR between the TRW and DBI series; the SNR was much higher for TRW (16.4 and 18.3)
and lower for DBI (6.9 and 7.4), whereas, correspondingly, the RBAR was higher for TRW
(0.51, 0.47) and lower for DBI (0.34, 0.33) (Table 1).
3.2. Statistical Analysis of Signals between the Periods
In the TRW analysis, there were significant differences before and after the resin-
tapping period. The average TRW before resin tapping (1935–1974) was 0.97 mm in the RT
Forests 2023,14, 593 6 of 14
and 0.91 mm in the NRT trees. After resin tapping (1981–2021), the averages were 1.38 and
1.10 mm, respectively (Table 2). Significant differences were observed in the variability of
the TRWs, with the standard deviation during resin tapping being 0.25 (RT) and 0.24 (NRT),
and after resin tapping, 0.40 (RT) and 0.35 (NRT). The coefficient of variability showed the
highest value for TRW over DBI.
Table 2. Descriptive statistics of the raw chronologies.
Statistic Period NRT RT
TRW
(mm) DBI TRW
(mm) DBI
Mean Before tapping 0.91 1.04 0.97 1.06
SD 1935–1974 0.239 0.07 0.254 0.069
CV 26.1% 7.05% 26.1% 6.6%
Mean Tapping period 0.57 0.89 0.55 0.81
SD 1976–1980 0.096 0.075 0.120 0.129
CV 16.7% 8.5% 21.6% 16%
Mean After tapping 1.1 0.98 1.38 0.93
SD 1981–2021 0.354 0.099 0.398 0.118
CV 32.1% 10.1% 28.8% 12.7%
Note. SD—standard deviation, CV—coefficient of variability.
A strong incremental response occurred in the years after resin tapping. There was
an abrupt increase in the TRWs (Figure 5), which continued for over 30 years, and then
the annual TRWs became aligned with the control trees (the red and grey lines overlap
in Figure 4). A completely different response was observed for the DBI values. The DBI
curves, despite a similar response direction, separated after resin tapping began. This
separation was maintained throughout, up to the year the samples were collected (Figure 5).
We observed a common point in the DBI values for both groups of trees only in 2006.
Another important observation was that reduced DBI values occurred when the resin
tapping began and also during the wound-making period (1975–1980), whereas the TRW
response occurred only after the wound-making had been completed.
Forests 2023, 14, x FOR PEER REVIEW 7 of 15
Figure 5. Raw chronologies of TRW (top) and DBI (boom) for the studied period. Colored lines—
RT trees, grey lines—NRT trees.
3.3. Correlations of TRW and DBI with Mean Temperature and Precipitation
Correlations of the daily data, performed using the bootstrap method, showed that
they were unstable over long periods of time, with both positive (blue) and negative (red)
correlations for the same months in different years (Figure A1). The most stable correlation
was for the average temperature in winter and early spring of the current year, with the
blue area in Figure A1 being visible for almost all years. A horizontal dashed line separates
the period before resin tapping (below the line) from the other years. There were no sig-
nificant differences on the heatmaps between the RT and control (NRT) trees (Figures A1
and A2). The main difference was seen only in the summer precipitation of the current
year. The DBI (Figure A2a) showed more negative correlations with precipitation than
TRW (Figure A1a). However, the differences between the RT and NRT trees were only
slight. Summer showed a slightly stronger negative correlation for the RT trees, more no-
ticeable for DBI than for TRW.
3.4. Correlations of TRW and DBI with Maximum and Minimum Temperatures
For the maximum and minimum temperatures, a stable correlation with TRW can
clearly be seen for winter and early spring (blue area on the heat maps in Figure A3). The
correlations were not stable or were not statistically significant in the other (parts of the)
seasons, however. Considering some observed trends, there is an apparent dominance of
negative correlations in recent decades, especially in April and the summer months. The
DBI was more sensitive to maximum temperature. We also observed more positive corre-
lations in summer in both the current year and the previous year, as well as negative cor-
relations in May of the previous year (Figure A4). These correlations only occurred in
some periods, and not across the entire range of years studied. There was also a tendency
for correlations to change from positive to negative in recent decades, especially after late
summer. These changes are visible for the maximum, minimum, and average tempera-
tures. We observed a slight difference between the RT and NRT trees in the years associ-
ated with wounding and just after wounding. The reference trees showed a larger nega-
tive correlation in the spring months (Figure A3b1,b2). A similar reaction was observed
between the minimum and maximum temperatures and DBI. The negative correlation
Figure 5.
Raw chronologies of TRW (
top
) and DBI (
bottom
) for the studied period. Colored lines—RT
trees, grey lines—NRT trees.
Forests 2023,14, 593 7 of 14
3.3. Correlations of TRW and DBI with Mean Temperature and Precipitation
Correlations of the daily data, performed using the bootstrap method, showed that
they were unstable over long periods of time, with both positive (blue) and negative (red)
correlations for the same months in different years (Figure A1). The most stable correlation
was for the average temperature in winter and early spring of the current year, with the
blue area in Figure A1 being visible for almost all years. A horizontal dashed line separates
the period before resin tapping (below the line) from the other years. There were no
significant differences on the heatmaps between the RT and control (NRT) trees (Figures A1
and A2). The main difference was seen only in the summer precipitation of the current
year. The DBI (Figure A2a) showed more negative correlations with precipitation than TRW
(Figure A1a). However, the differences between the RT and NRT trees were only slight.
Summer showed a slightly stronger negative correlation for the RT trees, more noticeable
for DBI than for TRW.
3.4. Correlations of TRW and DBI with Maximum and Minimum Temperatures
For the maximum and minimum temperatures, a stable correlation with TRW can
clearly be seen for winter and early spring (blue area on the heat maps in Figure A3). The
correlations were not stable or were not statistically significant in the other (parts of the)
seasons, however. Considering some observed trends, there is an apparent dominance
of negative correlations in recent decades, especially in April and the summer months.
The DBI was more sensitive to maximum temperature. We also observed more positive
correlations in summer in both the current year and the previous year, as well as negative
correlations in May of the previous year (Figure A4). These correlations only occurred in
some periods, and not across the entire range of years studied. There was also a tendency
for correlations to change from positive to negative in recent decades, especially after late
summer. These changes are visible for the maximum, minimum, and average temperatures.
We observed a slight difference between the RT and NRT trees in the years associated
with wounding and just after wounding. The reference trees showed a larger negative
correlation in the spring months (Figure A3b1,b2). A similar reaction was observed between
the minimum and maximum temperatures and DBI. The negative correlation (red color
in Figure A4b1,b2) manifested only in the reference (NRT) trees. In all the cases described
above, differences between the RT and NRT trees were only visible for about 20 years after
resin tapping. After this period, there was no significant difference between the RT and
NRT trees.
4. Discussion
Where the GLK values were above 60% and the EPS values were high (above 0.85),
the chronologies were consistent and suitable for climate–growth analysis [
44
,
45
]. The GLK
and EPS coefficients were similar for all chronologies, confirming the homogeneity of the
sample. The high AR1 value illustrated a significant influence of the previous year on the
current year’s growth [
46
]. For the SNR, a much lower value was obtained for the DBI,
and similarly for the RBAR, which is related to the SNR [
47
]. Other authors have reported
similar SNR values for BI [47,48].
Wounding pine trees at around 70% of their circumference must force an incremental
response in the life bands that occupy the remaining 30%. This is logical and has also been
confirmed by other studies, such as that of Zaluma et al. [
4
] in Latvia, where RT pines
showed wider growths after resin tapping than the control trees. Other authors have also
reported a similar phenomenon [
3
,
37
]. In all cases, wider rings were related to the life
bands at a height of 1.3 m. However, the increased TRW response was not present in higher
parts of the trunk (at 3.3 m) [3].
After several years, as a result of regeneration of the cross-section of the trunk, the
TRW again equaled that of the control trees. For the stand in Trzcianka, this occurred
after approximately 30 years. A similar situation has been reported from a stand in Golin,
Germany [
1
], where the TRW equaled the control TRW after approximately 30 years. At a
Forests 2023,14, 593 8 of 14
second site, in Kratzeburg, Germany [
1
], where resin tapping occurred in a later period,
the TRWs were still wider in the RT trees at the time of that study. The annual TRWs for a
site in the Lidzbark Forest District (Poland) continued to differ between the RT and NRT
trees for 35 years after wounding [
3
]. However, in both cases (Kratzeburg and Lidzbark)
the number of years was limited by the age of the trees.
Correlations with precipitation should be considered with caution. Here, these corre-
lations showed the greatest instability and were weak. The nature of precipitation is local
and only partially verifiable. We used gridded data, which did not reflect the precipitation
accurately at the study site. This is typical of studies in large forest complexes, including
the site we analyzed. In addition, precipitation is generally linked to several environmental
influences and hydrological conditions, the histories of which were unknown as they re-
lated to our study. In our analysis, the comparison of two groups of trees grown under the
same conditions is appropriate, as other researchers have made similar comparisons [
1
].
We are aware that references to other sites were to be made with caution. Sensitivity to
temperature and precipitation revealed similar correlations for the RT and NRT pines. Only
in some years were slight differences observable, during resin tapping and for a short time
afterward. This was visible for early autumn precipitation in the current season (TRW,
Figure A1) and summer precipitation (DBI, Figure A2). The correlations with temperature
and precipitation were similar for both groups. In relation to the climatic sensitivity of pine,
van der Mateen et al. [
1
] illustrated a high similarity in the responses of RT and NRT trees.
The differences between the periods before resin tapping and at 40 years after were similar
for both groups of trees. However, these were stationary correlations, and the responses of
the trees in specific years remain unknown. The similarity between the responses of RT
and NRT trees to temperature and precipitation has also been reported by Genova [
35
] for
P. pinaster in Spain. The authors even suggested the possibility of using the chronology of
RT pines in dendrochronological studies because the chronologies of the two groups were
so similar.
Because of the lack of extensive research on the climatic responses of RT trees, we can
only refer to the reactions of NRT pines, which have been tested in Poland and Central
Europe. The climate sensitivity of pines in Poland and Hungary has been studied by
Misi et al. [
6
], who found a strong positive relationship between the temperatures in
February and March and the annual TRW. A similar effect has been reported by other
researchers [
26
,
49
,
50
]. The moving correlations presented by Kalbarczyk et al. [
51
] showed
similar stability in late winter and early spring temperatures for different time intervals.
The results observed in Trzcianka are in agreement with all the results cited above for
temperature. However, slightly different responses were observed regarding precipitation.
In this study, the correlations with precipitation were mostly statistically insignificant and
differed in individual 20-year periods, indicating a lack of stability. Other studies have also
presented mixed results, suggesting a strong influence by local conditions.
Misi et al. [
6
] discovered a major role of summer precipitation on annual ring formation.
Waszak et al. [
49
] also found a correlation between TRW and precipitation, but mainly in
late spring. By examining the impact of precipitation on periods of years, different tree
responses have been reported for individual subperiods [
8
]. As the authors pointed out,
even short-term weather events can strongly affect annual TRW growth. Similarly, the
results presented by Kalbarczyk et al. [
51
] indicate the instability of the correlations in the
different periods they tested. Water-related impacts can also depend on human activity.
For example, the artificial improvement in water conditions through the construction of
retention facilities has a positive effect on annual TRW growth, regardless of the variability
in climatic conditions [7].
Both DBI and TRW commonly show sensitivity to temperatures in winter and early
spring. Janecka et al. [
52
] found that the TRW and latewood BI in Scots pine were similarly
susceptible to cold winters, and the differences between them were minor. The response
of annual TRW and latewood BI to temperature was presented somewhat differently
by Cao et al. [
48
] for Pinus massoniana Lamb. in China, however, with the BI of the
Forests 2023,14, 593 9 of 14
earlywood showing a similar correlation to TRW and being positively correlated with
temperature. By contrast, the DBI was negatively correlated [
48
]. Differences in the results
of studies conducted on managed stands may have been influenced by the management
treatments. As Candel-Pérez et al. [
53
] reported, thinning operations significantly affected
TRW, latewood, earlywood, BAI, and X-rayed wood density compared to control stands.
Only extreme climatic conditions, such as drought, might have a greater impact than forest
management. The difference between DBI and TRW is primarily related to maximum
temperatures, with the BI showing greater sensitivity. The sensitivity of BI to summer
temperatures is a frequently highlighted feature [
23
,
54
], and it may be considered to be a
good indicator for use in climate reconstructions. At Trzcianka, the DBI was found to be
slightly more sensitive to current summer precipitation than TRW. Studies on pine trees on
the Iberian Peninsula have also suggested a more pronounced response in BI than TRW
for use in the Standardised Precipitation–Evapotranspiration Index [
32
]. This seems to be
caused by seasonal fluctuations in the xylem. Other authors have suggested an association
between BI and precipitation (e.g., [
30
]). The DBI studies focused on RT trees are pioneering
and should be kept in mind for potential verification in the future, especially since they
show a different response to climate than TRW.
5. Conclusions
The climatic sensitivities of RT and NRT pines are similar. There were differences
only in some years, mostly in the wounding years and approximately 20 years after resin
tapping had ended. However, these are small differences, mainly related to the strength of
the correlations, but with the same trends being apparent for the RT and NRT trees. The
response, in terms of TRW and DBI, of the pine trees to climatic factors was found to differ,
with DBI displaying stronger correlations with maximum temperatures than TRW in the
current year. Negative correlations with summer precipitation in the current year were
correlated more strongly with DBI than TRW. This was true for both the RT and NRT pines.
In addition, the annual TRWs at breast height differed significantly for at least 30 years
after resin tapping ended, whereas the DBI in the RT and NRT pines maintained different
values until the wood was collected—that is, for 41 years.
Author Contributions:
For conceptualization and methodology, M.J. and M.D.; formal analysis, M.J.;
writing—original draft preparation, M.J.; writing—review and editing, M.J. and M.D.; visualization,
M.J.; revising the manuscript M.D. and M.J. All authors have read and agreed to the published
version of the manuscript.
Funding: This research received no external funding.
Data Availability Statement:
The data presented in this study are available on request from the
corresponding author.
Acknowledgments:
The authors would like to thank the authorities of Trzcianka Forest Inspectorate
for their help with the experiment.
Conflicts of Interest: The authors declare no conflict of interest.
Forests 2023,14, 593 10 of 14
Appendix A
Forests 2023, 14, x FOR PEER REVIEW 10 of 15
Author Contributions: For conceptualization and methodology, M.J. and M.D.; formal analysis,
M.J.; writing—original draft preparation, M.J.; writing—review and editing, M.J. and M.D.; visual-
ization, M.J.; revising the manuscript M.D. and M.J. All authors have read and agreed to the pub-
lished version of the manuscript.
Funding: This research received no external funding.
Data Availability Statement: The data presented in this study are available on request from the
corresponding author.
Acknowledgments: The authors would like to thank the authorities of Trzcianka Forest Inspectorate
for their help with the experiment.
Conflicts of Interest: The authors declare no conflict of interest.
Appendix A
Figure A1. Correlations ((top)—all correlations, (boom)—significant correlations at p < 0.05) be-
tween TRW and climatic data (sum of precipitation and mean temperature). Separate period before
resin tapping shown below horizontal doed line. (a) Possible negative correlations for RT trees;
and (b) lack of correlations for NRT trees. Lowercase leers—months in the previous year, upper-
case leers—months in the current year.
Figure A1.
Correlations ((
top
)—all correlations, (
bottom
)—significant correlations at p< 0.05) be-
tween TRW and climatic data (sum of precipitation and mean temperature). Separate period before
resin tapping shown below horizontal dotted line. (a) Possible negative correlations for RT trees; and
(b) lack of correlations for NRT trees. Lowercase letters—months in the previous year, uppercase
letters—months in the current year.
Forests 2023, 14, x FOR PEER REVIEW 11 of 15
Figure A2. Correlations ((top)—all correlations, (boom)—significant correlations at p < 0.05) be-
tween DBI and climatic data (sum of precipitation and mean temperature). Separate period before
resin tapping shown below horizontal doed line. (a) Possible negative correlations for RT trees;
and (b) lack of correlations for NRT trees. Lowercase leers—months in the previous year, upper-
case leers—months in the current year.
Figure A2.
Correlations ((
top
)—all correlations, (
bottom
)—significant correlations at p< 0.05) be-
tween DBI and climatic data (sum of precipitation and mean temperature). Separate period before
resin tapping shown below horizontal dotted line. (a) Possible negative correlations for RT trees; and
(b) lack of correlations for NRT trees. Lowercase letters—months in the previous year, uppercase
letters—months in the current year.
Forests 2023,14, 593 11 of 14
Forests 2023, 14, x FOR PEER REVIEW 12 of 15
Figure A3. Correlations ((top)—all correlations, (boom)—significant correlations at p < 0.05) be-
tween TRW and extreme temperatures. Separate period before resin tapping shown below horizon-
tal doed line. (a1,a2) Lack of correlations for RT trees; and (b1,b2) negative correlations for NRT
trees. Lowercase leers—months in the previous year, uppercase leers—months in the current
year.
Figure A3.
Correlations ((
top
)—all correlations, (
bottom
)—significant correlations at p< 0.05) be-
tween TRW and extreme temperatures. Separate period before resin tapping shown below horizontal
dotted line. (a1,a2) Lack of correlations for RT trees; and (b1,b2) negative correlations for NRT trees.
Lowercase letters—months in the previous year, uppercase letters—months in the current year.
Figure A4.
Correlations ((
top
)—all correlations, (
bottom
)—significant correlations at p< 0.05) be-
tween DBI and extreme temperatures. Separate period before resin tapping shown below horizontal
dotted line. (a1,a2) Lack of correlations for RT trees; and (b1,b2) negative correlations for NRT trees.
Lowercase letters—months in the previous year, uppercase letters—months in the current year.
Forests 2023,14, 593 12 of 14
References
1.
van der Maaten, E.; Mehl, A.; Wilmking, M.; van der Maaten-Theunissen, M. Tapping the Tree-Ring Archive for Studying Effects
of Resin Extraction on the Growth and Climate Sensitivity of Scots Pine. For. Ecosyst. 2017,4, 7. [CrossRef]
2.
Michalec, K.; W ˛asik, R.; Barszcz, A. Shaping of the Width of Tree rings in Scots pine as a Result of Resin Tapping. Acta Silvestria
2020,LVI, 49–60. [CrossRef]
3.
Magnuszewski, M.; Tomusiak, R. Effect of Resin-Tapping on the Radial Increment of Scots pine (Pinus sylvestris L.)—Case Study
of a Stand from Lidzbark Forest District. For. Res. Pap. 2013,74, 273–280. [CrossRef]
4.
Zaluma, A.; Strike, Z.; Rieksts-Rieksti
n
,
š, R.; Gaitnieks, T.; Vasaitis, R. Long-Term Pathological Consequences of Resin Tapping
Wounds on Stems of Scots Pine (Pinus sylvestris L.). Trees 2022,36, 1507–1514. [CrossRef]
5.
Garcia-Forner, N.; Campelo, F.; Carvalho, A.; Vieira, J.; Rodríguez-Pereiras, A.; Ribeiro, M.; Salgueiro, A.; Silva, M.E.; Louzada, J.L.
Growth-Defence Trade-Offs in Tapped Pines on Anatomical and Resin Production. For. Ecol. Manag.
2021
,496, 119406. [CrossRef]
6.
Misi, D.; Puchałka, R.; Pearson, C.; Robertson, I.; Koprowski, M. Differences in the Climate-Growth Relationship of Scots Pine: A
Case Study from Poland and Hungary. Forests 2019,10, 243. [CrossRef]
7.
Czy˙
zyk, K. Radial Growth Response of Scots Pine (Pinus sylvestris L.) after Increasing the Availability of Water Resources. Forests
2021,12, 1053. [CrossRef]
8.
Debel, A.; Meier, W.J.-H.; Bräuning, A. Climate Signals for Growth Variations of F. sylvatica,P. abies, and P. sylvestris in Southeast
Germany over the Past 50 Years. Forests 2021,12, 1433. [CrossRef]
9.
Popa, A.; Popa, I.; Roibu, C.-C.; Badea, O.N. Do Different Tree-Ring Proxies Contain Different Temperature Signals? A Case Study
of Norway Spruce (Picea abies (L.) Karst) in the Eastern Carpathians. Plants 2022,11, 2428. [CrossRef]
10.
Gunnarson, B.E.; Linderholm, H.W.; Moberg, A. Improving a Tree-Ring Reconstruction from West-Central Scandinavia: 900 Years
of Warm-Season Temperatures. Clim. Dyn. 2011,36, 97–108. [CrossRef]
11.
Rydval, M.; Larsson, L.-Å.; McGlynn, L.; Gunnarson, B.E.; Loader, N.J.; Young, G.H.F.; Wilson, R. Blue Intensity for Dendroclima-
tology: Should We Have the Blues? Experiments from Scotland. Dendrochronologia 2014,32, 191–204. [CrossRef]
12.
Wilson, R.; Wilson, D.; Rydval, M.; Crone, A.; Büntgen, U.; Clark, S.; Ehmer, J.; Forbes, E.; Fuentes, M.; Gunnarson, B.E.; et al.
Facilitating Tree-Ring Dating of Historic Conifer Timbers Using Blue Intensity. J. Archaeol. Sci. 2017,78, 99–111. [CrossRef]
13.
López, R.; Cano, F.J.; Rodríguez-Calcerrada, J.; Sangüesa-Barreda, G.; Gazol, A.; Camarero, J.J.; Rozenberg, P.; Gil, L. Tree-Ring
Density and Carbon Isotope Composition Are Early-Warning Signals of Drought-Induced Mortality in the Drought Tolerant
Canary Island Pine. Agric. For. Meteorol. 2021,310, 108634. [CrossRef]
14.
Pompa-García, M.; Hevia, A.; Camarero, J.J. Minimum and Maximum Wood Density as Proxies of Water Availability in Two
Mexican Pine Species Coexisting in a Seasonally Dry Area. Trees 2021,35, 597–607. [CrossRef]
15.
Camarero, J.J.; Hevia, A. Links between Climate, Drought and Minimum Wood Density in Conifers. IAWA J.
2020
,41, 236–255.
[CrossRef]
16.
Björklund, J.; von Arx, G.; Nievergelt, D.; Wilson, R.; Van den Bulcke, J.; Günther, B.; Loader, N.J.; Rydval, M.; Fonti, P.;
Scharnweber, T.; et al. Scientific Merits and Analytical Challenges of Tree-Ring Densitometry. Rev. Geophys.
2019
,57, 1224–1264.
[CrossRef]
17.
Babst, F.; Frank, D.; Büntgen, U.; Nievergelt, D.; Esper, J. Effect of Sample Preparation and Scanning Resolution on the Blue
Reflectance of Picea abies.TRACE Proc. 2009,7, 188–195.
18.
McCarroll, D.; Pettigrew, E.; Luckman, A.; Guibal, F.; Edouard, J.-L. Blue Reflectance Provides a Surrogate for Latewood Density
of High-Latitude Pine Tree Rings. Arct. Antarct. Alp. Res. 2002,34, 450–453. [CrossRef]
19.
Campbell, R.; McCarroll, D.; Loader, N.J.; Grudd, H.; Robertson, I.; Jalkanen, R. Blue Intensity in Pinus sylvestris Tree-Rings:
Developing a New Palaeoclimate Proxy. Holocene 2007,17, 821–828. [CrossRef]
20.
Björklund, J.A.; Gunnarson, B.E.; Seftigen, K.; Esper, J.; Linderholm, H.W. Blue Intensity and Density from Northern Fennoscan-
dian Tree Rings, Exploring the Potential to Improve Summer Temperature Reconstructions with Earlywood Information. Clim.
Past 2014,10, 877–885. [CrossRef]
21.
Wilson, R.; Rao, R.; Rydval, M.; Wood, C.; Larsson, L.-Å.; Luckman, B.H. Blue Intensity for Dendroclimatology: The BC Blues: A
Case Study from British Columbia, Canada. Holocene 2014,24, 1428–1438. [CrossRef]
22.
Kaczka, R.J.; Spyt, B.; Janecka, K.; Beil, I.; Büntgen, U.; Scharnweber, T.; Nievergelt, D.; Wilmking, M. Different Maximum
Latewood Density and Blue Intensity Measurements Techniques Reveal Similar Results. Dendrochronologia
2018
,49, 94–101.
[CrossRef]
23.
Reid, E.; Wilson, R. Delta Blue Intensity vs. Maximum Density: A Case Study Using Pinus uncinata in the Pyrenees. Den-
drochronologia 2020,61, 125706. [CrossRef]
24.
Heeter, K.J.; Harley, G.L.; Van De Gevel, S.L.; White, P.B. Blue Intensity as a Temperature Proxy in the Eastern United States: A
Pilot Study from a Southern Disjunct Population of Picea rubens (Sarg.). Dendrochronologia 2019,55, 105–109. [CrossRef]
25.
Blake, S.A.P.; Palmer, J.G.; Björklund, J.; Harper, J.B.; Turney, C.S.M. Palaeoclimate Potential of New Zealand Manoao colensoi
(Silver Pine) Tree Rings Using Blue-Intensity (BI). Dendrochronologia 2020,60, 125664. [CrossRef]
26.
Janecka, K.; Harvey, J.E.; Trouillier, M.; Kaczka, R.J.; Metslaid, S.; Metslaid, M.; Buras, A.; Wilmking, M. Higher Winter-Spring
Temperature and Winter-Spring/Summer Moisture Availability Increase Scots Pine Growth on Coastal Dune Microsites Around
the South Baltic Sea. Front. For. Glob. Chang. 2020,3, 578912. [CrossRef]
Forests 2023,14, 593 13 of 14
27.
Wilson, R.; D’Arrigo, R.; Andreu-Hayles, L.; Oelkers, R.; Wiles, G.; Anchukaitis, K.; Davi, N. Experiments Based on Blue Intensity
for Reconstructing North Pacific Temperatures along the Gulf of Alaska. Clim. Past 2017,13, 1007–1022. [CrossRef]
28.
Buckley, B.M.; Hansen, K.G.; Griffin, K.L.; Schmiege, S.; Oelkers, R.; D’Arrigo, R.D.; Stahle, D.K.; Davi, N.; Nguyen, T.Q.T.; Le,
C.N.; et al. Blue Intensity from a Tropical Conifer’s Annual Rings for Climate Reconstruction: An Ecophysiological Perspective.
Dendrochronologia 2018,50, 10–22. [CrossRef]
29.
Fuentes, M.; Salo, R.; Björklund, J.; Seftigen, K.; Zhang, P.; Gunnarson, B.; Aravena, J.-C.; Linderholm, H.W. A 970-Year-Long
Summer Temperature Reconstruction from Rogen, West-Central Sweden, Based on Blue Intensity from Tree Rings. Holocene
2018
,
28, 254–266. [CrossRef]
30.
Babst, F.; Wright, W.E.; Szejner, P.; Wells, L.; Belmecheri, S.; Monson, R.K. Blue Intensity Parameters Derived from Ponderosa Pine
Tree Rings Characterize Intra-Annual Density Fluctuations and Reveal Seasonally Divergent Water Limitations. Trees
2016
,30,
1403–1415. [CrossRef]
31.
Seftigen, K.; Fuentes, M.; Ljungqvist, F.C.; Björklund, J. Using Blue Intensity from Drought-Sensitive Pinus sylvestris in Fennoscan-
dia to Improve Reconstruction of Past Hydroclimate Variability. Clim. Dyn. 2020,55, 579–594. [CrossRef]
32.
Akhmetzyanov, L.; Sánchez-Salguero, R.; García-González, I.; Domínguez-Delmás, M.; Sass-Klaassen, U. Blue Is the Fashion in
Mediterranean Pines: New Drought Signals from Tree-Ring Density in Southern Europe. Sci. Total Environ.
2023
,856, 159291.
[CrossRef]
33.
Mills, C.M.; Crone, A.; Wood, C.; Wilson, R. Dendrochronologically Dated Pine Buildings from Scotland: The SCOT2K Native
Pine Dendrochronology Project. Vernac. Archit. 2017,48, 23–43. [CrossRef]
34.
Akhmetzyanov, L.; Sánchez-Salguero, R.; García-González, I.; Buras, A.; Dominguez-Delmás, M.; Mohren, F.; den Ouden, J.; Sass-
Klaassen, U. Towards a New Approach for Dendroprovenancing Pines in the Mediterranean Iberian Peninsula. Dendrochronologia
2020,60, 125688. [CrossRef]
35.
Génova, M.; Caminero, L.; Dochao, J. Resin Tapping in Pinus pinaster: Effects on Growth and Response Function to Climate. Eur.
J. For. Res. 2014,133, 323–333. [CrossRef]
36.
Soliño, M.; Yu, T.; Alía, R.; Auñón, F.; Bravo-Oviedo, A.; Chambel, M.R.; de Miguel, J.; del Río, M.; Justes, A.; Martínez-Jauregui,
M.; et al. Resin-Tapped Pine Forests in Spain: Ecological Diversity and Economic Valuation. Sci. Total Environ.
2018
,625,
1146–1155. [CrossRef]
37.
Zeng, X.; Sun, S.; Wang, Y.; Chang, Y.; Tao, X.; Hou, M.; Wang, W.; Liu, X.; Zhang, L. Does Resin Tapping Affect the Tree-Ring
Growth and Climate Sensitivity of the Chinese Pine (Pinus tabuliformis) in the Loess Plateau, China? Dendrochronologia
2021
,
65, 125800. [CrossRef]
38.
Hao-ran, W.U.; Yan-ru, F.a.N.; Xiao-yun, N.I.U.; Qi-fu, L.; Yan-jie, L.I.; Jing-min, J.; Jian-er, J.I.N. Effects of Resin-Tapping Year on
Wood Properties of Living Pinus elliottii.For. Res. 2022,35, 31–39. [CrossRef]
39.
Maxwell, R.S.; Larsson, L.-A. Measuring Tree-Ring Widths Using the CooRecorder Software Application. Dendrochronologia
2021
,
67, 125841. [CrossRef]
40.
R Core Team. R: A Language and Environment for Statistical Computing; R Foundation for Statistical Computing: Vienna, Austria,
2021; Available online: https://www.R-project.org/ (accessed on 10 March 2023).
41.
Jevšenak, J.; Levaniˇc, T. DendroTools: R Package for Studying Linear and Nonlinear Responses between Tree-Rings and Daily
Environmental Data. Dendrochronologia 2018,48, 32–39. [CrossRef]
42.
Jevšenak, J. New Features in the DendroTools R Package: Bootstrapped and Partial Correlation Coefficients for Monthly and
Daily Climate Data. Dendrochronologia 2020,63, 125753. [CrossRef]
43.
Cornes, R.C.; van der Schrier, G.; van den Besselaar, E.J.M.; Jones, P.D. An Ensemble Version of the E-OBS Temperature and
Precipitation Data Sets. J. Geophys. Res. Atmos. 2018,123, 9391–9409. [CrossRef]
44.
Wigley, T.M.L.; Briffa, K.R.; Jones, P.D. On the Average Value of Correlated Time Series, with Applications in Dendroclimatology
and Hydrometeorology. J. Appl. Meteorol. Climatol. 1984,23, 201–213. [CrossRef]
45. Speer, J.H. Fundamentals of Tree-Ring Research; The University of Arizona Press: Tucson, AZ, USA, 2010.
46.
Barbaroux, C.; Bréda, N. Contrasting Distribution and Seasonal Dynamics of Carbohydrate Reserves in Stem Wood of Adult
Ring-Porous Sessile Oak and Diffuse-Porous Beech Trees. Tree Physiol. 2002,22, 1201–1210. [CrossRef]
47.
Kilbride, J. New Dendrochronological Approaches to Identifying Climate Drivers in Northern Conifers. UVM Honors College
Senior Thesis, The University of Vermont, Burlington, VT, USA, 2016.
48.
Cao, X.; Hu, H.; Kao, P.; Buckley, B.M.; Dong, Z.; Chen, X.; Zhou, F.; Fang, K. Improved Spring Temperature Reconstruction Using
Earlywood Blue Intensity in Southeastern China. Int. J. Climatol. 2022,42, 6204–6220. [CrossRef]
49.
Waszak, N.; Robertson, I.; Puchałka, R.; Przybylak, R.; Pospieszy ´nska, A.; Koprowski, M. Investigating the Climate-Growth
Response of Scots Pine (Pinus sylvestris L.) in Northern Poland. Atmosphere 2021,12, 1690. [CrossRef]
50.
Matisons, R.; Jansone, D.; Elferts, D.; Adamoviˇcs, A.; Schneck, V.; Jansons,
¯
A. Plasticity of Response of Tree-Ring Width of Scots
Pine Provenances to Weather Extremes in Latvia. Dendrochronologia 2019,54, 1–10. [CrossRef]
51.
Kalbarczyk, R.; Ziemia´nska, M.; Nieróbca, A.; Dobrza´nska, J. The Impact of Climate Change and Strong Anthropopressure on the
Annual Growth of Scots Pine (Pinus sylvestris L.) Wood Growing in Eastern Poland. Forests 2018,9, 661. [CrossRef]
52.
Janecka, K.; Metslaid, S.; Metslaid, M.; Harvey, J.E.; Wilmking, M. Short-Term Effects of Droughts and Cold Winters on the
Growth of Scots Pine at Coastal Sand Dunes around the South Baltic Sea. Forests 2022,13, 477. [CrossRef]
Forests 2023,14, 593 14 of 14
53.
Candel-Pérez, D.; Lo, Y.-H.; Blanco, J.A.; Chiu, C.-M.; Camarero, J.J.; González de Andrés, E.; Imbert, J.B.; Castillo, F.J. Drought-
Induced Changes in Wood Density Are Not Prevented by Thinning in Scots Pine Stands. Forests 2018,9, 4. [CrossRef]
54.
Björklund, J.; Gunnarson, B.E.; Seftigen, K.; Zhang, P.; Linderholm, H.W. Using Adjusted Blue Intensity Data to Attain High-
Quality Summer Temperature Information: A Case Study from Central Scandinavia. Holocene 2015,25, 547–556. [CrossRef]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.
Long-Term Climate Sensitivity of Resin-Tapped and Non-Resin-Tapped Scots Pine Trees Based on Tree Ring Width and Blue Intensi
ty.pdf
Available via license: CC BY 4.0
Content may be subject to copyright.
2023_forests-14-00593-
v2.pdf
Content uploaded by Marcin Jakubowski
Author content
All content in this area was uploaded by Marcin Jakubowski on Mar 20, 2023
Content may be subject to copyright.
... Additionally, the creation of wounds through resin tapping can alter the physiological functioning of the tree and its response to climate stressors (García-Méijome et al., 2023;Jakubowski and Dobroczyński, 2023). The radial growth of Pinus wallichiana in response to climatic variability has been studied in the Nepal Himalayas and Western Nepal (Gautam et al., 2020). ...
... Tapped trees displayed a pronounced negative correlation with winter temperatures, suggesting heightened sensitivity to cold-season stress. In contrast, untapped trees demonstrated greater resilience, maintaining stable growth under similar conditions (Jakubowski and Dobroczyński, 2023). This result also aligns with previous studies showing complex interactions between temperature and tree growth, with other environmental factors often mediating the response (Buckley et al., 2011). ...
View
... While biochemical processes underpin resin production, the physical impact of resin tapping further influences the seedling growth dynamics and anatomical defenses. Successive tapping incisions negatively impacted the tree growth of the seedlings and mature pines and reduced their recovery capacity after stress [34,50,51]. In some previous studies, stem wounding reduced the hydraulic conductance, thereby limiting the water availability for transpiration and affecting the stomatal conductance (g s ), though without altering the water potential (Ψ) [52] or drought recovery [53]. ...
Toward Safer Resin Tapping: Assessing Alternative Chemical Stimulants for Pinus pinaster
Article
Full-text available
  • May 2025
The use of chemical stimulants in resin tapping is essential for prolonging the resin flow and enhancing production. Traditional stimulants, primarily composed of sulfuric acid, pose concerns related to workplace safety, environmental impact, and tree health. In this study, we compared alternative stimulant pastes containing ethrel, salicylic acid, and citric acid with the traditional Spanish and Brazilian stimulant pastes with higher contents of sulfuric acid. We tapped Pinus pinaster seedlings with five different stimulants, using untreated and mechanically wounded plants as controls. The resin yield, tree growth, and physiological parameters were compared. The pines stimulated with citric acid released ca. 50% more resin, while ethrel and salicylic acid yielded similar amounts to the traditional paste, suggesting their potential as viable alternatives. Although all stimulants reduced the seedling growth, no significant differences were observed in the midday water potential or stomatal conductance. The internal resin accumulation and resin canal density were strongly correlated with the total resin production, and more-acidic pastes tended to cause xylem damage and resin retention. Our findings suggest that moderate acidity is sufficient to trigger resin biosynthesis and release, and that safer, less corrosive formulations, like citric acid, may provide viable, safer, and more sustainable alternatives to conventional stimulants. While the results from the seedlings provide a rapid and cost-effective screening tool, anatomical and physiological differences from mature trees should be considered when extrapolating findings to operational settings.
View
... The width of each tree ring in the scanned images was determined using the CDendro 9.5 analysis system (http://www.cybis.se) (Jakubowski & Dobroczyński, 2023;Maxwell & Larsson, 2021), and the COFECHA program was used for cross-dating quality assessment (Holmes, 1983). A chronology of tree-ring widths was obtained using the ARSTAN program (Holmes et al., 1986). ...
Tree‐Ring Insights Into Past and Future Streamflow Variations in Beijing, Northern China
Article
Full-text available
As the largest city in northern China and the capital of China, the rapid increases in Beijing’s water consumption in recent years have made water resources provision an increasing problem. To rationally allocate water resources, it is important to obtain long‐term runoff information in Beijing. In this study we develop a 236‐year chronology of tree‐ring widths based on cores from Pinus tabuliformis from four sampling sites. The resulting regression model reconstructs December–July runoff of the Yongding River in Beijing, with 49.5% of the variance explained, back to 1786 CE. Among the last 236 years, 1868, 1956, 1991, 1998, 2018, and 2021 were extremely high runoff years; and 1900, 1906, 1999, and 2000 were extremely low runoff years. Comparison of the runoff reconstruction results with climate grid data demonstrated a large magnitude of climate change in North China during the study period. Linkage analysis between the reconstructed runoff and large‐scale water vapor indicated that the high runoff years occurred during negative phases of the Pacific Decadal Oscillation, which may be influenced by the East Asian Summer Monsoon. Projections indicate that the flow of the Yongding River will increase in the future. Supported by policies such as the Ecological Water Supply and South‐to‐North Water Diversion, regional vegetation productivity and Yongding River runoff have increased substantially since 2000. Vegetation growth interacts with runoff volume. It is unclear how long these increases will continue.
View
... The anatomical structure of wood significantly influenced physico-mechanical wood properties [78], both ring structures [79,80], and fiber share and dimension. The width of the annual ring depends on various factors, such as species, habitat, climate [81], mechanical damage [82], or other disturbances, e.g., regular flooding [79]. According to the literature, the average width of pendulate oak (Quercus robur L.) annual rings ranged between 1.2 mm and 3.2 mm [74,79,80]. ...
Wood Quality of Pendulate Oak on Post-Agricultural Land: A Case Study Based on Physico-Mechanical and Anatomical Properties
Article
Full-text available
  • Aug 2024
Oak is one of the most economically important hardwood tree species in Europe, and its prevalence will increase due to progressing global climate change, according to predictive models. With the increasing demand for timber and with the need for a balance between carbon emissions and sequestration, it is essential to address the afforestation of agricultural land. Therefore, this research aimed to investigate the physico-mechanical properties and anatomical structure of pendulate oak (Quercus robur L.) wood—specifically focusing on the trunk’s cross-section—in post-agricultural areas compared with the forest land in the western part of Poland. Wood density, bending strength, modulus of elasticity, and other parameters were analyzed from 1626 wood samples. The analysis of physico-mechanical properties reveals that, historically, agricultural land use has an almost negligible impact on wood quality. Despite significant differences in small vessel diameter and fiber length favoring trees from post-agricultural land, the physico-mechanical properties remain consistent. Large vessel measurements show comparable diameter and length in both land types. These findings suggest that post-agricultural land can serve as an effective alternative for high-quality pendulate oak wood production for industrial purposes. However, wood from post-agricultural land may exhibit a decrease in modulus of rupture by over 30% and potentially lower density above the trunk’s halfway point. This observation hints at the fact that oak trees in post-agricultural areas could be cultivated in shorter rotation periods compared to forest land.
View
... Chemical stimulation refers to the process of increasing pine resin production by the use of chemical products that are applied to pine trees. Several items have been tested since Hessel was given the first US patent in 1936 (Jakubowski et al., 2023) [6] . R.W. Clements [9] was granted a US patent in 1967 for describing the first paste-form chemical stimulant. ...
Harvesting liquid gold: Innovative techniques in pine resin tapping
Article
Full-text available
  • Jan 2024
Resin tapping in pine trees, a practice with deep historical roots, has significant ecological, economic, and social impacts. This review explores various resin tapping techniques, from traditional methods to modern innovations, and their effects on trees and forest ecosystems. It highlights resin's role as a vital raw material for numerous industries, underscoring its economic importance. Additionally, the article examines the societal benefits of resin tapping, such as job creation, community development, and cultural preservation. It further illustrates diverse resin-tapping methods and emphasizes the necessity of sustainable forest management. These examples show how resin extraction can be conducted in an environmentally responsible manner, balancing resource use with ecosystem health. By analyzing both the benefits and challenges of resin tapping, the review provides a comprehensive understanding of its multifaceted impacts, offering insights into best practices that support both economic growth and ecological sustainability.
View
... In the literature of the subject matter there are a number of studies concerning resin tapping and how resin tapping scars occur. However, the studies mainly refer to the increment and growth reaction of the tree, particularly in the context of climate change (Magnuszewski and Tomusiak 2013;Génova et al. 2014;Chen et al. 2015;Zaluma et al. 2022;Jakubowski and Dobroczyński 2023). There are no studies that comprehensively discuss the impact of resin blaze not only on the thickness increment, but also on physical and mechanical properties of wood in the resin blaze zone. ...
The Impact of Resin Harvest History on Properties of Scots Pine Wood Tissue
Article
Full-text available
  • Jul 2023
  • BIORESOURCES
This study was conducted in Central Europe (Poland) in pine forests that were subjected to the process of resin harvesting in the 1970s. Forty trees were designated for the study, which had one or two resin blazes. The objectives of the experiment were to determine the effect of resin tapping on the changes in annual growth, wood density, and mechanical strength of wood in the damaged trees. Resin tapping affected the development dynamics, especially in trees with a single resin blaze. In addition, bark cutting affected wood density over the cross-section. However, no significant variation was found in terms of the mechanical properties of wood, which may support the theory of adaptive tree growth and optimization of tree’s structure to its functions.
View
View
Blue is the fashion in Mediterranean pines: New drought signals from tree-ring density in southern Europe
Article
Full-text available
  • Oct 2022
  • SCI TOTAL ENVIRON
Long-term records of tree-ring width (TRW), latewood maximum density (MXD) and blue intensity (BI) measurements on conifers have been largely used to develop high-resolution temperature reconstructions in cool temperate forests. However, the potential of latewood blue intensity (LWBI), less commonly used earlywood blue intensity (EWBI), and delta (difference between EWBI-LWBI, dBI) blue intensity in Mediterranean tree species is still unexplored. Here we developed BI chronologies in moist-elevation limits of the most southwestern European distribution of Pinus nigra subsp. salzmanii Arnold. We tested whether BI variables derived from tree rings of black pine are better proxies than ring-width variables to reconstruct long-term changes in climatic factors and water availability. For this we applied correlations and regression analyses with daily and monthly climate data, a spatial and temporal drought index (Standardized Precipitation-Evapotranspiration Index-SPEI) and Vapour Pressure Deficit (VPD), as well as atmospheric circulation patterns: North Atlantic Oscillation (NAO), Southern Oscillation Index (SOI) and Western Mediterranean Oscillation (WeMO). We found a positive relation between black pine growth (RW) and temperature during the winter preceding the growing season. Among all variables LWBI and dBI were found to be more sensitive than TRW to SPEI at low-elevation site, with EWBI series containing an opposite climatic signal. LWBI and dBI were significantly related to June and September precipitation at high-elevation site. Winter VPD was related with higher EWI and LWI series, whereas dBI and EWBI were related with January SOI and February NAO. We confirm the potential of long-term dBI series to reconstruct climate in drought-prone regions. This novel study in combination with other wood anatomical measurements has wide implications for further use of BI to understand and reconstruct environmental changes in Mediterranean conifers forests.
View
Do Different Tree-Ring Proxies Contain Different Temperature Signals? A Case Study of Norway Spruce (Picea abies (L.) Karst) in the Eastern Carpathians
Article
Full-text available
  • Sep 2022
One of the most important proxy archives for past climate variation is tree rings. Tree-ring parameters offer valuable knowledge regarding how trees respond and adapt to environmental changes. Trees encode all environmental changes in different tree-ring parameters. In this study, we analyzed how air temperature is encoded in different Norway spruce tree-ring proxies along an altitude gradient in an intramountain valley of the Carpathians. The study area, in the Gheorgheni region, Romania (Eastern Carpathians), has a mountain climate with a frequent temperature inversion in winter. The climate–growth relationship was analyzed for two contrasting altitudes: low elevation, i.e., below 1000 m a.s.l., and high elevation, i.e., above 1500 m a.s.l. Two local weather stations, one in the valley and the other on the upper part of the mountains, provide daily temperatures (Joseni—750 m a.s.l. and Bucin—1282 m a.s.l.). The bootstrap Pearson correlation between cumulative daily temperature data and three tree-ring proxies (tree-ring width—TRW, basal area increment—BAI, and blue intensity—BI) was computed for each series. The results show that elevation modulates the climate response pattern in the case of BI, and remains relatively similar for TRW and BAI. The winter temperature’s positive influence on spruce growth was observed in both TRW and BAI chronologies. Additionally, the BAI chronology highlights a positive relationship with summer temperature. The highest correlation coefficient (r = 0.551, p < 0.05, n = 41) was recorded between BI residual chronology from high elevation series and summer/autumn temperature from the upper-part weather station for a cumulative period of 59 days (the second half of August to the beginning of October). Our results show that, for this intramountain valley of the Eastern Carpathians, different tree-ring proxies capture different climate signals.
View
Long-term pathological consequences of resin tapping wounds on stems of Scots pine (Pinus sylvestris L.)
Article
Full-text available
  • May 2022
  • TREES-STRUCT FUNCT
Key message After 5–6 decades since inflicting resin tapping wounds, overmature (> 120 years old) Pinus sylvestris stems remain undecayed and vigorous. Abstract Overmature trees of Pinus sylvestris bearing large wounds made by resin tapping decades ago are still present in woodlands of south-eastern Baltic Sea region. The aim of the present study was to investigate health condition of those trees focusing on fungal infections and to estimate impact of the injury on radial stem growth. The study was conducted in Latvia in three overmature stands of P. sylvestris , resin-tapped in 1950–1970 s. On the studied ninety 120–167-year-old trees, exposed sapwood constituted from 1140 to 7755 cm ² per individual stem. Of the 127 wounds sampled, 52 (41%) showed wood discoloration. The discoloration in its extent was limited, expanding beyond wound margins approx. 1 (max 3) cm in radial, and 6–7 cm in longitudinal directions. Of the 127 wood samples/wounds subjected to fungal isolations, 96% resulted in fungal growth, yielding 236 fungal isolates that represented 47 fungal taxa. The most common among macro-fungi was basidiomycete Porodaedalea pini , which was isolated from 9% of stems. The fungus is currently classed not as a tree pathogen, but instead as an indicator species for woodland sites to be considered for nature conservation. Data from tree ring widths have revealed that tree reacted to the resin tapping injury by increasing radial increment of the un-affected part of the circumference of the stem. Current study demonstrated that even on the long term, resin tapping has little influence on health condition and vitality of P. sylvestris , even at the very old age. This should be considered as a supporting message in case resin taping practices in the region are to be revived.
View
Short-Term Effects of Droughts and Cold Winters on the Growth of Scots Pine at Coastal Sand Dunes around the South Baltic Sea
Article
Full-text available
  • Mar 2022
Coastal dunes near the Baltic Sea are often stabilized by Scots pine forests and are characterized by a mild climate. These ecosystems are affected by water shortages and might be influenced by climate extremes. Considering future climate change, utilizing tree rings could help assess the role of climate extremes on coastal forest growth. We used superposed epoch analysis to study Scots pine responses to droughts and cold winters, with focus on frequency, timing, and duration. We measured ring widths (RW) and latewood blue intensity (LBI) on samples extracted from trees growing at dune ridge and bottom microsites at the south Baltic Sea. At the regional scale, we observed some similarities in tree responses to both extremes between RW and LBI within the same microsite type and region. At the local scale, RW and LBI were more frequently influenced by cold winters than droughts. RW and LBI from dune ridges were more frequently influenced by droughts than RW and LBI from dune bottoms. LBI from both microsites was more often influenced by droughts than RW. RW and LBI from both microsites were similarly often influenced by cold winters. At both scales, the response time of RW and LBI after droughts predominantly lagged by one year, while cold winters were recorded in the same year. The typical duration of growth reductions after both extremes was one year for both RW and LBI. Our study indicates that Scots pine from the Baltic Sea region is sensitive to climate extremes, especially cold winters.
View
Improved spring temperature reconstruction using earlywood blue intensity in southeastern China
Article
Full-text available
Because instrumental observations are too short to fully represent long‐term natural variability, high‐resolution temperature proxy records are essential to understanding past climate and assessing current climate variability in the context of long‐term patterns. In the subtropics, progress in this field has been hampered by a relative lack of long and truly temperature‐sensitive proxy records. In this study, we provide an assessment of the dendroclimatic potential of blue intensity (BI) and ring‐width (RW) measurements from two hot/humid Pinus massoniana sites in China. Our results show that RW exhibits a significant (p < .05) response to precipitation over a hydrological year (previous November to October) and to temperature over the winter–spring season (January to March). We find the earlywood blue intensity parameter to be the most robust parameter for reconstruction purposes; over the 1916–2015 period, it explains 36% of regional‐scale spring season (March–May) temperature variance. Strong agreements between the current reconstruction and observed temperature over a large area of southeastern China implied that our reconstruction exhibited high reliability and large spatial representation. As expected, our reconstructed temperature data are directly correlated with El Niño–Southern Oscillation. These results suggest that there is great potential to use BI to advance our understanding of temperature variability in regions hot and humid climate regimes. However, more studies are needed to understand (1) which subtropical tree species will be appropriate for use and (2) how to overcome biases from differential staining between sapwood and heartwood.
View
Investigating the Climate-Growth Response of Scots Pine (Pinus sylvestris L.) in Northern Poland
Article
Full-text available
  • Dec 2021
Research Highlights: This study used a 99-year time-series of daily climatic data to determine the climate-growth relationship for Scots Pine (Pinus sylvestris L.) growing in Northern Poland. The use of daily climatic data improved the calculated climatic response of the trees. Background and Objectives: It was hypothesised that daily temperature and precipitation data would more precisely identify climate–growth relationships than monthly data. We compared our results to a previous study conducted in the 1990s that utilised monthly precipitation and temperature data. Materials and Methods: The chronology construction and data analyses were performed using CooRecorder, CDendro and R packages (dplR, treeclim, dendrotools). Forty-nine cores from 31 trees were included in the final chronology. Results: The precipitation and temperature of March had the strongest influence upon ring-widths. Despite a statistically significant correlation between monthly temperature and ring-widths, reduction of error (RE) and coefficient of efficiency (CE) statistics confirmed that daily data better describe the effect of climate on tree rings width than monthly data. Conclusions: At this site, the growing season of Scots pine has changed with the observed association with precipitation now starting as early as February–March and extending to June–July.
View
Climate Signals for Growth Variations of F. sylvatica, P. abies, and P. sylvestris in Southeast Germany over the Past 50 Years
Article
Full-text available
  • Oct 2021
Since recent drought events have already caused severe damage to trees and droughts in the near future are expected to occur even more frequently, this study investigated the response of forest ecosystems to changing climate conditions in the topographically complex region of Bavaria, southeast Germany. For this purpose, climate–growth relationships of important European deciduous and coniferous tree species were investigated over the past 50 years at three middle mountain ranges and corresponding basins. A response analysis between tree-ring width and climate variables was applied to detect modifications in tree responses comparing two 25-year periods at individual forest sites. Furthermore, tree responses to climatic extreme years and seasons were analyzed using a superposed epoch analysis. The results showed that Scots pine (Pinus sylvestris) proved to be the most vulnerable and least drought-resistant of all investigated tree species. Likewise, Norway spruce (Picea abies) and European beech (Fagus sylvatica) revealed a higher drought sensitivity over the past 25 years, even though an extended growing season partially improved tree growth at high-elevation sites. In conclusion, all studied tree species were affected by drought events, even at humid high-elevation sites. Correlations with daily climate variables confirmed that even short-term weather conditions could strongly influence trees’ radial growth. Tree responses to climate conditions have shifted significantly between past and present periods but vary considerably among sites and are generally stronger in humid regions than in already dry areas.
View
Tree-ring density and carbon isotope composition are early-warning signals of drought-induced mortality in the drought tolerant Canary Island pine
Article
Full-text available
  • Nov 2021
  • AGR FOREST METEOROL
Tree death is not always preceded by a visible decline in vigor (canopy dieback) or a progressive loss in crown volume. Identifying early-warning signals of incipient decline can help to implement the necessary measures to prevent tree death. The aim of this work is to understand what functional alterations preceded the massive drought-induced death of adult Pinus canariensis trees in an arid stand, located in the Canary Islands. To this aim, we analyzed interannual variations in earlywood and latewood width, wood density and anatomy, and carbon isotope composition, and the relationships among these variables, in dead and living trees from 1980 to 2013. Dead trees grew less since the 1990′s, produced fewer parenchyma rays and resin canals, and exhibited a trend of decreasing latewood density and a marked shift in carbon isotope discrimination over the last 34 years that were reversed in living trees. Higher wood density in living trees resulted from thicker tracheid cell walls rather than narrower lumens. The intrinsic water use efficiency shifted from higher to lower values in dead trees after the 2000s. These results suggest a carbon limitation to maintain hydraulic safety under xylem tension, as well as to maintain storage and defense capacity, which can render trees more vulnerable to severe drought episodes. A long-term trend of decreasing tree-ring density and a reduced intrinsic water use efficiency in the short-term can be early-warning signals of carbon limitation and tree decline in drought-stressed P. canariensis. The analysis of these variables can be used to assess tree decline risks in similarly vulnerable conifer populations inhabiting drought-prone regions.
View
Radial Growth Response of Scots Pine (Pinus sylvestris L.) after Increasing the Availability of Water Resources
Article
Full-text available
  • Aug 2021
In the years 1998–2022, about eight thousand hydrotechnical facilities were built or planned for construction at the State Forests National Forest Holding in Poland, which could slow down the outflow of water from small forest catchments and store over 50 hm³ of water. Due to the innovative and unprecedented nature of investments retaining water resources on forest land, having a significant impact on the adaptation and mitigation of the negative effects of climate change, the literature on the subject lacks in studies describing their impact on the adjacent forest environment. The aim of the presented research is to determine the evolution of the tree-ring width of Scots pine (Pinus sylvestris L.) before and after the reconstruction of two water reservoirs and the construction of gates in drainage ditches as part of small retention projects in lowland areas. The research was carried out on the basis of core drillings collected in four forest districts and climate data provided by the Polish Institute of Meteorology and Water Management—National Research Institute. In the first stage of the work, no statistically significant influence of climatic conditions on the shaping of growths was demonstrated. In the next step, the variability of increments and their width in individual years before and after the investment was examined. Then, the distance of individual trees from reservoirs and drainage ditches was analyzed, as well as its importance in forming increments. The calculated statistical significance of differences in increments, average, minimum and maximum values, as well as standard deviation indicated the possible influence of retention reservoirs and valves on shaping the increments. The study did not confirm the importance of the distance of trees from the newly available water resources in the growth of the width of the increments.
View
Growth-defence trade-offs in tapped pines on anatomical and resin production
Article
  • Sep 2021
  • FOREST ECOL MANAG
Resin harvesting is a traditional forestry activity that provides economic revenue along with crucial ecosystem services (i.e., fire protection and employment) thus contributing to the socioeconomic development of rural areas. In the Iberian Peninsula, Pinus pinaster Aiton has traditionally been exploited for resin to complement the profitability of timber harvesting. Trade-offs between resin yield and radial growth are not fully understood, however. Resin ducts, the anatomical structures that produce and transport resin within the tree, have been used as a proxy for resin yield or resistance to pathogens as they represent the tree's investment on resin defences throughout its lifespan. It is not yet clear if these structures can be linked to growth or how well the resin duct network correlates with resin yield in tapped trees. To answer these questions, we investigate annual tree-ring width, resin duct traits (absolute and standardized), and resin yield of two maritime pine stands tapped for resin extraction in the North of Portugal (VPA and PCO). Resin duct features are assessed before and during tapping periods as may show the constitutive investment, as well as the combination of constitutive and induced ones. Before resin tapping, average tree-ring width in PCO and VPA was ~2.25 and ~1.13 mm year − 1 , respectively. During tapping, standardized growth rates increased by ca. 40% in VPA, the population living under lower water availability and shorter growing seasons, while growth rates were almost unaffected in PCO. Median resin production in 2016 was 2.9 kg (PCO) and 1.8 kg (VPA), but inter-tree variance was high in both sites. Resin duct production increased exponentially with tree-ring width similarly in the different sites and for the same periods, but wider rings and ducts in PCO resulted in greater areas occupied by resin ducts. Within the population , constitutive anatomical resin-based defences did not trade-off with radial growth, although, lower growth rates were related to higher resin duct investments in response to tapping. Despite this, annual resin production did not correlate with resin duct density or relative area. Conversely, resin yield was positively associated with trunk perimeter, average growth, and absolute resin duct traits. These variables will thus be the most valuable when trying to identify the best resin producers in a stand. Differences in growth sensitivity to resin tapping between sites suggested that the impact of resin harvesting on radial growth is site-dependent and may not be as negative as previously thought. Check it out for free until July 31, 2021 here: https://authors.elsevier.com/c/1dDgF1L~GwQwcD
View