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Climate responses of xylem anatomical traits favor the alien black locust over the coexisting native pedunculate oak in a temperate alluvial forest

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Climate responses of xylem anatomical traits favor the alien black locust over the coexisting native pedunculate oak
in a temperate alluvial forest
Paola Nola(1) , Francesco Bracco(1), Silvia Assini(1), Georg von Arx(2), Daniele Castagneri(2)
1University of Pavia, Dept. of Earth and Environmental Sciences, Italy.
2Swiss Federal Institute for Forest Snow and Landscape Research WSL CH-8903 Birmensdorf, Switzerland.
Introduction
Forest management strategies require knowledge on how
co-occurring native and alien species react to unprecedented
climate conditions, which can severely affect xylem
conductivity and growth performance.
Objective
We aimed at quantitatively comparing xylem anatomical
traits of co-occurring native Quercus robur L.(QURO) and alien
Robinia pseudoacacia L. (ROPS) and assessing similarities
and differences in their responses to climate variability.
Fig.1 “Siro Negri” Forest Reserve (Pavia), a natural broadleaf mixed forest, central Po Plain.
Material and methods
Increment cores from 10 oak and 15 black locust adult living
trees were collected in the State “Siro Negri Natural Forest
Reserve, an alluvial mixed broadleaf forest in the Po Plain,
Northern Italy - Fig.1). The cores were cut with a razor blade and
scanned at a 2400 dpi resolution. Vessels were measured on the
digital images using ROXAS (von Arx and Carrer, 2014).
After cross-dating, we built chronologies of mean ring width
and of different anatomical variables (Table 1), linked to vessel
number and to vessel size.
Anatomical parameters were correlated with monthly
temperature and precipitation (data from CRU dataset) from
previous year June to July of the ring formation year. Correlation
analysis was performed for the period 1954-2005. We also
assessed responses to extreme conditions in 2003.
Results
Anatomical features (Fig. 2, Fig. 3) - The two species showed relevant anatomical differences (Fig. 2, Fig. 3): in QURO, vessels were confined near to
the ring border and their size rapidly decreased; in ROPS, vessels size was highly variable with large and small conduits mixed even in the first part of
the ring.
Influence of climate (Fig. 4) - QURO formed larger vessels when previous summer precipitation was abundant and temperature was high in autumn
and spring. ROPS formed higher number of large vessels when precipitation was abundant in previous summer and current spring but not in winter.
Large vessels were formed when temperature was higher in autumn and in late spring, but not in winter and early spring.
Extreme events (Fig. 5) - The 2003 heatwave had no effects on vessel parameters of the contemporary year for both the species, but influenced vessel
parameters in the following year. Most parameters of the 2004 ring were sensibly reduced in QURO, while they were less affected in ROPS. For both the
species, parameters descriptive of large vessels were the most reduced.
Table 1 - Tree-ring and vessel parameters of the investigated species: acronym, definition,
unit, mean and standard deviation (SD) in the common period 1954-2005. All parameters are
statistically different between the two species (Kolmogorov-Smirnov test, p<0.01)
Discussion and Conclusion
Compared to QURO, ROPS produced smaller vessels and
modulated its responses to climate variability by adjusting the
balance between vessel number and size. Vessel traits of both
species were similarly favored by rainy previous summer and
mild autumn, while in winter ROPS showed higher sensitivity to
water excess. In the growing season ROPS seemed to delay
the onset of growth processes compared to QURO. The 2003
summer heatwave strongly affected vessels formed in the
following year in QURO, but much less in ROPS.
In conclusion, ROPS showed higher ability to cope with
both climate inter-annual variations and extreme events
compared to QURO. These differences could increase ROPS
future competitiveness, slowing down the natural succession
and the regression of the pioneer invasive species by the later-
stage QURO.
Ministry for the
Environment Land and Sea
Protection of Italy
University of Pavia
San Leucio -
Caserta, Italy
7-10 May 2019
TRACE 2019
Fig. 2 - Wood surface after preparation. In ROPS, red squares indicate
or rings with vessels concentrated in earlywood, blue squares the rings
with semi-ring porous appearance.
QURO ROPS
Mean ± SD Mean ± SD
RW Tree-ring width [mm] 1.88 ± 1.11 2.02 ± 1.00
NWA
Net wood area [mm2]4.87 ± 3.14 5.19 ± 2.65
VN Vessel number 16 ± 5 32 ± 18
NL Number of vessels larger than the mean 9 ± 3 14 ± 7
TVA
Total vessel area [mm2]0.78 ± 0.28 0.86 ± 0.46
Kr
Theoretical hydraulic conductivity [kg·m·MPa-1·s-1]1.65 ± 0.66 1.38 ± 0.70
Dh Hydraulic diameter [μm] 262 ± 31 201 ± 20
Max3
Mean area of the 3 largest vessels [μm2]83252 ± 19421 55631 ± 11704
A90
Vessel area corresponding to 90th percentile [μm2]79021 ± 18870 47384 ± 9784
Q1Dh
Hydraulic diameter for vessels over 75th percentile [μm] 319 ± 37 249 ± 25
A50
Vessel area corresponding to 50th percentile [μm2]44635 ± 14607 25348 ± 6348
Q4Dh
Hydraulic diameter for vessels under 25th percentile [μm] 158 ± 35 123 ± 18
A10
Vessel area corresponding to 10th percentile [μm2]15398 ± 8206 9940 ± 3486
Acronym
Tree-ring or vessel parameter
Fig. 3 - Vessel area
distribution within the
ring. The solid line
indicates the mean
value, the dashed
lines one standard
deviation.
Quercus robur Robinia pseudoacacia
Fig. 5 - Percentage reduction of anatomical
parameters in 2004 in Quercus robur and Robinia
pseudoacacia. Full bars indicate significant
difference from the reference period 2000-2002.
Fig. 4 - Correlations between tree-ring and vessel
parameters with monthly precipitation and
temperature. Months of the previous year are in
lowercase letters. Significance is coded
according to the key at the bottom.
Precipitation
Temperature
jun-jul
aug
sep
ott
nov
dec-Feb
Mar
Apr
May
Jun
Jul
jun-jul
aug
sep
ott
nov
dec-Feb
Mar
Apr
May
Jun
Jul
RW
00 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 000 0 00000
NWA
00 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 000 0 00000
VN
0 0 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 00 0 000000
NL
0 0 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 0 00 0 00000
TVA
0 0 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 0 00000000
Kr
0 0 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0000 0 00000
Dh
0 0 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 0 0 0 0 0 0000
Max3
00 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 0 00000000
A90
00 0 0 0 0 0 0 0 0 0 #DIV/0! 00 000 0 00000
Q1Dh
00 0 0 0 0 0 0 0 0 0 #DIV/0! 00000000000
A50
00 0 00 0 0 0 0 0 0 #DIV/0! 0 0 0 0 00 0 0000
Q4Dh
0 0 0 0 0 0 0 0 0 0 0 #DIV/0! 0 0 0 0 0 0 0 100 0
A10
00 000 0 000 0 0 #DIV/0! 0 0 0 0 00 0 0000
Precipitation
Temperature
jun
jul-aug
sep
ott
nov
dec-Feb
Mar
Apr
May
Jun
Jul
jun
jul-aug
sep
ott
nov
dec-Feb
Mar
Apr
May
Jun
Jul
RW
000 0 0 0 00000 00 000 0 00000
NWA
00 000 0 00000 00 000 0 00000
VN
00 000 0 00000 00 000 0 00000
NL
000 0 0 0 00000 00 000 0 00000
TVA
00 000 000000 00 000 0 00000
Kr
00000 000000 00 000 0 00000
Dh
00 000 0 00000 00 000 0 00000
Max3
00 000 000000 00 000 0 0 0000
A90
00 000 0 00000 00 000000000
Q1Dh
00 000 0 00000 00 000 0 00000
A50
00 000 0 00000 00 000 0 00000
Q4Dh
00 000 0 0 0 000 00 000 0 00000
A10
00 000 0 0000 0 0 0 0 0 0 0 0 0 00 0
Negative correlation Positive correlation
0
P>99.9%
0
P>99%
0
P>95%
n.s.
0
P>95%
0
P>99%
0
P>99.9%
Robinia pseudoacacia
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