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Climate change is implicating a two-fold impact on air temperature increase in the ripening period under the conditions of the Luxembourgish grapegrowing region

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Aim: Grape (Vitis vinifera L.) phenology is mainly temperature-driven. Consequently, the shift in thermal conditions due to climate change is supposed to have a distinct influence on grape phenology, grape maturity and wine typicity. This study aims to investigate (i) the future phenological development, as well as (ii) the consequences on the temperature conditions in specific phenophases under the conditions of the Luxembourg grapegrowing region. Methods and Results: A budburst model and a phenological model were combined with an ensemble of ten regional climate change projections for Luxembourg. Analyses comparing four 30-year time spans (reference period: 1971-2000; present: 2001-2030; near future: 2031-2060; far future: 2061-2090) demonstrated that each of the 27 phenological stages according to BBCH code is projected to be reached significantly earlier than in the reference period. According to these projections, the length of phenophases at the early stages is not affected, whereas the ripening period length is significantly shortened. The air temperature increase in the ripening period (far future compared to reference period: + 4.6 °C to + 5.3 °C) is projected to be markedly higher than in the annual averages (+ 2.6 °C). Conclusions: Since (i) air temperatures are generally projected to increase in the future and (ii) the ripening period will take place earlier (usually in the warmer parts of the season), climate change is implicating a two-fold impact on air temperature increase in the ripening period. Significance and impact of the study: This two-fold impact potentially threatens the wine typicity of the traditional grapegrowing regions and therefore calls for specific adaptation strategies.
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Climate change is implicating a two-fold impact
on air temperature increase in the ripening period under the conditions
of the Luxembourgish grapegrowing region
Daniel Molitor*and Jürgen Junk
Luxembourg Institute of Science and Technology (LIST), “Environmental Research and Innovation (ERIN)”
Department, 41, rue du Brill, L-4422 Belvaux, Luxembourg
Corresponding author : daniel.molitor@list.lu
Aim: Grape (Vitis vinifera L.) phenology is mainly temperature-driven. Consequently, the shift in thermal
conditions due to climate change is supposed to have a distinct influence on grape phenology, grape maturity and
wine typicity. This study aims to investigate (i) the future phenological development, as well as (ii) the
consequences on the temperature conditions in specific phenophases under the conditions of the Luxembourg
grapegrowing region.
Methods and Results: A budburst model and a phenological model were combined with an ensemble of ten
regional climate change projections for Luxembourg. Analyses comparing four 30-year time spans (reference
period: 1971-2000; present: 2001-2030; near future: 2031-2060; far future: 2061-2090) demonstrated that each of
the 27 phenological stages according to BBCH code is projected to be reached significantly earlier than in the
reference period. According to these projections, the length of phenophases at the early stages is not affected,
whereas the ripening period length is significantly shortened. The air temperature increase in the ripening period (far
future compared to reference period: + 4.6 °C to + 5.3 °C) is projected to be markedly higher than in the annual
averages (+ 2.6 °C).
Conclusions: Since (i) air temperatures are generally projected to increase in the future and (ii) the ripening period
will take place earlier (usually in the warmer parts of the season), climate change is implicating a two-fold impact on
air temperature increase in the ripening period.
Significance and impact of the study: This two-fold impact potentially threatens the wine typicity of the traditional
grapegrowing regions and therefore calls for specific adaptation strategies.
climate change, cumulative degree days, multi-model ensemble, phenology, ripening temperature
AB S T R A C T
K E Y W O R D S
Received: 9 October 2018
y
Accepted: 12 April 2019
y
Published: 8 July 2019
DOI: 10.20870/oeno-one.2019.53.3.2329
VINE AND WINE
OPEN ACCESS JOURNAL
409
OENO One 2019, 3, 409-422 © 2019 International Viticulture and Enology Society - IVES
Additional tables can be downloaded from https://oeno-one.eu/article/view/2329
INTRODUCTION
The grapevine (Vitis vinifera L.) is a perennial
plan t with an an nua l cycle that is hi ghly
dependent on environmental conditions (Parisi et
al., 2014) . Am ong the m, air tempe rat ure
represents a central factor for the cultivation of
grapevines. In cases where the water, nutrient
and radiation requirements of the plants are
fulfilled (Nendel, 2010, Webb et al., 2007),
thermal conditions control “with only minor
other influences” (Gladstones, 2011) grapevine
phe nolo gy and final grape ma tur ity.
Consequently, changes in thermal conditions are
impacting grape phenology, grape maturity, wine
typicity and, as a last consequence, the economic
sustainability of many traditional grapegrowing
regions such as Luxembourg, where the wine
industry traditionally represents an economically
important sector.
On the east- to south-faced vineyards along the
Moselle River grapevines have been cultivated
since the Roman times. The quality and th e
qua ntit y of a nnua l win e pro d uct ion i n
Luxembourg have been documented in a wine
chronicle since the beginning of the 9th century
A.C. (Molitor et al., 2016b). Nowadays (2017),
the tot al area of the Luxem bou rgi s h
grapegrowing regions covers 1303 ha between
Sc hen gen and R osp ort ove r approxim ate ly
42 km along the Moselle River (Anonymous,
2018). The position of the viticultural fields in
the Luxem bourgish grap egrowing regio n is
depicted in Figure 1. In 2017, most cultivated
cultivars were Müller-Thurgau (syn. Rivaner)
(23.3% of the total acreage), Pinot gris (15.2%),
Auxerrois (14.8%), Pinot blanc (12.6%),
Riesling (12.5%), Pinot noir (9.7%) and Elbling
(6.1%) (Anonymous, 2018). Total wine
pr oduct ion of t he r egion on ave rage of the
vi nta ges 2 008 to 20 17 reached 109 0 92 hl
(Anonymous, 2018).
Worldwide, thermal conditions have significantly
changed during recent decades at both global and
regional scale. According to the Intergovern-
mental Panel on Climate Change (IPCC), human
influence, primarily the burning of fossil fuels,
has been the dominant cause of global warming
for several decades (IPCC, 2013). Based on
regional climate change projections taken from
the ENSEMBLES and the CORDEX projects, an
air te mper atur e incre ase of up to 4 °C
dep endi ng o n th e emi ssio n sc enar io – is
projected for Luxembourg by the end of this
century (Goergen et al., 2013; Junk et al., 2016).
Also, changes in precipitation patterns towards
drier summers and wetter winters are projected
(Goergen et al., 2013).
Sin ce g rape ph enol ogic al dev elop ment is
predomi nantly air temperature-d riven (e.g.,
Duchene and Schneider, 2005; Gladstones, 2011;
Keller, 2015; Moncur et al., 1989), the projected
temperature increase due to climate change will
hav e sig nifi can t imp acts on vi ticu ltur e,
particularly close to the climatic frontiers of
vi tic ult ure w her e the dep end enc e of gr ape
phenology and maturity on climatic conditions is
mos t p rono unc e d ( Bra z dil et a l., 2008).
Ph enolo gy represen ts a maj or f actor in the
distribution of the viticultural areas (Garcia de
Cortazar-Atauri et al., 2017). With ongoing
climatic change, northern regions are expected to
become more suitab le (in terms of climatic
co ndi tions ) for rip ening g rapes ( Jones a nd
Sc hul tz, 2 016 ). In co ntr ast , reg ion s where
temperatures are already close to optimum for
be st wi ne q ualit y might bec ome too hot to
produce high quality wines with balanced fruit in
the future (Jones and Schultz, 2016). To assess
the viti cult ural oppo rtun itie s, ris ks an d
cha llen ges rel ate d to cl imat e chang e and
fu rther more to sup port th e de velop ment of
adequate adaptation strategies, numerical models
simulating the effects of temperature conditions
on plant development are helpful tools.
Daniel Molitor and Jürgen Junk
© 2019 International Viticulture and Enology Society - IVES OENO One 2019, 3, 409-422
410
FIGURE 1. The Luxembourgish grapegrowing
region. Vineyards are depicted in red, main rivers
in blue and borders between countries in black.
The weather station used for present
investigations is located in Remich.
4
Recently, Molitor et al. (2014b) developed a
high-resolution phenology model covering all
27 B B CH (Bio logi sch e Bu ndes anst alt ,
Bundessor-tenamt und Chemische Industrie)
plant phenological growth stages defined by
Lorenz et al. (1995) from budburst to grape
harvest (i.e., BBCH stage 89 describes “grapes
ripe for harvest”). The incorporation of (i) an
upper threshold temperature, above which a
further increase of the te mp er ature will not
accelerate plant development, and (ii) a heat
threshold, above which a further increase of the
temperature will slow down plant development,
in this model have been demonstrated to improve
the p r eci sion of the mo del compa red to
commonly used un-capped cumulative degree
day-based phenology models (e.g., Amerine and
Winkler, 1944; Duchene et al., 2010; Hoppmann,
2010; Nendel, 2010; Oliveira, 1998; Parker et
al., 2011; Schultz, 1992; Zapata et al., 2015).
Und er inc reas ed air t empe ratu re, th e
improvement in precision gained through the
inc orpo rat ion of add itio nal t hres hold s is
expected to be even more pronounced (Molitor
et al., 2014b).
Sin ce (i) air temp erat ure s are exp ect ed to
increase in the future due to climate change and
(ii) the ripening period will likely take place
earlier, usually in the warmer parts of the season
due to faster phenological development driven
by higher temperatures, a two-fold impact on air
temperature increase in the ripening period could
be expected (Duchene et al., 2010), while little is
known about the influence of climate change on
the temperature conditions in other phenophases.
In addi tion , a temp erat ure inc reas e in the
ripening period is expected to alter the typicity of
the wine (Jackson and Lombard, 1993).
Consequently, the aim of the present study was
to in ves tiga te the f utu re phe nolo gica l
development of the cultivars Müller-Thurgau,
Rie slin g and Pin ot noir, as wel l as the
consequences on the air temperature conditions
in spe cif ic phe nop hase s, esp eci ally i n the
ripening period, based on (i) the budburst model
of Molitor et al. (2014a), (ii) the high-resolution
phenological model of Molitor et al. (2014b) and
(iii) a multi-model ensemble of ten regional
climate change projections under the conditions
of the Luxembourgish grapegrowing region.
MATERIALS AND METHODS
1. Observation data: daily mean air
temperatures Remich 1970-2016
Air temperature data were recorded from 1970
thr ough 201 6 b y a wea the r s tati on of the
Luxembourgish national agricultural adminis-
tr ation ASTA ( Administrati on d es s ervic es
techniques de l’agriculture) located in the centre
of the Luxembourgish grapegrowing region in
Remich/Luxembourg (49.54° N, 6.35° E; 207 m
a.s.l.) (Figure 1). Unventilated air temperatures
were measured at 2 m above the ground. Daily
mea n air tem pera tur e s wer e c alc ulat ed as
av era ges o f daily m ini mum and m axi mum
temperatures.
2. Modelled data: daily mean air
temperatures 1970-2090
Time s eries o f daily m ean air t emp era ture
between 1970 and 2090 were extracted from the
online archives of the EU ENSEMBLES project
(http://ensembles-eu.metoffice.com/). In order to
assess the uncertainties related to climate change
projecti on s, a multi-model ense mb le of ten
regional climate change projections was used,
bas ed on th e A1B e miss ion sc enar io
(Supplementary Table 1).
The A1B e miss ion s cena rio d escr ibes
anthropogenic emissions of a future world with
rapid economic growth until the middle of this
century and a balanced use of fossil and non-
fossil energy resources (Nakicenovic and Swart,
2000). It is widely used in impact assessments
for Central Europe (Junk et al., 2015a; Junk et
al., 2015b; Junk et al., 2016; Lokys et al., 2015;
Molitor et al., 2014a).
The selected ensemble covers the overall range
of the available regional climate models (RCMs)
in terms of air temperature change signals and
accounts for the most widely used European
RCMs (van Pelt et al., 2012). Time series of
daily data for Remich were extracted from each
RCM. Instead of using the information from just
© 2019 International Viticulture and Enology Society - IVESOENO One 2019, 3, 409-422 411
TABLE 1. Optimized threshold temperatures for degree day accumulation as well as average coefficients
of variance in the three cultivars Müller-Thurgau, Riesling and Pinot noir.
Cultivar
Lower threshold
(°C)
Upper threshold
(°C)
Heat threshold
(°C)
Reference
Müller-Thurgau 5 20 22 0.1473 Molitor et al. (2014b)
Riesling 7 18 24 0.1465 Molitor et al. (2016)
Pinot noir 3 20 24 0.1572
one single grid cell of the model results, a spatial
mean of 3 × 3 grid cells around that central point
(Remich) was used (spatial resolution of 25 km
× 25 km per grid cell) (Goergen et al., 2013;
Junk e t al ., 20 12; Matza rakis et al. , 2013)
(Supplementary Figure 1). Regional climate
models show syst ema tic d iff ere nce s whe n
compared to direct point measurements. In our
study the impact models for budburst and the
BBCH stages are both based on absolute values
and therefore it is necessary to apply a bias
correction. We used long-term measurements
from the Remich site for the bias correction. The
applied method of quantile mapping is described
in detail in Molitor et al. (2014a) and Junk et al.
(2015b). Correction factors were calculated for
the period 1971-2000 and then applied to the
period of investigation from 1970 to 2090.
3. Phenological models
3.1. Budburst model
The budburst date (expressed as day of the year
– DOY) was cal cul ated fo r each en semble
me mber and each yea r ba sed on the mod el
developed by Molitor et al. (2014b) for the
Müller-Thurgau cultivar. This model represents a
parameterization of the DORMPHOT model
(Caffarra et al., 2011) simulating budburst for
photoperiod-sensitive plant species. It considers
(i) the dormancy induction process occurring in
late summer-autumn; (ii) the action of chilling
temperatures for dormancy release; and (iii) the
promoting effect of a long photoperiod on bud
development during dormancy release and bud
development (Caffarra and Eccel, 2011).
2. High-resolution cumulative degree day-based
models to simulate the phenological
development
The dates of reaching all 27 phenological stages
(according to the BBCH scheme (Lorenz et al.,
19 95)) bet ween bu dburs t an d ha rvest were
calculated for the three Vitis vinifera cultivars
Mül ler-Thu rga u, Rie slin g an d Pinot noir,
according to the high-resolution cumulative
degree day-based phenological model (Molitor
et al., 2014b). In contrast to linear cumulative
degree day approaches, this model takes into
co nsiderat ion that th e fo rcing e ff ect of ai r
temperature is limited at higher temperatures by
incorporating (i) an upper threshold, above
which a further increase of the temperature will
not accelerate plant development, and (ii) a heat
threshold, above which a further increase of the
temperature will slow down plant development
(Molitor et al., 2014b). Investigations of Molitor
et al. (2014b) demonst rated that o ptimized
tem per atur e thr esh olds f or veg eta tive and
generative development are almost identical with
those determined for the whole phenological
cycle. Hence, a single model covering the whole
phenological development was used according to
Mol itor et al. (2 0 14a ). Mos t adeq uat e
tem pera tur e t hres hold s to simu lat e t he
phenological development were selected based
on minimum average (average of all stages)
co effic ients o f va riation (CV; the standa rd
deviation divided by the mean) of the cumulative
degree days (Molitor et al., 2014).
The optimized thresholds (leading to minimum
coefficient of variation) for Müller-Thurgau and
Riesling were taken from Molitor et al. (2014b)
and Molitor et al. (2016), respectively (Table 1).
For Pinot noir, a parameterization took place
following the approach of Molitor et al. (2014b)
bas ed on 2 6 lon g-t e rm phen olog ical and
meteorolo gic al observa tio n dat a set s fro m
El tvill e (G ermany), Kin del (Germ any) and
Remich (Luxembourg).
Threshold triplets (cardinal temperatures) with
best predictive fit were determined based on the
coefficients of variance on the average of all
stages as described before (Molitor et al., 2014b;
Mol ito r et al. , 201 6). For P ino t noir, bes t
adaptation on the 26 long-term phenological data
sets (lowest average coefficient of variation
(0.1 57 2)) was achieved using the th reshold
triplet 3°C, 20°C and 24°C.
An overview of the optimized thresholds for
deg ree day ac c umu lati on in the diff ere nt
cultivars is given in Table 1.
Average (representing the average value of the
26 data sets) cumulative degree days reaching
specific BBCH stages for all three cultivars are
given in Supplementary Table 2.
The budburst date according to the budburst
model represents the starting date of the high-
resolution cumulative degree day-based model.
An aly ses of multi- ann ual obs erv ation d ata
recorded in Remich/Luxembourg (Supplemen-
tary Table 3) demonstrate that the DOYs of
budburst (BBCH 09) of Riesling and Pinot noir
do not differ significantly from the DOYs in
Müller-Thurgau (according to non-parametric
paired-sample t-test; p≤ 0.05). Hence, calculated
dates of budburst for Müller-Thurgau according
to Molitor et al. (2014b) were used for all three
cultivars.
A phenophase is defined as the time span
between reaching a specific BBCH stage and
reaching the subsequent stage (e.g., time span
BBCH 09 to 11 = phenophase 09).
Daniel Molitor and Jürgen Junk
© 2019 International Viticulture and Enology Society - IVES OENO One 2019, 3, 409-422
412
4. Determination of dates of reaching
phenological stages
Bas ed o n (i) the b udb u rst mo del , (ii) the
phenological model and (iii) the ensemble of ten
regional climate change projections, the DOYs
for reaching each of the 27 phenological stages
between budburst and harvest were calculated
for each year, each of the ten ensemble members
and each of the three cultivars. The average dates
(30 years 10 projections - n = 300) of all stages
in the subseq uent 30 -year time spans wer e
computed for all cultivars:
- the reference period (“past”) from 1971 to
2000,
- the “present” from 2001 to 2030,
- the “near future” from 2031 to 2060 and
- the “far future” from 2061 to 2090.
5. Determination of air temperatures in
different phases
Every year, for each of the ten regional climate
cha nge pro jec tion s and eac h of the t h ree
cultivars of investigation, the subsequent average
air temperatures were calculated:
- annual and monthly temperatures,
- pre-bloom temperature (budbreak (BBCH 09)
to beginning of flowering (BBCH 61)),
- bloom temperature (beginning of flowering
(BBCH 61) to end of flowering (BBCH 69)),
- post-bloom temperature (end of flowering
(BBCH 69) to veraison (BBCH 81)) and
- ripening temperature (veraison (BBCH 81) to
berries ripe for harvest (BBCH 89)).
Air temperatures in the four phases defined
above were calculated as mean air temperatures
in the period between the DOY after reaching
the starting stage (BBCH 09, BBCH 61, BBCH
69, BBCH 81, respectively) and the DOY of
reaching the terminal stage (BBCH 61, BBCH
69, BBCH 81, BBCH 89, respectively) for each
projection, each year and each cultivar. Average
air temperatures (30 years 10 projections - n =
300) were calculated in the four 30-year time
spans defined above and for the phases for each
cultivar.
Additionally, the average number of years, in
which the BB CH stage 89 berries ripe f or
ha rve st” was n ot re ach ed un til 3 1/10, w as
computed for each 30-year time span. In the
event that BBCH 89 (“berries ripe for harvest”)
was not reached by 31/10 (number of cases see
Supplementary Table 4), the terminal date for
ripening temperature calculation was fixed at
DOY 304 (31/10) to avoid the impact of low
temperatures after the vegetation period (such as
in November or December) on the calculated
average ripening temperature.
Moreover, the average daily air temperatures
were computed for all four time spans. Their
annual course was plotted (i) relative to 01/01 as
well as (ii ) relative to t he date of budburst
(BBCH 09).
6. Statistical analyses
Data sets consisting of 300 data per time span
(30 year s * 10 r egio nal cl imat e c hang e
projections) under present (2001-2030), near
future (2031-2060) and far future (2061-2090)
conditions were generally tested for significant
differences compared to the reference period
(past; 1971-2000) by non-parametric Mann-
Whi tney U- t est (p ≤ 0. 001) , us ing SPSS
Statistics 19 (IBM, Chicago, IL, USA). For the
phenological data sets, analyses were conducted
separately for each cultivar.
RESULTS
1. Annual temperature evolution
Figure 2 shows the observed annual mean air
temperatures for the weather station at Remich
as well as the multi-model mean of the te n
© 2019 International Viticulture and Enology Society - IVESOENO One 2019, 3, 409-422 413
FIGURE 2. Observed annual average
temperatures in Remich (red line) and projected
(A1B emission scenario; ten ensemble-based
regional climate change projections; multi-model
mean) annual average temperatures (blue line) in
the period 1970 to 2100. Ensemble spread (+/- 1
standard deviation) is indicated in grey.
ens embl e mem b ers ( bias c orre cted ). A
sig nifi can t inc rea se in the ann ual air
temperatures compared to the reference period is
projected (Table 2).
2. Projected average phenological dates
The DOYs of all 27 phenological stages are
modelled to occur significantly earlier in all
cultivars in the present, near future and far future
compared to the reference period (Figures 3
to 5). This shift in time increases continuously
from the present to the far future. The temporal
difference compared to the reference period
al rea dy exi sts a t bu dbu rst (BBCH 09 ) and
remains relatively constant until the beginning of
the ripening period (Supplementary Tables 5
to 7). Consequently, in the time span 2001-2030,
no sig nificant cha nges in the len gth of th e
different phenophases between BBCH 09 and
BBCH 77 were projected in comparison to the
reference period. In contrast, the phenophase 85
(period between BBCH 85 and BBCH 89) is
modelled to get significantly shorter in all three
cultivars. The decrease in the length of this
phenophase compared to the reference period is -
3.9 (Müller-Thurgau), -3.5 (Riesling) and -5.7
(Pinot noir) days in the present, -7.7 (Müller-
Thurgau), -7.7 (Riesling) and -10.2 (Pinot noir)
day s i n the ne ar f utur e and -9.3 (Müll er-
Thurgau), -9.7 (Riesling) and -13.0 (Pinot noir)
Daniel Molitor and Jürgen Junk
© 2019 International Viticulture and Enology Society - IVES OENO One 2019, 3, 409-422
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TABLE 2. Average (ten ensemble-based regional climate change projections) annual air temperatures,
monthly air temperatures, as well as pre-bloom (BBCH 09-61), bloom (BBCH 61-69), post-bloom
(BBCH 69-81) and ripening (BBCH 81-89) air temperatures in the Müller-Thurgau, Riesling and Pinot
noir cultivars in the different 30-year time spans. Δ (°C) = temperature difference (in Kelvin) compared to
the reference period (past; 1971-2000).
Past (1971-2000)
T (°C) T (°C) ! (°C) T (°C) ! (°C) T (°C) ! (°C)
Year (01/01-31/12)10.310.8 0.5 11.8 1.5 12.9 2.6
January 2.3 2.9 0.6 4.3 2.0 5.4 3.1
February 3.0 3.7 0.7 4.9 1.9 5.8 2.8
March 5.9 6.6 0.7 7.4 1.5 8.4 2.5
April 9.6 10.2 0.6 11 .1 1.5 11.4 1.8
May 13.8 14.2 0.4 15.0 1.2 15.6 1.8
June 16.8 17.3 0.5 18.1 1.3 19.4 2.6
July 18.9 19.5 0.7 20.2 1.3 21.4 2.5
August 18.3 19.0 0.7 19.9 1.7 21.1 2.8
September 15.2 15.7 0.5 16.6 1.4 17.8 2.6
October 10.8 11.2 0.4 12.2 1.4 13.3 2.5
November 5.6 6.1 0.6 7.3 1.8 8.7 3.2
December 2.7 2.9 0.2 4.3 1.5 5.9 3.1
Müller-Thurgau
Pre-bloom (BBCH 09-61) 14.4 14.4 0.0 14.6 0.2 14.5 0.1
Bloom (BBCH 61-69) 17.6 17.8 0.1 18.2 0.5 18.3 0.6
Post-bloom (BBCH 69-81) 18.8 19.3 0.5 19.7 0.8 20.7 1.8
Ripening (BBCH 81-89) 16.3 17.5 1.2 19.2 2.9 20.9 4.6
Riesling
Pre-bloom (BBCH 09-61) 14.5 14.6 0.0 14.7 0.2 14.7 0.1
Bloom (BBCH 61-69) 17.7 17.9 0.2 18.4 0.7 18.4 0.7
Post-bloom (BBCH 69-81) 18.7 19.3 0.6 19.9 1.2 20.9 2.2
Ripening (BBCH 81-89) 15.2 16.6 1.3 18.4 3.2 20.3 5.1
Pinot noir
Pre-bloom (BBCH 09-61) 14.4 14.4 0.0 14.5 0.2 14.5 0.1
Bloom (BBCH 61-69) 17.5 17.6 0.1 18.0 0.5 18.2 0.6
Post-bloom (BBCH 69-81) 18.7 19.3 0.5 19.8 1.0 20.7 2.0
Ripening (BBCH 81-89) 15.0 16.5 1.5 18.4 3.3 20.3 5.3
Present (2001-2030)
Near future (2031-2060)
Far future (2061-2090)
Temperatures of the same phases that differed significantly according to the non-parametric Mann-Whitney U-test (p= 0.001) compared to the
reference period (1971-2000) are marked in bold.
day s in th e far futu re (Fig ures 3 to 5;
Supplementary Tables 5 to 7).
The average number of years per 30-year time
span, in which stage BBCH 89 was not reached
until 31/10, is projected to decrease from 1.3
(Müller-Thurgau), 4.7 (Riesling), and 3.8 (Pinot
noir) in the reference period to 0.1 (ller-
Thurgau), 1.2 (Riesling), and 1.1 (Pinot noir) in
the present. In the near future and far future, no
such cases we re ob serv ed (Suppl eme nta ry
Table 4).
3. Temperature conditions in different
phenophases
Annual and monthly average air temperatures
(ex cept f or Jan uary, M a y, Octo ber and
December) a re modelled to be significan tl y
higher in the 2001-2030 time span than in the
reference period. In the near and the far future
annual as well as all monthly temperatures are
projected to be significantly higher than in the
ref eren ce peri od. The c ompu ted ann ual
temperature increase compared to the reference
period is 0.5 °C (present), 1.5 °C (near future)
and 2.6 °C (far future) (Table 2).
In all three cultivars, no significant differences
were projected in the pre-bloom temperatures
compared to the reference period. On the other
hand, the post-bloom and ripening temperatures
are modelled to increase significantly in the
present, near future and far future. The projected
increase (in comparison to the reference period)
is most pronounced in the ripening period. Here,
compared to the reference period, temperatures
are modelled to increase from 1.2 °C (Müller-
Thurgau), 1.3 °C (Riesling) and 1.5 °C (Pinot
noir) in the present to 2.9 °C (Müller-Thurgau),
3.2 °C (Riesling) and 3.3 °C (Pinot noir) in the
near future, to 4.6 °C (Müller-Thurgau), 5.1 °C
(Riesling) and 5.3 °C (Pinot noir) in the far
future (Table 2; Figure 6).
DISCUSSION
Present analyses revealed a constant increase of
the annu al ai r te mper ature in the
Luxembourgish grapegrowing region in the
future confirming previous studies (Junk et al.,
2015a, Junk et al., 2015b, Junk et al., 2016,
Lokys et al., 2015, Molitor et al., 2014b).
The sim ula tion of the fu tur e phe nol ogical
development took p lace based on the high-
© 2019 International Viticulture and Enology Society - IVESOENO One 2019, 3, 409-422 415
FIGURE 3. Days of the year (DOY) reaching the
phenological stages 09 to 89 according to the
BBCH scale (Lorenz et al., 1995) in the Müller-
Thurgau cultivar in the four 30-year time spans.
The box plots indicate the medians and the 25%
and 75% percentiles, whiskers are limited to one
standard deviation. Box plots of the days of the
year of the same BBCH stage that differed
significantly according to the non-parametric
Mann-Whitney U-test (p= 0.001) compared to
the reference period (1971-2000) are marked in
red.
FIGURE 4. Days of the year (DOY) reaching the
phenological stages 09 to 89 according to the
BBCH scale (Lorenz et al., 1995) in the Riesling
cultivar in the four 30-year time spans. The box
plots are indicating the medians and the 25% and
75% percentiles, whiskers are limited to one
standard deviation. Box plots of the days of the
year of the same BBCH stage that differed
significantly according to the non-parametric
Mann-Whitney U-test (p= 0.001) compared to
the reference period (1971-2000) are marked in
red.
resolution phenological model as proposed by
Molitor et al. (2014b). Here, optimized threshold
temperature triplets for phenology simulation are
defined statistically per cultivar based on long-
observation data. Even though these optimized
thresholds are purely statistical, model validation
for Müll er- Thu rga u over a broa d ran ge of
locations in Europe showed a high accuracy
(Molitor et al., 2014). Using this cumulative
degree day approach, in all three cultivars of
investigation, all 27 phenological stages were
computed to be reached significantly earlier in
the future time spans than in the reference period
confirming studies in other viticultural regions in
recent years (e.g., Caffarra and Eccel, 2011;
Duchene and Schneider, 2005; Duchene et al.,
2010; Fraga et al., 2016; Garcia de Cortazar-
Atauri et al., 2017; Ramos, 2017; Sadras and
Moran, 2013; Trought et al., 2015). Differences
in t he e xte n t o f ear lier appe aran ce of
phenological stages as well as in the length of
phenophases observed by the different authors
are supposed to be caused by differences in (i)
the phenological models used (e.g., taking into
account the effect above optimum temperatures
or not), (ii) cultivars of investigation as well as
(iii) t he climatic conditions in t he studied
regions.
In the past, BBCH stage 89 (“berries ripe for
harvest”) was simulated not to be reached in all
years in all three cultivars. This was especially
the case for the (compared to ller-Thurgau)
relatively late ripening cultivars Pinot noir and
Riesling. In the near as well as in the far future,
heat summatio n will according to present
analyses – not be a limiting factor for full grape
maturity – not even in Riesling or Pinot noir.
Due to generally increasing air temperatures,
budburst (BBCH 09) is modelled to be reached
significantly earlier in the future than in the past
confirming previous analyses (e.g., Caffarra and
Eccel, 2011; Fila et al., 2012, Molitor et al.,
2014a). The consequences of the earlier budburst
on the future late frost risk are controversially
Daniel Molitor and Jürgen Junk
© 2019 International Viticulture and Enology Society - IVES OENO One 2019, 3, 409-422
416
FIGURE 5. Days of the year (DOY) reaching the
phenological stages 09 to 89 according to the
BBCH scale (Lorenz et al., 1995) in the Pinot
noir cultivar in the four 30-year time spans. The
box plots are indicating the medians and the 25%
and 75% percentiles, whiskers are limited to one
standard deviation. Box plots of the days of the
year of the same BBCH stage that differed
significantly according to the non-parametric
Mann-Whitney U-test (p= 0.001) compared to
the reference period (1971-2000) are marked in
red.
FIGURE 6. Average (ten ensemble-based regional climate change projections) pre-bloom (BBCH 09-
61), bloom (BBCH 61-69), post-bloom (BBCH 69-81) and ripening (BBCH 81-89) air temperatures in
the cultivars Müller-Thurgau (left), Riesling (centre) and Pinot noir (right) in the different 30-year time
spans. *= temperatures of the same phases that differed significantly compared to the reference period
(1971-2000) according to non-parametric Mann-Whitney U-test (p= 0.001).
discussed in scientific literature (Kartschall et
al., 2015, Kotremba et al., 2014, Molitor et al.,
2014a, Mosedale et al., 2015, Sgubin et al.,
2018 ). While the an alyses of Molitor et a l.
(2014a) indicate that the late frost risk might
decrease in the future, other analyses revealed
inconsistent or even increasing late frost risks.
These contrary results might be explained by the
respective underlying budburst models used.
The total length of the period between BBCH 09
and BBCH 89 (season duration) is projected to
be shor tene d in the futu re in all cul tiva rs
confirming projected data of Webb et al. (2007)
for th e Au stra lia n gr apeg row i ng regi ons.
Int eres tin gly, th e len gth of the diff ere n t
phenophases prior to veraison is projected not to
change significantly in the future compared to
the reference period. That is, the shift of the
phenological development until veraison towards
the beginning of the year is mainly the result of
the earlier budburst. This is in accordance with
observations of Duchene and Schneider (2005)
in the Alsace region where the time span from
budburst to flowering was constant between
1965 and 2003. In contrast, the phenophase 85
representing the period between BBCH 85 and
BBCH 89 is projected to be up to 13 days shorter
in the far future in the case of Pinot noir. The
explanation for adverse effects on phenophase
lengths in different phases of development can
be attributed to the course of the daily average
air temperatures in the four time spans. Figure 7
demonstrates that this increase is relatively
constant in the course of the year (left) compared
to t he re fere nce p eri od. I n con tras t, when
pl otting th e daily av erage air tempera tures
relatively to the date of budburst, comparable
temperature conditions are projected in the
period around BBCH 09 in all four time spans
(Fi gure 7; ri ght) . As conse quen ce of the
relatively constant temperature conditions, the
length of the phenophases (mainly determined
by temperature conditions) is not significantly
affected in the early stages but shifted towards
the beginning of the year.
As a consequence, the computed pre-bloom air
tem pera tur es do not show any s igni fica nt
differences between the reference period and the
future time spans. This is the case because this
phase is shifted towards the earlier (usually
colder) part of the year. In consequence, mainly
tem pera tur e-de pend ent ste ps o f g rape
physiology between budburst and bloom (such
as inf loresce nce differe ntiatio n an d fl ower
initiation (Keller 2015; Molitor and Keller,
2016)) might not be systematically affected
(eve n though there is an increas e in spring
temperatures).
Whi le, ac cord ing to pr esen t resu lts, ai r
temperatures are already increasing significantly
in the post-bloom to veraison period, the length
of the phenophase stays relatively constant until
veraison. This apparent contradiction can be
explained by the fact that the air temperature
conditions in this period are situated in all time
© 2019 International Viticulture and Enology Society - IVESOENO One 2019, 3, 409-422 417
FIGURE 7. Course of daily average temperatures in the four time spans (past: 1971-2000; present: 2001-
2030; near future: 2031-2060; far future: 2061-2090) (i) relative to 01/01 (day of the year – DOY; left) or
(ii) relative to the date of budburst (BBCH 09; right).
spans predominately in the optimum range for
further phenological development (e.g., in the
case of Riesling between 18 °C and 24 °C daily
mean air temperature). Here, a further slight
increase of daily average air temperatures does
no t influ ence the pace of t he ph enolo gical
dev elop men t, i f the hea t t h res hold is not
exceeded.
For practical viticulture under given climatic
conditions, the relatively stable length of the
phe noph ase s prio r to ver aiso n mean s tha t
consequences on the temporal distribution of the
pr e-v era iso n workload i n the vineyard are
expected to be relatively slight. That is, since
phenological development is not accelerated in
this period, spray intervals and time frames for
canopy management measures, for example,
might not be affected.
However, higher air temperatures in the time
frame between bloom and veraison might have
an impact on annual yield. Recent studies have
demonstrated negative correlations between
yield and temperatures, especially maximum
temperatures, over the first three weeks after
bloom for the Riesling cultivar (Molitor and
Keller, 2016). Hence, higher air temperatures in
this period might lead to a decrease in annual
yield in the future while in other periods the
effect of higher temperatures on the annual yield
was observed to be mainly positive (Molitor and
Keller, 2016). To clarify the overall effect of
climate change on yield formation, in a further
step, the present data on future temperature and
phenological conditions will be combined with
the temperature- and precipitation-driven yield
models for the ller-Thurgau and Riesling
cultivars developed based on the multi-annual
yie ld re cord s for t he Lux emb o urg ish
grapegrowing region (Molitor and Keller, 2016).
The most distinct influences on the temperature
con dit ions as well as on t he le ngth o f the
phenophases are modelled for the ripening
pe rio d between verais on an d harvest. T he
increase in the ripening temperature is most
pronounced in late ripening cultivars such as
Riesling and Pinot noir. Here, the grapes are
ri pen ing at a lat er st age of the year where
tem pera tur e dif fer e nce s com pare d to t he
reference period temperatures are most distinct
(temperature decrease in the autumn), while in
case of ller-Thurgau, the ripening period is
closer to the summer plateau of air temperatures.
The p r oje cted inc reas e in the ripe nin g
temperatures in the near future is 1.9 °C (Müller-
Thurgau; 2.9 °C), 2.1 °C (Riesling; 3.2 °C) and
2.2 °C times higher (Pinot noir; 3.3 °C) than the
temperature increase in the month of September
(1.5 °C). This phenomenon is the result of two
additional effects: (i) the general temperature
incr ea se and (ii) t he shift of t he phenolo gy
towards the earlier, generally warmer period of
the year.
In fact, this two-fold effect demonstrates that
changes in temperature conditions in calendar-
based (=anthropogenic) time frames (such as in
the “Cool Night Index ( Tonie tto an d
Carbonneau, 2004), taking into account
min imum tem per atur es in th e mo nth of
September (northern hemisphere)), might not
completely reveal the real temperature changes
in specific developmental stages.
More generally, this fact is indicating a general
limitation of calendar-based climatic indices
used in viticulture such as the Winkler index
(Amerine and Winkler 1944), the heliothermic
index of Huglin (1978) or the average growing
season temperature according to Jones (2007)
since they do not take into account the plant
response to climate (Caubel et al., 2015) and,
hence, might not per fectly re flect th e rea l
veg etat ion pe riod of sp ecif ic cul tiva rs
(Holzkämper et al., 2010).
Present results furthermore demonstrate that the
length of the ripening period (BBCH 81-89) is
projected to decrease in the future (e.g., Riesling,
past: 44.6 days; far future: 33.9 days). This is
confirming the results of the analyses of Tomasi
et al. (2011) in Northern Italy. Authors observed
a significant decrease of the length of the period
between veraison and harvest in the period 1964
to 200 9 ca used by inc reasi ng t emper ature s
(Tomasi et al., 2011). Due to the fact that the
harvest date might under practical conditions be
inf luen ced b y se v era l fac tors (Gar cia d e
Co rtazar-At auri et al., 201 0) the imp act of
temperature on the length of the ripening period
is controversially discussed in the literature. For
example, v an Le euw en and De strac Ir vin e
(2017) found opposite trends in the length of the
period between veraison and harvest. However,
based on present results we assume that the
temperature-sum approach proposed here might,
at least under the climatic conditions of the
Luxembourgish grapegrowing region, better
reveal the real average temperature conditions in
the simulated ripening period (since its length is
ass umed to be in flue nce d by tem per atur e
conditions) than approaches which calculate the
temperature conditions in this period as the
average temperatures between veraison and a
tem pora lly fixe d d ate such as ( i) 35 days
thereafter (Duchene et al., 2010) or (ii) 60 days
thereafter (Schultz and Hofmann, 2017).
Th e str ong a ir te mpe rat ure i ncr eas e in t he
ripening period as described above is presumably
Daniel Molitor and Jürgen Junk
© 2019 International Viticulture and Enology Society - IVES OENO One 2019, 3, 409-422
418
linked to distinct changes in the wine typicity of
a specific region.
In fac t, hi ghe r te mpe ratur es ar e leadi ng to
altering fruit ripening rates (Martinez-Lüscher et
al., 2015), changes in flavour and aroma profiles
(Trought et al., 2015) as well as decoupled
an thocyanin and sugar syn theses in be rries
(Sadras and Mora n, 2013). Expected higher
su gar c onc ent rat ions ar e lea din g to h igh er
alcohol contents (Jackson and Lombard, 1993) in
the wines, and an acceleration of the degradation
of o rga nic acid s (Du chen e et al., 2010),
threatening both the freshness and lightness that
is esp ecial ly ex empla ry f or w hite wines in
(former) cool climate grapegrowing regions,
such as Luxembourg. Furthermore, the fruitiness
and aroma of grapes and wines is expected to be
neg ativ ely affect ed by high ri peni ng
temperatures (Duchene et al., 2010). To maintain
the wine ty pici ty o f the regio n, pot ent ial
ada ptat ion s tra tegi es to miti gate the
consequences of climatic change in general and
higher ripening temperatures in particular might
consist of measures leading to a temporal delay
of the maturation period. This might be achieved
by a shift towards cooler sites (e.g., with higher
elevations or lower exposition) or regions (e.g.,
at higher latitudes), cultivars or clones with a
later ripening characteristic, maturity-retarding
rootstocks, the application of antitranspirants
(Gatti et al., 2016) or specific crop cultural
measures including training systems (Molitor et
al., 2019), delayed winter pruning (Friend and
Trought, 2007) and adapted canopy management
(Parker et al., 2016, Stoll et al., 2013, Trought et
al., 2015).
CONCLUSIONS
Present analyses demonstrated that under the
cli mat ic con dit ions i n the L uxem bou rgi sh
grapegrowing region each of the 27 phenological
stages according to BBCH code are projected to
be reached significantly earlier in the future than
in the r efer enc e p eri od. Whil e sign ific ant
changes in the phenophase lengths are absent in
early stages , the r ipe nin g period le ngth is
significantly shortened in the future according to
these projections. Since (i) air temperatures are
generally projected to increase in the future and
(ii) the ripening period will take place earlier
(usually in the warmer parts of the season),
climate change is implicating a two-fold impact
on ripening period air temperature increase.
Consequently, the air temperature increase in the
ripening period (far future compared to reference
period: + 4.6 °C to + 5.3 °C) is projected to be
markedly higher than in the annual averages (+
2.6 °C). This significant increase of the ripening
period air temperatures potentially threatens the
wine typicity of the traditional grapegrowing
reg ions an d th ere fore cal ls for spe cifi c
adaptation strategies.
Ac knowled gements : The authors tha nk B.
Fuchs (Weinbauamt Eltville, Germany), O. Baus
(Hochschule Geisenheim University), S. Fischer,
R. Ma nnes and M. Schul tz ( Inst itu t Viti-
Vinicole, Remich, Luxembourg) for providing
par ts of the h ist oric al mete orol ogi cal and
phen ological d ata sets , F.K. Ronel lenfitsch
(L IST ) fo r GIS map s, M . Sulis ( LIST) f or
critical proof-reading, L. Auguin (LIST) for
language editing, B. Augenstein and R. Krause
(Geosens Ingenieurpartnerschaft, Schallstadt,
Germany) for running the phenological models
on the VitiMeteo platform, J. Niewind (LIST)
and P. Sinigoj (former CRP – Gabriel Lippmann)
for their support in data management, the Institut
Viti -Vinic ole for f inan cia l supp ort in the
framework of the research project “TerroirFuture
Impact of climate change on viticulture in
Lu xem burg: r isk -as ses sme nt an d pot ent ial
adaptation strategies” as well as the European
Union in the framework of the Clim4Vitis
research project (Horizon 2020 research and
innovation programme; grant agreement No.
810176).
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... All of these studies showed that the main phenological stages (budbreak, flowering, veraison) and harvest would advance in the future, but with a more pronounced advancement foreseen for veraison and harvest than for the earlier stages. According to these projections, the magnitude of warming impact on grape phenology will be dependent on the geo-localization of the wine-growing region (Webb et al., 2007;Koufos et al., 2018;Alikadic et al., 2019), on elevation (Caffarra and Eccel, 2011) and grape variety (Fraga et al., 2016b;De Cort azar-Atauri et al., 2017;Ramos, 2017;Leolini et al., 2018;Molitor and Junk, 2019). Due to the combination of generally increasing air temperatures projected for the future and the shift of the ripening period earlier in the growing season, usually to warmer periods, climate change may have a twofold impact on ripening (Molitor and Junk, 2019). ...
... In our study, under RCP4.5, the mean advancement of the veraison projected for the LFP (2070-2100) was between 2 days at T abua and 5 days at Viseu. Molitor and Junk (2019) suggested that the differences in the extent of earlier appearance of phenological stages projected by the different authors can be attributed to differences in the phenological models used (e.g., taking into account the above-optimum temperature effect or not), the cultivars studied, as well as the pedoclimatic conditions in the studied region. The use of different RCPs and climate model ensembles may also explain some discrepancies, hinting at the significant uncertainties that are inherent to climate projections. ...
... The changes in the phenological and maturity timings are due to the combination of budbreak advancement with a shortening of some phenophases. The total length of the period between EL4 and MS 2.0 (cycle/season duration) is projected to be shortened in the future, which coincides with the projected data of Webb et al. (2007) for the Australian wine regions and of Molitor and Junk (2019) for Luxembourg. In LFP under RCP8.5, the reduction in the duration of the EL4-MS 2.0 period will be of 10 days at T abua and 15 days at Viseu (Table S7). ...
Article
The present study is devoted to climate change impact assessment on the phenological development and ripening of cv. Touriga Nacional in the Dão Wine Region, Portugal. For this purpose, the dates of the three main phenological stages (budbreak, flowering and veraison) and two maturity stages are projected for two future periods (2041–2070 and 2071–2100), under two anthropogenic radiative forcing scenarios (RCP4.5 and RCP8.5), and compared against a baseline period (1991–2020). The phenological and maturity stages are simulated using phenological development models (PDMs) and a temperature‐based ripeness model (TRM), respectively. An overall advancement in both phenology and ripening stages are identified under future warmer climates, though site‐dependent. Furthermore, the advancements in phenology are more pronounced 1) for stages between the beginning of veraison and end of ripening than for the earlier stages, 2) for the long‐term future period (2071–2100) under RCP8.5, and 3) for the vineyard site “Viseu”. These changes are due to the combination of budbreak advancement with a shortening of some phenophases. The strongest shortening is found in the ripening period, while no significant changes in flowering timings and duration of the berry development period are projected. The advancement and the shortening of the grapevine growing season will shift ripening to the warmest part of the year. This two‐fold climate change impact of the air temperature on ripening may affect the sugar and organic acid balance, as well as the colour of the must. The current findings can be used by the regional winemaking sector in planning and implementing suitable climate change adaptation to enhance its climate resiliency and sustainability. Subsequent studies for this wine region should be carried out to assess the climate change impacts on late frost risk, on climatic viticultural zoning, on yield and berry quality at harvest. This article is protected by copyright. All rights reserved.
... However, in recent years, drought stress in summer has increasingly gained attention in many German winegrowing regions [18]. Increased drought stress mainly results from the effects of (i) increased temperatures, especially in the post-flowering phenophase, leading to a higher potential evapotranspiration rate [19], and (ii) increased chance of occurrence of prolonged heat waves [20,21]. The number of days per year with intense drought stress for grapevine is projected to increase in the future for shallow-soil, steep-slope vineyards in the Rheingau region [13]. ...
... A similar magnitude of advancement (10-20 days across scenarios) was found for the flowering stage between varieties, whereas a slightly greater advancement of veraison is projected for Müller-Thurgau (15-25 days across scenarios) than for Riesling (10-25 days across scenarios) (Figure 3). In comparison, Molitor and Junk [19] projected advanced flowering and veraison stages by 9 and 10 days for Müller-Thurgau and by 9 and 11 days for Riesling, respectively, over 2031-2060 under the A1B (comparable to RCP6.0) emission scenario in Luxembourg. The relatively higher magnitude of advancement in our study can be attributed to projected higher seasonal mean temperature increases by 1.5-2.5 • C (depending on the scenario) compared with <1.5 • C projected by Molitor and Junk [19]. ...
... In comparison, Molitor and Junk [19] projected advanced flowering and veraison stages by 9 and 10 days for Müller-Thurgau and by 9 and 11 days for Riesling, respectively, over 2031-2060 under the A1B (comparable to RCP6.0) emission scenario in Luxembourg. The relatively higher magnitude of advancement in our study can be attributed to projected higher seasonal mean temperature increases by 1.5-2.5 • C (depending on the scenario) compared with <1.5 • C projected by Molitor and Junk [19]. Many studies suggest that differences in the magnitude of earlier occurrence of simulated phenology stages under global warming can be explained by differences in the studied varieties, the phenology models applied and the extent of temperature increases [19,31,45,79]. ...
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With global warming, grapevine is expected to be increasingly exposed to water deficits occurring at various development stages. In this study, we aimed to investigate the potential impacts of projected climate change on water deficits from the flowering to veraison period for two main white wine cultivars (Riesling and Müller-Thurgau) in Germany. A process-based soil-crop model adapted for grapevine was utilized to simulate the flowering-veraison crop water stress indicator (CWSI) of these two varieties between 1976–2005 (baseline) and 2041–2070 (future period) based on a suite of bias-adjusted regional climate model (RCM) simulations under RCP4.5 and RCP8.5. Our evaluation indicates that the model can capture the early-ripening (Müller-Thurgau) and late-ripening (Riesling) traits, with a mean bias of prediction of ≤2 days and a well-reproduced inter-annual variability for more than 60 years. Under climate projections, the flowering stage is advanced by 10–20 days (higher in RCP8.5) between the two varieties, whereas a slightly stronger advancement is found for Müller-Thurgau than for Riesling for the veraison stage. As a result, the flowering-veraison phenophase is mostly shortened for Müller-Thurgau, whereas it is extended by up to two weeks for Riesling in cool and high-elevation areas. The length of phenophase plays an important role in projected changes of flowering-veraison mean temperature and precipitation. The late-ripening trait of Riesling makes it more exposed to increased summer temperature (mainly in August), resulting in a higher mean temperature increase for Riesling (1.5–2.5 °C) than for Müller-Thurgau (1–2 °C). As a result, an overall increased CWSI by up to 15% (ensemble median) is obtained for both varieties, whereas the upper (95th) percentile of simulations shows a strong signal of increased water deficit by up to 30%, mostly in the current winegrowing regions. Intensified water deficit stress can represent a major threat for high-quality white wine production, as only mild water deficits are acceptable. Nevertheless, considerable variabilities of CWSI were discovered among RCMs, highlighting the importance of efforts towards reducing uncertainties in climate change impact assessment.
... New climate conditions are affecting viticulture and the winemaking sector worldwide [1,2], modifying crop spatial distribution [3], development timings [4], agronomic techniques [5], and altering yields and quality [6,7]. From an agronomic viewpoint, climate change over the main viticultural regions in Southern Europe, such as the Douro winegrowing region (Portugal), is driving progressively warmer and drier conditions, increasing air, soil, and canopy temperatures [8,9]. ...
Article
Climate-smart agriculture involves practices and crop modelling techniques aiming to provide practical answers to meet growers’ demands. For viticulturists, early prediction of harvest dates is critical for the success of cultural practices, which should be based on accurate planning of the annual growing cycle. We developed a modelling tool to assess the sugar concentration levels in the Douro Superior sub-region of the Douro wine region, Portugal. Two main cultivars (cv. Touriga-Nacional and Touriga-Francesa) grown in five locations across this sub-region were studied. Grape berry sugar data, with concentrations between 170 and 230 g L−1, were analyzed for the growing season campaigns, from 2014–2020, as an indicator of grape ripeness conditioned by temperature factors. Field data were collected by ADVID (“Associação Desenvolvimento Da Viticultura Duriense”), a regional winemaker association, and by Sogrape, the leading wine company from Portugal. The “Phenology Modeling Platform” was used for calibrating the model with sigmoid functions. Subsequently, model optimizations were performed to achieve a harmonized model, suitable for all estates. Model performance was assessed through two metrics: root mean square error (RMSE) and the Nash–Sutcliffe coefficient of efficiency (EFF). Both a leave-one-out cross-validation and a validation with an independent dataset (for 1991–2013) were carried out. Overall, our findings demonstrate that the model calibration achieved an average EFF of 0.7 for all estates and sugar levels, with an average RMSE < 6 days. Model validation, at one estate for 15 years, achieved an R2 of 0.93 and an RMSE < 5. These models demonstrate that air temperature has a high predictive potential of sugar ripeness, and ultimately of the harvest dates. These models were then used to build a standalone easy-to-use computer application (GSCM—Grapevine Sugar Concentration Model), which will allow growers to better plan and manage their seasonal activities, thus being a potentially valuable decision support tool in viticulture and oenology.
... PCLS is re-emerging worldwide (Phillips, 2000;Wilcox et al., 2015;Caffi et al., 2020), because of three probable factors: climate change, which has advanced seasonal grapevine growth, including the time of budbreak (Caffarra and Eccel, 2011;Molitor and Junk, 2019); changes in the management of downy mildew from calendar-to risk-based criteria that eliminate early-season, unnecessary sprays ; and the progressive reduction in the application of broad-spectrum fungicides, which although highly effective (Nita et al., 2006a), may negatively affect human health and the environment (Wightwick et al., 2010;Epstein, 2014;Mostafalou and Abdollahi, 2017). At present, PCLS control is still mainly based on repeated treatments with protective broad-spectrum fungicides (mancozeb, dithianon, captan, or metiram), which are more effective than QoI or DMI fungicides (Hewit and Pearson, 1988;Nita et al., 2006a), starting from budbreak or at 2.5 cm shoot growth (Pscheidt and Pearson, 1991;Rawnsley, 2012;Wilcox et al., 2015). ...
Article
Full-text available
Phomopsis cane and leaf spot (PCLS), known in Europe as “excoriose,” is an important fungal disease of grapevines caused by Diaporthe spp., and most often by Diaporthe ampelina (synonym Phomopsis viticola ). PCLS is re-emerging worldwide, likely due to climate change, changes in the management of downy mildew from calendar- to risk-based criteria that eliminate early-season (unnecessary) sprays, and the progressive reduction in the application of broad-spectrum fungicides. In this study, a mechanistic model for D. ampelina infection was developed based on published information. The model accounts for the following processes: (i) overwintering and maturation of pycnidia on affected canes; (ii) dispersal of alpha conidia to shoots and leaves; (iii) infection; and (iv) onset of disease symptoms. The model uses weather and host phenology to predict infection periods and disease progress during the season. Model output was validated against 11 independent PCLS epidemics that occurred in Italy (4 vineyards in 2019 and 2020) and Montenegro (3 vineyards in 2020). The model accurately predicted PCLS disease progress, with a concordance correlation coefficient (CCC) = 0.925 between observed and predicted data. A ROC analysis (AUROC>0.7) confirmed the ability of the model to predict the infection periods leading to an increase in PCLS severity in the field, indicating that growers could use the model to perform risk-based fungicide applications.
... During the vegetation period mechanical leaf trimming is required two to three times per season. Because of their identical inter-row distance and heavily trimmed canopy, SMPH vineyards look similar to VSP vineyards once the canopy has developed; the only obvious difference is that grapes in SMPH are distributed over the entire canopy, rather than within a defined grape zone, and such vines differ widely in their leaf area to fruit weight range (Molitor and Junk, 2019). ...
Article
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Low-input training systems, such as minimal pruning (MP) and the semi-minimal pruned hedge (SMPH), require less working hours as a result of fewer viticultural process steps and permit a higher degree of mechanisation. However, their effect on viticultural costs and per litre costs on both flat terrain and steep slopes has not yet been analysed. This study quantifies the viticultural costs of vertical shoot positioning (VSP) and low-input training systems for standard processes on different types of flat terrain and steep slope vineyards. The costs were obtained from a dataset of 1,519 working time records of labour and machine hours from 20 vineyards belonging to five German wine estates over three years. The costs for standard viticultural processes were compared across three pairs of VSP and low-input training site types with different mechanisation intensities. The comparison was carried out by univariate analysis of variance with fixed and random effects, and by descriptive analysis of mean values. On flat terrain, SMPH significantly decreased the costs for the viticultural steps of winter pruning, tying, shoot positioning and defoliation, but it increased the cost for pest control. Hence, the total cost on flat terrain decreased marginally, but still significantly, by 46 %. The cost effects on steep slopes were similar, decreasing by 34 % for SMPH in unsupported steep slope harvester sites and by 46 % for MP rope and winch-supported steep slope sites. The per-litre costs were calculated for different yield levels. Since the yield in low input systems is higher than in VSP, the production costs per litre further decreased. The study confirmed the high cost-saving potential for wine growers of the mechanisation of canopy management and the omission of winter pruning in low-input systems. Combined with higher yields, the cost savings from low-input systems are particularly suitable for producers of bulk wine and market entry and mid-level wine profiles. By converting to low-input systems, the costs associated with mechanisable steep slope vineyards can be reduced to amounts approximating VSP on flat terrain. For certain wine profiles, low-input systems should therefore constitute an integral part of strategies to increase the economic sustainability of steep slope viticulture. The estimated cost benchmarks provide critical input for the cost-based pricing policy of steep slope growers. These benchmarks also give agricultural policy reliable indicators of the subsidies required for preserving steep slope landscapes.
... Nevertheless, over the last fifty years the average temperature during vegetation period increased by 0.9 • C with average values during the periods of 14.8 • C, 15.2 • C and 15.7 • C for 1971-2000, 1981-2010 and 1991-2020, respectively (data of Geisenheim weather station) causing a shift of the growing region of Rheingau from cool (13 • C to 15 • C) to intermediate (15 • C to 17 • C) climate (Hall and Jones, 2009). This may affect berry composition and wine profile (Jones et al., 2012;Molitor and Junk, 2019). Single vintages of previous years showed an immense increase of average temperature during vegetation period (2018: 17.8 • C, 2019: 16.4 • C, 2020: 16.7 • C; Table S1). ...
Article
Historically and under cooler climate conditions, steep slope vineyards yielded best quality wines and highest reputation, due to their distinctive microclimate, especially during ripening period. Nevertheless, steep slope vineyard sites primarily suffer from reduced competitiveness leading to abandonment, thus a loss of valuable vineyard sites. The aim of this work was to investigate differences in microclimatic conditions between different steep slope vineyard management systems and row orientations. Records of inner canopy microclimatic parameters were taken over two consecutive vegetation periods including seven vineyard pairs. A Bayesian mixed effect model was used to properly account for the complexity of the conducted experiment. Additionally, irradiation and canopy surface temperature data was compared. Grapevines planted downslope (control) exhibited a more even light distribution on canopy sides. Contrarily, at terraced vineyard sites canopy sides showed big differences regarding light interception, also affecting diurnal canopy surface temperature. Differences in N-S/E-W row orientation comparison were more pronounced compared to vineyard pairs aligned NE-SW/NW-SE. Night temperatures were slightly higher in terraced vineyards, while daily mean and maximum temperature and temperature amplitude were higher in vineyard rows planted in line of the greatest slope. While a treatment effect was not always clearly visible, an impact of row orientation on temperature microclimate was observed. Differences between treatments may become more pronounced under projected climate change conditions with consequences on physiological processes, thus grapevine performance influencing berry composition.
... Long-term records show a trend in Germany towards harvesting Riesling by around 14 days earlier than in the 1960s, and this shift is expected to continue according to climate projections (Schultz andJones 2010, Intergovernmental Panel on Climate Change 2015). On the other hand, a warmer temperature during the ripening phase causes an accelerated sugar accumulation rate and an increasing risk of grape rot, which greatly limits the flexibility in the timing of harvest (van Leeuwen and Destrac-Irvine 2017, Molitor and Junk 2019). ...
Article
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Background and Aims Leaf senescence induces a massive shift of the nitrogen (N) allocation within plants, but its influence on the storage of yeast-assimilable N (YAN) in grapevine berries is unclear. The aim of this work was to investigate whether the YAN concentration in grape must can be increased by a targeted induction of leaf senescence. Methods and Results Leaf senescence was induced in two consecutive seasons by an ethephon treatment of grapevines (Vitis vinifera cv. Riesling) before harvest, and its effect on the amino acid and ammonium balance of berries and must, as well as on alcoholic fermentation performance was investigated. The ethephon-induced senescence caused a significant increase in YAN concentration in berries and must, based on a general increase in most amino acids. Compared to natural senescence, the ethephon treatment led to a lower proline : arginine ratio, a lower sugar concentration in the must and a lower grape yield. Conclusions Ethephon-induced leaf senescence enhances the nutritional value of grapes and improves the fermentability of grape must. Significance of the Study Our results enable wine producers to improve the nitrogen use efficiency of vines and to ensure a balanced N nutrition of the yeast.
Chapter
Foreseen climate change points to shifts in viticultural production patterns worldwide, leading to some major impacts in the economy of the wine industry. In a climate change scenario, combination of water scarcity, high temperature, and radiation and salinity, experienced in many regions will be strengthened, worsening the negative effects on plant growth, berry composition, and yield. Hence, the interaction between several factors, such as terroir features, climate, grapevine stress responses, and management practices used, represents a real challenge for sustainable Mediterranean viticulture. The processed kaolin particle film (PKPF) application in vineyards has been renowned as a favorable short-term strategy for sustainable mitigation of adverse abiotic summer stress. Nevertheless, the mechanisms underlying stress alleviation by PKPF application continue minimally discussed, and far from consensus on its effects on different variables, including berry composition and wine quality. This short review illustrates some of the main PKPF functions and evaluates its impact on leaves and berry traits.
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In this study, we investigated the consequences of climate change on bioclimatic indices in vineyards along the edge of Lake Neuchatel in Switzerland. Like in other vineyards all around the world, the typicity of wines and the phenology of vines have changed, particularly since the 1970s. Trends in the growing season average temperature and in Huglin’s heliothermal index show that the climate in the Neuchatel vineyards changed from very cool or cool to temperate during the last decades. Trends in the cool night index and in the prior to harvest cool night index both indicate that in the near future this wine region will frequently experience temperate instead of cool nights during the weeks leading up to harvest. Our results highlight the need for adaptation strategies, such as an upward elevational shift for Pinot Noir, as climatic conditions will become too warm at its current location in the next decades. They also show that conditions in this region are already favorable for more thermophilic varieties such as Merlot. In the context of global warming, this kind of analysis should be conducted throughout winegrowing regions in order to develop efficient adaptation strategies at the microclimatic scale.
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Aim: Phenology is a key factor in explaining the distribution and diversity of current vineyards in France. This work has the objective to summarize the different studies developed in France to analyze grapevine phenology.Methods and results: Several topics are presented: a general description of all historical databases and observatory networks developed in France during the last 70 years; an overview of the different models developed to calculate the main phenological stages; an analysis of the main results obtained using these models in the context of studies of climate change impacts on viticulture in France; and finally a general discussion about the main strategies to adapt the phenological cycle to future climate conditions.Conclusion: This review emphasizes that even if phenology is not the only trait to be considered for adapting grapevine to climate change, it plays a major role in the distribution of the current variety x vineyard associations.Significance and impact of the study: It is therefore critical to continue to study phenology in order to better understand its physiological and genetic basis and to define the best strategies to adapt to future climatic conditions.
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Aim: Major effects of climate change are an increase in temperature, a modification in rainfall patterns and an increase in incoming radiations, in particular UV-Bs. Grapevines are highly sensitive to climatic conditions. Hence, plant development, grape ripening and grape composition at ripeness are modified by climate change. Some of these changes are already visible and will be amplified over the coming decades; other effects, although not yet measurable, can be predicted by modeling. The objective of this paper is to assess which modifications in wine quality and typicity can be expected and what levers growers can implement to adapt to this changing situation. Methods and results: This paper focusses on the effect of temperature, vine water status and UV-B radiation in viticulture. Vine phenology is driven by temperacture. A significant advance in phenology (i.e. budburst, flowering and veraison dates) has been observed since the early 1980’s in most winegrowing regions. The combined effect of advanced phenology and increased temperatures results in warmer conditions during grape ripening. In these conditions, grapes contain more sugar and less organic acids. Composition in secondary metabolites, and in particular aromas and aroma precursors, is dramatically changed. Increased drought, because of lower summer rain and/or because of higher reference evapotranspiration (ET0), induces earlier shoot growth cessation, reduced berry size, increased content in skin phenolic compounds, lower malic acid concentrations and modified aroma and aroma precursor profiles. Increased UV-B radiation enhances the accumulation of skin phenolics and modifies aroma and aroma precursor profiles. Over the next decades, an amplification of these trends is highly likely. Major adaptations can be reached though modifications in plant material (grapevine varieties, clones and root stocks), vineyard management techniques (grapevine architecture, canopy management, harvest dates, vineyard floor management, timing of harvest, irrigation) or site selection (altitude, aspect, soil water holding capacity). Conclusion: Climate change will induce changes in grape composition which will modify wine quality and typicity. However, these modifications can be limited through adaptations in the vineyard.Significance and impact of the study: This study assesses the impact of major climatic parameters (temperature, water and radiation) on vine physiology and grape ripening. It addresses the issue of how the expected changes under climate change will impact viticulture. It is shown that appropriate levers do exist to allow growers to adapt to this new situation. Among these, modifications in plant material and viticultural techniques are the most promising tools.
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The degree and time of canopy trimming can alter phenology, rates of increase or decrease in berry components during grape ripening, and may influence yield and its components. The objective of this study was to investigate the extent to which reducing canopy size, by mechanical trimming post-flowering, changed Vitis vinifera L. 'Pinot noir' fruit yield and composition. Vines were mechanically trimmed to three different canopy heights at fruitset: 1000 mm (100 % canopy height), 600 mm (60 % canopy height relative to the control treatment) and 300 mm (30 % canopy height relative to the control treatment). Total soluble solids concentration and content, titratable acidity, pH and fresh berry mass were measured throughout ripening, and yield and leaf area were measured at harvest. Reduced canopy size via trimming to 30 and 60 % of the control treatment height slowed total soluble solids accumulation and in some cases increased titratable acidity and increased pH. The total soluble solids-titratable acidity ratio was therefore reduced throughout ripening by these trimming treatments relative to the full canopy height. Trimming to reduce canopy size had two effects on the source-sink ratio; it reduced the source (canopy) but increased fruit yield, an important sink. Therefore, the time of trimming is an important management consideration because it can delay and slow ripening due to reduced source leaves but could potentially accentuate the delay via increasing yield (sink). This technique may represent a way to offset the acceleration of phenology and grape ripening that has been observed to occur as a result of warmer seasons.