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Climate trends in a specific Mediterranean viticultural area between 1950 and 2006

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Aims: An analysis of climate data between 1950 and 2006 in the Hérault department, situated in the Mediterranean of France is presented. Methods and results: Data presented include the evolution of mean annual and seasonal temperatures, the Huglin index, total solar radiation, night freshness index, the distribution and efficiency of rainfall and potential evapotranspiration (pET). Results showed an increase in mean annual temperatures of +1.3 °C between 1980 and 2006 and an increase in the mean pET which was 900 mm / year since 1999. Also, harvest dates advanced by up to three weeks and sugar concentrations at harvest increased by up to 1.5 % potential alcohol. Conclusion: The indicators show that in this area certain climatic parameters have evolved over the period studied. Changes are observable in some of the parameters (notably temperature) for the last 30 years whereas others have evolved only in the past few years (e.g. pET). Therefore it is necessary to be circumspect in drawing conclusions on climate change in the area, particularly as regards the possible consequences for viticulture. However, at the plot level, it is clear that irrigation of the vines is becoming increasingly necessary in this region. Significance and impact of study: Climate is a major factor in vine cultivation and in the understanding of viticultural terroirs and wine typicality. The climate trends observed over a 50-year period are discussed in the viticultural context of a Mediterranean region. However, the interaction between climate change and technical progress in viticulture and oenology complicate the analysis over the time frame under consideration.
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- 113 -
J. Int. Sci. Vigne Vin, 2008, 42,
n
°
3, 113-123
©
Vigne et Vin Publications Internationales (Bordeaux, France)
CLIMATE TRENDS IN A SPECIFIC MEDITERRANEAN
VITICULTURAL AREA BETWEEN 1950 AND 2006
F
. LAGET
1
, J.-L. T
ONDUT
1
, A. DELOIRE
2
and Mary T KELL
Y
3
1: ACH, 84 avenue d'Assas, 34000 Montpellier, France
2: SupAgro, Department of « Plant sciences », 2 place Pierre Viala, 34060 Montpellier, France
3: Centre de formation et de la recherche en œnologie, UMR 1083
« Sciences pour l'œnologie et la viticulture », Faculté de pharmacie, Université Montpellier I,
15 avenue Charles Flahault, 34093 Montpellier cedex, France
*Corresponding author: mary.kelly@univ-montp1.fr
Aims: An analysis of climate data between 1950 and 2006 in the
Hérault department, situated in the Mediterranean of France is
presented.
Methods and results: Data presented include the evolution of
mean annual and seasonal temperatures, the Huglin index, total
solar radiation, night freshness index, the distribution and
efficiency of rainfall and potential evapotranspiration (pET).
Results showed an increase in mean annual temperatures of
+1.3 °C between 1980 and 2006 and an increase in the mean pET
which was 900 mm / year since 1999. Also, harvest dates advanced
by up to three weeks and sugar concentrations at harvest increased
by up to 1.5 % potential alcohol.
Conclusion: The indicators show that in this area certain climatic
parameters have evolved over the period studied. Changes are
observable in some of the parameters (notably temperature) for the
last 30 years whereas others have evolved only in the past few
years (e.g. pET). Therefore it is necessary to be circumspect in
drawing conclusions on climate change in the area, particularly as
regards the possible consequences for viticulture. However, at the
plot level, it is clear that irrigation of the vines is becoming
increasingly necessary in this region.
Significance and impact of study: Climate is a major factor in
vine cultivation and in the understanding of viticultural terroirs and
wine typicality. The climate trends observed over a 50-year period
are discussed in the viticultural context of a Mediterranean region.
However, the interaction between climate change and technical
progress in viticulture and oenology complicate the analysis over
the time frame under consideration.
Key words : grapevine, Mediterranean climate, Hérault area, berry
sugar concentration
Objectifs : L'article présente, de 1950 à 2006, une analyse du
climat d'un département viticole français, l'Hérault, situé en zone
méditerranéenne.
Méthodes et résultats : Les données concernent l'évolution des
températures moyennes annuelles et saisonnières, les indices de
Huglin et de fraîcheur des nuits, la radiation solaire globale, la
distribution et l'efficience saisonnière des pluies et
l'evapotranspiration potentielle (Etp). Les résultats montrent une
augmentation des températures annuelles moyennes (+1,3 °C de
1980 à 2006), de l'Etp moyenne annuelle (900 mm/an depuis 1999)
et un changement dans la distribution saisonnière des pluies. Les
dates de vendange sont avancées de 2 à 3 semaines et le degré
alcoolique moyen des vins a augmenté de 1,5.
Conclusion : Les données climatiques analysées dans cette étude
montrent une évolution de certains paramètres du climat pour cette
zone méditerranéenne. Suivant les paramètres étudiées, les
changements sont observables depuis environ 30 ans
(températures) ou depuis quelques années seulement (distribution
des pluies et Etp notamment). Néanmoins, à l'échelle de la parcelle,
l'irrigation de la vigne devient de plus en plus une nécessité pour la
région considérée.
Signification et impact de l'étude : Le climat est un élément
majeur pour la culture de la vigne et pour la compréhension des
terroirs et de la typicité des vins. Les tendances climatiques
observées sur une période de 50 ans sont discutées dans le contexte
viticole d'une région méditerranéenne. L'interaction entre
l'évolution du climat et les progrès techniques en viticulture et en
œnologie complexifie l'analyse sur la période considérée.
Mots clés : vigne, climat méditérranéen, département de l’Hérault,
concentration en sucres de la baie
Abstract Résumé
manuscript received: 28th of February 2008 - revised manuscript received: 25th of July 2008
02-kelly 19/09/08 16:50 Page 113
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J. Int. Sci. Vigne Vin, 2008, 42, n°3, 113-123
©Vigne et Vin Publications Internationales (Bordeaux, France)
F. LAGET
et al.
INTRODUCTION
The Inter
governmental Panel on Climate Change
(IPCC) has predicted that average global temperatures
increased by 0.6
°C during the 20th century and the last
decade is «
very likely » to prove the warmest since
meteorological data have been recorded (GIEC, 2001).
This evolution is explained by an increase in the
concentrations of greenhouse gases in the atmosphere,
i.e. an annual increase in carbon dioxide concentration
(CO
2
) of 1.5 ppm from 1980 to 2000. Similar trends are
observed for methane (CH
4
) and nitrous oxide (N
2
O)
(GIEC, 2001). The accumulation of these gases is related
to human activities and CO
2
concentrations of 540 to
970 ppm are predicted for 2100, together with an increase
in the global average temperature on the earth's surface
of 1.4 to 5.8 °C (GIEC, 2001).
From an agronomic point of view, climatologists
measure climate change and translate these evolutions
into climatic indices relevant to agricultural production.
The aim of these endeavours is to enable the impact of
climate change on agricultural production to be evaluated.
All the more so when the culture of perennial plants is
concerned - vines, for example, the plantation of which
is renewed on average every 20-30 years, and where the
quality and typicality of the product is highly climate-
dependent (Vaudour, 2003; Seguin and Cortazar, 2004;
Jones
et al., 2005).
Mediterranean-type zones share certain characteristics
that lend them a special distinction among the world's
landscapes. Sun intensity is high, especially in inland
areas, due to clear skies and low humidity;
evapotranspiration rates can be considerable depending
also on the wind speed. Summers are warm to hot, and
winters are cool but mild; sub-freezing temperatures do
not occur more than 3
% of the total time.
The Hérault department of the Languedoc region of
France lies at a latitude of 43.6
°
North and a longitude of
3.9
° east. It extends over a surface of 6,100 km
2
(approximately 100 km long by 60 km wide) and is the
northernmost region of the Mediterranean Basin. It may
be divided into three principal geographical zones (the
coast, the plains and the hills rising to over 1000 m in
altitude). Vines are planted over more than 100,000
hectares and the annual wine production is nearly 5 million
hectolitres, representing approximately 10
% of the annual
French production.
The Association Climatologique de l'Hérault (ACH)
is a network of weather stations established since the
1970's, which registers, validates and analyses daily
measurements from over 70 different reference posts in
the department. The measurements are carried out on a
macro and/or meso-climate level, i.e. regional or local
production zones (1-20 Km
2
) levels. Data analysis carried
out by the ACH demonstrated that climate change has
principally been occurring since the 1980's and 1990's.
Several indicators pointing to this climate change are
presented in this article and the potential consequences
for viticulture in the region are discussed.
METHODOLOGY
1. Climate data
Data were collected on a daily basis at several
reference weather stations. The parameters measured
were temperature (maximum and minimum daily values),
night freshness index, Huglin index, total solar radiation
(joules/cm
2
), evapotranspiration (ETP, mm), and rainfall
(mm). These measurements were carried out according
to international norms and the rules of the International
Organisation of Metrology.
2. V
iticultural agroclimatic indicators
a- Huglin Index (1978)
The Huglin index (HI) is calculated from April 1
st
to
September 30
st
in the Northern hemisphere and is defined
as follows:
where T mean = mean air temperature in °C
T max = maximum air temperature in °C
k = « length of day coefficient » = 1.03
for latitudes between 42°1' and 44°0'
This index enables different viticultural regions of the
world to be classified in terms of the sum of temperatures
required for vine development and grape ripening, (Huglin,
1978). Specifically, it is the sum of mean and maximum
temperatures above +10
°C - the thermal threshold for
vine development. Different grape varieties are thus
classified according to their minimal thermal requirement
for grape ripening. For example, the HI is 1700 for
Chardonnay and 2100 for Syrah. The minimum Huglin
index for vine development is 1600.
3. Night freshness index
This is the mean night-time temperature for the month
preceding harvest. There are four levels of night freshness
as defined by T
onietto and Carbonneau, 2004).
CALCULATIONS
1. Sum
The April to September sum of daily values were
calculated in the case of extreme temperatures, solar
radiation and ETP
.
02-kelly 19/09/08 16:50 Page 114
2. Mean
For the evolution of mean annual and seasonal
temperatures, the mean was calculated from daily values
over a given time period. For example, the mean annual
temperature is the mean temperature from January 1
st to
December 31st and the mean springtime temperature is
the mean temperature from April 1st to June 30st.
3. Percentage
This is cumulative precipitation for a given period as
a percentage of total rainfall between April and September
.
For the type of rainfall (light, medium and heavy) it is the
cumulative rainfall divided into four classes (< 10 mm,
1
1-30 mm, 31-50 mm and <50 mm) and the total rainfall
registered between April and September.
4. Regr
ession total annual and total seasonal
temperatures
They were subjected to linear regression analysis from
1950 to 2006.
RESULTS AND DISCUSSION
1. Average seasonal temperatures (1950 to 2006)
a- Evolution of mean annual temperatures (figure 1)
Temperatures evolved in the Hérault over the period
(1950-2006), and figure 1 shows that two distinct periods
may be identified: 1950 to 1980 which were cool to cold,
and 1980 to 2006 which were mild to hot. It should also
be noted that the lowest temperatures in the period 1980-
2006 were greater than the highest temperatures in the
period 1950-1980. A thermal transition was observed
from the beginning of the 1980's (figure 1a) and regression
analysis (figure 1b) confirms an increase of +0.2 °C on
average for the 30-year period 1950-1980, as compared
to +1.3 °C for period 1980-2006. A short period of regular
temperature increase was observed from 1972 to 1975,
which precedes the dramatic temperature increase in the
years following 1980. A similar short period of
temperature increase was observed between 1998 and
2001.
b- Evolution of seasonal temperatures (figures 2)
On the basis of regression analysis (table 1) of the two
periods (1950-1980 and 1980-2006) certain observations
may be made in relation to both the period outside of
vegetative growth (autumn and winter) and during
vegetative growth (spring and summer):
- Outside the vegetative cycle:
. Autumn temperatures increased by + 1 °C from 1980
to 2006.
. Winter temperatures evolved in a cyclic fashion (cool
in the case of 1953-1956 and 1962-1965) or warm (in the
case in the case of 1957-1961 and 1988-2002).
- During the vegetative cycle:
. Springtime temperatures increased significantly (by
+2 °C) from 1980 to 2006.
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J. Int. Sci. Vigne Vin, 2008, 42, n°3, 113-123
©Vigne et Vin Publications Internationales (Bordeaux, France)
Figure 1 - Evolution of mean annual temperatures
from 1950 to 2006 in °C (1a) and regression curve (1b)
at a reference weather station in the Hérault.
Two phases may be distinguished in which there is a sharp increase
in temperatures since 1980 (0,05 °C per year on average, i.e. +1,3 °C
over 27 years).
Table 1 - Regression calculations of mean temperatures par season for the periods 1950-1980 and 1980-2006.
Note: Regression analysis may not be applied to winter data, which fluctuate according to the cycles.
02-kelly 19/09/08 16:50 Page 115
.
In summer
, temperatures increased by +1.6
°
C from
1980 to 2006.
These analyses presented in figure 2 demonstrate that
the temperature increase is more significant in spring than
in summer
, key periods in the vegetative cycle of the vine.
c- Particular case of « extreme » summer temperatures
(figure 3)
Summer temperatures are considered to be extreme
when maximum temperatures exceed +35 °C in the shade
(i.e. more than + 40 °C in the sun). These are so-called
« negative » temperatures for the vine, i.e., its physiology
and its biochemistry are inhibited or even blocked at
temperatures exceeding +35 °C. The consequences of
total or even partial inhibition of plant function depend
on the duration and frequency of elevated temperatures.
From 1970 to 2006, the number of days with extreme
temperatures between June and August has greatly
increased, particularly since 2000. Between 2001 and
2006 (apart from 2005) the number of days with extremely
high temperatures is always larger than 10, which had
never been previously observed. In fact, extremely high
June temperatures were recorded on seven days in 2001,
six days in 2002, nine days in 2003, and three days in
2005 and 2006. These temperatures were attained from
the end of spring onwards and would confirm the trend
of summer is extending into springtime. This is the vine's
period of bloom - fertilisation, a stage during which the
harvest potential - in terms of the number of berries per
bunch - is determined. The inhibitory ef
fect of elevated
temperatures at this stage has previously been reported
(Kliewer, 1977; Huglin and Schneider, 1998).
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J. Int. Sci. Vigne Vin, 2008, 42, n°3, 113-123
©Vigne et Vin Publications Internationales (Bordeaux, France)
F. LAGET
et al.
Figure 2 - Comparative evolution of mean seasonal temperatures from 1950 to 2006 (2a) and regression curves (2b)
at a reference weather station in the Hérault. Data were obtained from regression analysis. Spring and summer are
the two seasons with marked temperature increases (e +1,6°C from 1980 to 2006).
02-kelly 19/09/08 16:50 Page 116
d- Evolution of thermal amplitude, night freshness
and maximal decadal temperature indices during grape
ripening (figure 4)
Helio-thermic indices are useful in viticultural analysis,
notably in the classification of viticultural regions,
adaptation of cultivars to climatic conditions,
characterisation of terroirs, monitoring of vine
physiological and biochemical development, fruit ripening
and positioning of phenological stages (Tonietto and
Carbonneau, 2004 ; Lorenz
et al., 1995 ; Carbonneau et
al.
, 1992 ; Barbeau et al., 1998 ; Huglin and Schneider,
1998 ; Winkler
et al., 1974). It would therefore seem
important to have the capability to relate helio-thermic
indices to grape ripening and the typicality of finished
wines.
The following three indicators were compared for the
period 1950-1979 and 1980-2006:
. Decadal thermal amplitude: the mean difference in
daily maximum and minimum temperatures over a 10-
day period;
. Decadal night freshness index: the average night-
time temperature over a 10-day period;
. Maximal Decadal Temperature, the mean maximum
daily temperature over a 10-day period.
Figure 4 shows that the difference in the night
freshness index (1.1-2.5 °C) for the two periods is greater
than the dif
ference in thermal amplitude (0.2-0.8
°
C) or
maximum decadal temperatures (0.7-2.1 °C). Interestingly,
the dif
ference in night freshness index parallels that of
the maximum temperature from early August to early
September; though from mid-September onwards the
difference in maximum temperature remains relatively
constant, whereas the dif
ference in night freshness index
increases. This means that while maximum September
daytime temperatures do not greatly increase in the period
1980-2006 by comparison with 1950-1979, the nights
would appear to be warmer.
This has considerable implications for viticulture as
night-time temperature is important for the development
of grape aromas and juice pH in terms of the degradation
of malic acid under conditions of sustained elevated
temperatures. Night freshness index could be indirectly
related to the aromatic intensity of wine and to juice colour
of black grape varieties (Carbonneau
et al., 2007).
Furthermore, a relationship was shown to exist between
this index and wine aromas (Carey and Bonnardot, 2004,
T
onietto and Carbonneau, 2004.).
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©Vigne et Vin Publications Internationales (Bordeaux, France)
Figure 3 - Evolution of the mean number of days
with extreme temperatures (> +35°C in the shade)
from 1970 to 2006 at several reference stations.
Figure 4 - Temperature spread in °C between
the mean 1980-2006 and 1950-1979 values for the
three indicators (thermal amplitude, night freshness
index and maximum temperature) during grape
ripening in Mediterranean climates.
Table 2 - Evolution of seasonal rainfall distribution from 1976 to 2005.
02-kelly 19/09/08 16:50 Page 117
e- The Huglin Index (figure 5)
The Huglin index is calculated from mean daytime
temperatures, with a base value +10 °C (Huglin, 1978).
It is widely used in France as a helio-thermic reference
in viticulture in order to compare and classify the major
viticultural regions and to determine the plantation of
various grape varieties (Tonietto and Carbonneau, 2004;
Vaudour
, 2003)
Figure 5 shows that during the period April to
September (the complete development cycle of the vine)
the Huglin index evolved in all zones of the Hérault, with
the result that Central and Eastern zones which were
classified as «
warm - temperate
» (2100 > HI d 2400)
between 1975 and 1996 were re-classified as « warm »
(2400 > HI d 3000) between 1997 and 2005. Furthermore,
from 2000 onwards, the Western zone is at the limit of
« warm-temperate » and « warm » in the case of 2000,
2003 and 2006.
f- Seasonal rainfall distribution and its effectiveness
Seasonal rainfall distribution and its intensity (amount
per unit time) determine ef
ficiency in terms of deep soil
infiltration and surface run-off (terrain slope effect) after
very heavy daily rainfall. For example, daily precipitations
of less than 10 mm are of limited ef
ficiency
, as the
cumulative values are inadequate for in-depth infiltration
(Carbonneau
et al., 2007). Conversely
, cumulative values
greater than 50 mm/day with intense precipitations
(>
50
mm/hour) do not have time to infiltrate the soil;
thus this type of rainfall is of limited ef
ficiency lar
gely
due to the fact that it mostly forms surface run-off water,
a factor which is exacerbated on steeply sloping soils.
Precipitations of 1
1-30 mm are considered efficient
because they penetrate into the soil.
A database (results not shown) covering the period
1906-2006 shows that for the Montpellier area that the
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J. Int. Sci. Vigne Vin, 2008, 42, n°3, 113-123
©Vigne et Vin Publications Internationales (Bordeaux, France)
F. LAGET
et al.
Figure 5 - Evolution of the Huglin index in
°C
at two reference stations in the Hérault département
(county) from 1975 to 2005.
It may be observed that this index evolves for both zones increases
with the result that the Eastern departmental zone is reclassified
from warm temperate to warm since 1997, and that the Western
departmental zone is evolving towards the upper limit of warm
temperate.
Figures 6 - Evolution of the seasonal rainfall
distribution from 1976 to 2005 from April to June
(6a); July to August (6b) and September (6c)
from a reference weather station in the Hérault.
The rainfall cycle has evolved over recent years showing a tendency
towards a greater volumes of rainfall in September, which since
2000 represents between 35 and 60 % of total rainfall during the
vegetative cycle (April-September) (with the exception of 2002).
Over the period 1976-2005, September rainfall represented less
than 30 % of total vegetative cycle rainfall.
02-kelly 19/09/08 16:50 Page 118
mean annual rainfall was 764.4 mm and the mean April
to September rainfall was 305.2 mm. Over this 100-year
period April to Sept rainfall values never exceeded
670 mm; this highest value observed was in 1932. Analysis
of this data shows that neither annual nor April-Sept
rainfall changed over this period, however
, a significant
modification of rainfall distribution (figure 6) and
efficiency (figure 7) was observed which is more telling
than simple average rainfall values.
g- Seasonal rainfall distribution (figure 6)
Data from the Montpellier reference weather station
were used to analyse rainfall over three periods, April-
June (vine vegetative growth and bloom), July-August
(end of vegetative growth, berry development, veraison
and ripening-maturity) and September (end of ripening
and harvest). Figure 6 shows that rainfall cycles evolved
in Mediterranean climates over recent years in that 49 %
of total rainfall occurred in September between 2001 and
2005, whereas the figure for the same month between
1976 and 2000 was 22 %. The corresponding figure for
April-June were 35 % (2001 - 2005) and 54 % (1976 -
2000). There was also a considerable increase in heavy
rainfall at the end of September after the autumn equinox
(data not shown).
h- Rainfall efficiency (figure 7)
Using the same data, the 5-year averages of rainfall
efficiency may be analysed on the basis of four different
thresholds (table 3). From 1976 to 2000, effective rainfalls
(11-30 mm per day) are the most represented (40 % of
cumulative values). However
, for the period 2001-2005,
this type of rainfall event only represents a quarter of
cumulative values, and the most represented precipitations
are those greater than 51 mm per day. Taking 2003 as a
specific example, cumulative rainfall in the Montpellier
area during the vegetative cycle was close to the normal
value, i.e. 400 mm. However, if rainfall distribution and
ef
ficiency are taken into account, 2/3 rds of cumulative
values are concentrated in September in the form of heavy
rainfall.
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©Vigne et Vin Publications Internationales (Bordeaux, France)
Figure 7 - Evolution of rainfall efficiency of from April
to September over the period 1976 to 2005
at a reference weather station in the Hérault.
It may be observed that there are alterations in rainfall efficiencies
with high representation of heavy rainfall (> 51 mm/day) since
2000.
Figure 8 - Evolution of global solar radiation
in joules/cm
2
April to September over the period 1976
to 2005 at a reference weather station in the Hérault.
It may be observed that there is a significant increase since 1992
with record values in recent years (2003).
Table 3 - Efficiency of precipitations by 4-year periods from 1976 to 2005. Four thresholds are presented.
02-kelly 19/09/08 16:50 Page 119
2. Global solar r
adiation and evapotranspiration
(ETP)
a- Total solar radiation joules/cm
2
(figure 8)
Total solar radiation is the sum of the solar energy
received by the soil in joules/cm
2
over a specific time
period. The average value of total solar radiation between
April and September from 1976 to 2005 was
approximately 390,000 joules/cm
2
. A dramatic increase
in this parameter was observed between 1992 and 2006
particularly, with a variance of close to 40,000 joules/m
2
by comparison with the mean. From 2003 (where a record
of 406,560 joules/cm
2
was attained) to 2005, the
cumulative values were significantly greater than the
mean, more than 10,000 joules/cm
2
, which represents an
increase of close to 5 %.
b- Evolution of evapotranspiration (ET) (figure 9)
The potential evapotranspiration (pET) calculated
using the Penman formula is the sum of water loss incurred
by evaporation from the soil surface and transpiration by
plant. Potential (pET) evapotranspiration is always greater
than the real ET, as a result of which, specific and
optimised cultural techniques are applied in individual
cases.
From April to September, the mean pET is 900 mm
from 1976-2005, though significant increases in this figure
have been observed since 1992. Before this date, it was
estimated that for three out of four years, the pET is less
then 900 mm whereas since 1993, in only one year has
the value been less than this average. In no year since
1999 has the value been less than 900 mm, and the lowest
pET values in the period 1993-2005 correspond to the
highest values of the preceding period. The question that
arises from increased pET is the effect on plant water
function, i.e., soil water availability at bud-burst and its
evolution during the development cycle of the vine,
specifically in interaction with cultural practices (canopy
volume, total and exposed leaf areas), bunch load (yield)
and density (number of vinestocks per hectare). The pET
is a fundamental parameter in calculating water balance
(Riou, 1998).
It was recently calculated that the pET in the Hérault
increased by 100 mm from 1976 to 2007. By comparison,
vine pET (pETv) calculated for the same period increased
by 30 mm estimated for a standard vertical shoot
positioning training system with a canopy height of 1 m
at verasion and a mean plantation density of
5000 vinestocks per hectare, with a distance between the
rows of 2 m (ACH, personnal communication).
c- Correlation between climate indicators and pET
(figure 10)
There is a good correlation (Pearson correlation
coefficient close to 0.8) between pET and total solar
radiation expressed in joules/cm
2
over the period April-
September. Therefore, this result clearly shows that the
more intense the solar radiation, the greater the extent
of pET
.
3. Observed effects on viticulture
Studies on the effect of climate on viticulture in France
really began with the seminal work of Schultz in 2000
(Schultz, 2000). One of the most significant ef
fects of
global warming (estimated to be in the region of +0.9 °C
in France (Spagnoli, 2002)) in terms of viticulture is that
the different phenological stages of grape growth and
ripening are occurring earlier. Studies carried out in
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©Vigne et Vin Publications Internationales (Bordeaux, France)
F. LAGET
et al.
Figure 9 - Evolution of potential evapotranspiration
(pET) from April to September over the period 1976
to 2005 at a reference weather station in the Hérault.
The lowest pET values for the period 1993-2005 correspond to
highest pET values for the period 1976-1992.
Figure 10 - Correlation curves between pET
and global solar radiation from April to September
over the period 1976 to 2005
at a reference weather station in the Hérault.
There is a strong correlation between the two indicators. Furthermore
pET is an important indicator and integrator of several climatic
variables.
02-kelly 19/09/08 16:50 Page 120
dif
ferent regions of France indicate that the most significant
changes in bud-burst and bloom have taken place in the
approximate period 1985-2005: both these stages have
advanced by 7-15 days in the case of Alsace (Duchene
and Schneider, 2005) and Champagne (Moncomble
et
al.
, 2007). Similar effects were observed in the vineyard
of Château Lafitte Rothschild (Dubernet, 2007) for which
data have been recorded since 1954. The obvious
advantage of considering data from a single vineyard is
that variations in factors other than climate are virtually
non-existent; these include the planted cultivars, the
average age of the vines, cultural practices etc. However,
it is interesting to note that while harvest opening date
in Champagne and Alsace, has, in the same period
advanced to a similar degree (approximately 15 days)
as budburst and bloom, the latter are significantly less
affected than harvesting date in the more southerly
vineyards. For example, in Chateauneuf-du-Pape harvest
opening dates have advanced from early October in 1945
to early September in 2000 (Ganichot, 2002), an evolution
that may be only partially explained by modifications
of cultural practices. In a similar study, it was found that
harvest opening date in T
avel appellation area of the
Southern Rhone advanced by three weeks from 1951 to
2005 and moreover
, it appears that the process has been
accelerating over the last decade. Likewise, in Chateau
Lafitte Rothschild, the average harvesting date in the
1950's and 1960's was October 3rd, whereas it advanced
to September 19th for the Decade 1990-2000.
In the Mediterranean region of France, data obtained
from a single vineyard (Château la V
oulte Gasparet) where
vineyard practice has remained virtually unchanged since
the late 1960's demonstrated that harvesting has advanced
by 12 days (Figure 11).
Another effect of climate change on viticulture is
increased sugar content and reduced total acidity of grapes
at haverst. For example, Duchene and Schneider (2005)
presented results for the evolution of potential alcoholic
strength in Alsace between 1973 and 2003. The mean
was 9.34 % vol. for the period 1973-1990, whereas it was
10.58
% vol for the period 1991-2003, the highest value
of 11.8 % vol. being attained in 2003 (which was an
exceptionally hot year). Moreover
, it should be noted that
there is a greater degree of fluctuation in the values for
the first period and the increase is more linear for the
second period (r = 0.96).
At Château la Voulte Gasparet in the Languedoc, there
has been a steady increase in the sugar concentration at
harvest between 1986 and 2007. Figure 12a shows that
despite considerable year-to-year variations, the overall
trend is upwards, and as was previously observed for
Alsace, year-to-year variations tended to diminish in latter
years. The average potential alcohol % volume was
12.78 % for the 10-year period 1986-1996 as compared
to 13.53 % for the period 1997-2007.
- 121 -
J. Int. Sci. Vigne Vin, 2008, 42, n°3, 113-123
©Vigne et Vin Publications Internationales (Bordeaux, France)
Figure 11 - Example of evolution of harvest date
expressed as cumulative n° of days after August 31st
before harvest begins.
Data obtained from a single vineyard (Château la Voulte Gasparet)
in the Languedoc Region of France. The dotted line represents the
mobile mean.
Figures 12 - Example of evolution of sugar
concentration expressed as potential alcoholic strength
(%vol.) from 1984 to 2007, a) data from Château
la Voulte Gasparet; b) data from an oenological
laboratory in the Languedoc region; mean values
of several million hl of wine per year.
The dotted line represents the mobile mean.
02-kelly 19/09/08 16:50 Page 121
Data collated by an oenological laboratory in the
Mediterranean region representing more than 1 million
litres of wine per year over a 20-year period strongly
confirm this trend (Figure 12b), i.e. increased potential
alcohol strength particularly from the year 2000 onwards,
and reduced year-to-year variation in later years. In this
case the mean potential alcoholic strength was 11.68 %
for the period 1984-1996, and 12.62 % for the period
1997-2006. There is a strong correlation between the year
and the alcoholic strength over the 20-year period
(r = 0.927).
Two other linked oenological parameters that are
affected by increasing temperature are pH and total or
titratable acidity expressed in terms of g/l H
2
SO
4
. Results
(data not shown) from the set of samples above show
an increase in pH and a decrease in titratable acidity; mean
pH was 3.55 for the period 1984-1996 and 3.66 for the
period 1997-2006. The corresponding values for titratable
acidity were 3.72 and 3.38 g/l H
2
SO
4
, respectively. That
the increase in pH and decrease in titratable acidity were
not strongly correlated (r = -0.8) is explained by the fact
that although these two parameters are linked, the
relationship between them is complex.
CONCLUSION
It is possible to provide only general information for
the consideration of vine and grape physiology and
biochemistry in a hot climate context (Razungles
et al.,
1998 ; Ollat and Gaudillère, 1998 ; Ojeda et al., 2002 ;
Deloire and Hunter, 2005 ; Deloire
et al., 2005 ; Peyrot
des Gachons et al., 2005 ; Choné et al., 2006).
In Mediterranean areas, the « light » factor is not
limiting except in cases of certain vine architecture
configurations in situations of elevated vine vigour which
increases the number of shaded leaves. Nonetheless it
is worth stating that it has been suggested, notably in
the case of white grapes, that « air conditioning » of the
bunches by appropriate management of their microclimate
(shading of the bunches by leaves during ripening) could
be useful in maintaining aromatic potential (Razungles
et al., 1998 ; Marais et al., 1999)
It is likely that the most significant impact of climate
change on viticulture will result from an increase in
temperature and from the evolution of rainfall distribution
and efficiency. The possible consequences of elevated
temperatures are multiple: increased transpiration and
plant water consumption in addition to a modification of
canopy and/or bunch microclimate by leaf fall in the bunch
zone, for example. These modifications of plant
functioning and vigour can lead to: a) an inhibition of
photosynthesis; b) a partial or total inhibition of berry
development and biosynthesis of its principal components,
notably during vegetative growth of the berry c) inhibition
of ripening, d) loss of fruit volume with resulting
consequences for yields and harvest concentration; and
e) a possible increase in alcohol content of wines produced
in such « warm » areas due to the concentration in sugars
(loss of water by evapo-transpiration and limited water
entering the berry or back flow of water from the berry
to the plant).
Accelerated ripening has serious consequences for
precocious varieties in that they enter into the final phase
of ripening under increasingly warmer conditions. This
has potential implications in that high temperatures,
especially if associated with drought, can inhibit certain
biochemical pathways or physiological processes essential
for the production of quality grapes (Deloire
et al., 2004).
It may be appropriate to reflect on the evolution of
legislation pertaining to viticulture (e.g. irrigation,
plantation density, training system, yields, etc.) principally
in European areas of geographic denomination. It will
also be necessary to adapt oenological practices to musts
that are more concentrated and richer in sugar - maceration,
yeast activity to compensate for the loss of aroma
precursors; de-alcoholisation, partial dilution of musts,
more creative blendings, etc.
One of the immediate effects on vine culture in
Mediterranean areas is the management of drought and
of water resources for the purposes of irrigation. Increased
employment of innovative technologies may be envisaged
for viticultural cartography on the basis of parameters
such as water resource, soil reserve, irrigation strategies,
and the determination of harvest potential and harvesting
dates according to a desired wine style objective (Hall
et
al.
, 2008; Brenon et al., 2005; Vaudour, 2003).
It would be interesting to construct international viticultural
climate networks in order to compare the dif
ferent
situations of climate evolutions worldwide, particularly
in other Mediterranean climate areas and possibly to
exchange expertise in terms of plantation, rootstocks,
clones, vineyard practice etc to provide coherent solutions
in the face of global climate change.
Acknowledgements: The authors acknowldege Olivier Zebic of
Vivelys, France for his help with statistical treatment of the data and
Dr Marc Dubernet of Dubernet Oenological Laboratories for data on
the grape ripening in the Languedoc.
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... Even higher advancement of harvest dates has been demonstrated for southern France by Laget et al. (2008) [130]. Climate data analysis between 1950 and 2006 in the Hérault department (Mediterranean of France) has shown increases in mean annual temperatures of 1.3 • C between 1980 and 2006 (compared to 0.2 • C for the period 1950-1980). ...
... Even higher advancement of harvest dates has been demonstrated for southern France by Laget et al. (2008) [130]. Climate data analysis between 1950 and 2006 in the Hérault department (Mediterranean of France) has shown increases in mean annual temperatures of 1.3 • C between 1980 and 2006 (compared to 0.2 • C for the period 1950-1980). ...
... Laget et al. (2008) [130] performed an analysis of quality parameters at the Château la Voulte Gasparet (located in the Hérault department of southern France) between 1950 and 2006 in relation to CC. The increasing temperature trends mainly after 1980 (mean annual temperatures increase of 1.3 • C between 1980 and 2006) were linked to the higher concentrations of sugars at harvest by up to 1.5% potential alcohol. ...
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... Summer temperatures that exceed +35 °C in the shade (that is, more than +40 °C in the sun) are considered 'negative' for the vine as they impair vine physiology and biochemistry C . The consequences of a total or even partial inhibition of plant function depend on the duration and frequency of elevated temperatures (Laget et al., 2008). b) Earlier harvest is common. ...
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Climate change is a continuous spatiotemporal reality, possibly endangering the viability of the grapevine (Vitis vinifera L.) in the future. Europe emerges as an especially responsive area where the grapevine is largely recognised as one of the most important crops, playing a key environmental and socio-economic role. The mounting evidence on significant impacts of climate change on viticulture urges the scientific community in investigating the potential evolution of these impacts in the upcoming decades. In this review work, a first attempt for the compilation of selected scientific research on this subject, during a relatively recent time frame (2010–2020), is implemented. For this purpose, a thorough investigation through multiple search queries was conducted and further screened by focusing exclusively on the predicted productivity parameters (phenology timing, product quality and yield) and cultivation area alteration. Main findings on the potential impacts of future climate change are described as changes in grapevine phenological timing, alterations in grape and wine composition, heterogeneous effects on grapevine yield, the expansion into areas that were previously unsuitable for grapevine cultivation and significant geographical displacements in traditional growing areas. These compiled findings may facilitate and delineate the implementation of effective adaptation and mitigation strategies, ultimately potentiating the future sustainability of European viticulture.
Article
Unfavourable trends have been identified in the evolution of climate factors (temperatures, precipitation, etc.) over the past years, with a direct impact on the vegetative and productive potential of the vine. This calls for a reassessment of climate resources and the adaptation of cultivation technologies to the new conditions. Our paper analyses the climate data recorded between 1991 and 2020 for the Iaşi vineyard ecosystem, which allowed for the calculation of a series of bioclimatic indices and coefficients, deviations from the multiannual average values, soil moisture dynamics, and their influence on development of vegetation phenophases and grape production. The increasing tendency of the average annual temperature and the decreasing amounts of precipitation registered point to a marked warming of the vineyard climate, especially after 2000. The high values of temperatures, corroborated with the soil water deficit, determined an intensification of the atmospheric and pedological drought, a shift in vegetation phenophases, shortened development periods and a forced ripening of grapes, with a negative impact on yields, which fluctuated from one year to another. The analysis of the ecoclimate conditions over the past 30 years has highlighted an alternation of periods, a colder and wetter one between 1991 and 2006, and a warmer and dried one between 2007 and 2020.
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The impact of warming on the phenology of grapevine (Vitis vinifera L.) in conditions of Central Europe was evaluated at the locality of Dolné Plachtince in the Slovakian wine region. In Welschriesling and Pinot Blanc model varieties there was observed onset of phenophases as defined in BBCH scale over 1985–2018 period. Based on the data obtained there was evaluated the influence of average and average maximum temperature and GDD on the onset of phenophases. The results observed indicate earlier budburst by 5–7 days, earlier beginning of flowering by 7–10 days, and earlier berry softening by 18 days, and harvest dates advanced by 8–10 days on average. In both varieties there was found the highest influence of the average monthly temperature in March on budburst, the highest influence of the average monthly temperature and the average maximum temperature in May on the beginning of flowering, and the highest, statistically significant influence of the average maximum temperature in June on grape veraison. The warming observed in moderate climate conditions of northern wine regions in Central Europe (Slovakia) has not caused yet the changes in the grapevine phenology stable enough to require serious adaptation measures.
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Water is an important factor in the terroirs of grape-growing regions. The vine obtains water from rainfall and the water table and when it is in short supply, it is necessary either to irrigate or accept the effects of water stress. Depending on the intensity of the water stress and the period at which it occurs, it may or not be favourable for the harvest and the wine it is used to produce. The objective of this article is to provide some information on the relationship that exists between the vine and water. The climate and the soil, which are essential but not the sole elements of this relationship will only be touched upon, but we will discuss in a non exhaustive way, with information's from the bibliography or from our research, the following aspects: the root system, vegetative growth, the relationship between plant architecture and the water status of the vine, the carbon balance and the biochemical composition of the grape berry in relation to vine water status. We will also present the currently available techniques for measuring vine water status and its evolution during the vegetative cycle as a function of water reserves in the soil easy to use by the roots. Finally examples are presented of possible recommendations for vine cultural practices as a function of the vine water status evolution during the growth, according to the predawn leaf water potential thresholds.
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L’ouvrage, pédagogique et richement illustré, rassemble théorie et pratique au service d’une nouvelle vision de la viticulture. La première partie traite du fonctionnement de la vigne à partir du concept fondamental du « triptyque biologique » (signal – structure – système de régulation). Les effets de l’eau, du CO2, du rayonnement solaire, de la température et des éléments minéraux sur la physiologie de la vigne sont précisément décrits. Enfin, sont présentées les bases des applications techniques.
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In the framework of a research programme on the "terroirs" in viticulture, a red of experimental plots was established in the Loire Valley area in 1978 with the Cabernet Franc variety. In 1988, eleven of those plots were given an intensive follow-up, with special emphasis on the phenological stages, the growth and development of the vegetative apparatus and the composition of the grapes at harvest time. After a few years, we can consider that 1988 was an average year for the last fifteen vintages, both on the climatic side and on the wine quality side. Therefore it seems to be justified to use the data of that particular year to study the "terroir" effect on the composition of the grapes. The results show important differences between "terroirs" in terms of precocity of the phenological stages, stems growth, setting of the leaf area, vigour and productivity of the plants. These differences are found also during the maturity process and at harvest time; sugars, organic acids, anthocyanins and polyphenols are concerned. An index for measuring the precocity of the grapevine cycle on each "terroir" is used to compare the "terroirs" and to establish relationships with the composition of the grapes at harvest time. Through the analysis of the data, it is possible to distinguish two groups of factors which determine the behaviour of grapevine in a given "terroir". The first one is related to the precocity of the cycle of the plant ; it influences the quality of the grapes at harvest time. The second is related to the vigour ; it is linked to the productivity of the plants and the acidity of the must. The level of development of the primary leaf area at flowering time seems to play an important role in relation with the composition of the grapes in sugars, organic acids and anthocyanins ; the earlier the flowering, the better the relationship.
Article
As for any crop, the impact of an anthropogenic greenhouse effect will include the stimulating effect of increased CO2 concentration on photosynthesis, which will result in increased dry matter production and may lead to noticeable changes in cultural practices. However, it is more likely that the most significant impact will result from an increase in temperature, even if other climatic variables, such as rainfall are also considered. Apart from a significant displacement of the traditional limits for grapevine cultivation, serious questions may arise concerning 'terroirs': Will it be possible to keep the same cultivars by adjusting vineyard cultural and enological practices? How might viticulture and wine-making respond to the predicted increase in surface temperature? The warming trend of the last fifteen years in most of Western Europe and especially in France may provide some clues. The phenology of the grapevine has significantly advanced; one to two weeks for anthesis and almost one month for harvest date in the last 50 years. The advance in harvest date also has been accompanied by changes in sugar and acid concentrations. Expressed in terms of the Huglin Index, the increase in temperatures due to global warming will lead to vintages that are more uniform across years. However, there may be a tendency in which the climatic variables of a particular grape growing region will exceed the established limits for grape cultivars strongly associated with that location ('terroir'). The 2003 growing-season was characterized by very hot weather and drought (similar to the end of century climatic scenarios) and provides evidence that bio-climatic indices do not take into account the possible natural adaptation of some grape cultivars to the predicted changes in climate. Therefore, only the use of more sophisticated tools such as accurate crop models, currently under development, may provide a more valuable perspective on future viticulture.
Article
Carotenoids are considered precursors of C13-norisoprenoids in grape berries. The latter compounds can play an important role in the organoleptic quality of wines because their composition influences flavours and aromas. Sunlight effect on the berry carotenoid and C13-norisoprenoid compositions was studied before and after veraison. Syrah berries which were sun-exposed before veraison were found to be richer in carotenoids than shaded berries. However, after veraison, sunlight caused the degradation of these pigments. Sunlight modified the non-epoxyxanthophyll/epoxyxanthophyll ratios. Metabolic relationships between the glycosylated C13-norisoprenoids and their potential precursors were tentatively established between certain C13-norisoprenoids and carotenoids in specific sun-exposure treatments. In addition, the sunlight effect on the rise of other glycosidically bound compounds such as monoterpenes and phenols was evidenced.