Structure and Function in Agroecosystem Design and Management - Chapter 19 pps

CHAPTER 19
Effects of Climatic Change
in Finland on Growth and
Yield Formation of Wheat and
Meadow Fescue
Kaija Hakala
CONTENTS
Climatic Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
Climatic Change in Finland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
Agriculture in Finland Today . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
Implications of Climatic Change for Finnish Agriculture . . . . . . . . . . . . . . 400
Effects of Climate Warming and Increased CO
2
Concentration on
Growth and Yield of Wheat (Triticum aestivum L., cv. Polkka)
and Meadow Fescue (Festuca pratensis Hudson, cv. Kalevi) —
A Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
Simulation of Climatic Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
Determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
Effects of Simulated Climatic Change on Photosynthesis and
Rubisco Content of Wheat and Meadow Fescue . . . . . . . . . . . . . . 406
Effects of Climatic Change on Yield and Yield Quality of
Wheat and Meadow Fescue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408
Wheat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408
Meadow Fescue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
397
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CLIMATIC CHANGE
Water vapor, carbon dioxide (CO
2
), ozone (O
3
), nitrous oxide (N
2
O), and
methane (CH
4
) form the natural greenhouse gas layer above the Earth. Short-
wave solar radiation—part of UV-B, UV-A, visible light, and infrared radia-
tion—penetrates this layer. The long-wave heat radiation from the Earth to
the atmosphere is, however, partly absorbed by the greenhouse gases. The
Earth’s atmosphere is thereby warmed. In this way, the temperatures on the
Earth are high enough to maintain life in its present form.
Human activities are increasing the concentrations of greenhouse gases,
especially CO
2
. The main CO
2
emissions come from burning of fossil fuels
and through land use changes that release carbon bound in trees and soil. The
other greenhouse gases, O
3
, N
2
O and CH
4
, are also on the increase. In addi-

tion to this, the concentrations of halogenated hydrocarbons, such as CFCs,
have increased. These are long-lived gases which will stay in the atmosphere
long after their emissions have stopped. They are very effective in absorbing
the long-wave heat radiation of the Earth. On the other hand, they destroy
the stratospheric ozone layer, which has an opposite effect on the radiation
balance. The increase in the greenhouse gases caused by human activity is
about to lead to warming of the climate. According to a report of the
Intergovernmental Panel on Climate Change (IPCC, 1998), the mean annual
temperature on the Earth may increase by 1–3.5°C by 2100. At the same time,
there may be big spatial and temporal changes in precipitation, and the mean
sea level may rise by 15–95 cm.
CLIMATIC CHANGE IN FINLAND
A scenario of climate change in Finland (the central scenario, assuming
central emissions and central climate sensitivity; Carter, 1996) states that the
CO
2
concentration may be doubled (733 ppm) and the temperatures may be
4.4°C higher than now by the year 2100. According to the scenario, precipita-
tion will increase by 11% and the sea level will rise 45.4 cm by 2100. Because
the change is gradual, the CO
2
concentration would be 426 and 523 ppm, and
the temperature 1.2 and 2.4°C higher by 2020 and 2050, respectively (Carter,
1996). While the average temperature will increase 0.4°C per decade, the
increase is greatest (0.6°C) in winter and smallest (0.3°C) during the growing
season.
The increase in the mean temperature will also affect the length of the
growing season. According to the scenarios of Carter (1996, 1998), the grow-
ing season would be 25 days longer than at present in southern Finland
(Turku) and 23 days longer in northern Finland (Kajaani) by 2050. With an

increase in temperature of 4°C (approximately by the year 2100), the growing
season would be 48 days longer in southern Finland (Turku) and 37 days
398 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
920103_CRC20_0904_CH19 1/13/01 11:26 AM Page 398
longer in northern Finland (Kajaani) than at present (Tim Carter, personal
communication). (Growing season is defined here so that it starts when the
average daily temperature stays permanently above 5°C, and ends when the
temperature stays permanently below 5°C.) In 2050, with 2.4°C higher aver-
age temperature, the growing season would start 10 days earlier in both
southern and northern Finland and end 15 and 13 days later than at present
in southern and northern Finland, respectively. With 4°C higher temperature,
the growing season would start 21 and 16 days earlier and end 27 and 21 days
later than at present in southern and northern Finland, respectively (Tim
Carter, personal communication). The increase in growing season length may
be greater than when defined solely by the 5°C-threshold temperature. At
present, even when the mean temperature has permanently risen over 5°C,
the sowings of the spring cereals have to be delayed because of deep ground
frost, or because the ground is too wet and soft to carry heavy agricultural
machinery. In the warmer future climate, ground frost may be absent or melt
earlier, and the ground may dry earlier because of shorter duration or
absence of snow cover.
AGRICULTURE IN FINLAND TODAY
Agriculture in Finland is at present limited by low temperature and short
growing season. In addition to this, late spring and early autumn frosts limit
agriculture in areas where the average temperatures would be high enough
for successful agriculture (Mela, 1996). Low temperatures may damage over-
wintering crops, especially when the snow cover is thin during the winter.
On the other hand, pathogens thriving under a thick snow cover also present
a major problem for overwintering crops. Cultivation of spring-sown cereals,
again, is often complicated by delay in sowing because of long duration of

snow cover, ground frost, or too wet soil. Because of late sowing (usually in
early May in southern Finland), the crops fail to benefit from the conditions
of high radiation in early spring. In addition, the harvest of spring-sown
crops is often impeded by early autumn rain. Because of the short growing
season, the varieties of spring-sown cereals cultivated in Finland are bred for
a short growing period. The growing time and time for grain filling of these
varieties are short, and they are thus less productive than varieties of cereals
bred for warmer climates, having slower growth rate and longer growing
time. Despite the difficulties in cultivation of spring-sown cereals, they are
nevertheless often preferred to autumn-sown cereals because of the unpre-
dictable overwintering conditions.
The area of Finland stretches from 60° to 70°N. The great variation in cul-
tivation conditions in the different latitudes requires careful selection of crops
for cultivation in the different areas. The recommended cultivation area
of many grass and potato varieties covers the whole of Finland. The
EFFECTS OF CLIMATIC CHANGE IN FINLAND 399
920103_CRC20_0904_CH19 1/13/01 11:26 AM Page 399
recommended cultivation area of cereals is, however, quite limited. Thus,
some barley and oats varieties can be cultivated up to the polar circle in the
west of Finland, where the Gulf of Bothnia warms the local climate.
Otherwise, their cultivation is limited to areas south of 64°N. Spring wheat
and winter rye can be cultivated on areas south of 63°N, and winter wheat on
areas between 61° and 62°N (Komulainen, 1998). The actual cultivation area
of spring wheat is depicted in Fig. 19.1a.
IMPLICATIONS OF CLIMATIC CHANGE FOR FINNISH
AGRICULTURE
Increase in growing season temperature and growing season length would
expand the cultivation area of crops. With mean annual warming of 2.4°C (by
the year 2050), the regional suitability of spring wheat (Triticum aestivum) cv.
Ruso would shift 270 km north from the present baseline (calculated suitabil-

ity at present) in the west of Finland, and 460 km in the east (Figure 19.1c). The
figures for spring barley (Hordeum vulgare, cv. Arra) and oats (Avena sativa, cv.
Veli) would be 230 and 280 km north in the east and 340 and 500 km north in
the west, respectively. Mean rate of shift to the north of these spring-sown cere-
als by the year 2100 would be 45–58 km/decade (Carter et al., 1996).
However, when the growing season temperatures increase, the develop-
ment rate of the cereals increases (Saarikko and Carter, 1996). When this hap-
pens between anthesis and yellow ripening, the time of grain filling becomes
shorter. This may lead to decreased yield because less time is available for
carbohydrate production through photosynthesis. The effect of climate
warming on the duration of grain filling of spring barley (cv. Pomo) is pre-
sented in Figure 19.2, and the modeled effect on the yield in Figure 19.3.
In addition to the adverse effects on grain filling, increased temperatures
may increase the occurrence of pests and pathogens in Finland. For example,
a potato pest, potato cyst nematode (Globodera rostochiensis), may expand its
occurrence to Lappland, where it is not found at present (Carter et al., 1996).
This and other pests and pathogens not known in Finland at present may
cause yield losses of crop plants in the future warmer climate.
Increase in the concentration of CO
2
not only affects the climate but has
also direct effects on plant growth. Many investigations around the world
have demonstrated that elevated CO
2
increases crop yield through increased
photosynthesis and biomass production (Cure and Acock, 1986).
Experimental and modeling studies of Finnish crop plants have also shown
increases in yield in elevated CO
2
(Pehu et al., 1994; Hakala and Mela, 1996;

Carter et al., 1996; Hakala 1998a). An example of this is shown in Figure 19.2c.
Yield loss caused by increased growing season temperatures (Figures 19.2a
and b) is changed to yield gain with the projected concomitant increase of
CO
2
concentration to 523 ppm (Carter et al., 1996).
400 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
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EFFECTS OF CLIMATIC CHANGE IN FINLAND 401
Figure 19.1 (a) Actual cultivated area of spring wheat (Triticum aestivum) in 1990 as
a percentage of total arable land, (b) estimated probability of success-
ful ripening (percent) for spring wheat cv. Ruso under the baseline
(1961–1990) climate and (c) according to the climate change central
scenario (Carter, 1996) with 2.4°C warming of climate. Adopted from
Carter et al., 1996.
920103_CRC20_0904_CH19 1/13/01 11:26 AM Page 401
402 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
Figure 19.2 Simulated change in duration of the phase heading to yellow ripeness
in barley (Hordeum vulgare) cv. Pomo relative to the baseline climate
(1961–1990) for the climate change central scenario (Carter, 1996) by
(a) 2020 (1.2°C warming of climate), (b) 2050 (2.4°C warming), and (c)
2100 (4.4°C warming). Adopted from Carter et al., 1996.
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 402
EFFECTS OF CLIMATIC CHANGE IN FINLAND 403
Figure 19.3 Modeled grain yield (tn ha
Ϫ1
) of barley (Hordeum vulgare) cv. Pomo (a)
under the baseline climate (1961–1990), (b) according to the climate
change central scenario (Carter, 1996) by 2050 (with 2.4°C warming of
climate), and (c) according to the central scenario of climate change by

2050 with changes of CO
2
included. Adopted from Carter et al., 1996.
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 403
EFFECTS OF CLIMATE WARMING AND INCREASED
CO
2
CONCENTRATION ON GROWTH AND YIELD OF
WHEAT (TRITICUM AESTIVUM L., CV. POLKKA) AND
MEADOW FESCUE (FESTUCA PRATENSIS HUDSON,
CV. KALEVI)—A CASE STUDY
Simulation of Climatic Change
Climatic change was simulated so that the temperatures were increased
by 3°C both during the growing season and in the winter, and the CO
2
con-
centrations were increased to 700 µl l
Ϫ1
. The experiments were carried out
during four growing seasons in 1992–1995 at Jokioinen, southern Finland
(60°49’ N, 23°30’ E). Spring wheat (Triticum aestivum L.) cv. Polkka and
meadow fescue (Festuca pratensis Hudson) cv. Kalevi were grown under four
treatment regimes: (a) present-day conditions in the field; (b) conditions of
warmer climate (temperatures 3°C above ambient); (c) conditions with
higher CO
2
concentration 700 µl l
Ϫ1
, without warming of climate; and (d) con-
ditions of both warmer climate (temperatures 3°C above ambient) and higher

CO
2
concentration (700 µl l
Ϫ1
). The combination of experimental conditions
was based on the SILMU climate scenario developed for Finland (Carter,
1996; central scenario), according to which, in about 100 years from now
(2090), the ambient CO
2
concentration will be approximately 700 µl l
Ϫ1
and
the growing season temperatures 3°C higher than at present.
To raise the temperatures above ambient (conditions of warmer climate),
a greenhouse (20 m ϫ 30 m) was built over part of an experimental field
(Hakala et al., 1996). The experimental field outside the greenhouse, repre-
senting the present-day conditions in the field (later referred to as the open
field), was covered at a height of 3–4 m with the same plastic film as was used
in the construction of the greenhouse. This resulted in radiation conditions
comparable to those in the greenhouse. The greenhouse temperatures were
regulated so that they were constantly 3°C higher than the temperatures in
the open field. To increase the CO
2
concentrations to 700 µl l
Ϫ1
, the experi-
ments were conducted in open-top chambers (OTCs). The OTCs were big, 3
m in diameter, and 2 m high. Each OTC was divided in half. The northern half
was occupied by the spring wheat stand, and the southern half used for
experiments with meadow fescue. Four OTCs were set up in the greenhouse,

and the same number in the open field. In each location, two of the OTCs
were maintained at elevated CO
2
(700 µl l
Ϫ1
) and two at ambient CO
2
(two
replicates per treatment). In addition, two replicate plots similar to those with
the OTCs were sown in both temperature treatments, however with no OTC
on (open air plots) to study the chamber effect in the experiments (Hakala et
al., 1996). The CO
2
fumigation was started after the seedling emergence of the
sown crops in 1992, 1993, and 1994, and after the beginning of the thermal
growing season (before sowing of wheat) in 1995. The thermal growing
season was defined to begin after the average daily temperature of five
404 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 404
consecutive days had exceeded 5°C. There was no CO
2
fumigation during the
winter.
The crops were sown 9–10 May in the open field, the normal sowing time
in the Jokioinen region. To simulate the future conditions with average tem-
peratures 3°C higher than at present, and the growing season starting 2–3
weeks earlier than at present (Tim Carter, personal communication), the crops
were sown about 3 weeks earlier inside the greenhouse than in the open field,
as soon as the thermal growing season had started in the greenhouse.
The experiments were conducted on a heavy clay soil mixed with 1000

m
3
ha
Ϫ1
of peat containing 35% sand during 1992 and 1993. For growing sea-
sons 1994–1995, the clay-peat soil of the experimental site was replaced with
a lighter sandy loam soil brought from another field at Jokioinen. During all
the experimental years, the soil nitrogen was adjusted to about 120 kg N ha
Ϫ1
with a standard fertilizer (20% N, 6% P, 6% K), according to an analysis of the
soil nitrogen before sowing. A detailed description of the soil and nutrient
conditions is given in Hakala et al. (1996) and Hakala and Mela (1996). The
crops were sown directly in the field. The sowing density of wheat was 600
germinating seeds m
Ϫ2
in 1992 and 500 in 1993 and 1994. The sowing density
of meadow fescue was 1250 germinating seeds m
Ϫ2
in 1992 (first 2-year exper-
iment) and, to find out if the effect of CO
2
enrichment would increase at lower
sowing density, only 750 germinating seeds m
Ϫ2
in 1994 (second 2-year exper-
iment). For the same reason, the sowing density of wheat was lowered to 300
germinating seeds m
Ϫ2
in 1995.
In 1992 and 1993, the meadow fescue canopies were cut at about monthly

intervals. In 1994 and 1995, the cuttings were done each time the leaf area
index (LAI) of the stand reached a value of 5, as measured with an automatic
LAI meter (Licor, U.S.). Cutting according to LAI was adopted to make sure
that the effect of CO
2
enrichment on the photosynthesis and biomass accu-
mulation of meadow fescue would not be affected by differences in the
degree of canopy closure. An increase in the degree of canopy closure under
CO
2
enrichment has been shown to decrease the effect of increased CO
2
con-
centration (Nijs et al., 1989). LAI 5 was chosen as the cutting LAI, because
previous investigations had shown that at this LAI the light interception of
the sward is virtually complete, the net photosynthesis rate is at about maxi-
mum, and the rate of dry matter accumulation of the sward has just reached
a steady maximum (Brougham, 1956; Robson, 1973a and b). It was assumed
that the effect of CO
2
enrichment would be greatest when the growth rate
depended on the rate of photosynthesis of the canopy. Cutting according to
LAI resulted in a different number of cuts being made in each treatment.
Determinations
The photosynthetic activity of the crops was measured with a LCA-3 CO
2
analysis system (ADC Co., England). The measurements were conducted
throughout the growing season, on sunny days, when the photon flux
EFFECTS OF CLIMATIC CHANGE IN FINLAND 405
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 405

density was not lower than 800 µmol photons m
Ϫ2
s
Ϫ1
. This photon flux den-
sity was found to be close to light saturation for both wheat and meadow
fescue. The content of the key enzyme of CO
2
assimilation, ribulose-1,5-
bisphosphate carboxylase-oxygenase (Rubisco) in the flag leaves of wheat
and in the leaves of meadow fescue was measured in material collected in
1993 and 1994. The piece of the leaf where photosynthesis was measured was
cut off after the measurement and immediately frozen in liquid nitrogen. The
leaf pieces were kept in liquid nitrogen until the end of each measuring
period and then stored at Ϫ80°C. For determination of the content of
Rubisco, the protein was separated by SDS-PAGE by the modified Laemmli
(1970) method using 3.5% stacking gel and 13% separating gel. Purified
spinach Rubisco was used as standard. The amount of Rubisco in the gels
was determined densitometrically after staining with 0.1% Coomassie
Brilliant Blue R solution.
Samples for the determination of biomass dry weight, leaf area, yield com-
ponents, and nitrogen content of wheat and meadow fescue were collected in
connection with the cuts of meadow fescue and at anthesis and at harvest of
wheat. The nitrogen content (% nitrogen of the dry weight) of the samples was
determined in 1992 with the Kjeldahl method using a Kjeltec System 1026
Distilling Unit (Tecator AB, Sweden). Nitrogen content was not measured in
samples collected in 1993. In 1994 and 1995, the nitrogen content was deter-
mined with an automatic nitrogen analyzer, LECO FP-428 (LECO Corp., U.S.).
Effects of Simulated Climatic Change on Photosynthesis and Rubisco
Content of Wheat and Meadow Fescue

It has been found in earlier studies that as CO
2
assimilation becomes
more effective in increased CO
2
, the concentration of Rubisco is reduced
(Schmitt and Edwards, 1981; Bowes, 1991; Sage, 1994; Nie et al., 1995; Rogers
et al., 1998). The reduction may be due to accumulation of carbohydrates in
the leaves in conditions where the sink for photosynthetic products is not in
balance with the source (photosynthesis) (Stitt, 1991). Reduction in the
amount of Rubisco in conditions of increased CO
2
is a good acclimation sys-
tem for the plants, while it allows them to invest the nitrogen released from
Rubisco in processes limiting photosynthesis (e.g., light harvesting or elec-
tron transport) and in growth (Sharkey, 1985; Stitt, 1991; Quick et al., 1992;
Sage, 1994; Rogers et al., 1998). Rubisco makes up 50% of the total soluble
protein of plant leaves (Lawlor et al., 1989; Leegood, 1993). Therefore, a
decrease in the Rubisco content in elevated CO
2
may decrease the nitrogen
content of crops. Decrease in nitrogen content of grasses like meadow fescue
might decrease the nutritional value of their biomass as animal feed.
Moreover, a considerable part of the nitrogen of wheat leaves is used as a
source of nitrogen for the grain (Dalling et al., 1976; Waters et al., 1980;
406 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 406
Lawlor et al., 1989; Palta and Fillery, 1995). Therefore, a decrease in Rubisco
and thus protein content in the leaves of cereals might decrease the protein
content of the grain and the baking quality of the flour milled from it.

The photosynthetic activity of both wheat and meadow fescue increased
in elevated CO
2
both in the simulated warmer climate (elevated temperatures)
and in the present climate (ambient temperatures) (Hakala et al., 1999, Figure
19.4). The effect of increased CO
2
on Rubisco was different in wheat and
meadow fescue. The Rubisco content decreased in wheat under increased
CO
2
, especially after anthesis. Only when increased CO
2
assimilation was
accompanied by a significant increase in yield in elevated CO
2
was the
Rubisco content not decreased in the flag leaves of wheat (Hakala, 1998a and
b; Hakala et al., 1999). There was no change in Rubisco content connected with
EFFECTS OF CLIMATIC CHANGE IN FINLAND 407
a Wheat
b Meadow fescue
ambient temperatures
0
5
10
15
20
25
Pn, µmol CO2 m

-2
s
-1
µl l
-1
346
592
n=97
n=118
n=84
339
open air
aCO
2
eCO
2
elevated temperatures
0
5
10
15
20
25
352
367
645
n=60 n=92
n=95
µl l
-1

open air
aCO
2
eCO
2
ambient temperatures
0
5
10
15
20
25
Pn, µmol CO
2
m
-2
s
-1
open air
339
352 602
n=98
n=113
n=102
aCO
2
eCO
2
µl l
-1

elevated temperatures
0
5
10
15
20
25
µl l
-1
n=114 n=114
n=121
open air
aCO
2
eCO
2
353
374 631
Figure 19.4 Mean rates of flag leaf photosynthesis of spring wheat (Triticum aes-
tivum L.) cv. Polkka (a) and meadow fescue (Festuca pratensis Hudson)
cv. Kalevi (b) in the open air plots, in OTCs with ambient CO
2
(aCO
2
)
and in OTCs with elevated CO
2
(eCO
2
) in the open field (ambient tem-

peratures) and in the simulated warmer climate (elevated tempera-
tures). Combined data from all measurements in 1992–1995.
n ϭ number of measured leaves. Average CO
2
concentrations at meas-
uring time are shown below the columns. Bars on the columns indicate
the standard error of mean. Adopted from Hakala et al., 1999.
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 407
the increase in CO
2
concentration in meadow fescue (Hakala et al., 1999). The
differences in the effect of increased CO
2
on Rubisco content in wheat and
meadow fescue may be due to different source-sink balance of the two plant
species. Meadow fescue was cut regularly, and thus it had in principle an
indefinite sink for the photosynthetic products, even in increased CO
2
.
Therefore, decrease in Rubisco content connected with insufficient sink and
subsequent accumulation of carbohydrate (Bowes, 1991; Stitt, 1991; McKee
and Woodward, 1994; Rogers et al., 1998) was usually not observed in
meadow fescue. The absence of the effect of elevated CO
2
on Rubisco content
of wheat at elevated temperatures in 1993 (Hakala et al., 1999) was probably
also caused by the sink-source-balance of wheat. In 1993, at elevated temper-
atures, the growth rate was hastened considerably during grain filling
(Hakala, 1998a). However, the light intensity was considerably lower than in
the other experimental years. Thus, in 1993 the grain weight was exception-

ally low in ambient CO
2
, and elevation of CO
2
increased both grain weight and
yield (Hakala, 1998a). The sink was thus in balance with the source, or grain
filling may even have been source-limited in elevated CO
2
.
Effects of Climatic Change on Yield and Yield Quality of Wheat and
Meadow Fescue
Wheat
The grain yield of wheat tended to be higher in elevated CO
2
than in
ambient CO
2
. The increase in yield was mainly due to increase in the number
of ears m
Ϫ2
(Figure 19.5). An increase in grain number per ear sometimes also
contributed to the increase in yield in CO
2
enrichment, but an increase in
grain weight was seen only at elevated temperatures in 1993, when the grain
weight was exceptionally low in ambient CO
2
(Hakala, 1998a). This is in
agreement with earlier investigations, according to which the increase in
yield in CO

2
enrichment is a result of an increase in the number of ears and
grains rather than grain weight (Krenzer and Moss, 1975; Fischer and
Aguilar, 1976; Sionit et al., 1981; Goudriaan and de Ruiter, 1983; Havelka et
al., 1984; McKee and Woodward, 1994). The grain weight increases in CO
2
enrichment only when the photosynthate supply is not sufficient for grain fill-
ing in the ambient conditions (Krenzer and Moss, 1975; Fischer and Aguilar,
1976; Fischer and Maurer, 1976). In the present study, the crops grown in the
elevated temperature treatment matured earlier in the season. The higher
light intensities during the grain filling period may therefore have compen-
sated for the shorter duration of grain filling in years when the radiation con-
ditions were favorable. In 1993, however, the growth rate during grain filling
was even more hastened at elevated temperatures than in the other years,
and the radiation conditions were less favorable during the time of grain fill-
ing (Hakala, 1998a). Because the conditions were thus obviously source-lim-
ited for grain filling, increased CO
2
had an effect on grain weight.
408 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
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EFFECTS OF CLIMATIC CHANGE IN FINLAND 409
number of ears m
-2
0
100
200
300
400
500

600
700
800
900
1992 1993 1994 1995
aT, aCO2 aT, eCO2 eT, aCO2 eT, eCO2
a
total grain weight
0
100
200
300
400
500
600
700
800
900
1992 1993 1994 1995
g m-2
b
Figure 19.5 (a) Number of ears (m
Ϫ2
) and (b) total grain yield (g m
Ϫ2
) of spring wheat
(Triticum aestivum L.) cv. Polkka at Jokioinen, Finland, under different
temperature (T) and CO
2
treatments (e ϭ elevated, a ϭ ambient). The

sowing rate was 600 germinating seeds m
Ϫ2
in 1992, 500 in 1993 and
1994, and 300 in 1995. The columns represent the averages over two
replicate OTCs. In 1993, the grain yield was harvested from one repli-
cate only.
The growth of ear-bearing lateral shoots and the effect of CO
2
enrichment
on their growth was increased by low plant density. This was especially evi-
dent in 1995, when the sowing density was decreased to 300 grains m
Ϫ2
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 409
(Hakala, 1998b). However, because of the smaller number of grains in the lat-
eral shoot ears, their contribution to total yield was low. The increased num-
ber of lateral shoot ears was thus not able to compensate for the reduced
number of main shoot ears m
Ϫ2
, when the sowings were sparse. In agreement
with this, Mela and Paatela (1974) have found that a dense wheat canopy con-
sisting mainly of main shoots is the best cultivation method for maximum
yield with the spring wheat varieties bred for the present climatic conditions
in Finland. A short growing season favors rapid development, and this is
achieved best when only one to two ears per plant reach maturity. However,
the effect of elevated CO
2
manifested through increased photosynthesis is
possible only in conditions where the sink size can increase in balance with
photosynthesis. Increase in sink size takes place mainly through an increase
in the number of ears and thus number of grains per m

2
. The way to obtain
marked increases in grain yield under CO
2
enrichment is therefore to culti-
vate varieties of wheat with a long growing time for the photosynthetic prod-
ucts to accumulate, high leaf area for a maximum light interception for the
photosynthetic machinery, and with a capacity to increase sink size, e.g.,
through a higher number of ear-bearing lateral shoots reaching maturity.
If varieties with a long growing period and high tillering capacity are to
be cultivated in Finland, the growing period would need to be longer than it
is at present. This would probably be the case if the climate became warmer,
as predicted (Carter, 1996, 1998). However, in the long-day conditions of the
Finnish growing season, which would prevail in the future climate just as in
the present, strong apical dominance results in unsynchronous growth of the
main shoots and lateral shoots. This might cause problems for breeders in
finding wheat genotypes producing a larger number of high yielding lateral
shoots in Finnish conditions.
Even though the Rubisco and nitrogen content of wheat flag leaves was
decreased in increased CO
2
at both temperature treatments (Hakala et al.,
1999), the nitrogen content of wheat biomass at harvest and that of grain were
decreased only at ambient temperatures (Hakala, 1998a). The absence of
effect of CO
2
enrichment on the nitrogen content at elevated temperatures
may be due to better nitrogen availability, e.g., because of better growth of
soil microflora at higher temperatures. Because better nitrogen availability
increases nitrogen uptake of the cereals, the adverse effect of higher CO

2
on
grain quality can be corrected by higher fertilization or by otherwise improv-
ing the nitrogen availability for the plants.
Meadow Fescue
Because of earlier sowing and earlier beginning of growing season, the
growth of meadow fescue began several weeks earlier in the warmer climate
conditions than in the ambient temperature conditions. This together with
the higher growth rate in the higher temperatures during the growing season
resulted in a 30–40% higher yield in the warmer climate simulation in the
410 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 410
years of sowing (1992 and 1994). The increase in yield in higher temperature
was only 15% in the second growing season in 1993, but 65% in 1995 (Hakala
and Mela, 1996, Figure 19.6). The greater increase in yield in 1995 than in 1993
was probably due to the more frequent cuttings in 1995. When the cuttings
were done according to the growth of the grass, canopy closure restricted
growth less than in 1993, when the cuttings were done at about monthly
intervals in both temperature treatments.
CO
2
enrichment increased the yield of meadow fescue by 10% in both
temperature treatments in 1992 and at elevated temperatures in 1993. In 1994
and 1995, CO
2
enrichment increased the yield by 22–29% at elevated temper-
atures, but there was no increase in yield at ambient temperatures (Figure
19.6). Better light penetration because of the lower sowing density and more
frequent cuttings, as well as the better soil structure with better nutrient
availability, probably promoted tillering and growth in 1994 and 1995 (Evans

et al., 1976; Langer, 1979). The fact that biomass accumulation increased in
elevated CO
2
only at elevated temperatures was probably due to higher rates
of net photosynthesis and greater growth capacity at elevated temperatures.
Higher growth rates create bigger sinks and thus, also, higher rates of photo-
synthesis can be maintained (Farrar and Williams, 1991).
The nitrogen content of the biomass yield of meadow fescue changed
from year to year and from cut to cut (Hakala and Mela, 1996; Table 19.1), and
it seemed to depend on grass canopy structure and canopy age more than on
CO
2
enrichment. Thus, in 1994 and 1995, the nitrogen content of meadow fes-
cue was considerably higher (3–5% of dry weight) than in 1992 and 1993
(2–4% of dry weight). The reason for this may be that, firstly, the sowing of
the grass was sparser in 1994, and the tillering rate higher in the experiment
of 1994–1995. Higher tillering is likely to lead to higher leafiness of the
canopy, which increases the nitrogen content of grass because the leaves con-
tain higher concentrations of nitrogen than the sheaths and stems (Myhr
et al., 1978; Ryle et al., 1992). Secondly, the grass was cut in 1994 and 1995 every
time the LAI reached a value of 5. Therefore, the canopies were on average
younger at each cutting time than in 1992 and 1993, when the grass was cut
at about monthy intervals irrespective of the growth rate. Young leaves con-
tain higher concentrations of nitrogen than older leaves (Ryle et al., 1992;
Gastal and Nelson, 1994), and increased number of cuts has been shown to
increase the nitrogen content of the yield (Pulli, 1980; Nissinen and Hakkola,
1994). In addition, the soil was light sandy loam in 1994 and 1995, while in
1992 and 1993 it was heavy clay mixed with turf. The nitrogen availability
may thus have been better in 1994 and 1995.
The effects of elevated CO

2
on the nitrogen content of meadow fescue
may also be a result of changes in canopy structure rather than increased CO
2
per se. Thus, the nitrogen content was higher in increased CO
2
than in
ambient CO
2
in both ambient and elevated temperatures in 1992 (Hakala and
Mela, 1996; Table 19.1). The increase in the nitrogen content of the biomass
may have been caused by increased tillering (Hakala and Mela, 1996) and
EFFECTS OF CLIMATIC CHANGE IN FINLAND 411
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 411
412 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
0
5
10
15
20
25
30
35
g dw/15 cm of row
June
July August
September
0.21
0.09
0.26

0.09
0.22
0.18
0.10
0.21
0.18
0.10
1992
0
5
10
15
20
25
30
35
g dw/15 cm of row
June
July
August September
0.13
0.14
0.14
0.16
0.30
0.17
0.17
0.43
0.25
0.19

1994
Figure 19.6 Cumulative yield of meadow fescue (Festuca pratensis Hudson) cv.
Kalevi (g dry weight of above-ground biomass/15 cm of planted row)
during the growing seasons of 1992, 1993, 1994, and 1995. The num-
bers on the lines represent the daily growth rate of the grass during the
period between cuts. The number of samples (n) was 17–20 in all cuts
except at ambient temperatures in 1993, when it was 7, and at ambient
temperatures in 1995, when it was 14. The standard error of the mean
of the biomass samples at different cuts was in general around or less
than 10% of the mean, but in 1993, at ambient temperatures, it aver-
aged 19% of the mean. Squares: ambient temperatures; triangles: ele-
vated temperatures. Filled symbols: elevated CO
2
, open symbols:
ambient CO
2
. Adopted from Hakala and Mela, 1996.
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 412
subsequent increase in leaf area (Langer, 1979) and proportion of young leaf
material in the biomass.
Also in1994and1995, the nitrogen content was higher in elevated CO
2
than
in ambient CO
2
at ambient temperatures. This was probably caused by higher
tillering rates in elevated CO
2
throughout the growing seasons. At elevated
temperatures, in 1994 and 1995, when there was a clear increase in biomass in

CO
2
enrichment, the nitrogen content of the aboveground biomass was the
same or lower in elevated CO
2
than in ambient CO
2
. Even though tillering was
increased in elevated CO
2
in 1994 at elevated temperatures, the increase in
yield may have masked the increases in nitrogen content, the nitrogen content
being known to decrease with an increase in biomass in CO
2
enrichment
(Wong, 1979; Hocking and Meyer, 1991; Baxter et al., 1994). In 1995, when the
rate of tillering decreased in CO
2
, an increase in the proportion of stem and
sheath material probably also contributed to the decrease in nitrogen content.
EFFECTS OF CLIMATIC CHANGE IN FINLAND 413
0
5
10
15
20
25
30
35
g dw/ 15 cm of row

May June
July
August
September
0.10
0.27
0.11
0.11
0.18
0.17
0.16
0.18
0.13
0.15
0.19
0.18
1993
0
10
20
30
40
50
60
70
g dw/15 cm of row
May
June
July
August

September
0.14
0.23
0.12
0.27
0.15
0.18
0.28
0.27
0.27
0.29
0.21
0.4
0.35
0.47
0.39
0.31
1995
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 413
414 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
Table 19.1 Nitrogen Content (% Dry Weight) of Meadow Fescue (Festuca pratensis Hudson, cv. Kalevi) Above-ground
Biomass in 1992, 1994 and 1995
Date Amb. T, amb. CO
2
Amb. T, elev. CO
2
Date Elev. T, amb. CO
2
Elev. T, elev. CO
2

1992
9 July 1.88 (Ϯ0.10) n ϭ 20 2.29 (Ϯ0.13) n ϭ 17 15 June 2.75 (Ϯ0.14) n ϭ 20 3.31 (Ϯ0.09) n ϭ 20
14 Aug. 2.68 (
Ϯ0.10) n ϭ 17 2.83 (Ϯ0.13) n ϭ 15 15 July 2.10 (Ϯ0.15) n ϭ 16 2.40 (Ϯ0.11) n ϭ 16
24 Sept. 3.15 (
Ϯ0.19) n ϭ 17 3.34 (Ϯ0.14) n ϭ 18 20 Aug. 2.67 (Ϯ0.08) n ϭ 20 3.18 (Ϯ0.10) n ϭ 20
22 Sept. 3.65 (
Ϯ0.14) n ϭ 19 4.21 (Ϯ0.10) n ϭ 22
1994
29 July 3.32 (Ϯ0.08) n ϭ 20 3.38 (Ϯ0.10) n ϭ 20 17 June 4.47 (Ϯ0.10) n ϭ 20 4.06 (Ϯ0.15) n ϭ 20
24 Aug. 4.82 (
Ϯ0.11) n ϭ 20 5.23 (Ϯ0.10) n ϭ 20 18 July 4.10 (Ϯ0.06) n ϭ 21 3.97 (Ϯ0.08) n ϭ 20
21 Sept. 5.06 (
Ϯ0.10) n ϭ 20 5.34 (Ϯ0.05) n ϭ 17 15 Aug. 4.56 (Ϯ0.06) n ϭ 20 4.38 (Ϯ0.07) n ϭ 20
12 Sept. 4.93 (
Ϯ0.09) n ϭ 20 5.04 (Ϯ0.07) n ϭ 20
1995
6 June 3.41 (Ϯ0.11) n ϭ 19 6 June 3.46 (Ϯ0.12) n ϭ 20 22 May 3.26 (Ϯ0.12) n ϭ 20 22 May 3.19 (Ϯ0.15) n ϭ 21
12 July 4.09 (
Ϯ0.12) n ϭ 20 3 July 4.78 (Ϯ0.09) n ϭ 20 15 June 4.61 (Ϯ0.07) n ϭ 20 16 June 4.42 (Ϯ0.10) n ϭ 21
14 Aug. 3.62 (
Ϯ0.09) n ϭ 19 24 July 4.13 (Ϯ0.12) n ϭ 20 3 July 5.12 (Ϯ0.06) n ϭ 20 10 July 4.50 (Ϯ0.06) n ϭ 21
20 Sept. 2.39 (Ϯ0.10) n ϭ 20 18 Sept. 2.12 (Ϯ0.04) n ϭ 19 11 Sept. 2.57 (Ϯ0.13) n ϭ 20 6 Sept. 2.68 (Ϯ0.07) n ϭ 19
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 414
CONCLUSIONS
The wheat varieties currently cultivated in Finland are adapted to the cli-
matic conditions now prevailing. Even though the net photosynthesis
increases in elevated CO
2
concentrations, the extra photosynthate is not

transferred into marked increases in yield because of genetic restrictions on
the growth potential. If Finland is to benefit from a possible future climate
with elevated CO
2
and increased temperatures, varieties of wheat with
longer growing time and better capacity to produce ear-bearing lateral shoots
should be taken into cultivation.
The present varieties of crops with indeterminate growth habit, such as
grass, could benefit from the changed climatic conditions in Finland. Increase
in average temperatures and lengthening of the growing season would
increase the total yields, and elevated CO
2
concentrations would increase the
net photosynthesis and biomass production, particularly if temperatures
increased at the same time. However, changes in the canopy structure in ele-
vated CO
2
, such as an increase in leaf area, may lead to canopy closure and
shading, and in that way depress the enhancement of photosynthesis and
yield in CO
2
enrichment. New cultivation and cropping methods, such as
sparser sowing and more accurate timing of cuttings of grass cultivated for
silage, should be adopted if full benefit is to be achieved from the favorable
climatic conditions in the future.
Because management practices such as increasing nitrogen availability
and number of cuts affect the nitrogen content of the grass, a careful cutting
schedule and a balanced nitrogen fertilization will probably solve the prob-
lems brought about by a decrease in the nitrogen content in elevated CO
2

.
Increased nitrogen availability, e.g., by increased fertilization, probably will
also help in maintaining the nitrogen content of grain crops at a sufficiently
high level.
REFERENCES
Baxter, R., Gantley, M., Ashenden, T.W., and Farrar, J.F., 1994. Effects of elevated car-
bon dioxide on three grass species from montane pasture. II. Nutrient uptake,
allocation and efficiency of use.
J. Exp. Bot., 45:1267–1278.
Bowes, G., 1991. Growth at elevated CO
2
: photosynthetic responses mediated through
Rubisco.
Plant, Cell, Environ., 14:795–806.
Brougham, R.W., 1956. Effect of intensity of defoliation on regrowth of pasture.
Aust.
J. Agric. Res.,
7:377–387.
Carter, T.R., 1996. Developing scenarios of atmosphere, weather and climate for
northern regions.
Agric. Food Sci. in Finl., 5:235–249.
Carter, T.R., 1998. Changes in the thermal growing season in Nordic countries during
the past century and prospects for the future.
Agric. and Food Sci. in Finl.,
7:161–179.
EFFECTS OF CLIMATIC CHANGE IN FINLAND 415
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 415
Carter, T.R., Saarikko, R.A., and Niemi, K.J., Assessing the risks and uncertainties of
regional crop potential under a changing climate in Finland,
Agric. and Food Sci. in

Finl.,
5, 329–350.
Cure, J.D. and Acock, B., Crop responses to carbon dioxide doubling: a literature sur-
vey,
Agric. and For. Meteorol., 38, 127–145, 1986.
Dalling, M.J., Boland, G., and Wilson, J.H., Relation between acid proteinase activity
and redistribution of nitrogen during grain development in wheat,
Aust. J. Plant
Physiol.,
3, 721–730, 1976.
Delgado, E., Mitchell, R.A.C., Parry, M.A.J., Driscoll, S.P., Mitchell, V.J., and Lawlor,
D.W., Interacting effects of CO
2
concentration, temperature and nitrogen supply
on the photosynthesis and composition of winter wheat leaves,
Plant, Cell,
Environ.,
17, 1205–1213, 1994.
Evans, L.T., Wardlaw, I.F., and Fischer, R.A., Wheat, in
Crop Physiology. Some Case
Histories,
L.T. Evans, (Ed.), Cambridge University Press, Cambridge, U.K., 1976,
101–149.
Farrar, J.F. and Williams, M.L., The effects of increased atmospheric carbon dioxide
and temperature on carbon partitioning, source-sink relations and respiration,
Plant, Cell, Environ., 14, 819–830, 1991.
Fischer, R.A. and Aguilar, M.I., Yield potential in a dwarf spring wheat and the effect
of carbon dioxide fertilization,
Agron. J., 68, 749–752, 1976.
Fischer, R.A. and Maurer, O.R., Crop temperature modification and yield potential in

a dwarf spring wheat,
Crop Sci., 16, 855–859, 1976.
Gastal, F. and Nelson, C.J., Nitrogen use within the growing leaf blade of tall fescue,
Plant Physiol., 105, 191–197, 1994.
Goudriaan, J. and de Ruiter, H.E., Plant growth in response to CO
2
enrichment, at two
levels of nitrogen and phosphorus supply. 1. Dry matter, leaf area and develop-
ment,
Neth. J. Agric. Sci., 31, 157–169, 1983.
Hakala, K., Growth and yield potential of spring wheat in a simulated
changed climate with increased CO
2
and higher temperature, Eur. J. Agron., 9,
41–52, 1998a.
Hakala, K., Effect of Climate Change in the North on Growth, Yield Formation and
Photosynthesis of Spring Wheat and Meadow Fescue. Ph.D. thesis, Annales
Universitatis Turkuensis, 110, 1998b.
Hakala, K. and Mela, T., The effects of prolonged exposure to elevated temperatures
and elevated CO
2
levels on the growth, yield and dry matter partitioning of field-
sown meadow fescue (
Festuca pratensis, cv. Kalevi), Agric. Food Sci. Finl., 5,
285–298, 1996.
Hakala, K., Kaukoranta, T., Mela, T., and Laurila, H., Arrangement of experiments for
simulating the effects of elevated temperatures and elevated CO
2
levels on field-
sown crops in Finland,

Agric. Food Sci. Finl., 5, 25–47, 1996.
Hakala, K., Heliö, R., Tuhkanen, E., and Kaukoranta, T., Photosynthesis and Rubisco
kinetics in spring wheat and meadow fescue under conditions of simulated cli-
mate change with elevated CO
2
and increased temperatures. Agric. Food Sci. Finl.,
8, 441–457, 1999.
Havelka, U.D., Wittenbach, V.A., and Boyle, M.G., CO
2
-enrichment effects on wheat
yield and physiology,
Crop Sci., 24, 1163–1168, 1984.
Hocking, P.J. and Meyer, C.P., The effects of CO
2
enrichment and nitrogen stress on
growth, and partitioning of dry matter and nitrogen in wheat and maize,
Aust. J.
Plant Physiol.,
18, 339–356, 1991.
416 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 416
IPCC, 1998. The Regional Impacts of Climate Change. An Assessment of Vulnerability. R.T.
Watson, M.C. Zinyowera, R.H. Moss & D.J. Dokken (Eds.). Cambridge University
Press, Cambridge, U.K. 1998.
Komulainen, M. 1998 (Ed.), Peltokasvilajikkeet 1998, in:
Tieto Tuottamaan 76.
Maaseutukeskusten liiton julkaisuja No. 917. ISBN 951-808-057-7. West Point,
Rauma, Finland.
Krenzer, E.G., Jr. and Moss, D.N., 1975. Carbon dioxide enrichment effects upon yield
and yield components in wheat.

Crop Sci., 15:71–74.
Laemmli, U.K., 1970. Cleavage of structural proteins during the assembly of the head
of bacteriophage T4.
Nature, 227:680–685.
Langer, R.H.M., 1979.
How Grasses Grow (2nd ed.). Studies in Biology No. 34. Edward
Arnold Ltd, London.
Lawlor, D.W., Kontturi, M., and Young, A.T., 1989. Photosynthesis by flag leaves of
wheat in relation to protein, ribulose bisphosphate carboxylase activity and nitro-
gen supply.
J. Exp. Bot., 40:43–52.
Leegood, R.C., 1993. The Calvin cycle and photorespiration, In
Plant Biochemistry and
Molecular Biology.
Lea, P.J. and Leegood, R.C. (Eds.). John Wiley & Sons Ltd,
Chichester. U.K., 27 –45.
McKee, I.F. and Woodward, F.I., 1994. CO
2
enrichment responses of wheat: interac-
tions with temperature, nitrate and phosphate.
New Phytol., 127:447–453.
Mela, T. and Paatela, J., 1974. Grain yield of spring wheat and oats as affected by pop-
ulation density.
Annales Agriculturae Fenniae, 13:161–167.
Mela, T.J.N., 1996. Northern agriculture: constraints and responses to global climate
change.
Agric. Food Sci. Finl., 5, 229–234.
Myhr, K., Solberg, Y., and Selmer-Olsen, A.R., 1978. The content of minerals, fibre, pro-
tein and amino acids in reed canary grass, timothy and meadow fescue.
Acta

Agriculturae Scandinavica,
28:269–278.
Nie, G.Y., Long, S.P., Garcia, R.L., Kimball, B.A., Lamorte, R.L., Pinter, P.J., Jr., Wall,
G.W., and Webber, A.N., 1995. Effects of free-air CO
2
enrichment on the develop-
ment of the photosynthetic apparatus in wheat, as indicated by changes in leaf
proteins.
Plant, Cell, Environ., 18:855–864.
Nijs, I., Impens, I., and Behaeghe, T., 1989. Leaf and canopy responses of
Lolium perenne
to long-term elevated atmospheric carbon-dioxide concentration. Planta,
177:312–320.
Nissinen, O. and Hakkola, H., 1994. Korjuutavan ja kasvilajin vaikutus nurmen tuot-
tokykyyn Pohjois-Suomessa (Summary: The effect of the harvesting method and
plant species on the grassland productivity in North Finland).
Tiedote 19/94
Maatalouden tutkimuskeskus Finland.
Palta, J.A. and Fillery, I.R.P., 1995. N application enhances remobilization and reduces
losses of pre-anthesis N in wheat grown on a duplex soil.
Aust. J. Agric. Res.,
46:519–531.
Pehu, E., Karvonen, T., Kleemola, J., and Peltonen-Sainio, P., 1994. The impact of cli-
matic change on cereal crops in Finland, In: M. Kanninen and P. Heikinheimo
(Eds.),
The Finnish Research Programme on Climate Change. Second Progress Report.
Publications of the Academy of Finland 1/94. Painatuskeskus OY, Helsinki,
244–248.
Pulli, S., 1980. Growth factors and management technique used in relation to the
developmental rhythm and yield formation pattern of a pure grass stand.

J. Sci.
Agric. Soc. Finland,
52:281–330.
EFFECTS OF CLIMATIC CHANGE IN FINLAND 417
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 417
Quick, W.P., Fichtner, K., Schulze, E.D., Wendler, R., Leegood, R.C., Mooney, H.,
Rodermel, S.R., Bogorad, L., and Stitt, M., 1992. Decreased ribulose-1,5-bisphos-
phate carboxylase-oxygenase in transgenic tobacco transformed with “antisense”
rbcS. IV. Impact on photosynthesis in conditions of altered nitrogen supply.
Planta, 188:522–531.
Robson, M.J., 1973a. The growth and development of simulated swards of perennial
ryegrass I. Leaf growth and dry weight change as related to the ceiling yield of a
seedling sward.
Ann. Bot., 37:487–500.
Robson, M.J., 1973b. The growth and development of simulated swards of perennial
ryegrass. II. Carbon assimilation and respiration in a seedling sward.
Ann. Bot.,
37:501–518.
Rogers, A., Fischer, B.U., Bryant, J., Frehner, M., Blum, H., Raines, C.A., and Long, S.P.,
1998. Acclimation of photosynthesis to elevated CO
2
under low-nitrogen nutri-
tion is affected by the capacity for assimilate utilization. Perennial ryegrass under
free-air CO
2
enrichment. Plant Physiol., 118:683–689.
Ryle, G.J.A., Powell, C.E., and Tewson, V., 1992. Effect of elevated CO
2
on the photo-
synthesis, respiration and growth of perennial ryegrass.

J. Exp. Bot., 43:811–818.
Saarikko, R.A. and Carter, T.R., 1996. Phenological development in spring cereals:
response to temperature and photoperiod under northern conditions.
Eur. J.
Agron.,
5:59–70.
Sage, R., 1994. Acclimation of photosynthesis to increasing atmospheric CO
2
: the gas
exchange perspective.
Photosynthesis Res., 39:351–368.
Schmitt, M.R. and Edwards, G.E., 1981. Photosynthetic capacity and nitrogen use effi-
ciency of maize, wheat and rice: a comparison between C
3
and C
4
photosynthesis.
J. Exp. Bot., 32:459–466.
Sharkey, T.D., 1985. Photosynthesis in intact leaves of C
3
plants: physics, physiology
and rate limitations.
Botanical Rev., 51:53–105.
Sionit, N., Strain, B.R., and Hellmers, H., 1981. Effects of different concentrations of
atmospheric CO
2
on growth and yield components of wheat. J. Agric. Sci.,
97:335–339.
Stitt, M., 1991. Rising CO
2

levels and their potential significance for carbon flow in
photosynthetic cells.
Plant, Cell, Environ., 14:741–762.
Waters, S.P., Peoples, M.B., Simpson, R.J., and Dalling, M.J., 1980. Nitrogen redistrib-
ution during grain growth in wheat (
Triticum aestivum L.). I. Peptide hydrolase
activity and protein breakdown in the flag leaf, glumes and stem.
Planta,
148:422–428.
Wong, S.C., 1979. Elevated atmospheric partial pressure of CO
2
and plant growth. I.
Interactions of nitrogen nutrition and photosynthetic capacity in C
3
and C
4
plants.
Oecologia, 44:68–74.
418 STRUCTURE AND FUNCTION IN AGROECOSYSTEMS DESIGN AND MANAGEMENT
920103_CRC20_0904_CH19 1/13/01 11:27 AM Page 418