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The enhancement in photosynthesis at elevated concentration of carbon dioxide level than the ambient level existing in the atmosphere is widely known. However, many of the earlier studies were based on instantaneous responses of plants grown in pots. The availability of field chambers for growing trees, and long-term exposure studies of tree species to elevated carbon dioxide, has changed much of our views on carbon dioxide acting as a fertiliser. Several tree species showed acclimation or even down-regulation of photosynthetic responses while a few of them showed higher photosynthesis and better growth responses. Whether elevated levels of carbon dioxide can serve as a fertilizer in a changed climate scenario still remains an unresolved question. Forest-Air-Carbon dioxide-Enrichment (FACE) sites monitored at several locations have shown lately, that the acclimation or down regulation as reported in chamber studies is not as wide-spread as originally thought. FACE studies predict that there could be an increase of 23–28% productivity of trees at least till 2050. However, the increase in global temperature could also lead to increased respiration, and limitation of minerals in the soil could lead to reduced responses in growth. Elevated carbon dioxide induces partial closure of leaf stomata, which could lead to reduced transpiration and more economical use of water by the trees. Even if the carbon dioxide acts as a fertilizer, the responses are more pronounced only in young trees. And if there are variations in species responses to growth due to elevated carbon dioxide, only some species are going to dominate the natural vegetation. This will have serious implications on the biodiversity and the structure of the ecosystems. This paper reviews the research done on trees using elevated CO2 and tries to draw conclusions based on different methods used for the study. It also discusses the possible functional variations in some tree species due to climate change.
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ORIGINAL PAPER
Responses of trees to elevated carbon dioxide
and climate change
Jose Kallarackal
T. J. Roby
Received: 16 April 2011 / Accepted: 1 February 2012 / Published online: 16 February 2012
Ó Springer Science+Business Media B.V. 2012
Abstract The enhancement in photosynthesis at elevated concentration of carbon dioxide
level than the ambient level existing in the atmosphere is widely known. However, many of
the earlier studies were based on instantaneous responses of plants grown in pots. The
availability of field chambers for growing trees, and long-term exposure studies of tree
species to elevated carbon dioxide, has changed much of our views on carbon dioxide
acting as a fertiliser. Several tree species showed acclimation or even down-regulation of
photosynthetic responses while a few of them showed higher photosynthesis and better
growth responses. Whether elevated levels of carbon dioxide can serve as a fertilizer in a
changed climate scenario still remains an unresolved question. Forest-Air-Carbon dioxide-
Enrichment (FACE) sites monitored at several locations have shown lately, that the
acclimation or down regulation as reported in chamber studies is not as wide-spread as
originally thought. FACE studies predict that there could be an increase of 23–28% pro-
ductivity of trees at least till 2050. However, the increase in global temperature could also
lead to increased respiration, and limitation of minerals in the soil could lead to reduced
responses in growth. Elevated carbon dioxide induces partial closure of leaf stomata, which
could lead to reduced transpiration and more economical use of water by the trees. Even if
the carbon dioxide acts as a fertilizer, the responses are more pronounced only in young
trees. And if there are variations in species responses to growth due to elevated carbon
dioxide, only some species are going to dominate the natural vegetation. This will have
serious implications on the biodiversity and the structure of the ecosystems. This paper
reviews the research done on trees using elevated CO
2
and tries to draw conclusions based
on different methods used for the study. It also discusses the possible functional variations
in some tree species due to climate change.
Keywords Trees Climate change Responses Carbon dioxide Temperature
Growth FACE
J. Kallarackal (&) T. J. Roby
Sustainable Forest Management Division, Kerala Forest Research Institute, Peechi, Thrissur,
Kerala 680653, India
e-mail: jkallara@gmail.com
123
Biodivers Conserv (2012) 21:1327–1342
DOI 10.1007/s10531-012-0254-x
Abbreviations
lll
-1
Microlitre per litre
aCO
2
Ambient Carbon dioxide
A
sat
Light saturated photosynthetic assimilation
CO
2
Carbon dioxide
D Vapour pressure deficit
eCO
2
Elevated carbon dioxide
ET Evapotranspiration
FACE Forest-Air-Carbon dioxide-Enrichment
GPP Gross primary productivity
g
s
Stomatal conductance
IPCC International Panel on Climate Change
J
max
Maximum electron transport rate
LMA Leaf mass per unit area
mmol mol
-1
Millimol per mol
N Nitrogen
NEP Net ecosystem productivity
NPP Net primary productivity
PNUE Plant nitrogen use efficiency
R
A
Autotrophic respiration
R
H
Heterotrophic respiration
Rubisco Ribulose 1,5-biphosphate carboxylase oxygenase
RuBP Ribulose biphosphate
tCha
-1
Tonnes of carbon per hectare
T
l
Leaf temperature
V
c,max
Maximum carboxylation velocity
VPD Vapour pressure deficit
Introduction
Carbon dioxide (CO
2
) in the atmosphere has increased over the past 150 years from
approximately 270–380 mmol mol
-1
and is predicted to increase to approximately
700 mmol mol
-1
by 2100, as it is increasing at the rate of more than 2 mmol mol
-1
annually (Karnosky et al. 2007). Global temperatures have also risen by 0.74°C over the
last century, with twentieth century, the warmest century and the decade 2000–2009, the
warmest decade on record (Kennedy and Parker 2010). The surface temperature is pre-
dicted to increase by 2–4°C by 2100 (IPCC 2007).
Trees are important components in land-based and forest ecosystems, playing a major
role in providing various ecosystem goods and services. While looking at the responses of
trees to the global climate change, it is important to look at their response to these
environmental factors—future increase in CO
2
emissions, increasing day and night tem-
peratures, drought, fire and other extreme events and pest and diseases. The mechanisms
driving photosynthesis, tree growth, water use, phenology, species composition, etc. under
these conditions will provide insights into responses of trees in a changed environment in
the future (Fig. 1).
The diversity and distribution of the world’s terrestrial vegetation is the product of a
complex suite of interactions between individual plants and a multitude of environmental
1328 Biodivers Conserv (2012) 21:1327–1342
123
variables. Plants, especially trees, are well known as major regulators of the global climate,
and their collective responses to increased atmospheric CO
2
concentrations have played an
important role in mitigating climate change. The phenomenon of the uptake of CO
2
by
plants during photosynthesis is the major pathway by which carbon is stored in the bio-
sphere. Understanding the effects of climate change on trees is a fairly recent concern,
however, requiring long-term data sets. Some such data sets do exist, such as long-term
phenological records for some forests or vegetation, but analysis can be hampered because
data collection protocols and species selection generally were not set up to answer con-
temporary questions relevant to climate change. Except for very few experimental loca-
tions, research in this field relies heavily on modelling. Models have been used for
predicting responses of single tree species, multi-species assemblages, and global vege-
tation patterns. However, models are only as good as the data and assumptions on which
they are built, and are continually improving as we refine and test them using data from
past climate changes. Plant responses to changes in single variable such as CO
2
, water or
temperature are well understood. Scientists are only beginning to understand how the
interaction of these factors impacts plants and their role in regulating the global climate.
Recent discoveries reveal that plants sequester 15–30% of the emitted carbon to mitigate
the global warming, while illustrating the many ways in which the world’s plants can all-
too-easily loose their ability to act as a global carbon sink, becoming instead yet another
carbon source (Keith et al. 2009).
Fig. 1 Diagram showing the factors associated with climate change and their impact on various biological
processes in trees
Biodivers Conserv (2012) 21:1327–1342 1329
123
Response of trees to elevated carbon dioxide in the atmosphere
Several studies conducted in the past have confirmed that plant biomass and yield tend to
increase as CO
2
concentrations increase above current levels in the atmosphere (Jablonski
et al. 2002). However, the results tend to vary across the different experimental settings,
such as controlled environment closed chambers, greenhouses, open and closed field top
chambers, and free-air carbon dioxide enrichment (FACE) experiments. On average,
across several species and under unstressed conditions, compared with current atmospheric
CO
2
concentrations of 385 mmol mol
-1
, crop yields increase at 550 mmol mol
-1
CO
2
in
the range of 10–20% for C3 crops and 0–10% for C4 crops (Ainsworth and Long 2005;
Gifford 2004; Long et al. 2004). Using meta-analysis, increases in above-ground biomass
at 550 mmol mol
-1
CO
2
for trees was found maximum among all functional groups, with
28% increase in dry matter production. The higher dry matter production values were
observed in young trees but little to no response in productivity was observed in the few
experiments conducted to date in mature natural forests (Ainsworth and Long 2005;
Nowak et al. 2004; Norby et al. 2003;Ko
¨
rner et al. 2005). Results of FACE studies
conducted in the last couple of decades have helped us to further confirm the photosyn-
thetic down regulation and CO
2
fertilisation effects in several tree species (see review by
Ainsworth and Long 2005 and Karnosky et al. 2007).
Enclosure methods and FACE method
There are many differences between enclosure methods and FACE method. The advan-
tages of the enclosure methods are that the operational cost is relatively low, the studies
can be conducted almost in any place and at any time, and the levels of temperature,
humidity, and irrigation can be more easily controlled than the FACE method. The dis-
advantages of enclosure method are that enclosures are built up in smaller plot sizes, with
loosely controlled plant density, larger edge effect, often limited root growth when grown
in pots, and thus greater variations than the FACE method. Moreover, CO
2
stimulation
would be higher for a low-density population than for a high-density population since a
low density population would be less limited by light. Some chamber studies did not
strictly control the plant density and reported the responses on a single plant basis with
chances of bias (see review by McLeod and Long 1999). FACE facilities are closer to
natural field conditions than open top chambers, which, in turn, are closer than growth
chambers, thus better method for studying responses to eCO
2
. While the enclosure studies
have been enormously important in conducting well-controlled experiments to investigate
mechanisms, FACE studies conducted under realistic natural conditions so far provide the
best quantitative information about the response of plants to eCO
2
where interactions with
other factors such as weeds, insects, pathogens, microorganisms and microclimates are in
operation. Data from FACE experiments during the last 20-years are now available in
several geographical locations around the world, except the tropics, though the tropical
forests represent 50% of the carbon in terrestrial biomass (see Tables 1, 2).
Photosynthetic stimulation and eCO
2
In general, instantaneous eCO
2
concentrations stimulate photosynthesis, but the same
plants when exposed to long-term experiments showed varying results (Kubiske et al.
1997). There are instances of acclimation and down regulation of photosynthesis as well
(Hogan et al. 1996). In many instances it leads to increased plant productivity and modified
1330 Biodivers Conserv (2012) 21:1327–1342
123
water and nutrient cycles (Kimball et al. 2002; Nowak et al. 2004). Experiments under
optimal conditions show that doubling the atmospheric CO
2
concentration increases leaf
photosynthesis by 30%–50% in C3 plant species and 10%–25% in C4 species (Ainsworth
and Long 2005). Surprisingly, crop yield increase is lower than the photosynthetic
response. Most of the studies related to the response of eCO
2
on trees have been made on
temperate species (Ainsworth and Long 2005). Very limited studies on the tropical species
show that the response is more or less similar, for example, two tropical C3 tree species,
teak (Tectona grandis) and barrigon (Pseudobombax septenatum), when exposed to
600 lll
-1
CO
2
, net CO
2
uptake rates in shoots or leaves of seedlings increased by 28 and
52% respectively (Holtum and Winter 2003).
Current atmospheric CO
2
concentration is well below saturation for photosynthesis, so
the metabolic rate that limits photosynthesis in the majority of plants is carboxylation by
Rubisco rather than electron transport or RuBP regeneration, although sometimes a co-
limitation of both metabolic components has been suggested (Lambers et al. 2008). Plants
that show down-regulation of photosynthetic capacity at eCO
2
often have lower Rubisco
activity (Sage 1994). The decrease in Rubisco activity is often correlated with a decrease in
leaf nitrogen concentration (Pettersson and McDonald 1994). Both RuBP carboxylation
Table 1 Comparison of the general results of plant responses to eCO
2
from the analysis of large-scale
FACE experiments vs. previous quantitative reviews of eCO
2
experiments
Generality FACE Prior Certainty
Order of C3 functional
group responsiveness
Trees [ legumes [ C3 grasses Legumes [ grasses [
woody plants
No difference in
functional groups
Low
C3 vs. C4 response C3 C4
C3 & C4
C3 [ C4 Low
Sustained increase
in carbon uptake
Yes
No
Yes High
Acclimation of photosynthesis V
c, max
/J
max
No change in V
c, max
/J
max
High
Decrease in leaf N Specific to and accounted
for by Rubisco
Dilution effect Medium
Increase in leaf area index Trees only
No
Yes Low
Simulation in crop yield Small Large Medium
Table reproduced from Ainsworth and Long (2005) with permission of the New Phytologist Trust Ó 2005
Table 2 FACE experimental studies on trees
Tree species Duration
(years)
Parameters measured Result Reference
Acer saccharum 7 Above-ground volume
Total biomass
No increase
60% increase
Karnosky et al. (2005)
King et al. (2005)
Betula papyrifera 7 Above-ground volume
Total biomass
68% increase
45% increase
Karnosky et al. (2005)
King et al. (2005)
Populus tremuloides 7 Total biomass
Above-ground volume
25% increase
5–60% increase
King et al. (2005)
Karnosky et al. (2005)
Table modified from Karnosky et al. (2007) with permission from publisher CABI
Biodivers Conserv (2012) 21:1327–1342 1331
123
and RuBP regeneration processes need a substantial amount of nitrogen to maintain high
photosynthetic capacity. Photosynthetic acclimation is most commonly measured as a
decreased maximum carboxylation rate of Rubisco (V
c,max
) and maximum electron
transport rate leading to ribulose-1,5-bisphosphate (RuBP) regeneration (J
max
). However,
the V
c,max
estimated for photosynthesis did not show any variation within a species for the
ambient and eCO
2
treatments conducted on beech (Nothofagus fusca) and pine (Pinus
radiata). Hence Hogan et al. (1996) concluded that Rubisco activity was not affected by
CO
2
treatment. This was also supported by lack of difference in leaf nitrogen content
between the treatments. In beech, the down-regulation of photosynthesis observed during
spring season was not seen during the summer. It means that temperature has an important
role in regulating photosynthesis at eCO
2
. In pine also, there was no down-regulation, but
the plants acclimatized to the eCO
2
in the spring. It was found that in both the plants the
triose phosphate utilisation rates were slow, which prevented any up-regulation in pho-
tosynthesis as observed in several other species (Hogan et al. 1996). Photosynthesis in
summer time was greater in the eCO
2
treatment for beech and pine, and in spring time for
pine. Both species showed greater photosynthesis at a given stomatal conductance, which
should result in greater water use efficiency also.
While early studies of C3 plants grown in pots in controlled environments indicated that
acclimation of photosynthetic capacity might negate any stimulation in carbon assimilation
in some species (reviewed in Arp 1991; Stitt 1991; Sage 1994), more recent evidence from
FACE experiments overwhelmingly shows that despite small decreases in V
c,max
and J
max
,
the light-saturated rate of photosynthetic carbon uptake (A
sat
) is markedly stimulated in C3
plants grown at eCO
2
(Karnosky et al. 2003; Liberloo et al. 2006; Ainsworth and Rogers
2007). However, the evidence from FACE experiments also shows that the degree of
stimulation of A
sat
varies among species and experimental conditions (Nowak et al. 2004;
Ainsworth and Long 2005). When limited by RuBP regeneration capacity, the increase in
A
sat
resulted almost exclusively from the repression of photorespiration (Long et al. 2004).
This explanation provides a mechanistic basis for the greater than average stimulation in
A
sat
observed in trees (46%) and grasses (37%) grown at eCO
2
, compared to shrubs (21%),
C3 crops (13%), and legumes (19%). However, even within functional groups, environ-
mental and genetic factors also influence the magnitude of acclimation of photosynthetic
capacity, and the stimulation of A
sat
. Poplars grown for coppice sustained a 55% stimulation
in A
sat
at eCO
2
(Bernacchi et al. 2003) because of their large capacity for starch synthesis
and carbon export (Davey et al. 2006). Poplars exported[90% of their photosynthate during
the day and stored the rest of the overflow photosynthate as starch (Davey et al. 2006) which
enabled the trees to avoid acclimation of photosynthetic potential, and maintain maximal
stimulation of A
sat
at eCO
2
. Thus, it is apparent that the sink strength is an important factor
for an efficient transport of assimilates from the source of its production.
FACE experiments have provided ample evidence that photosynthetic capacity accli-
mates to eCO
2
in C3 plants, and the scale of down-regulation varies with genetic and
environmental factors. However, despite acclimation of photosynthetic capacity in some
species, carbon gain is markedly greater (19–46%) in plants grown at the CO
2
anticipated
for the middle of this century.
Net ecosystem production (NEP)
Experiments done at the ecosystem level have also been helpful in predicting responses of
trees to eCO
2
. In any growing tree we can see that there is a net removal of CO
2
from the
atmosphere and is fixed in the plant body and the soil. In an old growth forest, the net
1332 Biodivers Conserv (2012) 21:1327–1342
123
removal of CO
2
should be compensated by a net addition into the atmosphere (Jarvis and
Linder 2007). A net gain in carbon by trees means a lack of balance between the process of
taking in CO
2
from the atmosphere and the process of returning CO
2
to the atmosphere.
Net primary production (NPP) is the difference between the gross photosynthetic pro-
duction (GPP) and the losses of carbon resulting from autotrophic respiration (R
A
) asso-
ciated with growth and maintenance of live biomass.
NPP ¼ GPP R
A
ð1Þ
It follows that the net ecosystem production (NEP) is the difference between the net
primary production (NPP) and the respiration associated with decomposition and miner-
alization of organic materials in the soil by animals and micoorganisms, which is called the
heterotrophic respiration (R
H
).
NEP ¼ NPP R
H
ð2Þ
In an old growth forest at equilibrium, NEP should be zero, or NPP = R
H
or if NPP [ 0,
then NPP must exceed R
H
. Fortunately, forests worldwide are not at equilibrium, and that is
the reason they serve as a global sink accounting for up to 40% of emissions derived from
fossil fuels (Read et al. 2001). During the early stages of a tree plantation, though the
NEP \0 due to soil disturbance, etc., once the canopy closes, NEP stabilises for a number
of years amounting up to 8 t C ha
-1
for fast growing species in favourable conditions
(Magnani et al. 2007). Harvesting on a regular basis and putting the timber to long-term uses
can certainly help to sequester a great amount of carbon from the atmosphere. Similarly,
sporadic fire, wind throw and peripatetic cultivation may account for the significant NEP of
mixed old-growth tropical forest (Jarvis and Linder 2007). However, the NEP is greatly
dependent on the nutrition availability and also the temperature (Hyvo
¨
nen et al. 2007).
Plant nitrogen use efficiency (PNUE)
Because N availability often limits primary productivity through its effect on photosyn-
thesis and on the synthesis of proteins required for the construction and maintenance of
living tissue, increased N uptake from the soil and more efficient use of the N already
assimilated by trees is necessary to sustain the high rates of tree growth observed under
elevated CO
2
(Field 1983). FACE experiments demonstrate that the uptake of N increased
under elevated CO
2
, yet fertilization studies showed that tree growth and forest NPP were
strongly limited by N availability (Finzi et al. 2007; Norby et al. 2011). A combination of
increasing fine root production, increased rates of soil organic matter decomposition, and
increased allocation of carbon (C) to mycorrhizal fungi is likely to account for greater N
uptake under eCO
2
(Finzi et al. 2007). This increase is driven predominantly by enhanced
CO
2
uptake rather than by the saving and redistribution of leaf N which was found to be
smaller than anticipated. Results from the FACE experiments showed that under low N
conditions there was a 22% decrease in V
c,max
, and under high N conditions there was only
12% decrease in V
c,max
(Ainsworth and Long 2005). However, further improvements
in PNUE are anticipated later this century as the atmospheric CO
2
surpasses the
550 mol mol
-1
level used in the FACE experiments that have been conducted to date.
Water use efficiency and eCO
2
That eCO
2
reduces stomatal conductance (g
s
) in tree species has long been well established
from a wide range of experiments (Hogan et al. 1996). FACE experiments extend these
Biodivers Conserv (2012) 21:1327–1342 1333
123
findings showing that the decrease in g
s
is upheld when plants are grown under experi-
mental conditions that allow for the natural coupling of the plants and the atmosphere to be
upheld. A decrease in evapotranspiration (ET) of 5–20% has been noticed in many crop
plants using micrometeorological methods (Buchmann 2002). Although many sapflow
studies have not been done in FACE experimental sites, studies conducted in trees of a
mixed deciduous forest by Leuzinger and Ko
¨
rner (2007) indicate that 14% reduction in
evapotranspiration occurs under eCO
2
.CO
2
effect is greatest at low VPD, and that sap flow
saturation tends to occur at lower VPD in CO
2
-treated trees (Leuzinger and Ko
¨
rner 2007).
Most importantly, FACE experiments have shown that the leaf level and canopy level
responses are consistent—namely that leaf level decreases in water use scale to the canopy
and that the decrease in water use translates to higher soil moisture availability. This will
have important implications on the streamflow from watersheds in future.
Plant growth and eCO
2
Evidences show that eCO
2
enhances photosynthetic rates by increasing the carboxylation
rate of Rubisco and competitively inhibiting the oxygenation of Ribulose-1,5-biphosphate
(Drake et al. 1997). On an average, FACE studies have shown that there was a 31%
stimulation of light saturated photosynthesis and a 28% stimulation in diurnal photosyn-
thetic carbon assimilation due to eCO2. However, plant growth is stimulated less than
expected on the basis of the increased rate of photosynthesis per unit leaf area. This is due
to the fact that plants at eCO
2
have reduced leaf area on display per unit biomass, thereby
decreasing the relative amount of machinery (Poorter and Pe
´
rez-Soba 2002). As nitrogen
uptake is not stimulated as much as carbon uptake, CO
2
elevation alters the C/N balance in
the plant body. Plants respond to eCO
2
by changing biomass allocation to mitigate the
altered C/N balance. In plants with protein-rich seed, reproductive growth is limited by
nitrogen rather than by carbon. eCO
2
does not increase reproductive yield as much as
vegetative growth. Proportionate allocation of biomass to reproduction decreases when
reproductive growth is limited by nitrogen rather than by carbon. Effects of eCO
2
at
canopy and population levels are manifested through interactions between light and
nitrogen availability, and also through interactions among individuals. In a leaf canopy,
leaf area increases with CO
2
elevation when nitrogen uptake is simultaneously increased.
At all FACE sites the leaf area index of trees increased by an average 21% when the
response was negligible in shrubs and herbs in response to eCO
2
(Ainsworth and Long
2005). This was simultaneously followed by a 9% increase in girth of the trees. If dominant
plants increase their leaf area, they will reduce light availability in the lower layers of the
canopy and thus the growth of plants there, which makes competition among individuals
more asymmetric. Interaction among individuals makes responses to eCO
2
fairly sensitive
to nitrogen availability in the soil. Integrating these responses would be indispensable for
understanding functioning of plants in a high-CO
2
world.
Although experimental studies are lacking in the tropics, Lloyd and Farquhar (2008) found
little direct evidence that tropical forests should not be able to respond to eCO
2
and argue that
the magnitude and pattern of increases in forest dynamics across Amazonia observed over the
last few decades are consistent with a CO
2
-induced stimulation of tree growth.
Tree diversity
In a recent study conducted by Souza et al. (2010) on an understorey community in Oak
Ridge National Environmental Research Park, USA, it was found that the aboveground
1334 Biodivers Conserv (2012) 21:1327–1342
123
biomass of the understory community was on average 25% greater in eCO
2
than in ambient
CO
2
(aCO
2
plots). No difference was observed in plant species composition between aCO
2
and eCO
2
treatments. However, shifts in the relative abundance of plant functional groups
were noticed which reflected important structural changes in the understory community.
A gradual increase in the woody species in eCO
2
plots was also noted. These results
suggest that rising atmospheric CO
2
could accelerate successional development and
potential long term impact on forest dynamics.
Temperature effects on trees
The increased warming of the globe has been confirmed in the IPCC (2007) report. It is
generally assumed that climate change is likely to increase net primary production (NPP)
more in cold northern regions than close to the equator because of a greater proportional
growing season extension in temperature-limited environments (Rustad et al. 2001;
Morales et al. 2007). However, some studies show that the effects of temperature increase
are generally expected to reduce growth and survival, predispose forests to disturbance by
wildfire, insects, and disease; and, ultimately change forest structure and composition at the
landscape scale (Chmura et al. 2011). Recent warming has already resulted in earlier
flowering and vegetative bud burst in forest trees (Parmesan 2007;Ko
¨
rner and Basler
2010). These trends are expected to continue in most temperate climates at least for
moderate increases in temperature. Genetic differences in the timing of bud burst, bud set,
and flowering indicate that species and populations are generally adapted to their local
temperature environments (Howe et al. 2003). Thus, elevated temperatures will directly
affect adaptability of trees and forests through effects on plant phenology and growth, and
indirectly through interactions with other stressors and disturbances that will affect species
distributions, forest composition, and forest structure.
Temperature effects on photosynthesis and productivity
Hickler et al. (2008) predicts a very strong affinity between photosynthesis and temperature
that the direct CO
2
response of NPP will be stronger in warm regions compared to colder
regions. Regional differences in the modeled CO
2
response were to a large extent driven by
the temperature response of the relative affinity of enzyme Rubisco for CO
2
and O
2
.
Increased temperatures lead to an increased relative fixation of O
2
(oxygenation), causing
photorespiration, an energy-dependent process that reduces net photosynthesis (Jordan and
Ogren 1984). Using the models of Farquhar et al. (1980), and Farquhar and von Caem-
merer (1982), Long (1991) showed that this effect causes a much stronger CO
2
enhancement of photosynthesis at high temperatures than at low temperatures. According
to Long’s model, an increase in atmospheric CO
2
from 350 to 650 mmol mol
-1
could
increase light-saturated CO
2
uptake by 20% at 10°C and by 105% at 35°C. Thus, there
exists a strong physiological basis for a temperature dependence of NPP responses on
eCO
2
. Thus we need to have more field data on the affinity of photosynthesis with tem-
perature at eCO
2
. Unfortunately, the current long-running forest FACE experiments are all
located in the temperate zone, and hence subject to a limited range of growing season
temperatures.
There is a general apprehension that the tropical forests are close to their optimum
temperature range as the earth is warming and their productivity could drastically reduce
with temperature increase (Wright 2005). Although there are not many studies in the
Biodivers Conserv (2012) 21:1327–1342 1335
123
tropics, using a mixture of observations, climate model outputs and a simple parametri-
zation of leaf-level photosynthesis incorporating known temperature sensitivities, Lloyd
and Farquhar (2008) find no evidence for tropical forests currently existing ‘dangerously
close’ to their optimum temperature range. Their model suggests that although reductions
in photosynthetic rate at leaf temperatures (T
l
) above 30°C may occur, these are almost
entirely accountable for in terms of reductions in stomatal conductance in response to
higher leaf-to-air vapour pressure deficits D. This is as opposed to direct effects of T
l
on
photosynthetic metabolism. They also found that increases in photosynthetic rates asso-
ciated with increases in ambient CO
2
over forthcoming decades should more than offset
any decline in photosynthetic productivity due to higher D or T
l
or increased autotrophic
respiration rates as a consequence of higher tissue temperatures.
Phenology
In extratropical regions phenology is controlled by three important factors—winter chill-
ing, photoperiod and temperature (Chuine and Cour 1999; Hay 1990). In the early suc-
cession species, temperature plays an important role in bud bursting, flowering, etc.
However, in the late succession species winter chilling and photoperiod are important
drivers for the above processes. Hence due to global warming some opportunistic taxa may
profit from a warmer climate and may thus gain a competitive advantage over photoperiod-
sensitive taxa (Ko
¨
rner and Basler 2010). In tropical ecosystems, phenology might be less
sensitive to temperature and photoperiod, and more tuned to seasonal shifts in precipitation
which in turn are expected to occur in concert with rising global temperatures. However,
both the direction and magnitude of change vary regionally (Cubasch et al. 2001).
Although much progress has been achieved in modeling, the physiological bases for the
control of environment on tree phenology are not well understood. Observations in general,
show that leaf unfolding, flowering, fruit ripening and leaf colouring will shift in the next
few decades to earlier dates than those presently observed. A recent review on leaf
unfolding in major forest trees shows that, on average, this has been advancing at a mean
rate of 2.9 days per decade since 1950 in tree species from the temperate zone (Chuine
et al. 2007). If the phenological changes are linear with warming, Loustau et al. (2007)
estimate that leaf unfolding should advance at a rate of 5.4–10.8 days per decade over the
period 2000–2050. Thus by 2050 leaf unfolding of forest trees could occur 27–54 days
earlier than at present in temperate regions of the world.
The mechanisms that control the phenology of tropical trees are largely unexplored.
Certain evidences (Cubasch et al. 2001) suggest that the cloud cover and atmospheric
vapour pressure deficit are very critical. Tropical deforestation can reduce convectional
cloud cover and evapotranspiration. This has even the possibility to change the atmo-
spheric conditions in tropical locations.
Extreme events
Extreme events are going to be more frequent as predicted by the climate scientists as a
result of the global climate change (IPCC 2007). What would be the impact of these events
on the tree populations?
1336 Biodivers Conserv (2012) 21:1327–1342
123
Drought and fire
A study on the extreme drought and acute heat wave that impacted ecosystems across the
southeastern USA in 2007 including a 19-year-old sweetgum (Liquidambar styraciflua)
tree plantation exposed to long-term eCO
2
or ambient CO
2
treatments was done by Warren
et al. (2011). According to the study, in the eCO
2
exposed plantation, sap flow got reduced
by 28% during early summer, and by up to 45% late in the drought during record-setting
temperatures. Modelled canopy conductance declined more rapidly in eCO
2
plots during
this period, thereby directly reducing carbon gain at a greater rate than in ambient CO
2
plots. Consequently, premature leaf senescence and abscission increased rapidly during
this period, and was 30% greater for eCO
2
. While eCO
2
can reduce leaf-level water use
under droughty conditions, acute drought may induce excessive stomatal closure that could
offset benefits of eCO
2
to temperate forest species during extreme weather events. A study
on the drought and heat-induced tree mortality rate around the globe revealed that no
climate zone is free from this problem (Allen et al. 2010). However there are much
uncertainties in our understanding of the tree mortality mechanisms, especially the phys-
iological thresholds for the death of a tree and also interactions with pests and diseases.
According to the above authors forests could be particularly vulnerable to increase in
temperatures in addition to drought, thereby there could be carbon starvation along with
hydraulic failures. Evidences for considerable reduction due to drought in global NPP has
been shown by an analysis spreading a decade (Zhao and Running 2010). However, more
research is required to reveal the full extent of this problem in a climate change scenario.
Fire, which is a consequence of increasing temperature and drought, has enormous
influence on the tree population structure in different ecosystems (see review by Flannigan
et al. 2000). The increase in forest fires can change the forests that are presently considered
as important carbon sinks to carbon sources.
Migration and extinction of tree species
Besides phenology, species abundance in tropical forests has been shown to be very sen-
sitive to climate change. For example during a 25-year drought, at least 16 species of shrubs
and trees were on the verge of extinction in the Barro Colarado Island (Condit et al. 1996).
Studies on migration of tree species due to warming have been very few in the literature.
Iverson and Prasad (1998) in a model analysis predicted the fate of 80 tree species in the
United States. They showed that roughly 30 species could expand their range and/or
weighted importance at least 10% while an additional 30 species could decrease by at least
10% following equilibrium after a changed climate. Depending on the global change
scenario used, 4–9 species would potentially move out of the United States to the north.
Nearly half of the species assessed (36 out of 80) showed the potential for the ecological
optima to shift at least 100 km to the north, including seven that could move 250 km.
Given these potential future distributions, actual species redistributions will be controlled
by migration rates possible through fragmented landscapes.
Pests, diseases and invasive species
The impacts of pests, diseases and invasive species in a changed climate has been reviewed
by Moore and Allard (2008). Pest or disease attack can be at the leaf level. However, when
this is severe, it can enlarge to the tree level or stand level or even the landscape level. The
Biodivers Conserv (2012) 21:1327–1342 1337
123
impacts of the pests and diseases in a climate change situation have been modelled by
Pinkard et al. (2011). The above studies show that in a changed climate situation, it is not
easy to predict the impacts mainly because the interaction of various factors will be
enormous. Similarly invasive species can also bring in a lot of other interacting factors to
play in a climate change situation.
Physiological responses to climatic stresses are relatively well-understood at the organ
or whole-plant scale but not at the stand or landscape scale. In particular, the interactive
effects of multiple stressors is not well known. Genetic and silvicultural approaches to
increase adaptive capacities, and to decrease climate-related vulnerabilities of forests can
be based on ecophysiological knowledge. Effective approaches to climate adaptation are
required to include assisted migration of species and populations, and density management.
Use of these approaches to increase forest resistance and resilience at the landscape scale
requires a better understanding of species adaptations, within-species genetic variation, and
the mitigating effects of silvicultural treatments (Chmura et al. 2011).
Controlled laboratory and field chambers have provided an immense database on plant
responses to rising CO
2
and, more importantly, insight into potential mechanisms of
response. Most of the chamber studies have shown that productivity increases by appli-
cation of eCO
2
. FACE on the other hand, which allows treatment of plants under field
conditions at a realistic scale, has provided an important reality check. It has shown both
where hypotheses developed in controlled environments do or do not apply as well as
insights into the mechanisms that may cause the difference. Overwhelmingly, this has
shown that data from laboratory and chamber experiments systematically overestimate the
yields of the major food crops, yet may underestimate the biomass production of trees.
Improved projection of these hugely important parameterization data for predictive models
will require many more FACE experiments, since the large-scale FACE experiments have
been conducted at just one or two locations in a given ecosystem type. Data on different
species will also be important for modeling the fate of ecosystems in future. There is hardly
any FACE study on tropical tree species. This gap needs to be addressed in future.
Conclusions
Following conclusions may be drawn from studies using different methods on the response
of trees to eCO
2
:
1. In general, instantaneous eCO
2
concentrations stimulate photosynthesis but the same
plants when exposed to long-term experiments can down-regulate or acclimate
depending on species and growing conditions.
2. Increased photosynthetic rates need not be manifested in yield and productivity. FACE
studies, in general, report an increase in biomass yield of approximately 23% in trees
due to doubling of the CO
2
levels in the atmosphere compared to the present levels.
However, this yield increase is not manifested in older stands.
3. Water use efficiency of trees will increase in response to eCO
2
, as the stomatal
conductance decreases without any concomitant decrease in photosynthesis. This will
have important implications on the future water availability from catchments and also
species composition in natural ecosystems.
4. Increasing temperature has wide implications with regard to photosynthetic produc-
tivity in the temperate and tropics. The absence of FACE studies in the tropics is a
serious drawback for verifying models in this regard.
1338 Biodivers Conserv (2012) 21:1327–1342
123
5. Studies on the ecological implications, especially the structure, composition and
functioning of the future ecosystems are rare. Preliminary observations have shown
that these aspects are going to be affected. More research is needed on the different
ecosystems as the ecosystem services are very important for a sustained development.
6. More studies covering different ecosystems are needed in understanding phenological
changes as climate change effects can drastically change species composition in many
existing forests. More permanent plot monitoring is called for to solve the problem.
7. A mechanistic model which will take care of the various interactions between
physiological and climatic parameters is required to further enrich our understanding
of climate change impacts on trees.
Acknowledgments We are grateful to the Council of Scientific and Industrial Research, New Delhi for
funding support. I thank Professor Mukund Behera (IIT, Kharagpur) for inviting me to contribute this paper
for the special issue.
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... There are already examples of 'big laboratory' experiments that have manipulated the environment to understand future landscape changes that may not be observable otherwise. These include Free Air Concentration Enrichment (FACE) studies (Kallarackal and Roby, 2012), paired catchment studies where one catchment is intentionally disturbed (Ruprecht and Schofield, 1989) and the experiment of Livensperger et al. (2016), who induced changes in temperature and snowmelt independently over a plot in Alaska. Such forcing experiments, perhaps combined with rainfall simulation experiments (Martínez-Murillo et al., 2013;Zhao et al., 2014), could be used to study the landscape response to many different unprecedented changes. ...
... Increasing temperatures may increase atmospheric vapor 159 pressure deficit, which enhances the rate of transpiration and may compensate the effects of increased 160 stomatal closure [3,8] (Wright, 2010). Elevated carbon dioxide levels may enhance photosynthesis in a 161 process referred to as 'fertilization' [10] (Kallarackal et al., 2012). The fertilization effect is thought to be 162 greater for C3 species (most plant types including nearly all tree species) than C4 species (with a specific 163 adaptation to reduce photorespiration); this may give a competitive advantage to C3 plants, altering 164 future species composition (Ainsworth et al., 2004;Kallarackal et al., 2012). ...
... Elevated carbon dioxide levels may enhance photosynthesis in a 161 process referred to as 'fertilization' [10] (Kallarackal et al., 2012). The fertilization effect is thought to be 162 greater for C3 species (most plant types including nearly all tree species) than C4 species (with a specific 163 adaptation to reduce photorespiration); this may give a competitive advantage to C3 plants, altering 164 future species composition (Ainsworth et al., 2004;Kallarackal et al., 2012). However, a given species' 165 optimum temperature for photosynthesis may be exceeded more often in the future [9] , counteracting 166 the stimulating influence of carbon dioxide fertilization (Lindner et al., 2010). ...
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... This is not unusual since some studies elsewhere had also showed rainfall and temperature fluxes are not decisive factors in triggering flowering and fruiting in tropical ecosystems (e.g. Kallarackal and Roby 2012;Polansky and Boesch 2013;Harrison et al. 2016). Further placing our results into a broader context, we integrated our data with data from previous research in the study site and encountered some interesting observations (Fig. 6). ...
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Timber extraction is often cited as detrimental to wildlife ecology. Little information, however, in particular from the Southeast Asian tropics, is available on how exactly logging affects wildlife food security. To address the gap, this paper presents the first high-resolution comparison of fruit production between logged and intact forests in lowland Borneo. In the period of 2004–2008, dry weight of fruit litter was assessed as a proxy for food security of wildlife. The pheno-phases of 1,054 trees in 14 sampling plots were monitored for 54 months. A total of 143,184 fruits from 50 tree families were collected from six sampling transects totalling 810 km in 34 months. Surprisingly, logged forest (mean = 23.3 kg ha− 1, SD = 48.9) produced more fruit litter than intact forest (mean = 16.7 kg ha− 1, SD = 23.3), although the difference is not significant based on Student’s t test; t(66) = 0.702, p = 0.485. Pheno-phases could not be entirely explained by rainfall and temperature variables. Some evidence, however, indicates tree species composition, stand structure and sunlight exposure were likely determinants of flowering and fruit litter intensity. All things being equal, results imply selective logging if considerately practiced may increase food security for wildlife. The findings, however, should be interpreted with caution since tropical forest phenology and fruit productivity are also driven by a suite of small-scale edaphic attributes and large-scale spatio-temporal meteorological forcing. Although this research deals mainly with Borneo, the principles discussed and insights offered herein are valuable for furthering conversation around sustainable forestry in tropical Asia and elsewhere globally.
... On the other hand, carbon dioxide is an important substrate for photosynthesis and, because of this, vegetation, in particular, the world's forests, plays a key role in abating the rise in atmospheric CO 2 (Rogers et al. 1999;Coomes et al. 2014). During the last decades, the growth enhancement of different tree species under artificially elevated CO 2 has been reported in several studies (LaMarche et al. 1984;Jarvis 1998;Jach and Ceulemans 1998;Kallarackal and Roby 2012;Ainsworth and Long 2005;Smith et al. 2013) and assumes the sufficient nutrients supply has a decisive role on the tree growth under elevated CO 2 (Brown and Higginbotham 1986;Pettersson et al. 1993;Yazaki et al. 2005;Atwell et al. 2003 andDrake et al. 2011;Piñeiro et al. 2017). However, Norway spruce response to elevated CO 2 was different in the different studies. ...
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A 7-year study was conducted to examine the growth (diameter and root) response of Norway spruce (Picea abies (L.) Karst.) seedlings to elevated CO2 (CO2ELV, 770 μmol (CO2) mol⁻¹) in different mixture types (monospecific (M): a Norway spruce seedling surrounded by six spruce seedlings, group-admixture (G): a spruce seedling surrounded by three spruce and three European beech seedlings, single-admixture (S): a spruce seedling surrounded by six beech seedlings). After seven years of treatments, no significant effect from elevated CO2 was found on the root dry mass (p = 0.90) and radial growth (p = 0.98) of Norway spruce. Neither did we find a significant interaction between [CO2] × mixing treatments (p = 0.56), i.e. there was not a significant effect of CO2 concentrations [CO2] in all the admixture types. On the contrary, spruce responses to admixture treatments were significant under CO2AMB (p = 0.05), which demonstrated that spruce mainly increased its growth (diameter and root) in M and neighbouring with beech was not favourable for spruce seedlings. In particular, spruce growth diminished when growing beside high proportions/numbers of European beech (S). Here, we also evaluated the association between tree-ring formation and climatic variables (precipitation and air temperature) in different admixture types under elevated and ambient CO2 (CO2AMB, 385 μmol (CO2) mol⁻¹). Overall, our result suggests that spruce responses to climate factors can be affected by tree species mixing and CO2 concentrations, i.e. the interaction between climatic variables × admixture types × [CO2] could alter the response of spruce to climatic variables.
... Therefore, with increased photosynthesis and lower water loss, the water efficiency of plants is increased. Thus, it seems that more carbon dioxide in the atmosphere is good for plants that grow faster and use less water and more carbon sequestration 25 . Chlorophyll is a chemical substance absorbing and transferring energy from sunlight to high-energy electrons 26 . ...
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The composition of species can play an essential role in reducing atmospheric carbon dioxide. Forest trees are an important part of the functioning of the terrestrial ecosystem, predominantly in the cycling of carbon. However, tree physiology is much less studied than crop physiology for several reasons: a large number of species, difficulty in measuring photosynthesis of tall trees or forest species. This study aims to establish the relationship between physiological plant functional traits (photosynthesis rate, transpiration rate, stomatal conductance, leaf chlorophyll and carotenoid content) with soil carbon stock in Pinus roxburghii forest of Garhwal Himalaya. The present findings revealed that photosynthesis rate, chlorophyll a, chlorophyll b and carotenoid content positively correlated to the soil carbon stock. The different regression models also showed that photosynthesis rate with water-use efficiency, stomatal conductance and carotenoid content is a good predictor of soil carbon stock in Pinus roxburghii forest. Physiological plant functional characteristics are thus crucial for regulating the carbon cycle and ecosystem functioning in Garhwal Himalaya.
... Global climate change is a major concern to agriculture and forestry due to its impact on physiology and productivity of plants (Choi et al., 2017;Dusenge et al., 2019;Ehleringer et al., 1991;Eschenbach et al., 1998;Kallarackal & Roby, 2012;Lloyd & Farquhar, 2008;Peperkorn et al., 2005;Possell & Hewitt, 2009). In the context of plant invasions, elevated temperature and atmospheric CO 2 concentrations resulting from climate change have been shown to facilitate the spread of invasive plant species (Bradley et al., 2010;Hellmann et al., 2008). ...
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The impacts of climate change, in particular via elevated temperature and atmospheric CO2 concentrations, cause differential photosynthetic responses between native and invasive alien plants, often resulting in varying magnitudes of plant growth and productivity. This study investigated variations in photosynthetic responses of an invasive alien Acacia species and two successional groups of tropical heath forest species: early secondary (Bucha nania arborescens and Dillenia suffruticosa) and secondary (Calophyllum inophyllum and Ploiarium alternifolium) groups at elevated temperature (25to 30°C) and CO2 levels (400 to 700 ppm). Invasive A. mangium appears better adapted to higher temperature and CO2. High temperature improved CO2 assimilation of A. mangium compared to heath species, which was attributed to increased transpiration rate and stomatal conductance but decreased water-use efficiency. Photosynthetic responses showed no differences in early secondary species at elevated temperature and CO2 but invasive A. mangium and P. alternifolium were stimulated by elevated CO2. The greater maximum net photosynthesis of A. mangium coincided with lower light compensation point and electron transport rate for RuBP regeneration, to a certain extent. Findings provide insights into possible underlying ecophysiological mechanisms contributing to the invasion success of Acacias in degraded tropical heath forests in response to future climate change.
... The tamarind tree is able to absorb 28.5 tons of carbon dioxide (CO2) equivalent gas per year, Cassia sp. A flowering plant able to absorb 5.3 tons of CO2 gas per year, the banyan tree is able to absorb 0.53 tons of CO2 equivalent gas / year (Dahlan, 2008;Kallarackal and Roby, 2012). Trembesi leaves have a high effectiveness as an adsorbent, especially if used in absorbing exhaust emissions (Sentyaki, et al, 2018). ...
Article
The existence of carbon dioxide (CO2) in the atmosphere and global temperatures continues to increase. Plants, especially trees, are known as the main regulators of global climate and have played an important role in climate change mitigation. The purpose of this research is to identify the pattern of tree distribution and analyze the absorption of trees against carbon dioxide emissions on the UNNES campus. The research was conducted at the UNNES campus, with mapping units in 8 Faculties and one Postgraduate Campus. Qualitative research was applied in this study with a phenomenological approach. The focus of the study was on tree distribution patterns and tree absorption capacity of carbon dioxide. The results showed that the distribution pattern clustered on the western side of the campus, while the existence of trees on the eastern side of the campus was not as much. Distribution data in faculties and work units showed that the dominant tree distribution was in the Rectorate area with 54 species of trees totaling 4534 trees. Absorption of trees per faculty showed that the largest absorption capacity of trees was in the type of trembles tree, mango, and mahogany that were often found in the Faculty of Sport Sciences with emission absorption of 42% or 2,646,253.41 kg/year. There were many academic activities on the UNNES campus and were supported by electronic equipment.
... It is possible that climate-induced drought stress may eventually moderate such regional trends, although elevated carbon dioxide (CO 2 ) that drives a warming climate is thought to also enhance drought tolerance across a broad range of taxa (Peñuelas et al., 2011). Further, CO 2 fertilization is anticipated to enhance tree growth and productivity (Franks et al., 2013, Gustafson et al., 2018b, but tree species vary widely in their response to enriched CO 2 (Kallarackal and Roby, 2012). Warming climate lengthens growing seasons, and in some scenarios, the lengthening is dramatic, resulting in large increases in forest productivity (Duveneck and Thompson, 2017), although individual species may be negatively impacted by heat stress in mid-summer (Teskey et al., 2015). ...
Article
Forest managers have been wrestling with questions of how best to prepare today’s forests for a future climate that may be quite different from the climate under which they were established. We used the LANDIS forest landscape model to conduct a factorial simulation experiment to assess the landscape-wide effects of alternative cutting and planting practices in northern Wisconsin (USA) under three climate change scenarios simulated for 300 years to allow demographic legacies to be overcome by the experimental treatments. Our objective was to assess the relative ability of actionable components of silvicultural strategies to maintain productivity and economical and ecological values of forests under future climates compared to a “business as usual” (BAU) silviculture scenario representing current sustained yield practices. We found that the general effect of climate change was to increase the biomass of all species (CO2 fertilization and increased growing season), although the most cold-adapted species eventually declined under warming climate scenarios. Two alternative silvicultural strategies produced clearly different outcomes compared to the BAU scenario. Total landscape tree biomass was least under BAU, reflecting its high biomass removal rates, and greatest under the most aggressive climate-adapted silviculture strategy coupled with a high CO2 climate scenario due to increased growth and relatively high removal rates. Harvested outputs responded to both climate and silvicultural strategy, with the high CO2 scenario reducing biomass available for harvesting compared to a moderate CO2 scenario, except under the aggressive climate-adapted strategy. Our study suggests that creative silvicultural practices can be developed (and tested) to maintain productive and ecologically healthy forests under future climate conditions.
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The impact of eCO2 is crop and genotype specific. In order to access the impact of the elevated CO2 (550 ppm) two crops with different photosynthetic pathway maize (C4)-an important cereal and groundnut (C3)-leguminous oil seed crops were raised in OTCs. At harvest the biomass and yield parameters were recorded. It was observed that eCO2 improved biomass and yield of both the crops with different magnitudes. It was interesting to observe that the eCO2 condition improved more of reproductive components than vegetative biomass of both the crops. The increased seed number under eCO2 improved the seed yield of both the crops. The higher partitioning of biomass towards economic parts improved the harvest index of the crops.
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Global warming poses great challenges for forest managers regarding adaptation strategies and species choices. More frequent drought events and heat spells are expected to reduce growth and increase mortality. Extended growing seasons, warming and elevated CO2 (eCO2) can also positively affect forest productivity. We studied the growth, productivity and mortality of Fagus sylvatica L. and Abies alba Mill. in the Black Forest (Germany) under three climate change scenarios (representative concentration pathways (RCP): RCP2.6, RCP4.5, RCP8.5) using the detailed biogeochemical forest growth model GOTILWA+. Averaged over the entire simulation period, both species showed productivity losses in RCP2.6 (16–20%) and in RCP4.5 (6%), but productivity gains in RCP8.5 (11–17%). However, all three scenarios had a tipping point (between 2035–2060) when initial gains in net primary productivity (NPP) (6–29%) eventually turned into losses (1–26%). With eCO2 switched off, the losses in NPP were 26–51% in RCP2.6, 36–45% in RCP4.5 and 33–71% in RCP8.5. Improved water-use efficiency dampened drought effects on NPP by between 4 and 5%. Tree mortality increased, but without notably affecting forest productivity. Concluding, cultivation of beech and fir may still be possible in the study region, although severe productivity losses can be expected in the coming decades, which will strongly depend on the dampening CO2 fertilization effect
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Stream water temperature imposes metabolic constraints on the health of cold-water fish like salmonids. Timber harvesting can reduce stream shading leading to higher water temperatures, while also altering stream hydrology. In the Pacific Northwest, riparian buffer requirements are designed to mitigate these impacts; however, anticipated future changes in air temperature and precipitation could reduce the efficacy of these practices in protecting aquatic ecosystems. Using a combined modeling approach (Soil and Water Assessment Tool (SWAT), Shade, and QUAL2K), this study examines the effectiveness of riparian buffers in reducing impacts of timber harvest on stream water temperature in Lookout Creek, Oregon across a range of potential future climates. Simulations assess changes in riparian management alone, climate alone, and combined effects. Results suggest that maximum stream water temperatures during thermal stress events are projected to increase by 3.3–7.4 °C due to hydroclimatic change alone by the end of this century. Riparian management is effective in reducing stream temperature increases from timber harvesting alone but cannot fully counteract the additional effects of a warming climate. Overall, our findings suggest that the protection of sensitive aquatic species will likely require additional adaptation strategies, such as the protection or provisioning of cool water refugia, to enhance survival during maximum thermal stress events. HIGHLIGHTS A range of future climate conditions can negatively impact cold-water fish species during extreme thermal events.; Riparian forest management can help play a role to mitigate impacts of future climate conditions.; Cold-water species may be unable to thrive in pristine traditional ecosystems due to climate impacts which cannot be mitigated during extreme thermal events.; Mature forests are unlikely to shelter pristine freshwater streams from impacts of climate change.; The importance of cold-water refugia and alternative mitigation strategies are likely to become increasingly important by the end of the century to combat climate change.;
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The growth, reproduction, and geographical distribution of plants are profoundly influenced by their physiological ecology: the interaction with the surrounding physical, chemical, and biological environments. This textbook describes mechanisms that underlie plant physiological ecology at the levels of physiology, biochemistry, biophysics, and molecular biology. At the same time, the integrative power of physiological ecology is well suited to assess the costs, benefits, and consequences of modifying plants for human needs and to evaluate the role of plants in ecosystems. Plant Physiological Ecology, Second Edition is significantly updated, with full color illustrations and begins with the primary processes of carbon metabolism and transport, plant water relations, and energy balance. After considering individual leaves and whole plants, these physiological processes are then scaled up to the level of the canopy. Subsequent chapters discuss mineral nutrition and the ways in which plants cope with nutrient-deficient or toxic soils. The book then looks at patterns of growth and allocation, life-history traits, and interactions between plants and other organisms. Later chapters deal with traits that affect decomposition of plant material and with the consequences of plant physiological ecology at ecosystem and global levels. Plant Physiological Ecology, Second Edition features numerous boxed entries that extend the discussions of selected issues, a glossary, and numerous references to the primary and review literature. This significant new text is suitable for use in plant ecology courses, as well as classes ranging from plant physiology to plant molecular biology. From reviews of the first edition: ". the authors cover a wide range of plant physiological aspects which up to now could not be found in one book.. The book can be recommended not only to students but also to scientists working in general plant physiology and ecology as well as in applied agriculture and forestry." - Journal of Plant Physi logy "This is a remarkable book, which should do much to consolidate the importance of plant physiological ecology as a strongly emerging discipline. The range and depth of the book should also persuade any remaining skeptics that plant physiological ecology can offer much in helping us to understand how plants function in a changing and complex environment." - Forestry "This book must be regarded as the most integrated, informative and accessible account of the complexities of plant physiological ecology. It can be highly recommended to graduate students and researchers working in all fields of plant ecology." - Plant Science ". there is a wealth of information and new ideas here, and I strongly recommend that this book be on every plant ecophysiologist's shelf. It certainly represents scholarship of the highest level, and many of us will find it a useful source of new ideas for future research." - Ecology. © 2008 Springer Science+Business Media, LLC. All rights reserved.
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Radiata pine (Pinus radiata D.Don) and red beech (Nothofagus fusca (Hook. f.) Oerst.) were grown for over 1 year at elevated (ELEV, 64 Pa) and ambient (AMB, 38 Pa) CO2 partial pressure in open-top chambers. Springtime measurements of overwintering leaves showed that light- and CO2-saturated photosynthetic rates (Amax) of pine leaves were similar for the two treatments (AMB: 6.7 ± 1.08 μmol m-2 s-1, mean ± 1 s.e.; ELEV: 6.6 ± 0.47) but, for beech leaves, Amax was greater for AMB plants (8.8 ± 0.90 μmol m-2 s-1) than for ELEV plants (6.10 ± 0.71). Summertime measurements of leaves grown that spring showed that for pine, Amax was similar in the two CO2 treatments (AMB 14.9 μmol m-2 s-1 ± 0.80; ELEV: 13.5 ± 1.9) while, for beech, Amax was higher in AMB plants (21.0 ± 1.1) than in ELEV plants (17.2 ± 1.9), although the difference was not statistically significant. These results indicate downregulation of photosynthetic capacity of beech but not pine. Vcmax did not differ between treatments within species, suggesting that there was no acclimation of rubisco activity. Triose phosphate utilisation limitation may have contributed to the downregulation of Amax in beech. For pine, photosynthesis at treatment CO2 partial pressures was greater in ELEV plants in both spring and summer. For beech measured at treatment CO2 partial pressures, photosynthesis was greater in ELEV plants in summer, but was similar between treatments in the springtime.
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Projected climate warming will potentially have profound effects on the earth's biota, including a large redistribution of tree species. We developed models to evaluate potential shifts for 80 individual tree species in the eastern United States. First, environmental factors associated with current ranges of tree species were assessed using geographic information systems (GIS) in conjunction with regression tree analysis (RTA). The method was then extended to better understand the potential of species to survive and/or migrate under a changed climate. We collected, summarized, and analyzed data for climate, soils, land use, elevation, and species assemblages for >2100 counties east of the 100th meridian. Forest Inventory Analysis (FIA) data for >100 000 forested plots in the East provided the tree species range and abundance information for the trees. RTA was used to devise prediction rules from current species-environment relationships, which were then used to replicate the current distribution as well as predict the future potential distributions under two scenarios of climate change with twofold increases in the level of atmospheric CO2. Validation measures prove the utility of the RTA modeling approach for mapping current tree importance values across large areas, leading to increased confidence in the predictions of potential future species distributions. With our analysis of potential effects, we show that roughly 30 species could expand their range and/or weighted importance at least 10%, while an additional 30 species could decrease by at least 10%, following equilibrium after a changed climate. Depending on the global change scenario used, 4-9 species would potentially move out of the United States to the north. Nearly half of the species assessed (36 out of 80) showed the potential for the ecological optima to shift at least 100 km to the north, including seven that could move >250 km. Given these potential future distributions, actual species redistributions will be controlled by migration rates possible through fragmented landscapes.
Article
The nature of photosynthetic acclimation to elevated CO2 is evaluated from the results of over 40 studies focusing on the effect of long-term CO2 enrichment on the short-term response of photosynthesis to intercellular CO2 (the A/Ci response). The effect of CO2 enrichment on the A/Ci response was dependent on growth conditions, with plants grown in small pots (< 5 L) or low nutrients usually exhibiting a reduction of A at a given Ci, while plants grown without nutrient deficiency in large pots or in the field tended to exhibit either little reduction or an enhancement of A at a given Ci following a doubling or tripling of atmospheric CO2 during growth. Using theoretical interpretations of A/Ci curves to assess acclimation, it was found that when pot size or nutrient deficiency was not a factor, changes in the shape of A/Ci curves which are indicative of a reallocation of resources within the photosynthetic apparatus typically were not observed. Long-term CO2 enrichment usually had little effect or increased the value of A at all Ci. However, a minority of species grown at elevated CO2 exhibited gas exchange responses indicative of a reduced amount of Rubisco and an enhanced capacity to metabolize photosynthetic products. This type of response was considered beneficial because it enhanced both photosynthetic capacity at high CO2 and reduced resource investment in excessive Rubisco capacity. The ratio of intercellular to ambient CO2 (the Ci/Ca ratio) was used to evaluate stomatal acclimation. Except under water and humidity stress, Ci/Ca exhibited no consistent change in a variety of C3 species, indicating no stomatal acclimation. Under drought or humidity stress, Ci/Ca declined in high-CO2 grown plants, indicating stomata will become more conservative during stress episodes in future high CO2 environments.