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Journal ArticleDOI

Partitioning of remobilised N in young beech (Fagus sylvatica L.) is not affected by elevated [CO2]

01 Apr 2005-Annals of Forest Science (EDP Sciences)-Vol. 62, Iss: 3, pp 285-288
TL;DR: Les effets de concentrations elevees en CO 2 sur la remobilisation de l'azote interne de plants de hetre (Fagus sllvatica L.) âges de 3 ans ont ete etudies dans une experimentation avec marquage as discussed by the authors.
Abstract: Les effets de concentrations elevees en CO 2 sur la remobilisation de l'azote interne de plants de hetre (Fagus sllvatica L.) âges de 3 ans ont ete etudies dans une experimentation avec marquage. Les arbres ont ete pretraites avec du 15N pendant un an et la remobilisation de l'azote stocke a ete suivie a des concentrations de 350 ppm et de 700 ppm l'annee suivante. L'azote fixe pendant le pretraitement correspond a 24,7 % de l'azote total au debut de l'experi-mentation. Cette valeur etait presque diminuee de moitie apres 24 semaines de croissance pour les deux traitements etudies. Des differences significatives dans la partition de l'azote remobilise ont ete observees seulement de facon passagere apres 6 semaines de croissance mais il n'a pas ete observe d'effet du CO 2 a la fin de la periode de croissance.

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2. MATERIALS AND METHODS

  • The results were expressed as arithmetic means with standard deviation.
  • The t-test was used to determine significant differences between the treatments in individual plant organs.

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285
Ann. For. Sci. 62 (2005) 285–288
© INRA, EDP Sciences, 2005
DOI: 10.1051/forest:2005021
Note
Partitioning of remobilised N in young beech (Fagus sylvatica L.)
is not affected by elevated [CO
2
]
Jens DYCKMANS
a,b
, Heiner FLESSA
c
a
Centre for Stable Isotope Research and Analysis, Forest Ecosystems Research Centre, University Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
b
Environmental Resource Management, Faculty of Agriculture, University College Dublin, Belfield, Dublin 4, Ireland
c
Institute of Soil Science and Forest Nutrition, University Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
(Received 13 May 2004; accepted 27 September 2004)
Abstract – Effects of elevated CO
2
concentration ([CO
2
]) on the remobilisation of tree internal nitrogen (N) of 3-year-old beech (Fagus
sylvatica L.) was determined in a labeling experiment. Trees were pre-treated with
15
N for 1 year and the remobilization of stored N was
monitored in ambient (350 ppm) or elevated [CO
2
] (700 ppm) in the subsequent year. N taken up during the pre-treatment made up 24.7% of
total N at the start of the experiment. This value was almost halved after 24 weeks of growth for both CO
2
-treatments. Significant differences
in the partitioning of the remobilized N were only observed transiently after 6 weeks of growth but no CO
2
-effect was observed at the end of
the growing season.
elevated carbon-dioxide / N cycling / N partitioning / remobilization / stable isotope
Résumé – La partition de N remobilisé chez de jeunes hêtres (Fagus sylvatica L.) n’est pas affectée par une concentration élevée en CO
2
.
Les effets de concentrations élevées en CO
2
sur la remobilisation de l’azote interne de plants de hêtre (Fagus silvatica L.) âgés de 3 ans ont été
étudiés dans une expérimentation avec marquage. Les arbres ont été prétraités avec du
15
N pendant un an et la remobilisation de l’azote stocké
a été suivie a des concentrations de 350 ppm et de 700 ppm l’année suivante. L’azote fixé pendant le prétraitement correspond à 24,7 % de
l’azote total au début de l’expéri-mentation. Cette valeur était presque diminuée de moitié après 24 semaines de croissance pour les deux
traitements étudiés. Des différences significatives dans la partition de l’azote remobilisé ont été observées seulement de façon passagère après
6 semaines de croissance mais il n’a pas été observé d’effet du CO
2
à la fin de la période de croissance.
concentration élevée en gaz carbonique / cycle de N / partition de N / remobilisation / isotope stable
1. INTRODUCTION
Tree internal N cycling allows uncoupling of growth from
N uptake; especially in spring, growth of deciduous trees relies
to a great extent on the remobilisation of stored N [5, 9, 20].
Elevated [CO
2
] has been shown to increase C uptake and
growth in trees. However, especially in nutrient poor environ-
ments, the effect of elevated [CO
2
] might be limited by N avail-
ability [11, 13, 17]. Many studies deal with the effects of ele-
vated [CO
2
] on the uptake of N from the soil (e.g. [1]) but there
has been only little work on N remobilisation in trees under ele-
vated [CO
2
]. Temperton et al. [15] found for two year old Pinus
sylvestris that N remobilisation was unaffected by elevated
[CO
2
].
The formation and remobilisation of internal N stores play
an important role for tree growth [9] and thus probably for the
long-term response to elevated [CO
2
]. Generally, tissue N con-
centration in trees under elevated [CO
2
] tends to decrease [2],
indicating that store formation is not increased under elevated
[CO
2
]. It has been shown, that N stores formation in beech
(Fagus sylvatica L.) was not increased under elevated [CO
2
],
but might even be decreased under unfavourable conditions [6].
The aim of the present study was to examine the effect of
elevated [CO
2
] on the partitioning of internal N remobilisation
in young beech. Therefore, trees were pretreated with
15
N for
1 year under ambient [CO
2
] and the remobilization of stored
15
N was monitored in the subsequent growing season under
ambient and elevated [CO
2
].
* Corresponding author: jdyckma@gwdg.de
Article published by EDP Sciences and available at http://www.edpsciences.org/forestor http://dx.doi.org/10.1051/forest:2005021

286 J. Dyckmans, H. Flessa
2. MATERIALS AND METHODS
Three-year-old beech trees (Fagus sylvatica L.) from a tree nursery
were examined in our experiment. To obtain trees with labelled N
stores, the trees were grown on sand for one year and fertilized with
a
15
NH
4
15
NO
3
(25 atom%) nutrient solution (pre-treatment). During
the experiment in the following year, trees were placed into growth
chambers (see below), supplied with 2 mM unlabelled NH
4
NO
3
and
grown at 350 or 700 ppm CO
2
in the chamber atmosphere. At the
beginning of the CO
2
-experiment, trees had an average dry weight of
17 g which increased to 29 g at week 24 for both treatments.
For the experiment, beeches were planted on sand into cylinders
of PVC (height 0.3 m, diameter 0.14 m). Irrigation was achieved by
weekly feeding of 130 cm
3
of a Hoagland-based nutrient solution
(2 mM NH
4
NO
3
). The microcosms were installed in closed growth
chambers at an atmospheric CO
2
concentration of 350 and 700 ppm
CO
2
for the two treatments, respectively. During the CO
2
experiment,
the chamber atmosphere was labelled in CO
2
to assess the C uptake during
the experiment. The trees grew at a light level of 130 µmol m
–2
s
–1
for a 12 h day length. Temperatures varied between 13 °C in the night
and 18 °C during daytime. Relative humidity was maintained at 75%.
Details of the growth chamber system are given in Dyckmans et al. [4].
At the beginning of the experiment (after the pre-treatment) and
after 6, 12, 18 and 24 weeks of growth, five plants per treatment were
harvested. The plants were divided into seven plant organs: buds,
leaves, new branches, old branches, stem, coarse roots (> 2 mm) and
fine roots (< 2 mm). Plant samples were dried at 65 °C and finely
ground. To distinguish between the formation of new plant organs and
the growth of old tissues the plant compartments were combined to
new shoots (buds, leaves and new branches), old shoots (old branches,
stem) and roots (coarse and fine roots) for the presentation in the results
section.
The labelling of the N uptake during the pre-treatment allowed ana-
lysing the remobilization of stored N. The labelled N represents only
a part of the total remobilised N during the CO
2
-experiment since N
taken up during earlier seasons will also be remobilised.
The relative specific allocation (RSA) describes the fraction of
labelled C or N in the tissue relative to total C or N in a given sample.
The partitioning describes the proportion of the labelled element in a
given plant organ relative to the total labelled element in the whole
plant [3, 6].
The results were expressed as arithmetic means with standard devi-
ation. The t-test was used to determine significant differences between
the treatments in individual plant organs. Probabilities of less than 0.05
were considered to be significant whereas probabilities of 0.1 > P
0.05 were considered to indicate a trend.
3. RESULTS AND DISCUSSION
Carbon uptake during the experiment was significantly
increased under elevated [CO
2
], as was indicated by the
increase in RSA of new C in the elevated treatment by 27%
from 30.5 ± 2.8 under ambient to 38.6 ± 5.7% under elevated
[CO
2
], which is comparable to results we obtained earlier [6].
Labelled N made up 24.7% of total N before bud break (Fig. 1).
As a result of N uptake from the soil, this value gradually
decreased to 13.7 and 12.3% at Week 24 under ambient and ele-
vated [CO
2
], and throughout the experiment, no CO
2
-effect
was observed.
Before bud break, 75.4% of the labelled N was located in
the root system. During the first 6 weeks after bud break, large
quantities of N were allocated to the new shoot (which at that
time consisted mainly of leaves) and at Week 6, 26.6 and 19.4%
of labelled N were found in the new shoot for the 350 and
700 ppm treatment, respectively (Fig. 2). Both old shoot and
coarse roots acted as a source of remobilised N during this
period. The partitioning to the old shoot dropped from 23% to
10 and 7% in the ambient and elevated treatment (Fig. 2), the
partitioning to coarse roots similarly decreased from 22 to 11%
in both treatments (data not shown). It has been shown earlier
that perennial organs (i.e. roots and stem) served as N stores
for spring growth in deciduous trees, e.g. Betula pendula [10],
Juglans regia [19] or Prunus persica [14]. Marmann et al. [8]
showed that in Fraxinus excelsior N was mainly stored in the
roots, whereas our data indicate that in beech N stocks in coarse
roots and stem contributed about the same portion to new shoot
growth.
Significant differences in the partitioning of labelled N
between the ambient and elevated treatment were only
observed at Week 6: The partitioning to roots was higher under
elevated [CO
2
], while partitioning to new shoot was signifi-
cantly decreased (Fig. 2), combined with a trend of decreased
partitioning to old shoots under elevated [CO
2
]. This was asso-
ciated with a significant decrease in N concentration in the
aboveground compartments under elevated [CO
2
] (data not
shown). These data might indicate that N demand was
increased for root growth to increase N uptake and as a conse-
quence less N was allocated to the aboveground compartments
under elevated [CO
2
] as compared to ambient. During the fol-
lowing weeks, however, partitioning of labelled N increased in
the shoots and decreased in the roots in the elevated treatment,
and at Week 12, no difference in the partitioning of labelled N
was observed between the two treatments, nor were there dif-
ferences in N concentration.
Figure 1. Fraction of labelled N (i.e. taken up during the previous
year) on total N (RSA) on the whole plant level during the CO
2
expe-
riment. Means and standard deviation (n =5).
Article published by EDP Sciences and available at http://www.edpsciences.org/forestor http://dx.doi.org/10.1051/forest:2005021

N cycling in beech is not affected by elevated [CO
2
] 287
In both treatments, partitioning of remobilised N in the old
shoot increased after Week 6, while partitioning to new shoot
decreased after Week 12. The partitioning to roots did not alter
significantly after Week 12. At Week 24, 68.1 and 61.0% of
remobilised N was found in the roots for the 350 and 700 ppm
treatment, respectively.
Our data indicate that the partitioning of remobilised N is
largely unaffected by the atmospheric [CO
2
]. In an earlier study
this was also found for the partitioning and amount of new N
uptake although the partitioning of new C to roots and root res-
piration was increased under elevated [CO
2
] as compared to
ambient [6]. In this latter study, we could also show that no
increased N store formation was observed under elevated
[CO
2
]. Temperton et al. [15] reported similar results for Pinus
sylvestris, where N store formation and the partitioning of
remobilised N were not altered under elevated [CO
2
]. For the
N
2
fixing Alnus glutinosa, however, they reported an increased
N store formation in winter and increased N remobilisation for
leaf growth in spring under elevated [CO
2
]. Similar results of
increased N stores formation have been reported earlier for
Alnus glutinosa [18] but also for Robinia pseudoacacia [7, 12],
and the tropical tree species Gliricidia sepium [16].
Taken together these data suggest that young non-fixing tree
species are less responsive to increased C assimilation in terms
of increasing N uptake than N
2
-fixing trees. Ultimately, this
might indicate that the effect of elevated [CO
2
] on tree growth
in non-fixing species will be limited by N availability. The tree
internal cycling of N might help to overcome this N deficiency
under elevated [CO
2
]. Nevertheless, our results give no evi-
dence for a response of internal N cycling to elevated [CO
2
] in
young beech.
However, it should be taken into account that our results only
reflect the short-term response to elevated [CO
2
] and so far
there are no results on the long-term CO
2
-effect on internal C
cycling in trees.
Acknowledgements: The research was founded by the DFG (Schwer-
punktprogramm “Stoffwechsel und Wachstum der Pflanze unter
erhöhter CO
2
-Konzentration”). J. Dyckmans was partly financially
supported by COFORD (National Council for Forest Research and
Development), Ireland.
REFERENCES
[1] Bauer G., Berntson G., Ammonium and nitrate acquisition by
plants in response to elevated CO
2
concentration: the roles of root
physiology and architecture, Tree Physiol. 21 (2001) 137–144.
[2] Cotrufo M.F., Ineson P., Scott A., Elevated CO
2
reduces the nitro-
gen concentration of plant tissues, Glob. Change Biol. 4 (1998) 43–54.
[3] Deléens E., Cliquet J.B., Prioul J.L., Use of
13
C and
15
N plant label
near natural abundance for monitoring carbon and nitrogen partitio-
ning, Aust. J. Plant. Physiol. 21 (1994) 133–146.
[4] Dyckmans J., Flessa H., Polle A., Beese F., The effect of elevated
[CO
2
] on uptake and allocation of
13
C and
15
N in beech (Fagus syl-
vatica L.) during leafing, Plant Biol. 2 (2000) 113–120.
[5] Dyckmans J., Flessa H., Influence of tree internal N status on
uptake and translocation of C and N in beech: a dual
13
C and
15
N
labelling approach, Tree Physiol. 21 (2001) 395–401.
[6] Dyckmans J., Flessa H., Influence of tree internal nitrogen reserves
on the response of beech (Fagus sylvatica) trees to elevated atmos-
pheric carbon dioxide concentration, Tree Physiol. 22 (2002) 41–49.
[7] Feng Z., Dyckmans J., Flessa, H., Effects of elevated [CO
2
] on
growth and N
2
fixation of young Robinia pseudoacacia, Tree Phy-
siol. 24 (2004) 323–330.
[8] Marmann P., Wendler R., Millard P., Heilmeier H., Nitrogen sto-
rage and remobilization in ash (Fraxinus excelsior) under field and
laboratory conditions, Trees 11 (1997) 298–305.
[9] Millard P., Ecophysiology of the internal cycling of nitrogen for
tree growth, Z. Pflanzenernähr. Bodenkd. 159 (1996) 1–10.
[10] Millard P., Wendler R., Hepburn A., Smith A., Variations in the
amino acid composition of xylem sap of Betula pendula Roth. trees
due to remobilization of stored N in the spring, Plant Cell Environ.
21 (1998) 715–722.
[11] Murray M.B., Smith R.I., Friend A., Jarvis P.G., Effect of elevated
[CO
2
] and varying nutrient application rates on physiology and bio-
mass accumulation of Sitka spruce (Picea sitchensis), Tree Physiol.
20 (2000) 421–434.
[12] Olesniewicz K.S., Thomas R.B., Effects of mycorrhizal coloniza-
tion on biomass production and nitrogen fixation of black locust
Figure 2. Partitioning of labelled N (i.e. taken up during the previous
year) in different plant compartments during the CO
2
experiment
under ambient (squares, solid lines) and elevated [CO
2
] (dots, broken
lines). Means and standard deviation (n = 5). An asterisk indicates
significant differences between treatments (P < 0.05) and ° indicates
a trend (P < 0.1).
Article published by EDP Sciences and available at http://www.edpsciences.org/forestor http://dx.doi.org/10.1051/forest:2005021

288 J. Dyckmans, H. Flessa
(Robinia pseudoacacia) seedlings grown under elevated atmo-
spheric carbon dioxide, New Phytol. 142 (1999) 133–140.
[13] Saxe H., Ellsworth D.S., Heath J., Tree and forest functioning in an
enriched CO
2
atmosphere, New Phytol. 139 (1998) 395–436.
[14] Tagliavini M., Millard P., Quartieri M., Marangoni B., Timing of
nitrogen uptake affects winter storage and spring remobilisation of
nitrogen in nectarine (Prunus persica var. nectarina) trees, Plant
Soil 211 (1999) 149–153.
[15] Temperton V.M., Millard P., Jarvis P.G., Does elevated atmosphe-
ric carbon dioxide affect internal nitrogen allocation in the tempe-
rate trees Alnus glutinosa and Pinus sylvestris? Glob. Change Biol.
9 (2003) 286–294.
[16] Tissue D.T., Megonigal J.P., Thomas R.B., Nitrogenase activity
and N
2
fixation are stimulated by elevated CO
2
in a tropical N
2
-
fixing tree, Oecologia 109 (1997) 28–33.
[17] Tognetti R., Johnson J.D., Responses of growth, nitrogen and car-
bon partitioning to elevated atmospheric CO
2
concentration in live
oak (Quercus virginiana Mill.) seedlings in relation to nutrient sup-
ply, Ann. For. Sci. 56 (1999) 91–105.
[18] Vogel C.S., Curtis P.S., Thomas R.B., Growth and nitrogen accre-
tion of dinitrogen-fixing Alnus glutinosa L. Gaertn. under elevated
carbon dioxide, Plant Ecol. 130 (1997) 63–70.
[19] Weinbaum S.A., van Kessel C., Quantitative estimates of uptake
and internal cycling of
14
N-labeled fertilizer in mature walnut trees,
Tree Physiol. 18 (1998) 795–801.
[20] Wendler R., Millard P., Impacts of water and nitrogen supplies on
the Physiol., leaf demography and nitrogen dynamics of Betula
pendula, Tree Physiol. 16 (1996) 153–159.
To access this journal online:
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Citations
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Journal ArticleDOI
TL;DR: The role of carbon (C) and nitrogen (N) storage by trees will be discussed in terms of uncoupling their growth from resource acquisition, allowing trees to uncouple seasonal growth from N uptake by roots and allowing recovery from disturbances such as browsing damage.
Abstract: Summary The role of carbon (C) and nitrogen (N) storage by trees will be discussed in terms of uncoupling their growth from resource acquisition. There are profound differences between the physiology of C and N storage. C storage acts as a short-term, temporary buffer when photosynthesis cannot meet current sink demand and remobilization is sink driven. However, the majority of C allocated to non-structural carbohydrates such as starch is not reused so is in fact sequestered, not stored. In contrast, N storage is seasonally programmed, closely linked to tree phenology and operates at temporal scales of months to years, with remobilization being source driven. We examine the ecological significance of N storage and remobilization in terms of regulating plant N use efficiency, allowing trees to uncouple seasonal growth from N uptake by roots and allowing recovery from disturbances such as browsing damage. We also briefly consider the importance of N storage and remobilization in regulating how trees will likely respond to rising atmospheric carbon dioxide concentrations. Most studies of N storage and remobilization have been restricted to small trees growing in a controlled environment where 15 N can be used easily as a tracer for mineral N. We highlight the need to describe and quantify these processes for adult trees in situ where most root N uptake occurs via ectomycorrhizal partners, an approach that now appears feasible for deciduous trees through quantification of the flux of remobilized N in their xylem. This opens new possibilities for studying interactions between N and C allocation in trees and associated mycorrhizal partners, which are likely to be crucial in regulating the response of trees to many aspects of global environmental change.

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  • ...N remobilization by deciduous trees appears to be unaffected by elevated CO2 (Dyckmans and Flessa 2005, Vizoso et al. 2008)....

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TL;DR: Through effects on the C and N content of perennial organs, elevated [CO(2)] and HN increased remobilization capacity, thereby supporting multiple shoot flushes, which increased leaf area and subsequent C acquisition in a positive feedback loop.
Abstract: Soil nitrogen can alter storage and remobilization of carbon and nitrogen in forest trees and affect growth responses to elevated carbon dioxide concentration ([CO(2)]). We investigated these effects in oak saplings (Quercus robur L.) exposed for two years to ambient or twice ambient [CO(2)] in combination with low- (LN, 0.6 mmol N l(-1)) or high-nitrogen (HN, 6.1 mmol N l(-1)) fertilization. Autumn N retranslocation efficiency from senescing leaves was less in HN saplings than in LN saplings, but about 15% of sapling N was lost to the litter. During the dormant season, nonstructural carbohydrates made up 20 to 30% of the dry mass of perennial organs. Starch was stored mainly in large roots where it represented 35-46% of dry mass. Accumulation of starch increased in large roots in response to LN but was unaffected by elevated [CO(2)]. The HN treatment resulted in high concentrations of N-soluble compounds, and this effect was reduced by elevated [CO(2)], which decreased soluble protein N (-17%) and amino acid N (-37%) concentrations in the HN saplings. Carbon and N reserves were labeled with (13)C and (15)N, respectively, at the end of the first year. In the second year, about 20% of labeled C and 50% of labeled N was remobilized for spring growth in all treatments. At the end of leaf expansion, 50-60% of C in HN saplings originated from assimilation versus only 10-20% in LN saplings. In HN saplings only, N uptake occurred, and some newly assimilated N was allocated to new shoots. Through effects on the C and N content of perennial organs, elevated [CO(2)] and HN increased remobilization capacity, thereby supporting multiple shoot flushes, which increased leaf area and subsequent C acquisition in a positive feedback loop.

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References
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Journal ArticleDOI
TL;DR: It is concluded that positive effects of CO2 on leaf area can be at least as important in determining canopy transpiration as negative, direct effects ofCO2 on stomatal aperture and that elevated CO2 can accelerate the appearance of nutrient limitations with increasing time of treatment.
Abstract: Forests exchange large amounts of CO2 with the atmosphere and can influence and be influenced by atmospheric CO2. There has been a recent proliferation of literature on the effects of atmospheric CO2 on forest trees. More than 300 studies of trees on five different continents have been published in the last five years. These include an increasing number of field studies with a long-term focus and involving CO2×stress or environment interactions. The recent data on long-term effects of elevated atmospheric CO2 on trees indicate a potential for a persistent enhancement of tree growth for several years, although the only relevant long-term datasets currently available are for juvenile trees. The current literature indicates a significantly larger average long-term biomass increment under elevated CO2 for conifers (130%) than for deciduous trees (49%) in studies not involving stress components. However, stimulation of photosynthesis by elevated CO2 in long-term studies was similar for conifers (62%) and deciduous trees (53%). Recent studies indicate that elevated CO2 causes a more persistent stimulation of biomass increment and photosynthesis than previously expected. Results of seedling studies, however, might not be applicable to other stages of tree development because of complications of age-dependent and size-dependent shifts in physiology and carbon allocation, which are accelerated by elevated CO2. In addition, there are many possible avenues to down-regulation, making the predicted canopy CO2 exchange and growth of mature trees and forests in a CO2-rich atmosphere uncertain. Although, physiological down-regulation of photosynthetic rates has been documented in field situations, it is rarely large enough to offset entirely photosynthetic gains in elevated CO2. A persistent growth stimulation of individual mature trees has been demonstrated although this effect is more uncertain in trees in natural stands. Resource interactions can both constrain tree responses to elevated CO2 and be altered by them. Although drought can reduce gas-exchange rates and offset the benefits of elevated CO2, even in well watered trees, stomatal conductance is remarkably less responsive to elevated CO2 than in herbaceous species. Stomata of a number of tree species have been demonstrated to be unresponsive to elevated CO2. We conclude that positive effects of CO2 on leaf area can be at least as important in determining canopy transpiration as negative, direct effects of CO2 on stomatal aperture. With respect to nutrition, elevated CO2 has the potential to alter tree–soil interactions that might influence future changes in ecosystem productivity. There is continued evidence that in most cases nutrient limitations diminish growth and photosynthetic responses to elevated CO2 at least to some degree, and that elevated CO2 can accelerate the appearance of nutrient limitations with increasing time of treatment. In many studies, tree biomass responses to CO2 are artefacts in the sense that they are merely responses to CO2-induced changes in internal nutritional status of the tree. There are numerous interactions between CO2 and factors of the biotic and abiotic environment. The importance of increasing atmospheric CO2 concentrations for productivity is likely to be overestimated if these are not taken into account. Many interactions, however, are simply additive rather than synergistic or antagonistic. This appears to hold true for many parameters under elevated CO2 in combination with temperature, elevated O3, and other atmospheric pollutants. However, there is currently little evidence that elevated CO2 will counteract O3 damage. When the foliage content of C, mineral nutrients and secondary metabolites is altered by elevated CO2, tree×insect interactions are modified. In most trees, mycorrhizal interactions might be less important for direct effects of CO2 than for alleviating general nutrient deficiencies. Since many responses to elevated CO2 and their interactions with stress show considerable variability among species/genotypes, one principal research need is for comparative studies of a large variety of woody species and ecosystems under realistic conditions. We still need more long-term experiments on mature trees and stands to address critical scaling issues likely to advance our understanding of responses to elevated CO2 at different stages of forest development and their interactions with climate and environment. The only tools available at present for coping with the consequences of rising CO2 are management of resources and selection of genotypes suitable for the future climate and environment.

719 citations

Journal ArticleDOI
TL;DR: Data are presented to support the hypothesis that reductions in the quality of plant tissue commonly occur when plants are grown under elevated CO2, as the reported reductions in N have been larger in C3 plants than in C4 plants and N2-fixers.
Abstract: We summarize the impacts of elevated CO2 on the N concentration of plant tissues and present data to support the hypothesis that reductions in the quality of plant tissue commonly occur when plants are grown under elevated CO2. Synthesis of existing data showed an average 14% reduction of N concentrations in plant tissue generated under elevated CO2 regimes. However, elevated CO2 appeared to have different effects on the N concentrations of different plant types, as the reported reductions in N have been larger in C3 plants than in C4 plants and N2-fixers. Under elevated CO2 plants changed their allocation of N between above- and below-ground components: root N concentrations were reduced by an average of 9% compared to a 14% average reduction for above-ground tissues. Although the concentration of CO2 treatments represented a significant source of variance for plant N concentration, no consistent trends were observed between them.

641 citations

Journal ArticleDOI
Peter Millard1
TL;DR: In this paper, a review of the internal cycling of nitrogen in trees is presented, along with the methods used to quantify their contribution to tree growth and their effect on the seasonal growth of both evergreen and deciduous trees.
Abstract: Internal cycling of nitrogen has been shown to be a major source of nitrogen used for the seasonal growth of both evergreen and deciduous trees providing up to 90% of N used for leaf growth of some species. The processes of internal cycling comprise seasonal nitrogen storage, followed by remobilisation during either periods of growth (e.g. in the spring) or during leaf senescence. The ecophysiology of these processes is reviewed, along with the methods used to quantify their contribution to tree growth. Nitrogen budget studies have been widely used to estimate internal cycling, particularly in relation to soil fertility. These studies have shown that as trees develop their rate of N uptake decreases, but as they grow their storage capacity increases, However, budget studies are imprecise and have not always quantified remobilisation adequately. An alternative approach has been the use of 15N to quantify N uptake and partitioning, allowing precise measurements of N storage and remobilisation to be made. The use of isotopes has allowed experiments to be run which have shown that environmental factors such as soil fertility influence the amount of N stored, but have no direct influence upon the amount of N remobilised. These methods are discussed in light of recent research on N remobilisation, which has provided an understanding of the processes of storage and remobilisation which potentially allows direct measurements to be made in field grown trees for the first time.

299 citations


"Partitioning of remobilised N in yo..." refers background in this paper

  • ...The formation and remobilisation of internal N stores play an important role for tree growth [9] and thus probably for the long-term response to elevated [CO2]....

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  • ...Tree internal N cycling allows uncoupling of growth from N uptake; especially in spring, growth of deciduous trees relies to a great extent on the remobilisation of stored N [5, 9, 20]....

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Journal ArticleDOI
TL;DR: It is shown that the use of stable isotopes near their naturally occurring concentrations allows the tracing of new C or N input with precision, and is suitable for monitoring long-term partitioning.
Abstract: Tracing with stable isotopes by using naturally or weakly labelled compounds has become a reliable approach in metabolic studies due to the high precision of isotope measurement by mass spectrometers fitted for natural range. Rapid and numerous isotope ratio determinations are now possible due to the recent automation of analyses. Three methods of analysis of carbon and nitrogen partitioning are reviewed from experiments on maize plants: (a) use of natural differences in organ isotope composition; (b) labelling with industrial CO2 naturally depleted in 13C; (c) double C and N labelling with CO2 and NO3 slightly enriched in 13C and 15N. For method (c) which is the most precise, the obtaining of plant matter with 13C and 15N label near their natural isotope abundance (1.1% for C and 0.36% for N) as well the principles of exposure and apparatus for feeding plants are described. Calculations of distribution parameters (relative specific allocation, RSA, and partitioning, %P) are presented and compared with their use in high-enrichment experiments. The precision of parameters and the theoretical or practical limitations of the methods are discussed. We show that the use of stable isotopes near their naturally occurring concentrations allows the tracing of new C or N input with precision, and is suitable for monitoring long-term partitioning. The significant advantages of this method with respect to precision, security and cost of handling compared with high abundance or radioactive tracing are discussed.

90 citations

Journal ArticleDOI
TL;DR: It is concluded that the growth of beech is strongly determined by the availability of tree internal N stores, whereas the current N supply is of less importance.
Abstract: Influence of plant internal nitrogen (N) stocks on carbon (C) and N uptake and allocation in 3-year-old beech (Fagus sylvatica L.) was studied in two 15N- and 13C-labeling experiments. In the first experiment, trees were grown in sand and received either no N nutrition (-N treatment) or 4 mM unlabeled N (+N treatment) for 1 year. The -N- and +N-pretreated trees were then supplied with 4 mM 15N and grown in a 13CO2 atmosphere for 24 weeks. In the second experiment, trees were pretreated with 4 mM 15N for 1 year and then supplied with unlabeled N for 24 weeks and the remobilization of stored 15N was monitored. On the whole-plant level, uptake of new C was significantly reduced in -N-pretreated trees; however, partitioning of new C was not altered, although there was a trend toward increased belowground respiration. The amount of N taken up was not influenced by N nutrition in the previous year. In +N-pretreated trees, partitioning of new N was dominated by the fine roots (59.7% at Week 12), whereas in -N-pretreated trees, partitioning of new N favored stem, coarse roots and fine roots (24, 21 and 31.9%, respectively, at Week 12), indicating the formation of N stores. The contribution of previous-year N to leaf N was about 15%. The N remobilized for leaf formation had been stored in stem and coarse roots. We conclude that, within a growing season, the growth of beech is strongly determined by the availability of tree internal N stores, whereas the current N supply is of less importance.

81 citations


"Partitioning of remobilised N in yo..." refers background in this paper

  • ...Tree internal N cycling allows uncoupling of growth from N uptake; especially in spring, growth of deciduous trees relies to a great extent on the remobilisation of stored N [5, 9, 20]....

    [...]

Frequently Asked Questions (1)
Q1. What contributions have the authors mentioned in the paper "Partitioning of remobilised n in young beech (fagus sylvatica l.) is not affected by elevated [co2]" ?

In this paper, the effects of elevated CO2 concentration ( CO2 ) on the remobilization of tree internal nitrogen ( N ) of 3-year-old beech ( Fagus sylvatica L. ) was determined in a labeling experiment.