Effects of water availability, nitrogen supply and atmospheric CO2 concentrations on plant nitrogen natural abundance values

The relative effects of soil N, water supply and elevated atmospheric CO2 on foliar δ15N values were examined. Phalaris arundinacea L. (Holdfast) and Physalis peruviana L. (Cape Gooseberry) were grown for 80 d with three water availability treatments, two atmospheric CO2 concentrations and four N supply rates. Elevated CO2 increased total plant biomass and N for each treatment and decreased allocation to roots, leaf N concentrations and stomatal conductance. Leaves had less negative leaf δ13C values under low water supply associated with decreased stomatal conductance and increased leaf N concentration, which decreased the ratio of intercellular to ambient CO2 concentration. The δ15N value of the supplied nitrate (4.15‰) was similar to the value for Phalaris leaves (4.11‰), but Cape Gooseberry leaves were enriched (6.52‰). The effects of elevated CO2 on leaf δ15N values were small, with Phalaris showing no significant change, while Cape Gooseberry showed a significant (P < 0.05) decline of 0.42 ‰. Variation in δ15N values was unrelated to stomatal conductance, transpiration, differential use of N forms or denitrification. Plants with low foliar N concentrations tended to be depleted in 15N. We suggest that changes in N allocation alter foliar δ15N values under different CO2 and water treatments.

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The hot and the cold: unravelling the variable response of plant respiration to temperature

Functional Plant Biology ◽

10.1071/fp03176 ◽

2005 ◽

Vol 32 (2) ◽

pp. 87 ◽

Cited By ~ 320

Author(s):

Owen K. Atkin ◽

Dan Bruhn ◽

Vaughan M. Hurry ◽

Mark G. Tjoelker

Keyword(s):

Water Availability ◽

Thermal Acclimation ◽

Atmospheric Co2 ◽

Co2 Efflux ◽

Co2 Concentrations ◽

Long Term Changes ◽

Q10 Values ◽

Atmospheric Co2 Concentrations ◽

Plant Respiration

When predicting the effects of climate change, global carbon circulation models that include a positive feedback effect of climate warming on the carbon cycle often assume that (1) plant respiration increases exponentially with temperature (with a constant Q10) and (2) that there is no acclimation of respiration to long-term changes in temperature. In this review, we show that these two assumptions are incorrect. While Q10 does not respond systematically to elevated atmospheric CO2 concentrations, other factors such as temperature, light, and water availability all have the potential to influence the temperature sensitivity of respiratory CO2 efflux. Roots and leaves can also differ in their Q10 values, as can upper and lower canopy leaves. The consequences of such variable Q10 values need to be fully explored in carbon modelling. Here, we consider the extent of variability in the degree of thermal acclimation of respiration, and discuss in detail the biochemical mechanisms underpinning this variability; the response of respiration to long-term changes in temperature is highly dependent on the effect of temperature on plant development, and on interactive effects of temperature and other abiotic factors (e.g. irradiance, drought and nutrient availability). Rather than acclimating to the daily mean temperature, recent studies suggest that other components of the daily temperature regime can be important (e.g. daily minimum and / or night temperature). In some cases, acclimation may simply reflect a passive response to changes in respiratory substrate availability, whereas in others acclimation may be critical in helping plants grow and survive at contrasting temperatures. We also consider the impact of acclimation on the balance between respiration and photosynthesis; although environmental factors such as water availability can alter the balance between these two processes, the available data suggests that temperature-mediated differences in dark leaf respiration are closely linked to concomitant differences in leaf photosynthesis. We conclude by highlighting the need for a greater process-based understanding of thermal acclimation of respiration if we are to successfully predict future ecosystem CO2 fluxes and potential feedbacks on atmospheric CO2 concentrations.

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Nitrogen inputs and losses in response to chronic CO<sub>2</sub> exposure in a sub-tropical oak woodland

Biogeosciences Discussions ◽

10.5194/bgd-11-61-2014 ◽

2014 ◽

Vol 11 (1) ◽

pp. 61-106 ◽

Cited By ~ 1

Author(s):

B. A. Hungate ◽

B. D. Duval ◽

P. Dijkstra ◽

D. W. Johnson ◽

M. E. Ketterer ◽

...

Keyword(s):

Elevated Co2 ◽

Atmospheric Co2 ◽

15N Tracer ◽

Carbon Limitation ◽

N Fixation ◽

Oak Woodland ◽

N Losses ◽

Co2 Concentrations ◽

Nitrogen Inputs ◽

Atmospheric Co2 Concentrations

Abstract. Rising atmospheric CO2 concentrations could alter the nitrogen (N) content of ecosystems by changing N inputs and N losses, but responses vary in field experiments, possibly because multiple mechanisms are at play. We measured N fixation and N losses in a subtropical oak woodland exposed to 11 yr of elevated atmospheric CO2 concentrations. We also explored the role of herbivory, carbon limitation, and competition for light and nutrients in shaping response of N fixation to elevated CO2. Elevated CO2 did not significantly alter gaseous N losses, but lower recovery and deeper distribution in the soil of a long-term 15N tracer indicated that elevated CO2 increased leaching losses. Elevated CO2 had no effect on asymbiotic N fixation, and had a transient effect on symbiotic N fixation by the dominant legume. Elevated CO2 tended to reduce soil and plant concentrations of iron, molybdenum, phosphorus, and vanadium, nutrients essential for N fixation. Competition for nutrients and herbivory likely contributed to the declining response N fixation to elevated CO2. These results indicate that positive responses of N fixation to elevated CO2 may be transient, and that chronic exposure to elevated CO2 can increase N leaching. Models that assume increased fixation or reduced N losses with elevated CO2 may overestimate future N accumulation in the biosphere.

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Elevated atmospheric CO2 concentrations increase wheat root phosphatase activity when growth is limited by phosphorus

Functional Plant Biology ◽

10.1071/pp97045 ◽

1998 ◽

Vol 25 (1) ◽

pp. 87 ◽

Cited By ~ 27

Author(s):

Damian J. Barrett ◽

Alan E. Richardson ◽

Roger M. Gifford

Keyword(s):

Phosphatase Activity ◽

Elevated Co2 ◽

Atmospheric Co2 ◽

Organic P ◽

Wheat Seedlings ◽

P Deficiency ◽

Co2 Concentrations ◽

Wide Range ◽

Atmospheric Co2 Concentrations ◽

Ambient Co2

Wheat seedlings were grown in solution culture under adequate and limited phosphorus treatments at current ambient and elevated (approximately 2× ambient) CO2 concentrations. Acid phosphomonoesterase (‘phosphatase’) activity of root segments was measured using p-nitrophenyl phosphate as substrate. When plant growth was P-limited, elevated CO2 concentrations increased phosphatase activity more than at ambient CO2. This result (1) was evident when expressed on a unit root dry weight or root length basis, indicating that increased root enzyme activity was unlikely to be associated with CO2-induced changes in root morphology; (2) occurred when plants were grown aseptically, indicating that the increase in phosphatase activity originated from root cells rather than root- associated microorganisms; (3) was associated with shoot P concentrations below 0.18%; (4) occurred only when wheat roots were grown under P deficiency but not when a transient P deficiency was imposed; and (5) suggest that a previously reported increase in phosphatase activity at elevated CO2 by an Australian native pasture grass (Gifford, Lutze and Barrett 1996; Plant and Soil 187, 369–387) was also a root mediated response. The observed increase in phosphatase activity by plant roots at elevated CO2, if confirmed for a wide range of field pasture and crop species, is one factor which may increase mineralisation of soil organic P as the anthropogenic increase of atmospheric CO2 concentrations continues. But, whether a concomitant increase in plant uptake of P occurs will depend on the relative influence of root and microbial phosphatases, and soil geochemistry in determining the rate of mineralisation of soil organic P for any given soil.

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Nitrogen inputs and losses in response to chronic CO<sub>2</sub> exposure in a subtropical oak woodland

Biogeosciences ◽

10.5194/bg-11-3323-2014 ◽

2014 ◽

Vol 11 (12) ◽

pp. 3323-3337 ◽

Cited By ~ 8

Author(s):

B. A. Hungate ◽

B. D. Duval ◽

P. Dijkstra ◽

D. W. Johnson ◽

M. E. Ketterer ◽

...

Keyword(s):

Elevated Co2 ◽

Atmospheric Co2 ◽

15N Tracer ◽

Carbon Limitation ◽

N Fixation ◽

Oak Woodland ◽

N Losses ◽

Co2 Concentrations ◽

Nitrogen Inputs ◽

Atmospheric Co2 Concentrations

Abstract. Rising atmospheric CO2 concentrations may alter the nitrogen (N) content of ecosystems by changing N inputs and N losses, but responses vary in field experiments, possibly because multiple mechanisms are at play. We measured N fixation and N losses in a subtropical oak woodland exposed to 11 years of elevated atmospheric CO2 concentrations. We also explored the role of herbivory, carbon limitation, and competition for light or nutrients in shaping the response of N fixation to elevated CO2. Elevated CO2 did not significantly alter gaseous N losses, but lower recovery and deeper distribution in the soil of a long-term 15N tracer indicated that elevated CO2 increased leaching losses. Elevated CO2 had no effect on nonsymbiotic N fixation, and had a transient effect on symbiotic N fixation by the dominant legume. Elevated CO2 tended to reduce soil and plant concentrations of iron, molybdenum, phosphorus, and vanadium, nutrients essential for N fixation. Competition for nutrients and herbivory likely contributed to the declining response of N fixation to elevated CO2. These results indicate that positive responses of N fixation to elevated CO2 may be transient and that chronic exposure to elevated CO2 can increase N leaching. Models that assume increased fixation or reduced N losses with elevated CO2 may overestimate future N accumulation in the biosphere.

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Pest and disease abundance and dynamics in wheat and oilseed rape as affected by elevated atmospheric CO2 concentrations

Functional Plant Biology ◽

10.1071/fp12162 ◽

2013 ◽

Vol 40 (2) ◽

pp. 125 ◽

Cited By ~ 5

Author(s):

Viktoriya Oehme ◽

Petra Högy ◽

Jürgen Franzaring ◽

Claus P. W. Zebitz ◽

Andreas Fangmeier

Keyword(s):

Elevated Co2 ◽

Oilseed Rape ◽

Spring Wheat ◽

Co2 Enrichment ◽

Plant Phenology ◽

Plant Diseases ◽

Atmospheric Co2 ◽

Pest Species ◽

Co2 Concentrations ◽

Atmospheric Co2 Concentrations

Future atmospheric CO2 concentrations are predicted to increase, and directly affect host plant phenology, which, in turn, is assumed to mediate the performance of herbivorous insects indirectly as well as the abundance and epidemiology of plant diseases. In a 4-year field experiment, spring wheat (Triticum aestivum L. cv. Triso) and spring oilseed rape (Brassica napus L. cv. Campino) were grown using a mini- free-air CO2 enrichment (FACE) system, which consisted of a control (CON), an ambient treatment (AMB) and FACE treatments. The CON and AMB treatments did not receive additional CO2, whereas the FACE plots were moderately elevated by 150 μL L–1 CO2. The impact of elevated CO2 was examined with regard to plant phenology, biomass, leaf nitrogen and carbon, abundance of insect pest species and their relative population growth by either direct counts or yellow sticky traps. Occurrence and damage of plants by pathogens on spring wheat and oilseed rape were directly assessed. Disease infestations on plants were not significantly different between ambient and elevated CO2 in any of the years. Plant phenology, aboveground biomass, foliar nitrogen and carbon concentrations were also not significantly affected by CO2 enrichment. In contrast, the abundance of some species of insects was significantly influenced by elevated CO2, showing either an increase or a decrease in infestation intensity.

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