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  • 1
    Electronic Resource
    Electronic Resource
    A model of the long-term response of carbon allocation and productivity of forests to increased CO2concentration and nitrogen deposition (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 2 (1996), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We present a simple theoretical analysis of the long term response of forest growth and carbon allocation to increased atmospheric [CO2] and N deposition. Our analysis is based on a recent model which predicts that plant light-use efficiency increases with [CO2] but is independent of plant N supply. We combine that model with simple assumptions for nitrogen fluxes in the soil. A quasi-equilibrium analysis of the short term tree and soil pools is then used to develop a simple graphical depiction of the long term carbon and nitrogen supply constraints on total growth, stem growth and foliar allocation.Our results suggest that long-term growth responses to [CO2] and N deposition depend strongly on the extent to which stem allocation and foliage allocation are coupled. At one extreme (‘no coupling’), when stem allocation is fixed and independent of foliage allocation, there is no response of total growth or stem growth to increased [CO2] unless N deposition increases. At the other extreme (‘linear coupling’), when stem allocation is proportional to foliage allocation, there is a significant long-term increase in total growth following a doubling of [CO2], even when N deposition is unchanged, but stem growth decreases because of a long-term decrease in foliage allocation. For both types of coupling, total growth and stem growth increase with increasing N deposition. In the case of linear coupling, however, the N deposition response of stem growth is significantly larger than that of total growth, because of a long-term increase in foliage allocation. We compare our results with those obtained previously from an alternative model of canopy light-use efficiency involving a dependence on the foliar N:C ratio in addition to [CO2].Our results highlight the need for more experimental information on (i) the extent to which canopy light-use efficiency is independent of N supply, and (ii) the relationship between foliage allocation and stem allocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.1996.tb00087.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Acclimation of the respiration/photosynthesis ratio to temperature: insights from a model (1999)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 5 (1999), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Based on short-term experiments, many plant growth models – including those used in global change research – assume that an increase in temperature stimulates plant respiration (R) more than photosynthesis (P), leading to an increase in the R/P ratio. Longer-term experiments, however, have demonstrated that R/P is relatively insensitive to growth temperature. We show that both types of temperature response may be reconciled within a simple substrate-based model of plant acclimation to temperature, in which respiration is effectively limited by the supply of carbohydrates fixed through photosynthesis. The short-term, positive temperature response of R/P reflects the transient dynamics of the nonstructural carbohydrate and protein pools; the insensitivity of R/P to temperature on longer time-scales reflects the steady-state behaviour of these pools. Thus the substrate approach may provide a basis for predicting plant respiration responses to temperature that is more robust than the current modelling paradigm based on the extrapolation of results from short-term experiments. The present model predicts that the acclimated R/P depends mainly on the internal allocation of carbohydrates to protein synthesis, a better understanding of which is therefore required to underpin the wider use of a constant R/P as an alternative modelling paradigm in global change research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1999.00253.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of elevated [CO2] on forest growth and carbon storage: a modelling analysis of the consequences of changes in litter quality/quantity and root exudation (2000)
    Springer
    Plant and soil 224 (2000), S. 135-152 
    Details
    ISSN: 1573-5036
    Keywords: carbon–nitrogen interactions ; carbon storage ; CO2-fertilisation effect ; litter quality ; litter quantity ; net primary production ; root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Many researchers have proposed that the stimulus of plant growth under elevated [CO2] observed in short-term experiments will be moderated in the longer term by a reduction in soil nitrogen (N) availability linked to decreased litter quality and/or increased litter production. However, these negative feedbacks may be offset to some extent by a stimulus in N fixation linked to increased root exudation. The aim of this modelling study is to examine how changes in litter quality/quantity and root exudation –- if they occur –- will affect the CO2 responses of net primary productivity and ecosystem carbon (C) storage on different timescales. We apply a model of C and N cycling in forest ecosystems (G’DAY) to stands of Norway spruce (Picea abies, L. Cast) growing at a N-limited experimental site at Flakaliden, Sweden, and draw the following conclusions: (1) in the absence of changes in litter quality and root exudation, the short-term CO2 stimulus of litter quantity leads to only a minimal CO2 stimulus of productivity or C storage in the medium term (≈ 20 years) and long term (≈ 200 years), because of constraints on soil N availability; (2) increasing plant nitrogen use efficiency (via a decrease in the N:C ratio of new litter) makes little impact on these results; (3) a significant CO2 response in the medium term requires a substantial decrease in the N:C ratio of older litter, when it is approaching stabilisation as soil organic matter, although the long-term CO2 response remains small; and (4) an increase in N fixation leads to a small effect on productivity in the short term, but a very large effect on both productivity and C storage in the long term. These results suggest that soil N constraints on the long-term CO2-fertilisation effect can be overcome to a significant extent only by increases in N acquisition, although only modest increases may be required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004711707787
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