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Changes in biomass allocation buffer low CO₂ effects on tree growth during the last glaciation.

ABSTRACT: Isotopic measurements on junipers growing in southern California during the last glacial, when the ambient atmospheric [CO₂] (c_a) was ~180?ppm, show the leaf-internal [CO₂] (c_i) was approaching the modern CO₂ compensation point for C₃ plants. Despite this, stem growth rates were similar to today. Using a coupled light-use efficiency and tree growth model, we show that it is possible to maintain a stable c_i/c_a ratio because both vapour pressure deficit and temperature were decreased under glacial conditions at La Brea, and these have compensating effects on the c_i/c_a ratio. Reduced photorespiration at lower temperatures would partly mitigate the effect of low c_i on gross primary production, but maintenance of present-day radial growth also requires a ~27% reduction in the ratio of fine root mass to leaf area. Such a shift was possible due to reduced drought stress under glacial conditions at La Brea. The necessity for changes in allocation in response to changes in [CO₂] is consistent with increased below-ground allocation, and the apparent homoeostasis of radial growth, as c_a increases today.

SUBMITTER: Li G

PROVIDER: S-EPMC5324044 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Changes in biomass allocation buffer low CO2 effects on tree growth during the last glaciation.

Li Guangqi G Gerhart Laci M LM Harrison Sandy P SP Ward Joy K JK Harris John M JM Prentice I Colin IC

Scientific reports 20170224

Isotopic measurements on junipers growing in southern California during the last glacial, when the ambient atmospheric [CO2] (ca) was ~180 ppm, show the leaf-internal [CO2] (ci) was approaching the modern CO2 compensation point for C3 plants. Despite this, stem growth rates were similar to today. Using a coupled light-use efficiency and tree growth model, we show that it is possible to maintain a stable ci/ca ...[more]

PMID: 28233772

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Project description:Background and aimsSeedling herbivory is an important factor underlying plant community diversity and structure. While considerable research has characterized seedling defence in terms of resistance, very little is known about seedling tolerance of herbivory. Moreover, few studies have attempted to identify mechanisms of tolerance across a range of plant species.MethodsSeedling tolerance of simulated herbivory was tested in a diverse pool of ten Hawaiian plant species, including several lobeliad species (family Campanulaceae), a grass, a herb and common woody trees and shrubs. Tolerance was measured as the relative survival and growth of damaged plants receiving 50 % defoliation with simultaneous jasmonic acid application compared with undamaged control plants, assessed 1·5 and 5 weeks after damage. Putative mechanisms of tolerance were measured, including photosynthetic parameters, light use efficiency, and biomass allocation reflecting growth priorities, and analysed using species-level regression analyses on tolerance indices.Key resultsNo species fully tolerated 50 % defoliation at either harvest date, and simulated herbivory significantly reduced shoot as well as root biomass. Lobeliad species had particularly low tolerance. Species varied considerably in size, biomass allocation parameters and their constitutive (pre-damage) and induced (post-damage) photosynthetic parameters. However, only constitutive levels of non-photochemical quenching were significantly related to tolerance, indicating that species with more efficient light use (and less heat dissipation) are better at tolerating damage than species with high levels of heat dissipation.ConclusionsNative Hawaiian plants expressed low tolerance to a conservative level of simulated herbivory. Root growth decreased in response to damage, but this was not associated with greater tolerance, suggesting this response may be due to allocation constraints following defoliation and not due to adaptive plasticity. Conservation of native island plants threatened by invasive herbivores should prioritize protection for seedlings for improved regeneration and the persistence of native plants in disturbed habitats.

Dataset Information

Changes in biomass allocation buffer low CO₂ effects on tree growth during the last glaciation.

Publications

Changes in biomass allocation buffer low CO<sub>2</sub> effects on tree growth during the last glaciation.

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