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Available from: Vincent Gutschick, Oct 13, 2014
    • "This can be due to increased photosynthesis at higher temperatures, where the extra fixed carbon is allocated belowground to sustain new root growth (Pregitzer and King 2005). However, high temperatures often increase evapotranspiration and lead to drought, and low soil moisture reduces nutrient availability and nutrient uptake in the rooting zone, thus decreasing nutrient uptake rates (Gutschick and Pushnik 2005). Even though elevated CO 2 is expected to increase plant growth, this increase may not be sustained in the long term if nutrients or water are limited. "
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    ABSTRACT: Ecosystems exposed to elevated CO2 are often found to sequester more atmospheric carbon due to increased plant growth. We exposed a Danish heath ecosystem to elevated CO2, elevated temperature and extended summer drought alone and in all combinations in order to study whether the expected increased growth would be matched by an increase in root nutrient uptake of NH4+-N and NO3- -N. Root growth was significantly increased by elevated CO2. The roots, however, did not fully compensate for the higher growth with a similar increase in nitrogen uptake per unit of root mass. Hence the nitrogen concentration in roots was decreased in elevated CO2, whereas the biomass N pool was unchanged or even increased. The higher net root production in elevated CO2 might be a strategy for the plants to cope with increased nutrient demand leading to a long-term increase in N uptake on a whole-plant basis. Drought reduced grass root biomass and N uptake, especially when combined with warming, but CO2 was the most pronounced main factor effect. Several significant interactions of the treatments were found, which indicates that the responses were nonadditive and that changes to multiple environmental changes cannot be predicted from single-factor responses alone.
    Functional Plant Biology 01/2014; 41(1-1):1-10. DOI:10.1071/FP13117 · 3.15 Impact Factor
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    ABSTRACT: Background and aims Accurate predictions of nutrient acquisition by plant roots and mycorrhizas are critical in modelling plant responses to climate change. Methods We conducted a field experiment with the aim to investigate root nutrient uptake in a future climate and studied root production by ingrowth cores, mycorrhizal colonization, and fine root N and P uptake by root assay of Deschampsia flexuosa and Calluna vulgaris. Results Net root growth increased under elevated CO2, warming and drought, with additive effects among the factors. Arbuscular mycorrhizal colonization increased in response to elevated CO2, while ericoid mycorrhizal colonization was unchanged. The uptake of N and P was not increased proportionally with root growth after 5 years of treatment. Conclusions While aboveground biomass was unchanged, the root growth was increased under elevated CO2. The results suggest that plant production may be limited by N (but not P) when exposed to elevated CO2. The species-specific response to the treatments suggests different sensitivity to global change factors, which could result in changed plant competitive interactions and belowground nutrient pool sizes in response to future climate change.
    Plant and Soil 08/2013; 369(1-2). DOI:10.1007/s11104-013-1601-8 · 2.95 Impact Factor