Nitrogen forms affect root structure and water uptake in the hybrid poplar
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The study analyses the effects of two different forms of nitrogen fertilisation (nitrate and ammonium) on root structure and water uptake of two hybrid poplar (Populus maximowiczii x P. balsamifera) clones in a field experiment. Water uptake was studied using sap flow gauges on individual proximal roots and coarse root structure was examined by excavating 18 whole-root systems. Finer roots were scanned and analyzed for architecture. Nitrogen forms did not affect coarse-root system development, but had a significant effect on fine-root development. Nitrate-treated trees presented higher fine:coarse root ratios and higher specific root lengths than control or ammonium treated trees. These allocation differences affected the water uptake capacity of the plants as reflected by the higher sapflow rate in the nitrate treatment. The diameter of proximal roots at the tree base predicted well the total root biomass and length. The diameter of smaller lateral roots also predicted the lateral root mass, length, surface area and the number of tips. The effect of nitrogen fertilisation on the fine root structure translated into an effect on the functioning of the fine roots forming a link between form (architecture) and function (water uptake).
KeywordsNitrogen fertilisation Hybrid poplars Root structure Fine roots Proximal roots Water uptake Sapflow
This project was made possible through several funding sources: a Collaborative Research and Development NSERC grant for a project titled: Soil fertility and productivity of poplar plantations in southern Quebec (awarded to Dr. James Fyles of McGill and co-researchers including Dr. Christian Messier), a Canada Research Chair in Forest Productivity (awarded to Dr. Frank Berninger), an internal UQÀM subsidy (PARFAC awarded to Dr. Frank Berninger) and a FARE bursary awarded to Susy Domenicano (UQÀM). LC was supported by a Ramon y Cajal contract (RYC-2009-04985) from the Ministerio de Ciencia e Innovación of Spain. We would like to thank the reviewers for their invaluable comments and suggestions, as well as Stéphane Daigle for his statistical advice.
- Albaugh TJ, Allen HL, Kress LW (2006) Root and stem partitioning of Pinus taeda. Trees-Struct Funct 20:176–185Google Scholar
- Dickmann DI, Isebrands JG, Blake TJ, Kosola K, Kort J (2001) Physiological ecology of poplars. In: Dickmann DI (ed) Poplar culture in North America. NRC Research Press, Ottawa, pp 77–118Google Scholar
- Fitter AH (1986) The topology and geometry of plant-root systems—influence of watering rate on root-system topology in Trifolium pratense. Ann Bot-Lond 58:91–101Google Scholar
- Fitter AH (2002) Characteristics and functions of root systems. In: Waisel Y, Eshel A, Uzi Kafkafi U (eds) Plant roots: the hidden half, 3rd edn. Marcel Dekker, Inc., New York, pp 15–32Google Scholar
- Huang B, Eissenstat DM (2000) Linking hydraulic conductivity to anatomy in plants that vary in specific root length. J Am Soc Hortic Sci 125:260–264Google Scholar
- Pregitzer KS, Zak DR, Maziasz J, Deforest J, Curtis PS, Lussenhop J (2000) Interactive effects of atmospheric CO2 and soil-N availability on fine roots of Populus tremuloides. Ecol Appl 10:18–33Google Scholar