Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging

Ross E. McMurtrie*, Colleen M. Iversen, Roderick C. Dewar, Belinda E. Medlyn, Torgny Näsholm, David A. Pepper, Richard J. Norby

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

CO2-enrichment experiments consistently show that rooting depth increases when trees are grown at elevated CO2 (eCO2), leading in some experiments to increased capture of available soil nitrogen (N) from deeper soil. However, the link between N uptake and root distributions remains poorly represented in forest ecosystem and global land-surface models. Here, this link is modeled and analyzed using a new optimization hypothesis (MaxNup) for root foraging in relation to the spatial variability of soil N, according to which a given total root mass is distributed vertically in order to maximize annualNuptake. MaxNup leads to analytical predictions for the optimal vertical profile of root biomass, maximum rooting depth, and N-uptake fraction (i.e., the proportion of plant-available soil N taken up annually by roots). We use these predictions to gain new insight into the behavior of the N-uptake fraction in trees growing at the Oak Ridge National Laboratory free-air CO2-enrichment experiment. We also compare MaxNup with empirical equations previously fitted to root-distribution data from all the world's plant biomes, and find that the empirical equations underestimate the capacity of root systems to take up N.

Original languageEnglish
Pages (from-to)1235-1250
Number of pages16
JournalEcology and Evolution
Volume2
Issue number6
DOIs
Publication statusPublished - 2012

Bibliographical note

Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging. McMurtrie, R. E., Iversen, C. M., Dewar, R. C., Medlyn, B. E., Näsholm, T., Pepper, D. A. and Norby, R. J. Ecology and Evolution Vol.2 Iss.6 Copyright (c) 2012 The Authors. http://dx.doi.org/10.1002/ece3.266

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    McMurtrie, R. E., Iversen, C. M., Dewar, R. C., Medlyn, B. E., Näsholm, T., Pepper, D. A., & Norby, R. J. (2012). Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging. Ecology and Evolution, 2(6), 1235-1250. https://doi.org/10.1002/ece3.266