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

Ecology and Evolution

Ross E. McMurtrie⁵  Colleen M. Iversen¹  Roderick C. Dewar³  Belinda E. Medlyn⁴  Torgny Näsholm²  David A. Pepper⁵ 

[1] Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6301;Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden;Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia;Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia;School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, NSW 2052, Australia

关键词: Elevated CO2;    nitrogen‐uptake efficiency;    nitrogen‐uptake fraction;    nitrogen‐uptake model;    nitrogen‐use efficiency;    optimal foraging by roots;    optimal rooting depth;    root distributions;    root strategies;   

DOI  :  10.1002/ece3.266

来源: Wiley

【 摘 要 】

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 annual N uptake. 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.

【 授权许可】

CC BY-NC   
© 2011 The Authors. MicrobiologyOpen published by Blackwell Publishing Ltd.

Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.