title: Contrasts between whole-plant and local nutrient levels determine root growth and death in Ailanthus altissima (Simaroubaceae).
abstract: •
  
  
  
  There is an ongoing debate about the importance of whole-plant control vs. local modular mechanisms for root growth. We conducted a split-root experiment with different patch/background levels of nitrogen to examine whether local root growth and death are controlled by local resource levels or at the whole-plant level.•
  
  
  
  Three microrhizotrons with 0, 10, and 100 µg N/g growth medium levels (74 g growth medium each) were attached to pots of high or low soil N in which one Ailanthus altissima individual was growing. One fine root was guided into each of the microrhizotrons and photographed every 4 d. Plants were harvested after 28 d; root growth and mortality in the microrhizotrons were recorded. Changes in root length, number of laterals, and interlateral length were determined from the photos and analyzed.•
  
  
  
  While overall plant growth was influenced by background N level, both patch and background N levels influenced root growth and mortality in patches. Local roots proliferated most when the patch N level was high and background level low, and they proliferated least and showed highest mortality when patch N was low and the background level high.•
  
  
  
  The fate of roots growing in a patch is influenced by the resource environment of the plant's other roots as well as the resource levels in the patch itself. Thus, the growth and death of roots in patches is determined by both modular and whole-plant mechanisms.
authors.affiliation: The Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875, China Institute of Soil Science, Chinese Academy of Sciences, No. 71 Beijing East Road, Nanjing 210008, China.
authors.forename: Fengqin
authors.initials: F
authors.lastname: Hu
authors.affiliation: The Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875, China.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Mou
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Weiner
authors.affiliation: The Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875, China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Li
mesh_terms: D032268:Ailanthus / Q000254:growth & development* / Q000502:physiology; D009584:Nitrogen / Q000032:analysis*; D018517:Plant Roots / Q000254:growth & development* / Q000502:physiology; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: Ailanthus altissima; Simaroubaceae; nitrogen levels; root modularity; root plasticity; soil heterogeneity; soil patches; tree of heaven