Oecologia

, Volume 112, Issue 4, pp 557–565

Effects of labile soil carbon on nutrient partitioning between an arctic graminoid and microbes

  • Inger K. Schmidt
  • Anders Michelsen
  • Sven Jonasson
Article

DOI: 10.1007/s004420050345

Cite this article as:
Schmidt, I., Michelsen, A. & Jonasson, S. Oecologia (1997) 112: 557. doi:10.1007/s004420050345

Abstract

We measured partitioning of N and P uptake between soil microorganisms and potted Festuca vivipara in soil from a subarctic heath in response to factorial addition of three levels of labile carbon (glucose) combined with two levels of inorganic N and P. The glucose was added to either non-sterilized or sterilized (autoclaved) soils in quantities which were within the range of reported, naturally occurring amounts of C released periodically from the plant canopy. The aims were, firstly, to examine whether the glucose stimulated microbial nutrient uptake to the extent of reducing plant nutrient uptake. This is expected in nutrient-deficient soils if microbes and plants compete for the same nutrients. Secondly, we wanted to test our earlier␣interpretation that growth reduction observed in graminoids after addition of leaf extracts could be caused directly by labile carbon addition, rather than by phytotoxins in the extracts. Addition of high amounts of N did not affect the microbial N pool, whereas high amounts of added P significantly increased the microbial P pool, indicating a luxury P uptake in the microbes. Both plant N and in particular P uptake increased strongly in response to soil sterilization and to addition of extra N or P. The increased␣uptake led to enhanced plant growth when both elements were applied in high amounts, but only led to increased tissue concentrations without growth responses when the nutrients were added separately. Glucose had strong and contrasting effects on plant and microbial N and P uptake. Microbial N and P uptake increased, soil inorganic N and P concentrations were reduced and plant N and P uptake declined when glucose was added. The responses were dose-dependent within the range of 0–450 μg C g−1 soil added to the non-sterilized soil. The opposite responses of plants and microbes showed that plant acquisition of limiting nutrients is dependent on release of nutrients from the soil microbes, which is under strong regulation by the availability and microbial uptake of labile C. Hence, we conclude, firstly, that the microbial populations can compete efficiently with plants for nutrients to an extent of affecting plant growth when the microbial access to labile carbon is high in nutrient deficient soils. We also conclude that reduced growth of plants after addition of leaf extracts to soil can be caused by carbon-induced shifts in nutrient partitioning between plants and microbes, and not necessarily by phytotoxins added with the extracts as suggested by some experiments.

Key words Arctic soilAllelopathyMicrobial immobilizationPlant-microbe interactionsSoil labile carbon

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Inger K. Schmidt
    • 1
  • Anders Michelsen
    • 1
  • Sven Jonasson
    • 1
  1. 1.Botanical Institute, Department of Plant Ecology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark Fax: +45 35 32 23 21; e-mail: IngerKS@bot.ku.dkDK