Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates

New Phytol. 2010 Dec;188(4):1055-64. doi: 10.1111/j.1469-8137.2010.03427.x. Epub 2010 Sep 6.

Abstract

Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g(-1) soil) to soils amended with and without (13) C-labeled plant residue. We measured CO(2) respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g(-1)) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g(-1)) had no impact on plant residue decomposition, while greater concentrations of C (>7.2 mg C g(-1)) reduced decomposition (-50%). Concurrently, high exudate concentrations (>3.6 mg C g(-1)) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (<3.6 mg C g(-1)) increased metabolic activity rather than gene copy numbers. These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacteria / drug effects
  • Bacteria / genetics
  • Biodegradation, Environmental / drug effects
  • Carbon / metabolism*
  • Carbon / pharmacology
  • Carbon Dioxide / metabolism
  • Cell Respiration / drug effects
  • Fungi / drug effects
  • Fungi / genetics
  • Gene Dosage / drug effects
  • Panicum / cytology
  • Panicum / drug effects
  • Panicum / metabolism*
  • Soil / analysis*
  • Soil Microbiology*

Substances

  • Soil
  • Carbon Dioxide
  • Carbon