Nutrient limitations to bacterial and fungal growth during cellulose decomposition in tropical forest soils

Research output: Contribution to journalArticle

Abstract

Nutrients constrain the soil carbon cycle in tropical forests, but we lack knowledge on how these constraints vary within the soil microbial community. Here, we used in situ fertilization in a montane tropical forest and in two lowland tropical forests on contrasting soil types to test the principal hypothesis that there are different nutrient constraints to different groups of microorganisms during the decomposition of cellulose. We also tested the hypotheses that decomposers shift from nitrogen to phosphorus constraints from montane to lowland forests, respectively, and are further constrained by potassium and sodium deficiency in the western Amazon. Cellulose and nutrients (nitrogen, phosphorus, potassium, sodium, and combined) were added to soils in situ, and microbial growth on cellulose (phospholipid fatty acids and ergosterol) and respiration were measured. Microbial growth on cellulose after single nutrient additions was highest following nitrogen addition for fungi, suggesting nitrogen as the primary limiting nutrient for cellulose decomposition. This was observed at all sites, with no clear shift in nutrient constraints to decomposition between lowland and montane sites. We also observed positive respiration and fungal growth responses to sodium and potassium addition at one of the lowland sites. However, when phosphorus was added, and especially when added in combination with other nutrients, bacterial growth was highest, suggesting that bacteria out-compete fungi for nitrogen where phosphorus is abundant. In summary, nitrogen constrains fungal growth and cellulose decomposition in both lowland and montane tropical forest soils, but additional nutrients may also be of critical importance in determining the balance between fungal and bacterial decomposition of cellulose.

Details

Authors
Organisations
External organisations
  • University of Edinburgh
  • Smithsonian Tropical Research Institute
  • Pontifical Catholic University of Peru
  • Australian National University
  • National University of Saint Anthony the Abbot in Cuzco
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Microbiology
  • Physical Geography

Keywords

  • Decomposition, Ecological stoichiometry, Phospholipid fatty acids, Soil carbon, Soil microorganisms, Tropical lowland forest, Tropical montane forest
Original languageEnglish
Pages (from-to)219-228
JournalBiology and Fertility of Soils
Volume54
Issue number2
Early online date2017 Nov 8
Publication statusPublished - 2018 Feb
Publication categoryResearch
Peer-reviewedYes