Fertilization effects on fineroot biomass, rhizosphere microbes and respiratory fluxes in hardwood forest soils

• Published in: The New phytologist 2007-01, Vol.176 (3), p.655-664
• Main Authors: Phillips, Richard P, Fahey, Timothy J
• Format: Article
• Language: English
• Subjects: Acer - growth & development; Acer - metabolism; Acer - microbiology; Acer saccharum; Betula; Betula - growth & development; Betula - metabolism; Betula - microbiology; Biomass; Carbon - metabolism; Carbon Dioxide - analysis; Cell Respiration - physiology; Fertilization; Fertilizers; forest fertilization; Forest soils; Forestry; Maple sugar; northern red oak (Quercus rubra); nutrient availability; Plant roots; Plant Roots - growth & development; Plant Roots - metabolism; Plant Roots - microbiology; Quercus - growth & development; Quercus - metabolism; Quercus - microbiology; Quercus rubra; rhizodeposition; Rhizosphere; root exudates; Soil - analysis; Soil biology; Soil ecology; Soil Microbiology; Soil microorganisms; Soil organic matter; Soil respiration; sugar maple (Acer saccharum); Trees - growth & development; Trees - metabolism; Trees - microbiology; yellow birch (Betula allegheniensis)
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2007.02204.x

Fertilizer-induced reductions in CO₂ flux from soil ( [graphic removed] ) in forests have previously been attributed to decreased carbon allocation to roots, and decreased decomposition as a result of nitrogen suppression of fungal activity. Here, we present evidence that decreased microbial respiration in the rhizosphere may also contribute to [graphic removed] reductions in fertilized forest soils. Fertilization reduced [graphic removed] by 16-19% in 65-yr-old plantations of northern red oak (Quercus rubra) and sugar maple (Acer saccharum), and in a natural 85-yr-old yellow birch (Betula allegheniensis) stand. In oak plots, fertilization had no effects on fine root biomass but reduced mycorrhizal colonization by 18% and microbial respiration by 43%. In maple plots, fertilization reduced root biomass, mycorrhizal colonization and microbial respiration by 22, 16 and 46%, respectively. In birch plots, fertilization reduced microbial respiration by 36%, but had variable effects on root biomass and mycorrhizal colonization. In plots of all three species, fertilization effects on microbial respiration were greater in rhizosphere than in bulk soil, possibly as a result of decreased rhizosphere carbon flux from these species in fertile soils. Because rhizosphere processes may influence nutrient availability and carbon storage in forest ecosystems, future research is needed to better quantify rhizo-microbial contributions to [graphic removed] .