Effects of mycorrhizal roots and extraradical hyphae on 15N uptake from vineyard cover crop litter and the soil microbial community

• Published in: Soil biology & biochemistry Vol. 38; no. 9; pp. 2665 - 2675
• Main Authors: Cheng, Xiaomei, Baumgartner, Kendra
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2006; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Arbuscular mycorrhizae; Biochemistry and biology; biodegradation; Biological and medical sciences; carbon; Chemical, physicochemical, biochemical and biological properties; community structure; cover crops; Decomposition; Economic plant physiology; Fundamental and applied biological sciences. Psychology; grapes; hyphae; Hyphosphere; Medicago polymorpha; microbial biomass; Microbiology; Mycorrhizosphere; N uptake; nitrogen; nutrient uptake; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant litter; PLFA; rhizosphere; roots; soil microorganisms; Soil science; stable isotopes; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); vesicular arbuscular mycorrhizae; Vitis vinifera; PLFA; Mycorrhizosphere; Medicago polymorpha; Arbuscular mycorrhizae; Decomposition; Hyphosphere; Vitis vinifera; N uptake; Microbial activity; Isotope labelling; Cover crop; Phospholipid; Absorption; Vineyard; Vitidaceae; Dicotyledones; Angiospermae; Soil science; Microbial community; Litter; N-15; Nutrient uptake; Symbiont; Fatty acids; Rhizosphere; Soils; Endomycorrhiza; Leguminosae; Fruit crop; Hypha; Mycorrhiza; Spermatophyta; Fodder crop
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2006.03.023

The objectives of this study were to evaluate the contribution of arbuscular mycorrhizal (AM) fungal hyphae to 15N uptake from vineyard cover crop litter ( Medicago polymorpha), and to examine the soil microbial community under the influence of mycorrhizal roots and extraradical hyphae. Mycorrhizal grapevines ( Vitis vinifera) were grown in specially designed containers, within which a polyvinyl chloride (PVC) mesh core was inserted. Different sizes of mesh allowed mycorrhizal roots (mycorrhizosphere treatment) or extraradical hyphae (hyphosphere treatment) to access dual labeled 15N and 13C cover crop litter that was placed inside the cores after 4 months of grapevine growth. Mesh cores in the bulk soil treatment, which served as a negative control, had the same mesh size as the hyphosphere treatment, but frequent rotation prevented extraradical hyphae from accessing the litter. Grapevines and soils were harvested 0, 7, 14, and 28 days after addition of the cover crop litter and examined for the presence of 15N. Soil microbial biomass and the soil microbial community inside the mesh cores were examined using phospholipid fatty acid analysis. 15N concentrations in grapevines in the hyphosphere treatment were twice that of grapevines in the bulk soil treatment, suggesting that extraradical hyphae extending from mycorrhizal grapevine roots may have a role in nutrient utilization from decomposing vineyard cover crops in the field. Nonetheless, grapevines in the mycorrhizosphere treatment had the highest 15N concentrations, thus highlighting the importance of a healthy grapevine root system in nutrient uptake. We detected similar peaks in soil microbial biomass in the mycorrhizosphere and hyphosphere treatments after addition of the litter, despite significantly lower microbial biomass in the hyphosphere treatment initially. Our results suggest that although grapevine roots play a dominant role in the uptake of nutrients from a decomposing cover crop, AM hyphae may have a more important role in maintaining soil microbial communities associated with nutrient cycling.