Access to mycorrhizal networks and roots of trees: importance for seedling survival and resource transfer

• Published in: Ecology (Durham) Vol. 90; no. 10; pp. 2808 - 2822
• Main Authors: Teste, Francois P, Simard, Suzanne W, Durall, Daniel M, Guy, Robert D, Jones, Melanie D, Schoonmaker, Amanda L
• Format: Journal Article
• Language: English
• Published: Washington, DC Ecological Society of America 01-10-2009
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; British Columbia; Canada; Carbon; Carbon - metabolism; carbon and nitrogen transfer; Carbon Isotopes; Douglas-fir; Dry forests; Ecosystem; ectomycorrhizae; ectomycorrhizas; Effects; facilitation; Forest ecology; forest soils; forest trees; Fundamental and applied biological sciences. Psychology; Fungi; General aspects; hyphal mesh barriers; mortality; mycorrhizae; Mycorrhizae - physiology; mycorrhizal fungi; mycorrhizal network; natural regeneration; Nitrogen; Nitrogen - metabolism; Plant ecology; Plant roots; Plant Roots - microbiology; Plants; Pseudotsuga menziesii; Pseudotsuga menziesii var. glauca; roots; seedling growth; seedling survival and establishment; Seedlings; Seedlings - microbiology; Seedlings - physiology; Seeds; soil ecology; Soil Microbiology; source–sink relationships; Studies; Taxa; Trees; Trees - microbiology; Trees - physiology; British Columbia; Canada; North America; America; Plant juvenile growth stage; Barrier; Douglas-fir; mycorrhizal network; Pseudotsuga menziesii; Gymnospermae; hyphal mesh barriers; Tree; Ectomycorrhiza; carbon and nitrogen transfer; ectomycorrhizas; Facilitation; Root; source-sink relationships; British Columbia; Nitrogen; Plant emergence; Source sink relationship; Symbiont; Carbon; Survival; Canada; seedling survival and establishment; Pseudotsuga menziesii var. glauca; Mycorrhiza; Coniferales; Spermatophyta
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/08-1884.1

Mycorrhizal networks (MNs) are fungal hyphae that connect roots of at least two plants. It has been suggested that these networks are ecologically relevant because they may facilitate interplant resource transfer and improve regeneration dynamics. This study investigated the effects of MNs on seedling survival, growth and physiological responses, interplant resource (carbon and nitrogen) transfer, and ectomycorrhizal (EM) fungal colonization of seedlings by trees in dry interior Douglas-fir (Pseudotsuga menziesii var. glauca) forests. On a large, recently harvested site that retained some older trees, we established 160 isolated plots containing pairs of older Douglas-fir "donor" trees and either manually sown seed or planted Douglas-fir "receiver" seedlings. Seed- and greenhouse-grown seedlings were sown and planted into four mesh treatments that served to restrict MN access (i.e., planted into mesh bags with 0.5-, 35-, 250-μm pores, or without mesh). Older trees were pulse labeled with carbon (¹³CO₂) and nitrogen (¹⁵NH₄¹⁵NO₃) to quantify resource transfer. After two years, seedlings grown from seed in the field had the greatest survival and received the greatest amounts of transferred carbon (0.0063% of donor photo-assimilates) and nitrogen (0.0018%) where they were grown without mesh; however, planted seedlings were not affected by access to tree roots and hyphae. Size of "donor" trees was inversely related to the amount of carbon transferred to seedlings. The potential for MNs to form was high (based on high similarity of EM communities between hosts), and MN-mediated colonization appeared only to be important for seedlings grown from seed in the field. These results demonstrate that MNs and mycorrhizal roots of trees may be ecologically important for natural regeneration in dry forests, but it is still uncertain whether resource transfer is an important mechanism underlying seedling establishment.