Continuity of ectomycorrhizal fungi in self-regenerating boreal Pinus sylvestris forests studied by comparing mycobiont diversity on seedlings and mature trees. New Phytol

Swedish University of Agricultural Sciences, Uppsala, Uppsala, Sweden
New Phytologist (Impact Factor: 7.67). 03/1999; 142(1):151 - 162. DOI: 10.1046/j.1469-8137.1999.00383.x

ABSTRACT Seedlings and old trees of Scots pine in self-regenerating, old, virgin boreal forest in northern Sweden were compared in terms of the species composition of their associated ectomycorrhizal (EM) fungi. The natural regeneration of seedlings was mimicked by annual seeding for 10 yr (1986–1995) in intact field vegetation at three sites. In 1995, all seedlings were harvested, and 171 were examined for mycorrhizas. Twenty-five soil cores were taken in order to study the mycorrhizas on the established trees. Most short roots were mycorrhizal. Using mycorrhizal morphology and restriction fragment length polymorphisms (RFLP) analysis, we were able to distinguish 43 ectomycorrhizal taxa. Fourteen of these taxa were identified using a sporocarp and mycelial culture based internal transcribed spacer (ITS)-RFLP reference database, and another three were identified by mycorrhizal morphology. Cenococcum geophilum, Piloderma croceum and Suillus variegatus were present on the seedlings, irrespective of age, as well as on the old trees. At one forest, 23 ectomycorrhizal taxa were found as mycorrhizas, of which 10 occurred on both seedlings and old trees. These 10 species accounted for 92 and 73% of the mycorrhizas on the seedlings and old trees, respectively. A 3-yr survey of ectomycorrhizal sporocarps at the same site revealed 62 EM taxa. The degree of similarity between the composition of EM species reflected by sporocarps and by mycorrhizas, was low. Ectomycorrhizal species present in our ITS-RFLP database constituted 7.5–19% of the mycorrhizas on seedlings and old trees, whereas they constituted 80–95% of the total production of epigeous sporocarps. The unidentified taxa comprised 70–87% of the mycorrhizas. Our findings support the view that the species composition of mycorrhizas colonizing naturally regenerated seedlings in forests is similar to that of mycorrhizas colonizing surrounding trees. We suggest that the concept of the mycelial network be expanded in order to embrace both the significance of interconnections between different trees as well as the continuity or perpetuation of EM fungal communities.

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    • "The former explanation is unlikely. Firstly, several studies have shown that naturally regenerated forest seedlings are colonized primarily by the same ectomycorrhizal fungi as the mature trees in the forest (Bradbury 1998; Bradbury et al. 1998; Jonsson et al. 1999). Furthermore, during greenhouse bioassays, colonization is generally highest when seedlings are grown in forest soils from locations where the same plant species is present, as occurred in this case (Brundrett et al. 1996; Hashimoto and Hyakumachi 1998b). "
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    ABSTRACT: The Sicamous Creek silviculture systems trial, which is located at a subalpine forest, comprises five replicated treatments. One-third of the timber volume was removed from 30-ha treatment units using cutblocks of 0.1, 1.0, or 10 ha or single-tree selection. Openings were mechanically site prepared by mounding and planted with nursery-grown containerized Picea engelmannii Parry ex Engelm. seedlings. Seedlings were planted in mineral soil exposed by mounding in all four of the harvested treatments as well as in undisturbed soil in the uncut control treatment. Neither the overall ectomycorrhiza colonization nor the number of ectomycorrhizal morphotypes per seedling varied across the cutblocks or among cutblocks of different sizes. This is in contrast to earlier studies at this site that showed inoculum levels to be significantly higher at 2 m from the forest edge, within the rooting zone of forest trees. We hypothesize that the difference here is due either to (i) competition between native ectomycorrhizal fungi and the ectomycorrhizal fungi present on the spruce at planting or (ii) more homogeneous levels of inoculum in the mineral soil exposed by mounding. Fewer native fungi colonized these seedlings than the nonmycorrhizal seedlings from earlier studies, which had been planted between the mounds.
    Canadian Journal of Forest Research 02/2011; 32(8):1425-1433. DOI:10.1139/x02-069 · 1.66 Impact Factor
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    • "Many ECM fungal species have rhizomorphs or abundant emanating hyphae that allow translocation of resources through the soil (Cairney 1992; Agerer 2001). ECM fungal species with these features are often host-generalists (colonize numerous tree species) and relatively abundant, allowing for numerous potential linkages between understory and canopy trees (Jonsson et al. 1999; Kennedy et al. 2003). Light availability has generally been a good proxy for predicting juvenile tree growth in northern latitude forests (e.g., Wright et al. 1998; Coates and Burton 1999; Claveau et al. 2002), but the degree to which CMN linkages influence shade tolerance and subsequent patterns in understory development is unclear. "
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    ABSTRACT: The possible benefit of common mycorrhizal network linkages to seedling growth was tested in a low light partial-cut forest understory. Naturally regenerated western hemlock (Tsuga heterophylla Raf.) and hybrid spruce (Picea glauca × Picea sitchensis [Moench] Voss) seedlings were transplanted directly into soil or within bags of different pore sizes to restrict the amounts of root and ectomycorrhizal contact. The 5-year study included "full contact" (no bag), "moderate contact" (250-µm openings), and "low contact" (4-µm openings) treatments. Height increment was lowest for full contact seedlings over most of the experiment, and highest for low contact seedlings by years 4 and 5. Full contact seedlings also had slightly lower foliar N content than moderate and low contact seedlings. There were no significant interactions in growth detected between tree species and treatments, despite the higher potential for common mycorrhizal network linkages between a western hemlock understory and canopy. Fifty-eight ectomycorrhizal fungal morphotypes were identified on the seedlings, including many with smooth mantles or with only sparse emanating hyphae, which likely reduced the potential for common mycorrhizal network linkages. These results would support the more traditional concepts of competition for scarce resources by isolated seedlings as the primary interaction for the understory of these mature forests.Key words: common mycorrhizal networks, facilitation, shade tolerance, competition.
    Canadian Journal of Botany 02/2011; 83(6):638-646. DOI:10.1139/b05-035 · 1.40 Impact Factor
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    • "Mycorrhizal fungi form mutualistic symbiotic association with the roots of a host plant and are therefore of ecological significance. Many studies performed to assess the effect of silvicultural practices on mycorrhizal communities in forests of the Mediterranean, temperate, and boreal zones have been only focused on ectomycorrhizal (ECM) fungi, the type of mycorrhizal fungi associated with the dominant woody species in those ecosystems (Bradbury et al., 1998; Hagerman et al., 1999; Jonsson et al., 1999; Buée et al., 2005). There are some studies dealing with the seasonal variations (Brundrett and Abbott, 1994) and spatial patterns (Brundrett and Abbott, 1995) of the propagules of both arbuscular mycorrhizal (AMF) and ECM fungi in a jarrah forest of Australia, the seasonal patterns in AMF in a melic-beech forest (Mayr and Godoy, 1989), or the effect of root zone temperature on ECM and AMF formation (Parke et al., 1983a); however, only the forests in the last of these studies had been disturbed by silvicultural practices. "
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    ABSTRACT: Clear-cutting, a management practice applied to many beech forests in the North of Spain, modifies microclimate and, consequently, the composition of the understory plant community in the disturbed areas. The objectives of this study were to assess if changes in the understory vegetation caused by altered light microclimate after clear-cutting affect the infectivity of arbuscular mycorrhizal fungi (AMF) on herbaceous plant species in beech (Fagus sylvatica L.) forests naturally regenerating from clear-cutting and to test if the use of bioassays for studying the infectivity of native AMF could provide useful information to improve the management of clear-cut areas. Three nearby beech forests in northwest Navarra, Spain, a region in the northwest part of the Pyrenees, were selected: an unmanaged forest, a forest clear-cut in 1996, and another forest clear-cut in 2001. High stem density in the forest clear-cut in 1996 (44 000 trees ha−1) attenuated photosynthetic active radiation (PAR) and impaired the growth of herbaceous species within the ecosystem. The percentage of AMF colonization of plants in bioassays performed on soil samples collected from the forest clear-cut in 1996 was always lower than 10%. In the forest clear-cut in 2001, where soil was covered by perennial grasses, PAR was high and the infectivity of native AMF achieved minimum values in spring and autumn and a maximum value in summer. In contrast, the infectivity of native AMF in the unmanaged forest remained similar across the seasons. Our results demonstrated that changes in the composition of understory vegetation within beech forests strongly affected the infectivity of native AMF in clear-cut areas and suggested that the assessment of the infectivity of native AMF through bioassays could provide helpful information for planning either the removal of overstory when the tree density is so high that it impairs the correct development of herbaceous species or the plantation of new seedlings when high light intensity negatively affects the establishment of shade species.
    Pedosphere 02/2011; 21(1-21):65-74. DOI:10.1016/S1002-0160(10)60080-X · 1.38 Impact Factor
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