Colonization of decomposing Sphagnum moss litter by mycorrhizal roots in two types of peatland ecosystems

During a 35-month study on the decomposition of Sphagnum moss litter in poor fen and pine bog forest, an intensive colonization of litter-bags by mycorrhizal roots was observed during the decomposition process. Content of mycorrhizal roots in litter-bags, expressed as % mass of roots, was generally increasing during the decomposition in pine bog forest, and fluctuating during decomposition on poor fen, although in both cases the results were statistically insignificant. Two morphotypes of ericoid roots and two morphotypes of ectomycorrhizal roots were recorded from litter-bags on poor fen during the decomposition experiment, while in pine bog forest one morphotype of ericoid and nine morphotypes of ectomycorrhizal roots were recorded. Molecular identification of mycorrhizal roots succeeded only in the case of one ericoid and six putatively ectomycorrhizal morphotypes. Most morphotypes were recorded only once during the whole 35-month decomposition period, and only one ericoid and one ectomycorrhizal morphotypes were shared between the poor fen and pine bog forest communities.

Mycorrhizal fungal community relationship to root nitrogen concentration over a regional atmospheric nitrogen deposition gradient in the northeastern USA

Increased nitrogen (N) input has been found to alter ectomycorrhizal fungal communities over short deposition gradients and in fertilization experiments; however, its effects over larger spatial scales have not been determined. To address this gap, we reanalyzed data from a study originally designed to examine the effects of soil aluminum/calcium (Al/Ca) ratios on the vitality of red spruce fine roots over a regional acid and N deposition gradient in the northeastern USA. We used root N as an indicator of stand N availability and examined its relationship with the abundance of ectomycorrhizal morphotypes. The dominant morphotypes changed in relative abundance as a function of stand N availability. As root N concentrations increased, Piloderma spp. - like, Cenococcum geophilum Fr., and other unidentified mycorrhizal morphotypes declined in abundance, while other smooth-mantled morphotypes increased. Root N concentration in the 1–2 mm diameter class was the best predictor of the abundance of multiple morphotypes. The morphotype responses were consistent with those found in experimental and small-scale studies, suggesting that N availability is altering ectomycorrhizal communities over broad spatial scales in this region. This finding provides an impetus to conduct a more detailed characterization of mycorrhizal community responses to N deposition across large-scale gradients.

Scots pine ectomycorrhizal fungal inoculum potential and dynamics in podzol-specific humus, eluvial and illuvial horizons one and four growth seasons after forest clear-cut logging

The aims of this microcosm-based study were to characterize Scots pine ectomycorrhizal (EcM) inoculum potential in humus (O) and underlying eluvial (E) and illuvial (B) mineral podzol soil horizons and to compare the inoculum potential 1 and 4 years following clear-cut logging. The specific horizons were collected from a Scots pine control uncut stand, the adjacent interface zone (3–10 m from the forest edge), and the adjoining clear-cut area. The highest Simpson's reciprocal diversity indices (SRDI) of ectomycorrhizal morphotypes and polymerase chain reaction – internal transcribed spacer – restriction fragment length polymorphism (PCR-(ITS)-RFLP) taxa were detected in the humus and E horizon. The B horizon supported the lowest SRDI, but the community consisted of mycorrhizas representing active rhizomorph-forming species. Identified RFLP taxa, confirmed via ITS sequence analysis, highlighted horizon specificity for some genera and species. With respect to clear-cutting impacts, the most dominant ectomycorrhizal morphotypes detected and diversity indices were the same irrespective of the sampling time, which strongly indicates that inoculum potential is maintained up to four growth seasons after the clearcut. No forest treatment dependent differences in Scots pine seedling biomass were detected, but, compared with humus, significantly reduced biomass was recorded in deeper mineral soil horizons. The data are discussed in relation with recent vertical profile studies and forest silvicultural practices.

Ectomycorrhizal colonization of greenhouse-grown Douglas-fir (Pseudotsuga menziesii) seedlings by inoculum associated with the roots of refuge plants sampled from a Douglas-fir forest in the southern interior of British Columbia

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown in the greenhouse in a sterilized mixture of forest soil and vermiculite, which had been inoculated with root fragments from one of six different ectomycorrhizal under story plant species (Arctostaphylos uva-ursi (L.) Spreng, P. menziessi, Salix bebbiana Bebb, Alnus viridis subsp. sinuata (Regel) Ä. Löve & and D. Löve (alder), Betula papyrifera Marsh. (paper birch), Populus tremuloides Michx.) and arbuscular mycorrhizal Calamagrostis rubescens Buckl. (pinegrass) sampled from a dry Douglas-fir forest in the southern interior of British Columbia. The overall objective of the present study was to investigate the inoculum potential of these ectomycorrhizal roots for colonizing Douglas-fir seedlings. A total of seven ectomycorrhizal morphotypes formed on the bioassay seedlings, which were colonized by all treatments except the control. Seedlings growing in soil inoculated with root fragments of Douglas-fir, Arctostaphylos, and paper birch had greater ectomycorrhizal richness and a higher percentage of colonized fine roots relative to the pinegrass and alder treatments. The community of ectomycorrhizal fungi that colonized the bioassay seedlings differed from that associated with some of the same refuge plants assessed in a previously reported field-based study at this site. Different ectomy corrhizal fungal colonization strategies and the retention of refuge plants are discussed in relation to the colonization of outplanted seedlings following clearcutting.Key words: ectomycorrhizae, refuge plants, inoculum potential, soil bioassay, Pseudotsuga menziesii.

Ectomycorrhizal colonization and richness of previously colonized, containerized Picea engelmannii does not vary across clearcuts when planted in mechanically site-prepared mounds

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.

Characterization of Pinus ectomycorrhizas from mixed conifer and pygmy forests using morphotyping and molecular methods

We used morphotyping and molecular methods to characterize ectomycorrhizas of bishop pine (Pinus muricata D. Don) and Bolander pine (Pinus contorta ssp. bolanderi (Parl.) Critchf.) from mixed conifer and hydric pygmy forests on the northern California coast. Sixteen ectomycorrhizal morphotypes were described, producing 15 internal transcribed spacer restriction fragment length polymorphism (ITS-RFLP) types, and 12 were identified via ITS sequencing. From a given site, all root tips of a specific morphotype produced identical ITS-RFLP patterns. However, sometimes two morphotypes produced the same ITS-RFLP type, and sometimes samples of the same morphotype from two different sites produced two different ITS-RFLP types. These results indicate that surveys of ectomycorrhizal fungi based on morphology alone are not sufficient, and that grouping morphotypes prior to molecular analysis can expedite the process. Ectomycorrhizas from mixed conifer included Russuloid sp., Tomentella sublilacina (Ellis & Holw.) Wakef., Tuber sp., and two Thelephoroid species. Ectomycorrhizas from hydric pygmy included two Dermocybe spp., a Cortinarius sp., two Thelephoroid spp., and Suillus tomentosus (Kauffman) Singer. Both plant communities contained Cenococcum geophilum Fr.:Fr. The hydric pygmy sites were more similar to each other than to the mixed conifer site (Jaccard similarity). The presence of ectomycorrhizal taxa in one plant community type may reflect biotic (host specificity) or abiotic (soil fertility or hydrology) adaptation.Key words: ectomycorrhiza, bishop pine, Pinus muricata, Bolander pine, Pinus contorta ssp. bolanderi, morphotyping, ITS-RFLP.

Comparison of ericoid and ectomycorrhizal colonization and ectomycorrhizal morphotypes in mixed conifer and pygmy forests on the northern California coast

On the northern California coast, mixed conifer forests occur on younger, relatively fertile terraces, whereas mesic and hydric pygmy forests occur on older, infertile, poorly drained terraces. We characterized mycorrhizal associations, ectomycorrhizal morphotypes, and colonization levels for nine plant species from three plant communities (mixed conifer, mesic pygmy, and hydric pygmy). Pinus contorta ssp. bolanderi (Parl.) Critchf. and Pinus muricata D. Don were ectomycorrhizal; all ericaceous plants formed ericoid mycorrhizas except Arctostaphylos nummularia A. Gray, which formed only arbutoid mycorrhizas. Arbuscular mycorrhizas were not observed, even on Cupressus goveniana ssp. pigmaea (Lemmon) J. Bartel. Ectomycorrhizal colonization was significantly lower in pygmy forests, while ericoid mycorrhizal colonization was significantly higher, as compared with the mixed conifer forest. Ectomycorrhizal and ericoid mycorrhizal colonization was greater on hummocks than in swales at hydric pygmy sites. Thirteen distinct ectomycorrhizal and arbutoid mycorrhizal morphotypes were observed: eight only on Pinus spp. and two only on A. nummularia. Two morphotypes were found only in mixed conifer, and eight were found only in pygmy communities. Distribution of morphotypes may reveal habitat and (or) host adaptation by ectomycorrhizal fungi.Key words: ectomycorrhizal morphotypes, ericoid mycorrhizas, pygmy forest, Ericaceae, mycorrhizal colonization, low-fertility soils.