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The American cranberry (Vaccinium macrocarpon Aiton) is a perennial plant in northern latitudes that co-occurs with sphagnum mosses in uncultivated populations, in habitats characterized by high acidity, low nitrogen, and fungal pathogens that thrive in wet environments. We investigated the association of Actinobacteria with cranberry and co-inhabiting sphagnum moss and their antifungal properties, across several natural populations. Based on 16S-rRNA gene phylogeny, the majority of these species were in the genus Streptomyces. Neither site nor plant source explained the phylogenetic relationships of these isolates. Most sequences did not group with known Streptomyces sequences, indicating a potentially high diversity of novel strains from this environment. We observed antibiosis by some Actinobacteria isolates against the phytopathogenic fungus Colletotrichum acutatum and a general antagonistic fungus, Trichoderma sp. Individual isolates varied in antifungal ability within and between fungi. Variation in bacterial antifungal properties was not explained by plant species or site, but was partially related to phylogenetic relationship. These results document novel associations between cranberry and sphagnum moss with Actinobacteria, including strains capable of inhibiting fungi. These results suggest candidates for development as biological control agents in agriculture.

The high water retention of hummock-forming Sphagnum species minimizes soil moisture fluctuations and might protect forest floor organic matter from burning during wildfire. We hypothesized that Sphagnum cover reduces overall forest floor organic matter consumption during wildfire compared with other ground-layer vegetation. We characterized variability in soil organic layer depth and organic matter stocks in two pairs of burned and unburned black spruce ( Picea mariana (Mill.) BSP) stands in interior Alaska. In the unburned stands, microsites dominated by Sphagnum had more than twice as much soil organic matter·m–2 as microsites dominated by feather moss and (or) lichens. Whereas 20% of soil organic matter was consumed during fire in microsites dominated by Sphagnum, 45% was consumed in microsites dominated by the feather moss and (or) lichens. Across 79 recently burned black spruce stands, unburned moss abundance (primarily remnant Sphagnum hummocks), landscape position (backslope, flat upland, flat lowland classes), and the interaction among these variables explained 60% of postfire organic soil depths. We suggest that “Sphagnum sheep” could serve as a useful visual indicator of variability in postfire soil carbon stocks in boreal black spruce forests. Sphagnum mosses are important ecosystem engineers not only for their influence on decomposition rates, but also for their effect on fuel consumption and fire patterning.

Sphagnum mosses are assumed to be effective at acquiring low amounts of nitrogen (N) in precipitation to support annual growth. However, N concentrations in precipitation have increased from anthropogenic sources over the last 150 years. I hypothesized that N retention from wet atmospheric deposition decreases with increased N availability, by comparing Sphagnum mosses in a high N deposition region in the Adirondack Park, New York, to a low-deposition region in eastern Maine. A 15NH415NO3 tracer was applied to mosses in both regions, and retention after 24 h was estimated. Nitrogen retention ranged from 50 to 90% of N applied. Most 15N was recovered from the apical capitula and upper stems. Nitrogen retention was greater in the Maine sites in 1998. However, in 1999, a drought year, particularly in Maine, N retention was less in Maine than in New York. The drier climate appeared to lower N retention, possibly through its physiological effects on the mosses. Although atmospheric deposition might be the only exogenous source of N, it satisfied only a small fraction of N required for annual growth. These data suggest that internal cycling processes, such as mineralization, may be much more important N sources to support Sphagnum growth.Key words: Sphagnum mosses, atmospheric nitrogen deposition, nitrogen-use efficiency, nitrogen retention, peatlands, bogs, drought.

The lipid content in the annual increments of different ages (1 to 5 years) of Sphagnum fuscum (Schimp.) Klinggr., S. angustifolium (Russow) C. Jens., and S. papillosum Lindb. has been determined by thin-layer chromatography. It was highest in the youngest portion of the moss shoot, ranging from 4.8 to 5.2% of the dry weight and decreased with increasing age to about 40–60% of the original value.The main lipid fractions of the youngest section, the capitulum, of the S. fuscum shoot were steryl and wax esters, triglycerides, and more polar lipids and accounted for 0.4, 0.3, and 3.5%, respectively, of the dry weight. The amounts of these lipids were found to decrease during senescence at independent rates.