Trees in the ecosystem pt V: Trees & slime molds

Single-celled organisms that may create larger structures as groups in order to reproduce, slime molds, whilst not considered active wood decayers, can be found colonising deadwood (Heilmann-Clausen, 2001). Deadwood of 10-22 years of age, Heilmann-Clausen (2001) alleges, is most optimal for slime molds – at least, for the species observed on the decaying beech logs that featured within the study. This correlates with current understanding of slime molds, which suggests species strongly prefer moist, well-decayed wood.

Enteridium lycoperdon Pyrus
The false puffball (Enteridium lycoperdon) on the well-decayed remains of a pear (Pyrus sp.) stem.

The presence of wood-decay fungi sporophores, or even simply mycelium within the wood substrate, may also act as a source of energy for slime molds (Ing, 1994). As mycelial networks and their associated sporophores may take some time to develop within deadwood, this may perhaps be a further reason for why slime molds are found in greater abundance on older woody debris. The presence of bacteria, also greater in abundance on older and heavily-decayed wood, may also influence slime mold presence, as bacteria can be utilised as a further source of energy (Heilmann-Clausen, 2001). Lodge (1997) describes some slime molds as “predators of decomposers”. Slime molds may also utilise decaying leaves as a habitat (Ko et al., 2009; Raper, 1941; Raper, 1951; Stephenson, 1989). Therefore, the decaying leaf litter-soil ‘zone’ is another potential niche for slime mold species (Landolt & Stephenson, 1986). Moreover, slime molds may be found upon the bark of living trees (Olive & Stoianovitch, 1973; Stephenson, 1989).

Fuligo septica Betula
Fuligo septica, known commonly as ‘dog sick slime mold’ or ‘scrambled eggs’, growing on birch (Betula pendula).

Away from wood, decaying leaves, and soil exclusively, the composition of a forest ecosystem may also have an impact upon slime mold density. Landolt et al. (2006) found that, whilst species diversity did not differ between deciduous-broadleaved and coniferous stands, the broadleaved sites were host to slime mold populations over four times more abundant than coniferous sites. The same study also identified that different species of slime mold would be found at different altitude levels within forests, and suggested different micro-habitats perhaps act as refugia for different slime mold species that may have once colonised greater ranges of forest.

References

Heilmann-Clausen, J. (2001) A gradient analysis of communities of macrofungi and slime moulds on decaying beech logs. Mycological Research. 105 (5). p575-596.

Ing, B. (1994) Tansley Review No. 62: The phytosociology of myxomycetes. New Phytologist. 126 (2). p175-201.

Ko, T., Stephenson, S., Jeewon, R., Lumyong, S., & Hyde, K. (2009) Molecular diversity of myxomycetes associated with decaying wood and forest floor leaf litter. Mycologia. 101 (5). p592-598.

Landolt, J. & Stephenson, S. (1986) Cellular slime molds in forest soils of southwestern Virginia. Mycologia. 78 (3). p500-502.

Landolt, J., Stephenson, S., & Cavender, J. (2006) Distribution and ecology of dictyostelid cellular slime molds in Great Smoky Mountains National Park. Mycologia. 98 (4). p541-549.

Lodge, D. (1997) Factors related to diversity of decomposer fungi in tropical forests. Biodiversity & Conservation. 6 (5). p681-688.

Olive, L. & Stoianovitch, C. (1974) A cellular slime mold with flagellate cells. Mycologia. 66 (4). p685-690.

Raper, K. (1941) Dictyostelium minutum, a second new species of slime mold from decaying forest leaves. Mycologia. 33 (6). p633-649.

Raper, K. (1951) Isolation, cultivation, and conservation of simple slime molds. The Quarterly Review of Biology. 26 (2). p169-190.

Stephenson, S. (1989) Distribution and ecology of myxomycetes in temperate forests. II. Patterns of occurrence on bark surface of living trees, leaf litter, and dung. Mycologia. 81 (4). p608-621.

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Trees in the ecosystem pt V: Trees & slime molds

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