Slime Moulds at Black Sugarloaf, Birralee

by Sarah Lloyd

Trichia decipiens

Trichia decipiens (height 3 mm) appears frequently on bark and decaying wood

The recent attention grabbing headline - Slime mold uses an externalized spatial “memory” to navigate in complex environments - about research at the University of Sydney, was carried out in the comfort of a laboratory where the plasmodium of Physarum polycephalum moves about on an algal film in a Petri dish.

My study of plasmodial slime moulds involves the next phase in the life of these extraordinary organisms - searching for their reproductive structures. Physarum polycephalum is the ‘lab rat’ of slime moulds that would rarely, if ever, be seen in the field. But other species of Physarum along with an extraordinary array of other minute forms (most around 2 millimetres high) are frequently encountered in the tall wet eucalypt forests of northern Tasmania.

Plasmodial slime moulds (also known as myxomycetes) are common and widespread in terrestrial ecosystems where suitable habitat (i.e. decaying plant material) exists. Despite the fact that they are known to be abundant in temperate regions of the world, and that several type specimens were collected in Tasmania, there has been very little research on slime moulds here.
I started a study of slime moulds in the tall eucalypt forest at Black Sugarloaf, Birralee, in May 2010. I am fortunate enough to live permanently in my study area and so can make daily visits to monitor the progress of species in the field. After the first year of observation I thought I had begun to get a sense of the frequency of appearance of some species, but observations over the following two years have confused the picture. My limited experience tells me that even with daily visits to a number of sites it is too early to make assumptions about whether species are rare or common as there seems to be great variation in the abundance of particular species from year to year.

Black Sugarloaf (41° 23’ 42” S 146° 48’ 23” E) is located in central north Tasmania. It has well-drained, rocky, dolerite-derived soils and its forests are dominated by Eucalyptus species. Over the past one hundred or so years these have been cut for sawlogs, railway sleepers, telegraph poles and, more recently, for woodchips. 130 acres of forest at approximately 450m asl is privately owned land protected by a conservation covenant. Current land management practices do not include removal or burning of coarse woody debris or the understorey vegetation. The areas most often surveyed for slime moulds (Big Tree Track, Thismia Gully and Swamp) are all within about 100-200 metres from Home. Big Tree Track is visited at least once each day; the other areas are usually visited once a week.

Tall wet Eucalypt forest
Tall wet Eucalypt forest

'Home' is open eucalypt forest dominated by gumtopped stringybark (Eucalyptus delegatensis), black peppermint (E. amygdalina), stringybark (E. obliqua), white gum (E. viminalis) and swamp gum (E. ovata). The diverse understorey has silver banksia (Banksia marginata), forest daisybush (Olearia lirata), native cherry (Exocarpos cupressiformis), guitarplant (Lomatia tinctoria), prickly moses (Acacia verticillata), dollybush (Cassinia aculeata) and mountain correa (Correa lawrenciana). Ground layer vegetation includes sagg (Lomandra longifolia), forest flaxlily (Dianella tasmanica), cutting grass (Gahnia grandis), swordsedge (Lepidosperma sp.), bracken fern (Peridium esculentum) and other ferns. Some clearing of understorey vegetation for fire protection occurs around the house but old logs are left in situ.

Melaleuca Swamp Forest
Melaleuca Swamp Forest

'The Swamp' is approximately 100 metres north of 'Home'. It is a damp shady area with a permanent small creek that overflows onto a level flood plain after extended rainy periods. The closed canopy forest is dominated by blackwood (Acacia melanoxylon) and swamp gum (E. ovata) with a mid layer of tall swamp paperbark (Melaleuca ericifolia) and scented paperbark (M. squarrosa). The ground is mostly devoid of vegetation except for cutting grass, hard waterfern (Blechnum watsii) soft waterfern (B. nudum), treefern (Dicksonia antarctica) and mother shieldfern (Polystichum proliferum). There is a small patch of rainforest species including sassafras (Atherosperma moschatum) and the endemic heartberry (Aristotelia peduncularis). There are numerous logs and lots of leaf litter.

Old growth Eucalypt sp.
Old growth Eucalypt sp.

Big Tree Track
The Big Tree Track (BTT) is so called because when we first moved to Black Sugarloaf a large old-growth tree, the only remaining such tree on Black Sugarloaf, was still standing. The tree fell in about 1990 and the stump and large log now provide substrate for numerous bryophytes, fungi and slime moulds. The 1 km track meanders through closed wet forest dominated by stringybark (Eucalyptus obliqua) and blackwood (Acacia melanoxylon). The midstorey species include silver banksia (Banksia marginata), dogwood (Pomaderris apetala), blanketleaf (Bedfordia salicina), treefern (Dicksonia antarctica), forest daisybush (Olearia lirata), and musk (O. argophylla). The ground layer is mostly devoid of vegetation except for patches of hard waterfern (Blechnum nudum). There is a deep layer of leaf litter and numerous rotting logs covered in mosses, leafy liverworts and lichens.

Shaded wet forest
Shaded wet forest

Thismia Gully
Thismia Gully (TG) is a southeast facing slope approximately 100 metres downslope from ‘home’. It has a watercourse with an ephemeral creek that flows only after extended rainy periods. It has a closed wet forest dominated by blackwood and swamp gum. The mid layer vegetation is mostly dogwood (Pomaderris apetala), musk (Olearia argophylla) and native currant (Coprosma quadrifida). The ground is devoid of vegetation except for occasional ferns including hard waterfern, treefern and tender brake (Pteris tremula). There is a litter layer of leaves, many fallen small trees, particularly dogwood, and numerous very large old bryophyte-covered eucalypt logs.

The area is referred to as Thismia Gully because of the occurrence of Thismia rodwayi a small saprotrophic plant whose common name is fairy lanterns.

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