Coarse woody debris, macrofungal assemblages, and sustainable forest management in a Eucalyptus obliqua forest of southern Tasmania
thesisposted on 2023-05-26, 04:01 authored by Genevieve GatesGenevieve Gates
This study focussed on two components of the forest ecosystem at a small spatial scale: coarse woody debris (CWD), defined as fallen dead wood vîvá‚â•10cm diameter and vîvá‚â•1m length, and the macrofungal assemblages found on wood, soil and litter in native forest at different times of regeneration since the natural disturbance of wildfire. The CWD on the forest floor and standing dead wood (stags) in four 50x50m plots (=1ha total area) with differing wildfire histories in a Eucalyptus obliqua dominated native wet sclerophyll forest in southern Tasmania, Australia, were quantified and mapped. The CWD volumes obtained were amongst the highest in the world. Analyses showed that although a plot size of 0.25ha was too small to give an accurate measurement of volume, it was large enough to contain dead wood having attributes that reflected the stand structure resulting from wildfire disturbance. Therefore, a plot's wildfire history can be deduced from the CWD and stags of a 0.25ha plot. The substrates wood (dead wood and standing trees), soil and litter in each plot were surveyed for macrofungal fruit bodies at approximately fortnightly intervals for 14 months. A total of 849 macrofungal species was recorded from 1ha of native forest. Wood supported 410 species of which 295 were on CWD but not exclusively, i.e. a few species were found on CWD and soil or on CWD and litter. The majority of the remaining species on wood was supported by 'other dead wood' (a category containing dead wood that did not fit into CWD), which contained many species not in common with those on CWD. It was concluded that macrofungal species richness on CWD is not affected by decay class; however, length or surface area explained between 45-48% of the variation in species richness. Of the 495 species found fruiting on soil, 330 were known to be ectomycorrhizal and 165 were considered decomposers. In addition, 146 species of macrofungi were associated with litter. It was found, using temperature and rainfall data, that the appearance of fruit bodies is seasonal but not directly attributable to rainfall events. There was a better correlation using the indigenous peoples' concept of three seasons than when using the four European-based seasons. In essence, each plot contained a distinctive mycota, reflecting its chronosequence history, site characteristics (e.g. soil type, soil pH) or microclimate. To maintain the macrofungal diversity associated with the differing plots, a mosaic of multi-aged stands in the managed forest landscape is needed to provide inoculum for the reestablishment of macrofungal communities in forests at different times of regeneration. In addition, reserves should be as large as possible (at least 1ha) to encompass the variability (due to site characteristics, vegetation type, etc.) in the forest landscape and the associated macrofungal diversity as evidenced by the appearance of fruit bodies. This has particular implications for the silvicultural treatment of ARN (aggregated retention) where the retained aggregates provide refugia for macrofungal assemblages associated with the pre-treatment forest type. The results of the study also suggest that there should be some coupes assigned to longer rotations to provide a continuum of dead wood sizes and decay classes in the forest landscape, thereby maintaining associated macrofungal diversity.