Creators:

David Bowman (0000-0001-8075-124X) , Ben French (0000-0001-5046-4047)

Co-Creators:

Lynda Prior (0000-0002-5511-2320)

Biological Sciences

The primary goal of this trial was to identify best-practice methods (interventions) for restoring burnt pencil pine (𝘈𝘵𝘩𝘳𝘰𝘵𝘢𝘹𝘪𝘴 𝘤𝘶𝘱𝘳𝘦𝘴𝘴𝘰𝘪𝘥𝘦𝘴) stands. We selected five study sites in the Lake Mackenzie area. We sought to develop methods to rehabilitate burnt Pencil Pine stands (not create new stands) and hence targeted areas with fire-killed Pencil Pines. We selected three sites burnt in the 2016 fires (Burnt sites henceforth) and two which were not burnt in 2016, but contained dead Pencil Pines from the 1960’s fires (Unburnt sites henceforth). We chose sites which were relatively accessible and which captured environmental variability. Sites did not have formal boundaries or fixed size; they were simply a tool to achieve geographic spread.

Five sites containing fire-killed pencil pines were selected and a number of plots (ranging from 262 to 290) were established within each site. Three sites were burnt by the 2016 fires (recently burnt hereafter) and two were outside the 2016 fire boundary but contained dead pencil pines from the 1960/61 fires (historically burnt hereafter), indicating their potential suitability for the species. Sites were selected that were relatively accessible, represented the topography and vegetation of the Lake Mackenzie area and achieved geographic spread. Sites had no boundaries; rather, a cache of materials was dropped by helicopter at each site, and field workers moved outwards from these caches when choosing plot locations. For both direct sowing and transplant interventions, plots were spread across a range of substrate types and depths, ground cover and topography within each site. Only positions within 5 m of an existing pencil pine stem (including live trees, dead trees and dead fallen dead trunks) were considered, because the focus was restoring damaged stands (not creating new ones). Plots were restricted to areas where tree guards could be constructed (i.e. stakes could be driven into the ground). Each site was also searched for wild seedlings, or groups of seedlings, around which tree guards could be constructed in situ - these positions were targeted for the natural germinant interventions. 𝗜𝗻𝘁𝗲𝗿𝘃𝗲𝗻𝘁𝗶𝗼𝗻𝘀: 𝘕𝘢𝘵𝘶𝘳𝘢𝘭 𝘨𝘦𝘳𝘮𝘪𝘯𝘢𝘯𝘵𝘴 - Thirty-five plots were established in March 2019, to assess the practicality and effectiveness of restoring pencil pines by protecting naturally germinated seedlings from herbivores. Such seedlings were only found near living adult pencil pines, and mostly on Sphagnum. Seedlings sometimes occurred on their own, or in groups of two or three, but often were in dense clusters, with more than 100 small germinants present per 1m² in some cases. Plots were situated where a seedling, or group of seedlings, could be enclosed within tree guard in situ. For half of these plots, tailored tree guards were constructed using stainless-steel mesh and aluminium tubes to create a perimeter impervious to vertebrate herbivores. Remaining plots were left as open controls, with a perimeter marked using several aluminium posts but no mesh. 𝘋𝘪𝘳𝘦𝘤𝘵 𝘴𝘰𝘸𝘪𝘯𝘨 - 300 plots were established in March 2019, in which seeds were sown directly into the field. Seeds were donated by the Tasmanian Seed Collection Centre at the Royal Tasmanian Botanical Gardens (RTBG); an ex-situ seed bank aimed at conserving native Tasmanian flora and facilitating restoration efforts. Seed counts were adjusted such that an expected 15 viable seeds were sown per plot (17-20 total seeds). Three sowing methods were trialled; (i) undisturbed, whereby seeds were sown onto the natural ground surface; (ii) scratched, whereby seeds were sown onto a disturbed surface, which was created by removing surface vegetation over a small area (~30 cm diameter) using a mattock to mimic an animal dig, and; (iii) dug, in which seeds were sown into a small pit (5 cm deep) created using the tip of a mattock, and a handful of soil replaced on top of the seeds. Half the sowing plots were left open but marked using coloured plastic disks to make them visible in a subsequent aerial survey. The other half were caged, using a robust stainless-steel tree guard; a ‘tee-pee’ design, built from aluminium tubing, tie wire and stainless-steel mesh, pegged down with mild steel jute pins. Sowing plots were re-surveyed in December 2021 and germinant presence, or absence, was recorded. 𝘛𝘳𝘢𝘯𝘴𝘱𝘭𝘢𝘯𝘵𝘴 - 1007 transplant plots were established between February and April 2020. In each, two small pencil pines were planted as tube stock: one propagated from seed (seedling henceforth) and one propagated from cutting material (‘cutting’ henceforth), which allowed the two propagation methods to be compared. Tube stock were grown at Habitat Plants Nursery (Liffey, Tasmania), who obtained seeds and cutting material from several provenances, including both local from the Lake Mackenzie area and non-local stock. The intention of including non-local material was to embed a simple provenance trial into our plantings, which could be assessed both in the present study and following future re-surveys. Tube stock of several age classes were also included. Half of the transplant interventions were protected from herbivores using tree guards, and half were left open (as described for sowing interventions above). Trials of various tree guard material were embedded in the design.After planting, the topographic position of each plot was classified according to macrotopography (3 m scale) and microtopography (0.5 m scale), so that the influence of both on establishment could be tested. Half of the interventions we established were enclosed within tree guards, protecting them from vertebrate herbivores (referred to as ‘caged’ interventions), while half were left open to herbivory (referred to as ‘open’ interventions).