According to a report by news website ScienceNetwork WA, a team led by Murdoch University expert Dr Michael Craig – including researchers from Alcoa and the University of Western Australia – undertook a study on a series of three-year old restored bauxite mine pits in south-western Western Australia.
The aim of the research was to further explore the poorly studied use of “coarse woody debris” (CWD) as an important consideration in forest and woodland restoration.
“CWD is very slow to develop naturally so, to accelerate the return of CWD-dependent species to restored areas, CWD is commonly returned manually. However, few studies have tested the effectiveness of such a strategy,” the study’s abstract explained.
The research found that recolonisation success using CWD was limited, with several reptile and mammal species found to be abundant in natural forest while completely absent from the restored mine sites. Conversely, one species of mouse was found to be abundant in the restored areas and absent in the unmined forest.
“The provision of CWD did reduce barriers and accelerate recolonisation for some species, but overall, the effects were not strong,” Craig told ScienceNetwork WA. “Restored forests were primarily inhabited by species that did not require CWD.”
Research recommendations
The research results suggested that in order to achieve greater success with recolonisation, further consideration would need to be given to the density and spatial arrangement of the CWD “habitat piles”.
Craig said biodiversity would be more likely to increase if CWD was arranged as clumped logs instead of with scattering, adding that 50 logs per hectare would be a better reflection of natural home ranges for species such as the south-western crevice skink, which had been completely absent from the restored mine sites studied.
The research also indicated that long-term management of CWD distribution was important to improve recolonisation success given that the manually restored CWD would likely be lost in controlled burns or wildfires within 75 years and that natural CWD might develop too slowly to replace it.
“The management of restored forest will need to accelerate the growth of suitably-sized trees and return a proportion of that tree growth as CWD to the forest floor by either killing or felling branches or whole trees,” Craig explained.
While the study only focused on mineral mines, Craig said the research could be extended to quarries.
“The issue here is really about encouraging fauna back into any post-mining revegetation and there are a lot of fauna that rely on logs and CWD, so any mining company should aim to return logs where possible,” he told Quarry.
“The problem might lie in sourcing the logs if you are mining in an area that lacks remnants of natural vegetation, which might be the case for some quarrying operations, but this is still important to aim to do.”
The full study can be accessed via www.sciencedirect.com