Plant Ecology & Physiology | Soil Microbiology | Above/Belowground Linkages | Ecological Restoration | Environmental Stewardship
GUIDING PRINCIPLES
The successful recovery of disturbed landscapes is dependent upon its starting point, especially the integrity of landform, lithology and soil. Thereafter, more subtle environmental drivers appear to be responsible for the convergence (or divergence) of rehabilitation outcomes relative to natural systems, including:
the composition of plant biodiversity;
their ability to form above- & belowground linkages;
their impact toward soil/growth conditions.
Within this context, this research module generally seeks to quantify the role of these small-to-large-scale plant-soil interactions in the form, function and resilience of natural vs. degraded ecosystems.
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Landscape Rehabilitation Following Sand Mining on North Stradbroke Island
This study depicts broad-scale revegetation patterns following sand mining on North Stradbroke Island, south-eastern Queensland, Australia. Based on an ecological timeline spanning 4–20 years post-rehabilitation, the structure of these ecosystems (n = 146) was assessed by distinguishing between periods of ‘older’ (pre-1995) and ‘younger’ (post-1995) rehabilitation practices.
The general rehabilitation outlook appeared promising, whereby an adequate forest composition and suitable levels of native biodiversity (consisting of mixed-eucalypt communities) were achieved across the majority of rehabilitated sites over a relatively short time. Still, older sites (n = 36) appeared to deviate relative to natural analogues as indicated by their lack of under-storey heath and simplified canopy composition now characterised by mono-dominant black sheoak (Allocasuarina littoralis) reaching up to 60% of the total tree density. These changes coincided with lower soil fertility parameters (e.g., total carbon, total nitrogen, and nutrient holding capacity) leading us to believe that altered growth conditions associated with the initial mining disturbance could have facilitated an opportunistic colonisation by this species. Once established, it is suspected that the black sheoak’s above/belowground ecological behaviour (i.e., relating to its leaf-litter allelopathy and potential for soil-nitrogen fixation) further exacerbated its mono-dominant distribution by inhibiting the development of other native species.
Although rehabilitation techniques on-site have undergone refinements to improve site management, our findings support that putative changes in edaphic conditions in combination with the competitive characteristics of some plant species can facilitate conditions leading to alternative ecological outcomes among rehabilitated ecosystems. Based on these outcomes, future studies would benefit from in depth spatio-temporal analyses to verify these mechanisms at finer investigative scales.
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Site-Specific Climate Analyses Elucidate Rehabilitation Challenges for Post-Mining Landscapes
In eastern Australia (as elsewhere worldwide), the availability of water is critical for the successful rehabilitation of post-mining landscapes and climatic characteristics of this diverse geographical regional are closely defined by factors such as erratic rainfall and periods of drought and flooding. Despite this, specific metrics of climate patterning are seldom incorporated into the initial design of current land rehabilitation strategies.
This series of studies examines climate parameters (mostly related to rainfall and water availability) to characterize bioregional climate sensitivity and their impact on the restoration of 'natural' ecosystems. Overall, the manner in which these climatic factors are identified and ultimately addressed by land managers and rehabilitation practitioners could be a key determinant of ecosystem development at the planning stages of rehabilitation design.
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