Monitoring of rehabilitated areas is carried out to assess the success of rehabilitation, identify areas where re-work is required, to allow improvements to rehabilitation techniques and to determine the long-term sustainability of rehabilitation and its ability to be integrated into normal forestry management practices.
The completion criteria specify standards that Alcoa’s rehabilitation must achieve in order for the State Government to accept management responsibility for the rehabilitated areas. Monitoring provides an indication of whether these standards have been attained.
Monitoring conducted during the first couple of years of rehabilitation development indicates areas where re-work is required to ensure that the rehabilitation meets the completion criteria in the future.
Long-term monitoring provides useful feedback to Alcoa on the development of the rehabilitation, and the long-term sustainability of rehabilitated areas, and the ability for these areas to be integrated into standard forest management programs.
Botanical Monitoring at 9 months old
The 30th June each year is considered as the starting age of the rehabilitation. All rehabilitated pits and haul roads are monitored in March, the year following rehabilitation, to determine that jarrah and marri stocking rates are adequate, there are enough legume seedlings, weed invasions are minimal and there are no large erosion gullies. The timing of this monitoring at 9 months old, allows remedial work to be carried out prior to the second winter.
For rehabilitated pits and haul roads, eucalypts and zamias are counted within two metre wide belts traversing the pit. Legumes, non-legumes and weeds are counted in quadrats at predetermined intervals along the belt.
At nine months of age the rehabilitated pits must meet the following criteria;
- A minimum of 600 eucalypt stems per hectare;
- A minimum of 150 marri stems per hectare;
- A maximum of 2500 eucalypt stems per hectare (with the exception of haul roads and pits less than 2ha);
- A minimum legume density of 0.5 plants per square metre.
- Less than 50 declared perennial weed plants per hectare.
- No large erosion gullies.
Areas not meeting any of these criteria are inspected by Alcoa and DEC staff and remedial treatments are applied where needed.
Botanical Monitoring to measure species richness
When the rehabilitated areas are 15 months old, intensive counts of plant species numbers are carried out in randomly located monitoring plots. Fifteen months is the second spring after the completion of rehabilitation and by this age the plants are large enough to be identified and many species are flowering at this time of the year. It is also after the first summer dry period and seedlings that have survived the first summer are likely to persist.
The purpose of this monitoring is to determine the species richness of the rehabilitation areas and compare this to species richness counts in the unmined forest. The monitoring plots are 20m x 20m in size within which the health and size of trees are recorded. The plot contains 5 understorey quadrats in the four corners and in the middle of the plot. Identical plots are set up and monitored in the unmined forest for comparison.
Alcoa’s internal target for species richness in the rehabilitated areas is to establish the same number of species as in the unmined forest plots, that is a value of 100% on average over all pits. The government agreed completion criteria require that at 15 months of age, the rehabilitation must have a minimum of 60% of the number of species in the surrounding forest. Higher species richness is achieved through optimum topsoil return, seeding and the planting of recalcitrant plants.
Long-Term Vegetation monitoring plots
Each year some of the 15 month old monitoring plots are retained as permanent long term monitoring plots. The purpose of these plots is;
- To provide dependable data for tracking of floristic and structural changes in rehabilitation;
- To provide baseline floristic data from the forest to compare to rehabilitated areas;
- To provide data for feedback to the Nursery regarding seeding and planting success;
- To eventually enable a “model” of vegetation development in rehabilitation to be determined;
- To determine the factors affecting vegetation development in rehabilitation; and
- To provide reliable data and study sites for other related studies to be conducted.
There are now more than 900 permanently marked plots covering a wide range of rehabilitation ages and unmined forest areas. To date 479 species have been recorded (native and non-native). The data from this monitoring program are stored in an access database which can be used to study specific plant groups or to examine vegetation changes over time.
Fauna Monitoring in rehabilitated areas
A Long term Fauna Monitoring Program (LTFMP) was developed in 1991 to standardise Alcoa’s fauna-related monitoring and research activities.
Surveys are carried out at each site on a 5-yearly basis. Mammals, birds and reptiles are assessed using transects, pitfall traps, cage traps and elliot traps. Frogs are assessed by listening to their calls during the spring. Ants are assessed using small pitfall traps.
There are monitoring sites at the Jarrahdale, Huntly and Willowdale mines. Sites are also located at an area of forest undisturbed by mining at Karnet.
The monitoring program has the following objectives:
- To monitor the re-establishment of a jarrah forest–like ecosystem in the rehabilitated mined areas;
- To provide input for the improvement rehabilitation methods;
- To develop an understanding of successional trends of fauna;
- To increase the understanding of key ecological processes;
- To monitor and control species which could become pests; and
- To provide information for the public.
Results to date have shown that most fauna species return to rehabilitated areas when the appropriate habitat has developed.