Mine Site Rehabilitation and Tree Species Selection
Stawell Gold Mine
- Location: Western Victoria, Australia.
- Gold mining in Stawell extends back over 120 years.
- Certain areas near the mine will be rehabilitated with vegetation.
- Three tree species were examined for their tolerance to the hot, dry environment using the SFM1 Sap Flow Meter (HRM Method)
The Sap Flow Meter
- Measures sap flow (water movement) or transpiration in woody plants.
- Data can be used to accurately measure total plant water use on an hourly or daily basis.
- The SFM1 can measure stems as narrow as 1cm as well as the largest trees on earth.
In relation to Stawell Gold Mine
- Sap Flow Meters were installed on nine trees selected from three different native tree species.
- Sap Flow Data was collected over 18 months and correlated with temperature and vapour pressure deficit (VPD).
- Temperature was a measure of hotness.
- VPD was a measure of dryness.
- Sap flow response to increased hotness and dryness was used as a measure of tolerance.
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Installation of Equipment
Measuring Correction Factors
18 Months of Sap Flow Monitoring
- Sap flow was recorded over an 18 month period. Gaps in the data were caused by solar panel malfunction.
- J (cm3 cm-2 day-1) is sap flux density corrected for stem diameter.
- Eucalyptus cladocalyx has up to 4 times the amount of sap flux of the other species.
- Sap flux showed a strong seasonal pattern: lower in winter, higher in summer.
Temperature and Sap Flow
Mild Day:
Maximum Temperature: 28°C
Transpiration: 24L
Species: E. cladocalyx
Warm Day:
Maximum Temperature: 36°C
Transpiration: 20L
Species: E. cladocalyx
Hot Day:
Maximum Temperature: 41°C
Transpiration: 17L
Species: E. cladocalyx
Note: Transpiration declines once temperature reaches approximately 30°C. Tree is still transpiring in order to not over heat and cause damage to leaves and photosynthetic systems.
Tolerance to Temperature
The optimal range of temperature (°C) for maximum sap velocity (Vs, cm hr-1) in each stem measured in this study.
There was a significant difference following one way ANOVA (F = 17.321, d.f. = 8, p < 0.001)and the results of Tukey’s HSD post-hoc test are indicated by letters above each box plot.
Results indicate Eucalyptus cladocalyx can tolerate hotter weather.
Optimal temperature range:
Eucalyptus cladocalyx: 21°C to 30°C
Eucalyptus melliodora: 20°C to 27°C
Eucalyptus polybractea: 16°C to 26°C
Tolerance to Dryness
The optimal range of VPD (kPa) for maximum sap velocity (Vs, cm hr-1) in each stem measured in this study.
There was a significant difference following one-way ANOVA (F = 15.232, d.f. = 8, p < 0.001)and the results of Tukey’s HSD post-hoc test are indicated by letters above each box plot.
Results indicate Eucalyptus cladocalyx can tolerate drier weather.
Optimal VPD range:
Eucalyptus cladocalyx: 1.5 kPa to 3.2 kPa
Eucalyptus melliodora: 1.1 kPa to 2.5 kPa
Eucalyptus Polybractea: 1.0 kPa to 2.7 kPa
Total Tree Water Use
Summary of average daily water use (Q, L day-1) throughout the various seasons of the study period. Values are total tree water use including multiple stems of E. melliodora and E. polybractea. Values are litres of water per day (±SD).
| Species | Summer ’10 | Autumn ’10 | Winter ’10 | Spring ’10 | Summer ’11 |
| E. cladocalyx | 26.35 (±8.49) | 17.02 (±6.59) | 11.21 (±4.29) | 17.25 (±4.33) | 26.59 (±4.18) |
| E. melliodora | 4.63 (±2.53) | 2.67 (±1.43) | 2.12 (±1.56) | 4.59 (±2.52) | 9.21 (±4.60) |
| E. polybractea | 7.46 (±7.82) | 4.76 (±5.01) | 3.62 (±3.52) | 8.16 (±7.57) | 4.97 (±1.36) |
Conclusion
The SFM1 Sap Flow instrument measured sap flow in nine trees over an 18 month period.
Eucalyptus cladocalyx showed the highest amount of water use, up to 4 times as much as the other species.
E. cladocalyx had greater tolerance to hotter and drier weather.
Successful rehabilitation at Stawell Gold Mine should involve E. cladocalyx.
