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Mine Site Rehabilitation and Tree Species Selection

Stawell Gold Mine

Mine Site Rehabilitation

  • 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

Mine Site Rehabilitation 2

  • 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

Mine Site Rehabilitation 3

  • 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

Mine Site Rehabilitation 5 AMine Site Rehabilitation 5

Measuring Correction Factors

Mine Site Rehabilitation 6

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.Sap Flux in Eucalyptus for Mine Site Rehabilitation

Temperature and Sap Flow

Mild Day:

Mild Day Water Use

Maximum Temperature: 28°C
Transpiration: 24L
Species: E. cladocalyx

Warm Day:

Water Use - Warm Day

Maximum Temperature: 36°C
Transpiration: 20L
Species: E. cladocalyx

Hot Day:

Sap Volume - 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.

Temperature Tolerant Species

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.

Dryness Tolerant Species

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.

Eucalyptus cladocalyx, sugar gum.

E. cladocalyx had greater tolerance to hotter and drier weather.

Successful rehabilitation at Stawell Gold Mine should involve E. cladocalyx.

 

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