The Australian Transect Network (ATN) studies bioclimatic gradients to evaluate ecological changes across four primary transects, focusing on species dynamics, carbon fluxes, and biodiversity. Key research questions include the response of species and ecosystems to environmental changes and climate resilience. The ATN serves as a vital framework for environmental monitoring, decision-making, and policy formulation related to climate change impacts on ecosystems.

1. The Australian Transect Network
Bioclimatic gradients for assessing and
monitoring ecological change
Stefan Caddy-Retalic, Alan Andersen & Ian Fox

2. Terrestrial Environmental Research Network

3. ATN – Four primary transects
NATT
North Australian Tropical
Transect
SWATT
South West Australian
Transitional Transect
BATS
Biodiversity and
Adaptation Transect
Sydney
TREND
TRansect for
ENvironmental monitoring
and Decision making

4. ATN – Four primary transects
Spinifex Hummock Grassland
Tropical Savanna
NATT
North Australian Tropical
Transect
SWATT
South West Australian
Transitional Transect
BATS
Biodiversity and
Adaptation Transect
Sydney
Acacia Shrubland
TREND
TRansect for
ENvironmental monitoring
and Decision making
Eucalypt Open
Forest
Subtropical forest
Eucalypt Open
Woodland

5. Why bioclimatic transects?
• Scaling-up from local, plot-based studies
• Biogeographic framework for locating plots

6. Why bioclimatic transects?
• Scaling-up from local, plot-based studies
• Developing, calibrating and validating ecological models and
remote sensing products

7. Why bioclimatic transects?
• Scaling-up from local, plot-based studies
• Developing, calibrating and validating ecological models and
remote sensing products
• Identifying sensitive zones in relation to environmental stress
and disturbance
• Space as a proxy for time for climate-change research

8. Key Science Questions
1. How do species abundances, richness and composition, and
ecological function change along large-scale environmental
gradients?

9. Key Science Questions
1. How do species abundances, richness and composition, and
ecological function change along large-scale environmental
gradients?
2. Is there predictable variation in ecosystem resilience?

10. Key Science Questions
1. How do species abundances, richness and composition, and
ecological function change along large-scale environmental
gradients?
2. Is there predictable variation in ecosystem resilience?
3. How might ecosystems respond to climate change?
• Turnover in species, adaptive traits and genes

11. ATN – NATT and TREND
NATT
TREND

12. Overarching research framework of responses of ecosystems to stress
(PAM, AN) and disturbance (fire, grazing)
North Australian Tropical Transect
IGBP-GCTE Global Network of Transects

13. DARWIN
TENNANT CREEK
500 mm
750 mm
1000 mm
1250 mm
1500 mm
Photos: Adam Liedloff
North Australian Tropical Transect

14. NATT Focal Areas
DARWIN
TENNANT
CREEK
Growth of tagged trees
• Site every 100 km
• 12 eucalypts tagged per site
• Initial measurements 2000
• Re-measured 2012
1. Tree dynamics

15. Tree growth along NATT
0
0.05
0.1
0.15
0.2
0.25
0
0.1
0.2
0.3
0.4
0.5
0 500 1000 1500 2000
Heightincrement(m/yr)
DBHincrement(cm/yr)
Median annual rainfall (mm)
G. D. Cook, unpublished
Height (for tree with 25 cm dbh)
DBH

16. Monitoring tree dynamics using LiDAR

17. NATT Focal Areas
2. Carbon stocks and fluxes
0
0.2
0.4
0.6
0.8
1
1.2
0 500 1000 1500 2000
Sand
Loam
Tree cover and rainfall

18. NATT Focal Areas
2. Carbon stocks and fluxes
0
0.2
0.4
0.6
0.8
1
1.2
0 500 1000 1500 2000
Sand
Loam
0
2
4
6
8
0 1 2 3 4 5
log DBH (cm)
logBiomass(kg)
-1
0
1
2
3
4
5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
log tree DBH (cm)
logrootbiomass(kg/m2)
Tree carbon stocks – above ground Tree carbon stocks – below ground
Tree cover and rainfall
Biomass as predicted by DBH

19. NATT Focal Areas
2. Carbon stocks and fluxes
• LiDAR for landscape-scale
assessments

20. NATT Focal Areas
2. Carbon stocks and fluxes
• LiDAR
• Integration with flux-tower
measurements
Collaborating institutions:
• CDU (Hutley and Maier)
• Max Planck (Levick)

21. 0
20
40
60
80
100
120
1500 1250 1000 750 500
Annual rainfall (mm)
No.species
Sand
Loam
Plot (1 ha) richness
Tropical
Arid
Ants as a focal taxon for biodiversity studies
NATT Focal Areas
3. Biodiversity

22. Ant biogeographic discontinuities
0
20
40
60
80
100
120
1500 1250 1000 750 500
Annual rainfall (mm)
No.species Sand
Loam
Plot richness
Mesic Semi-arid Arid

23. Finer resolution of the sensitive areas in
relation to climate change
U.S. Fulbright PhD scholar Israel Del Toro, University of Amherst

24. NATT Focal Areas
4. Ecological processes - Fire
• 400,000 km2 burnt each
year
• Biodiversity declines
• GHG abatement

25. NATT Focal Areas
4. Ecological processes - Fire
y = -2E-07x2 + 0.0008x - 0.145
R² = 0.8489
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 200 400 600 800 1000 1200 1400 1600 1800
Mean % area burnt
Mean annual rainfall

26. NATT Focal Areas
4. Ecological processes - Fire
y = 2E-07x2 - 3E-05x + 0.0106
R² = 0.787
0
0.1
0.2
0.3
0.4
0.5
0.6
0 500 1000 1500 2000
Early dry season
y = -4E-07x2 + 0.0008x - 0.1556
R² = 0.6897
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 500 1000 1500 2000
Late dry season
Mean annual rainfall Mean annual rainfall

28. Transect for Environmental Monitoring and
Decision-making
Vegetation turn-over quantified
Guerin & Lowe EMAS 2012
Guerin et al. 2013
 35 Plots
 Soil characterisation
 Floral composition
 Vegetation structure
 Ant communities
 Metagenomics
 Photopoints
Temperature loggers
 δ13C & δ15N isotopes

29. Current and
predicted
future
species
distributions
Now
2050

30. Current and
predicted
future
species
distributions
Now
2050
Mapping
sensitivity to
climate change

31. Detecting ecosystem changes over time: implications for the future
Orchids flowering
20 days earlier
than 20 years ago
Flowering phenology

32. Detecting ecosystem changes over time: implications for the future
Orchids flowering
20 days earlier
than 20 years ago
Hop Bush leaves
narrowing over
the last century
Flowering phenology Functional traits

33. Using new genomics
techniques
Plants
•DNA barcoding
•Biogeography
•Population Genetics/Genomics
Soils
•Metabarcoding
McCallum et al AustEcol 2013
Gene turn-over in plants and soil
Genomics, metagenomics and transcriptomics

34. Integrating information on biodiversity distribution
and climate sensitivity for biodiversity resilience
• Weighted benefit maps for policy and land
management decision makers

35. Connecting the public to research is a TREND priority.
This should be a two-way dialogue.

36. Australian Transect Network
A powerful tool for enhanced
ecosystem understanding and
management in the face of
climate change