Final Report for CERF Significant Project :Using tree rings of an Australian

conifer as a bio-indicator of decadal-scale environmental change

University of Tasmania

With collaborators from

University of Western Australia

Australian Nuclear Science and Technology Organization

Western Australian Department of Environment and Conservation

The amount of Funds and the total cost/value of the Activity $2,021,654 (including $799 336 cash from CERF the remainder in-kind from host organization

($552,241) or collaborators ($670,077)

The Period of the project: 1 December 2007 to 30 June 2010

1. A summary of the major activities undertaken by the organization:

For this project, we:

Measured size class distributions of a total of 97 stands of Callitris columellaris from 17

regions across the continent (details in Table 1)

Measured size classes of 70 additional stands in the Top End to compare areas under

Aboriginal management in Arnhem Land with those in remote parts of Kakadu NP. The fire

management of land under these two tenures is very different, and this is reflected in their

stand structures.

Twice re-measured approximately 1500 trees on an Aboriginal estate that were originally

tagged and measured by Prof. Bowman in 2006. Their size and condition have since been

re-assessed each year as part of this CERF project.

Sampled cores from 15 trees per site at a total of 85 sites, and measured ring widths of each

core (details in Table 1). These data are currently being analysed for publication.

Measured dimensions of tracheids in the xylem of Callitris cores

Sampled and analysed soil from 85 sites for pH, C, N, P (Table 1). These results have been

summarized in a manuscript to be submitted for scientific publication by Nov 2010 (see

below).

Sampled and analysed foliage samples from 85 sites for C, N, P, δ13

C and δ18

O (Table 1).

Maintained a research collaboration with Professor Yuji Isagi, Kyoto University, who is

undertaking a molecular analysis of foliage from all populations we sampled (Table 1). To

date we have sent him over 2500 samples of Callitris foliage from around Australia. Prof

Mike Crisp (ANU) has also joined this collaboration on the evolutionary history of Callitris

in Australia.

Used facilities at ANSTO to obtain AMS radiocarbon dates on selected tree cores, to

determine whether tree ring formation is annual at a range of locations in contrasting

environments.

Collaborated with Professor Mike Evans, Tree Ring Laboratory at University of Arizona, to

apply the new method of ultra fast delta 13C and delta 18O isotopic analyses from tree

cores. Prof Evans has analysed cores from continental transect and these results are being

written up for publication.

Integrated the CERF research with an allied ARC funded project on rainforest dynamics and

Callitris tree growth led by Professor Bowman.

A UTAS Honours project was carried out by Zoe Lee in conjunction with NT Parks &

Wildlife, surveying Callitris populations in the West MacDonnell Ranges of Central

Australia. This was a direct spin off from the CERF project.

One continuing UTAS PhD project is also a direct spin-off of the CERF project, together

with Prof Bowman’s ongoing involvement with traditional Aboriginal people in Arnhem

Land. The student, Clay Trauernicht, is studying Aboriginal fire regimes in Arnhem Land

and is analysing data from and preparing a scientific publication based on our work on

Callitris trees in Arnhem Land, to gain a better understanding of the effects of Aboriginal

land management on tree growth, recruitment and mortality.

2. An outline of any demonstration/communication activities undertaken Prepared 7 editions of the Callitris newsletter. Our distribution list had grown to 125

stakeholders and interested people by the most recent edition. All project newsletters are

available at the following website:

http://www.utas.edu.au/docs/plant_science/fe/newsletters.htm

We have established a Tasmanian on-line dendrochronological database and repository for

tree cores and images of cores. This facility allows sharing of cores and images among the

dendrochronological community, subject to appropriate conditions. Available at:

http://tasdendro.org/html/intro.html

We have had a paper accepted by the Australian Journal of Botany (BT10045), based on the

Central Australian project by UTAS honours student Zoe Lee. (Prior LD, Lee Z, Brock C,

Williamson GJ, Bowman DJMS. What limits the distribution and abundance of the native

conifer Callitris glaucophylla (Cupressaceae) in the West MacDonnell Ranges, Central

Australia? )

Our UTAS student, Zoe Lee, completed her Honours thesis “Demographics of a native

conifer in Arid Australia”. This project was done on Callitris stands in Central Australia in

conjunction with NT Parks & Wildlife, and was a direct spin off from the CERF project.

We have submitted a paper based on the AMS radiocarbon dates of Callitris cores to the

Australian Journal of Botany. (Pearson S, Hua Q, Allen K, Bowman DJMS. Nuclear

weapon testing aids dendrochronological analysis of Callitris, a widespread Australian

conifer)

We will present our results at the Ecological Society of Australia conference in Canberra in

December 2010

In addition, we are preparing scientific publications on:

Our continental survey of population structure of Callitris columellaris. A draft of this

manuscript has been completed and will soon be submitted to Global Ecology and

Biogeography

Tracheid dimensions and ring widths in a range of Callitris species from around Australia

Growth patterns of Callitris columellaris trees from around Australia

Soil and foliar nutrient content and isotopic analyses from Callitris columellaris stands

across the continent

The effects of Aboriginal land management on tree growth, recruitment and mortality, based

on our work on Callitris trees in Arnhem Land.

A comparison of size class structures of Callitris populations under Aboriginal management

in Arnhem Land (see above) with those in Kakadu National Park

A comprehensive review of this, and closely related species, across the continent as a whole.

Previous studies have focused on particular regions, but our study provides the opportunity

to integrate the information at a national level.

Availability of research outputs over the next four years

The project newsletters will continue to be available through the UTAS website, or on

request to Prof. Bowman.

The peer- reviewed scientific publications will be permanently available as part of the

scientific literature. Interested people can also request copies directly from Prof. Bowman.

The Honours thesis is available on request to Prof. Bowman, as will be the PhD thesis after

it is accepted.

3. The benefits and outcomes of the Activity as a whole We have demonstrated the value of using Callitris columellaris as a bio-indicator of

environmental change. An intriguing finding of our investigation is that changes in Callitris populations have mirrored Australia’s mammal decline. For both groups of organisms, problems were evident first in the arid zone, and have recently emerged in the tropics. The temperate zone, although subject to far more intensive anthropogenic disturbances such as land-clearing and forestry, has proven to be relatively resilient. The inherently low productivity of the arid zone renders it much more vulnerable to change.

Using our stand structure data, we have documented the status of a wide range of Callitris

populations across Australia. This has shown that many populations in arid and semi-arid

Australia are in decline, probably because of grazing from introduced herbivores such as

rabbits and sheep, consistent with reports of poor regeneration of tree populations in general

in the drier parts of the continent (e.g. Auld & Keith 2009, Ecological Management and

Restoration 10, S79-S87). Some tropical populations are also at risk from increased fire

frequency and severity. We have almost completed a draft of a manuscript documenting this

aspect of the project (see above).

We have also reported on the status of Callitris populations in Central Australia. Our

findings suggest that fire is a key factor controlling their distribution in this region. There

has been little regeneration at many sites in the last few decades, but this may be because

there has been insufficient rainfall. A key recommendation from this work is that permanent

plots should be established and populations monitored, with the juvenile stage being of

critical importance.

Using AMS radiocarbon dating we have showed that Callitris trees growing in arid and

semi-arid environments do not form rings annually. Rather, in some years more than one

ring may be formed, while other years do not produce any growth ring. We also verified that

Callitris trees form annual rings in the seasonal tropics and in the maritime climate of

Eastern Tasmania. This finding helps define where Callitris can be usefully sampled for

future climatological studies.

From a global perspective, our survey represents a national snapshot of stand condition of

one of the most important tree species in arid and semi-arid Australia. It has also provided a

consistent framework within which to contextualise a broad range of existing studies of this

and other, closely related species.

We have established a network of people interested in the ecology and phylogeography of

Callitris species

One Honours project has been completed (Zoe Lee, UTAS). This was a direct spin off from

the CERF project

One PhD project is well under way (Clay Trauernicht, UTAS). Again, this was a direct spin

off from the CERF project

A state-of-the art dendrochronological laboratory was established at UTAS under this

project. The facility includes a scanner, measuring stage and microscope, and a fully

equipped workshop (built by UTAS to support this project).

We have established a Tasmanian on-line dendrochronological database and repository for

tree cores and images of cores. This facility allows sharing of cores and images among the

dendrochronological community, subject to appropriate conditions. Available at:

http://tasdendro.org/html/intro.html

Continuing projects arising from or linked to the CERF program:

Four Corners analysis of ecophysiological processes (Brett Murphy and Tim Brodribb, UTAS)

Climatic influences on Callitris water status and growth have been measured at four contrasting

sites over a two year period, using dendrometers and climate sensors. These have been

complemented by intensive glasshouse measurements of the effects of experimentally imposed

drought on growth of Callitris seedlings.

Fire and regeneration under Aboriginal and KNP management in Arnhem Land: Our PhD student,

Clay Trauernicht, is continuing to make measurements of Callitris populations under contrasting

management regimes in NT savannas. In July/August 2010, Clay measured the intensity of

experimental fires inside and outside patches of Callitris, to test the theory that Callitris trees

partially suppress fires through reducing grassy fuel loads beneath their canopy.

Oxygen isotope transect (Mike Evans, University of Maryland) Rainfall originating from cyclones

appears to have a different isotopic signature from other types of rainfall. This project aims to

quantify the frequency of tropical cyclones in northern Australia from the oxygen isotope signal in

individual tree rings, using cutting edge technology.

Molecular phylogeny and Phylogeography (Prof.Yuji Isagi, Kyoto University and Prof. Mike Crisp,

ANU). Analysis of DNA by Prof. Isagi’s group will be used to study the evolutionary history of the

genus, and to help resolve the ongoing taxonomic uncertainty of this group.

4. The degree to which the Activity has effectively achieved its objectives

(These are discussed in relation to the Outcomes listed on p6 of our original proposal)

1. Compare Callitris columellaris populations in environments with different land management histories (particularly with respect to grazing and fire). We have almost completed a draft of a paper that analyses stand basal area, density of juvenile and adult trees, proportion of seedlings, saplings and dead trees, stand structures of transects across Australia in relation to climate, fire and grazing. It discusses population structures in relation to the biophysical characteristics and prevailing disturbances each region. We aim to submit this paper in October 2010.

2. Determine how changes in growth rate of C. columellaris differ between southern, central

and monsoonal Australia, where there are contrasting climatic trends (wetter in the north,

drier in the south) over the last 200 years.

We have submitted a publication documenting climatic controls on tree ring formation for a range

of Callitris species across Australia (see above).

Additional AMS measurements will establish the effects of climate on tree ring formation for our

focal study species, Callitris columellaris. These data will be included in a paper we are preparing

based on an analysis of xylem characteristics in relation to climate from all sites across Australia.

Tree rings are made up of xylem cells, which transport water from the roots to the shoots of a plant.

Our preliminary analysis showed that the lumen diameters of tracheids (the cells that constitute the

xylem in conifers) vary systematically with climate. This analysis, together with our AMS

radiocarbon dating of rings, will provide information on the climatic controls on growth of Callitris

columellaris trees, and in what regions annual growth rings are formed.

We will then write a second paper presenting two aspects of Callitris growth, based on the growth

ring data we have collected during this project: (i) a simple model of temporal trends at each site,

going back 100 growth events, and controlling for tree size; and (ii) average growth over last 10

growth events in relation to rainfall, temperature, soil nutrients, tree diameter and inter-tree

competition. This will show how growth trends have varied from temperate to arid and tropical

Australia.

3. Measure changes in tree physiology through time using oxygen and carbon isotopic signatures of individual annual tree rings. We have sent samples of tree cores collected along a continental transect with a steep rainfall gradient to Prof. Mike Evans, University of Maryland. Prof Evans has measured the oxygen and carbon isotopic content of individual rings, with a focus on years with extreme events. The results are being written up in collaboration with Dr Brett Murphy, who is working on a closely related project (see below).

In addition, we have measured the δ13

C and δ18

O content of foliage and the nutrient content of soils

and foliage collected from all our sample sites across Australia. Using these data, we will be able to

quantify how changes in physiology affect tree growth. 4. Estimate likely changes to tree growth in response to predicted climate change by extrapolating from past trajectories in trees of woody vegetation cover and tree growth rates. Our analyses of tree growth will enable us to predict the effects of various climate change scenarios on Callitris growth rates and cover. (see 2, 3 and 5). 5. Provide new data on past climates cycles and the return times of extreme events including droughts, continental penetration of the summer monsoon and major tropical cyclones over the past 200 years.

See (3) above 6. Deliver to land managers a bio-indicator to detect changes to the landscape ecology of outback Australia. This project confirmed that Callitris is a sensitive bio-indicator, with some sites exhibiting extremely dense regeneration, and others no regeneration for at least 100 years. We have demonstrated that much information about the environmental history of a strategically selected site can be inferred from a single measurement of size class distribution of its Callitris population. One intriguing finding from our project is that changes in Callitris populations have mirrored Australia’s mammal decline. For both groups of organisms, problems were evident first in the arid zone, and have recently emerged in the tropics. The temperate zone, although subject to far more intensive anthropogenic disturbances such as land-clearing and forestry, has proven to be relatively resilient. The inherently low productivity of the arid zone renders it much more vulnerable to change. 7. Provide evidence to resolve long-standing debates about the impact of the cessation of Aboriginal landscape burning and effect of domestic and feral stock on rangelands.

See (3) and (6) above

This project highlighted that although there are generally high densities of seedlings in the tropics, many do not survive to the sapling size class because of high fire frequencies, and as a result, some populations are at risk. This concords with many reports in the literature about the adverse effects resulting from cessation of Aboriginal landscape burning. We also found that there has been a chronic shortage of Callitris regeneration in much of the arid zone, but were unable to demonstrate an effect of grazing from our study because of the scarcity of un-grazed control sites. However, the literature conclusively documents the detrimental effect of sheep and rabbit grazing on Callitris, and we conclude this is a major contributor to the worrying status of Callitris across arid Australia. 8.Build dendrochronological capacity in Australia.

Under this project we have established a state-of-the art dendrochronological laboratory at UTAS.

The facility includes a scanner, measuring stage and microscope, and a fully equipped workshop

(built by UTAS to support this project). We have also established a Tasmanian on-line

dendrochronological database and repository for tree cores and images of cores. This facility allows

sharing of cores and images among the dendrochronological community, subject to appropriate

conditions. Available at: http://tasdendro.org/html/intro.html

5. The appropriateness of the approaches used in the development and

implementation of the Activity

(i) Using size class distributions to infer the health of Callitris populations proved a very successful

approach, and demonstrated important differences amongst climate zones. While most tropical and

temperate sites exhibited a distribution consistent with continuous regeneration, most arid sites did

not. This indicates a chronic lack of recruitment of Callitris over much of the continent, consistent

with reports for many other tree species. It will be possible to re-measure these sites in future, to

follow current trends in population health.

(ii) Using a traditional dendrochronological approach to infer climate from tree ring widths proved

problematic because we found that Callitris does not form annual rings over most of its range, and

trees at individual sites typically do not cross-date. However, we have used ring widths to

investigate the most important determinants of tree growth.

Table 1: Summary of number of sites sampled in each region.

Region Climate zone Stand structure transects

cores, soil & foliage DNA

Top End & Arnhem Land Tropical wet-dry 13 12 13

NT Gulf Tropical wet-dry 7 6 6

Kimberley Tropical wet-dry 9 9 9

North Queensland Tropical monsoonal 1 1 1

North Queensland Humid sub-tropical 4 4 4

Southern Queensland Humid sub-tropical 6 6 6

Queensland Coastal Humid sub-tropical 1 1 1

Pilliga Humid sub-tropical 11 7 7

Pilbara Arid 1 1 5

Central Australia Arid 5 5 5

Roxby Downs Arid 3 3 3

Western NSW Semi-arid 8 8 8

Flinders Ranges Semi-arid 7 6 6

WA- Goldfields Semi-arid 5 5 5

WA- Murchison Semi-arid 6 4 4

Terrick Terrick Semi-arid 3 2 2

Snowy River Temperate 7 5 5

TOTAL

97 85 90

Project Staff

Dr Lynda Prior, a tree ecophysiologist and landscape ecologist, undertook the field program

and the ecological, tree ring growth data and isotopic analyses.

Dr Kathryn Allen, who carried out dendrochronology in the early stages of the project

Mr David Tng, who measured and undertook initial analysis of the tree rings. Dr Pauline

Grierson is providing traditional dendrochronological expertise for the project.

Mr Scott Nichols, who undertook a research support role as well as working on an allied

Australian Research Council project on the ecophysiology of Callitris tree growth.

A number of people were employed on a casual basis to help with the field program,

including Alison O’Donnell, Phillip Moser, Marj King, David Tng, Sharyn Yelverton. We

were also assisted by many volunteers.

Engagement of co-researchers:

All co-researchers and project staff participated in the field program in at least one region. This was

fruitful in generating suggestions and discussion, and contributed greatly to everyone’s

understanding of the data collected, and the possibilities for its analysis and publication. Dr Prior

worked at every site, ensuring consistency in the sampling and giving her an overall picture of the

project that is invaluable for analysing the data and writing up the project. Dr McCaw accompanied

the southern WA and Kimberley field trips, and provides a land management perspective for the

project. Dr Grierson accompanied the Snowy River and NSW mallee field trips, as well as advising

on site selection in the Pilbara. She also supervised the analysis of soil and foliage samples. Dr Hua

participated in the Snowy River field trip, and was responsible for the AMS analysis of selected

cores samples to accurately date these cores, allowing us to estimate how many growth events occur

each year in selected regions.