After two years of analysis, planning, consulting and collaborating, the Climate-Ready Revegetation Project has moved from concept to action!
At Bush Heritage's Nardoo Hills Reserve in central Victoria climate change is causing extensive dieback of Grey Box (Eucalyptus microcarpa) and Yellow Box (E. melliodora) trees. To address this dieback, the Climate-Ready Revegetation Project will provide long-term guidance on viable, climate-ready eucalypt revegetation options for the reserve and this region using climate-adjusted provenancing. The trial will run over many decades.
Once an experimental design was chosen, seed was collected from geographically diverse seed ‘climate analogue’ regions and was propogated at the ArborLine nursery in collaboration with GreenFleet. In preparation for a winter planting rip lines were cut through the soil across100 hectares at trial sites on the reserve.
Nardoo Hills, the Bush Heritage Australia reserve in central Victoria, near Wedderburn, has areas of eucalypts that are stressed or have died through the influence of intense drought and/or heat stress, most likely linked to climate change. The affected area now covers over one hundred hectares of the resrve. Most at risk are Grey box (Eucalyptus microcarpa) and to some extent yellow box (E. melliodora). The dieback is affecting both older and younger trees; some having died outright while others have experienced the death of mature trunks and then survived with coppiced shoots or epicormic regrowth.
Traditional revegetation programs use locally sourced seed, based on the expectation that they are the most suited to the local environment. This approach is now considered high risk due to the changing climate (Breed et al., 2013). Bush Heritage seeks to develop better climate adaptation options for its Reserves. To achieve this, the project aims to establish a large field trial that will:
- mix and compare the performance of seedlings grown from seed sourced from a range of provenances of these species, including both climate-challenged provenances and provenances from less extreme environments, and
- optimise the genetic potential for subsequent generations of trees to enhance survival in the face of a gradually warming and drying climate.
Selecting seed/provenances from ‘climate analogue’ regions
We followed the suggestions of Hancock et al., (2016) to bring together genetically diverse and climatically robust populations of grey box and yellow box using the ‘Climate-adjusted provenancing strategy’. To do this, we initially used the Bureau of Meteorology’s Climate Analogues tool to pinpoint regions that are currently experiencing a climate that is similar to that which is expected at Nardoo Hills (central Victoria) in 30-70 years’ time. Such a long-term outlook is needed as the trees planted should persist for at least 70 years.
Using the Climate Analogues tool and the Australasian Virtual Herbarium (and Atlas of Living Australia), we identified three ‘harsh’ climate analogue regions that also had records of reasonable populations of grey box and/or yellow box: Quorn SA, Griffith NSW and Condobolin NSW. We also chose two provenances from climatically softer analogues (Deniliquin NSW and Wagga NSW) and the local provenance of each species from the Wedderburn/St Arnaud area of Victoria.
|The regional analogues & their modelled attributes*
||Analogue climate severity rating
||Max temp (oC) vs Wedderburn
||Annual rainfall vs Wedderburn
|Quorn: Warr, RCP 4.5, Max consensus, 2090 (+2.0°C, -4%rainfall)
||1 (hotter, much drier)
|Griffith: Warr, RCP 4.5, Max consensus, 2090 (+2.0°C, -4%rainfall)
||1 (hotter, much drier)
|Condobolin: Warr, RCP 8.5, Least hot & wettest 2090 +2.8°C, +11% rainfall
||2 (much hotter, wetter)
|Deniliquin: Warr, RCP 4.5, 2050, Max consensus, +1.2°C, +1% rainfall
||3 (hotter, similar rainfall)
|Narrandera: Warr, RCP 4.5, Max consensus, 2090, +2.0°C, -4%rainfall
||1 (hotter, much drier)
|Condobolin: Warr, RCP 8.5, 2090, Least hot & wettest, +2.8°C, +11% rainfall
||2 (much hotter, wetter)
|Deniliquin: Warr, RCP 4.5, 2050, +1.2°C, +1% rainfall
||3 (hotter, similar rainfall)
|Wagga: Bend, RCP 4.5, Max consensus, 2050, +1.0°C, +1% rainfall
||3 (warmer, similar rainfall)
Sourcing seed from climate analogue regions
For those analogue regions that have established communities of Grey Box or Yellow Box, professional seed collectors or community members with a deep knowledge of their local eucalypt flora surveyed the regions to locate and collect seed from 10 well-spaced Grey Box or Yellow Box ‘mother trees’. Prolonged dry and now drought conditions in NSW added greatly to the difficulty in finding trees bearing adequate amounts of mature seed. Seed capsules were harvested using a variety of methods and stored in order to dry and extract the seed. The seed was packaged along with site details, including GPS coordinates.
Seed from five Grey Box provenances and Four Yellow box provenances was successfully collected. Seed collectors were unable to find seed-bearing trees for only one of the provenance/analogue regions: Yellow Box around Condobolin. Ironically, many trees in this immensely dry landscape were in flower at the time of collection. We aim to collect and propogate the seed of this provenance in 2019.
Yellow Box distribution highlighting areas (red circles) where the species has been reported in a climate analogue for Nardoo Hills (red dot).
The recorded locations of seed sourced from mother trees of Grey Box (blue) and Yellow Box (red) in NSW and Victoria. Note the Flinders Ranges (SA) Grey Box seed sourced site is not included. Nardoo Hills is represented by red square in the most northern red square in the SW corner of the map.
We are evaluating 5 provenances for each of the two species in a range of varying aspects. To do this, we have settled on a standard experimental design comprised of 18 blocks (1 ha each) placed in upper, mid and lower slope sites. The blocks are located across a ~90 ha undulating paddock on the north-west flank of the Nardoo Hills Reserve, and the nearby Lawan Reserve.
There are 18 blocks, each consisting of 25 plots (5 provenances replicated 5 times), each plot planted with one of the 5 provenances. Nine have been planted with Yellow Box and nine with Grey Box. The provenance plots will be replicated 5 times and the plots randomised across the block. Each plot will contain 25 plants from one provenance, with individual seedlings representing each of the 10 'families' (a family being seedlings all propogated from seeds collected from a single mother tree).
All seedlings were planted at 4m x 4m spacings in August 2019 (except the missing yellow box provenance). One row of buffer trees was planted around each block.
Propagation: Seed cleaning and sowing
Seed from nine provenances (and 90 families) were delivered to the Arborline Nursery in Hamilton for propagation. The process of producing tube stock commenced with seed cleaning which involved carefully removing of the chaff (packing material around seed in the gum nuts) and sorting the seeds into large and smaller categories. This enabled only strong seed only to be sown directly into individual cells of seed trays, optimising the survival and strength of the germinating seedlings. This was challenging for the Nursery because of the need to isolate and keep track of the seed and seedlings from 90 families.
Site preparation for planting commenced in early winter. The first step was to cut narrow rip lines across the trial site to capture and allow the deeper penetration of rainfall, and to allow subsequent planting of tube stock. In early December, GreenFleet organised contractors from Maine Environmental (Castlemaine) to undertake ripping down to about 40 cm, applying a double rip spaced by 4 metres. The timing was excellent: about 90 mm of rainfall subsequently occurred through December (27% of the total 2018 rainfall).
After we had recorded the precise coordinates of the rip lines, the position of the trial blocks was planned, and the site was marked with stakes.
Seedlings were planted in Winter 2019 with each seedlings individually labelled and bar coded to identify their parental lines and provenances. Plant health and growth rates, as well as any subsequent regeneration at the site (many years down the track!), will be monitored closely in the 450 plots over the following years. As the trees will take many years to mature, the monitoring program is expected to continue in some form for many decades. It is anticipated that the short-term results will help guide further climate-adjusted revegetation works by Bush Heritage, Vic Roads and other organisations as well as local farmers and other landowners.
The metadata underpinning this trial design and principles will be made available publicly for reference in planning future research on any aspect of the Climate-Ready Revegetation project. Universities and other research organisations wishing to undertake research on the trial are welcomed and encouraged to approach Bush Heritage Australia to establish such a collaboration.
This trial is a collaboration between Bush Heritage Australia and GreenFleet. This project received scientific guidance from Prof Ary Hoffmann, The University of Melbourne; Drs Suzanne Prober, Linda Broadbent and Rebecca Jordan, CSIRO; Dr Martin Breed, University of Adelaide and Dr Peter Harrison and Prof Brad Potts (University of Tasmania). Additional and extensive technical guidance was provided by GreenFleet (Eoghan O'Connor and Jo Sasse) and Arborline (Keith Cumming). Both GreenFleet and Arborline have gone to special lengths, well beyond commercial expectations, to support the establishment of the quality requirements of this project. Financial support was generously provided by VicRoads for seed collection.
Seed collections were generously organised/undertaken by Andrew Knop (Outback Seeds); Dan Frost (Creswick Harvest); The Australian Tree Seed Centre; Nella Smith (Narrandera, NSW); Dick Green (Wagga, NSW) and Anne Brown (Wirrabara, SA). We do applaud the extra lengths to which our seed collectors went to secure appropriate quantities of seed in a very challenging season and environment. We also thank Sue Logie (Land Services Officer, Murray Seedbank); Jess Hill (Senior Local Land Services Officer, Riverina LSS), Martin Driver (Wagga NSW) and Nicki Taws (Greening Australia) for their assistance in locating either seed-bearing trees or seed collectors.
Breed, M.F., Stead, M.G., Ottewell, K.M., Gardner, M.G., Lowe, A.J., 2013.
Which provenance and where?: Seed sourcing strategies for revegetation in a changing environment.
Conserv Genet 14, 1-10.
Hancock, N., Harris, R., Broadhurst, L., Hughes, L., 2016.
Climate-ready revegetation. A guide for natural resource managers.
Macquarie University, Sydney.
Garry McDonald, Matt Appleby and Angela Hawdon.