From Weeds to Wildfire: Restoring Woodland Understoreys #3

Dear readers, welcome to the third newsletter from the White Box woodland understorey restoration project. This update brings both good tidings and some bad news, courtesy of the recent Gerogery wildfire. But more of that later, first to the latest news.

Field day

Fig. 1. Participants enjoy the field day at Bakes TSR in September 2009

Last year’s field trip was a great success. A total of 22 participants, including land-holders and agency staff from three states (NSW, Vic & ACT) took a guided tour of the two demonstration sites at Bakes and Cumberoona TSRs (Fig. 1). The ‘chauffeured’ CSU minibus provided a great opportunity for everyone to catch up on news, and extensive discussions and feedback at the demonstration sites gave us some great ideas to consider as the project progresses. Having everyone pitch in at the end of the day to get the bogged bus out of a ditch was a great way to enhance interactions amongst government agencies across three states too!

Irrigation

Fig. 2. The new sprinklers in action at Cumberoona

In spring 2009, we installed irrigation pipes and water tanks at both sites (Fig. 2). We aimed to maximize establishment of native grasses from the (expensive) seed we sowed, and the system also allows us to simulate climate change impacts by comparing  watered and unwatered sub-plots. The system includes piping and sprinkler heads in all plots and a 25,000L tank, which is regularly filled by a local water truck. Plots have been watered weekly, depending on rainfall, from spring 2009 onwards. While the Bakes system proved short-lived (see below), the Cumberoona system provides a valuable backup to help maximize native grass establishment.

Treatment impacts

Cumberoona sugar boundary Aug 209

Fig. 3. Boundary between no sugar (left) and sugar (right) in grazed plots at Cumberoona TSR in August 2009. Paterson’s Curse and Capeweed dominate on the left and Austrostipa on the right

As participants at last year’s field trip observed, our restoration trials (fencing, crash grazing, spring burning and sugar application) had big effects on ground vegetation at the two field sites (Fig. 3). Ian Cole is busy analyzing the results this summer, but initial analyses indicate significant differences among many treatments, especially for the worst weeds at these two sites, the broad-leaf weeds Paterson’s Curse and Capeweed. We shall summarise more trends in later newsletters.

Controlling broad-leaf weeds

Fig. 4. Effects of treatments on cover of broad-leaf weeds at Cumberoona TSR in spring 2009

The most dramatic outcome from last spring was the extraordinary suppression of broad-leaf weeds by sugar. This was most obvious at the weediest site, Cumberoona, where sugar diminished weed cover from 100% to 15% or less (Figs. 3-4). A similar trend occurred at the Bakes TSR (Fig. 5). Unfortunately, our other two treatments, burning and crash grazing in spring, did not have any discernible effects on the cover of broad-leaf weeds in the following year, except where they were combined with sugar (however some of these treatments did affect exotic annual grasses – see below).

Other weeds

Fig. 5. Effects of treatments on cover of broad-leaf weeds at Bakes TSR in spring 2009

The results clearly demonstrate that activities that don’t affect nutrient levels – including fencing (i.e. the control), spring burning and crash grazing alone, cannot be used to control broadleaf weeds. However, our data show that some of these treatments suppressed exotic annual grasses, so these treatments may be useful in many other remnants, depending on which weeds are abundant. More results will be provided in the next newsletter after we have completed the analyses.

Native grass establishment

Fig. 6. Healthy Kangaroo Grass (Themeda) seedling at Cumberoona TSR in January 2010

While treatments had big impacts on the existing swards of native and exotic plants, they have not resulted in strong establishment of native grasses as we had hoped. We spread seed of four native grasses in spring 2008, autumn 2009 and spring 2009: Tussock Grass (Poa), Wallaby Grass (Austrodanthonia), Red Grass (Bothriochloa) and Kangaroo Grass (Themeda). Kangaroo Grass seeds appear to have established the best (Fig. 6), although they are patchy in many plots. We have just re-sown Kangaroo Grass and Red Grass one extra time in case summer rain promotes further establishment of these C4 grasses (fingers crossed).

We will re-monitor seedling establishment in autumn 2010 to see how well grass seedlings have survived through summer. The disappointing results to date highlight the need to develop more reliable methods for establishing native grasses, for both restoration and commercial purposes.

Gerogery fire

Fig. 7. Bakes TSR three days after the Gerogery fire

Thursday 17th December brought bad news to the Gerogery district as a wildfire driven by gale force winds destroyed four houses and 1000s of hectares of farmland. Our plots in Bakes TSR didn’t escape, and the fire destroyed our recently installed irrigation system as well as many beautiful hollow trees at this magnificent site (Figs. 7-8).

Fig. 8. Aftermath of the Gerogery fire. Plot fences and our water tank survived

Unfortunately we do not have enough funds to replace the irrigation system so we will be keeping our eyes open for extra funding sources and will review this part of the project next year.

Nevertheless, all is not lost. The fences still stand and plots were burnt relatively uniformly, so we can continue to assess treatments at Bakes TSR in the future.

Following good rains over Christmas, scattered Kangaroo Grass from our sown seeds were among the first plants to resprout in the burnt areas (Fig. 9). Hopefully they will prosper in the absence of competition.

Recent Papers

Fig. 9. One positive outcome. Kangaroo Grass plants growing from sown seed have resprouted rapidly in some burnt plots

We recently published the following papers on related work. Please let us know if you would like us to send you a copy.

Prober, S.M. & Lunt, I.D. (2009). Restoration of Themeda australis swards suppresses soil nitrate and enhances ecological resistance to invasion by exotic annuals. Biological Invasions, 11(2), 171-181.

Prober, S.M., Lunt, I.D. & Morgan J.W. (2009). Rapid internal plant-soil feedbacks lead to alternative stable states in temperate Australian grassy woodlands. In: New Models for Ecosystem Dynamics and Restoration. (Eds R.J. Hobbs & K.N. Suding), pp. 156-168. (Island Press, USA).

We’ve kept this news sheet brief, and have left out many details. If you’d like to learn more about the project, please contact us and we’ll be happy to describe the project in more detail. To view all blogs on this project, select the Projects/Restore tab above. You can also download a pdf file of this newsletter.

Related Blogs

Project Sponsors

Once again, we thank all of our project sponsors and the many helpers who have kept the project running over the past year, especially Neil Padbury. Droughts and fires aside, we look forward to developing better ways to restore woodland understoreys in 2010 and beyond.

Ian Lunt, Suzanne Prober & Ian Cole January 2010

Contact details

Dr Suzanne Prober                Suzanne.Prober@csiro.au

Assoc.Professor Ian Lunt      ilunt@csu.edu.au

Ian Cole                                    Ian.Cole@environment.nsw.gov.au

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