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Serotiny and WWI memorials

April 27th, 2021 Leave a comment Go to comments

On ANZAC Day (25 April; the national day of Australia, see wikipedia) I received the following query from an Australian colleague.

Apparently one of the few Australian soldiers that survived the Gallipoli battle (Turkey, 1915, WWI) picked up a pine cone (from a ‘Lone pine’), and took it back to Australia. The cone was kept on a shelf until 1933 when a horticulturalist extracted 5 seeds and germinated them. The seedlings were planted in botanic gardens; the 78-year-old trees now have special symbolic value to war veterans and the like (Fig. 1). The returned veterans are often referred to as ‘lone pine soldiers’ (and the battle, as the battle of the lone pine). My colleague asked me if the cone story had some credibility, for instance, would a pine seed germinate after 18 years?

Fig. 1. Plaque at the foot of pine tree in Kings Park, Perth, Western Australia. From [4]

The plaque in Kings Park (Fig. 1) suggest that the pine is a Pinus halepensis (Aleppo pine). However, the pines in Gallipoli peninsula (and in most Turkey) are of another species: Pinus brutia (Turkish Red Pine) [2]; the two species are very close related. So the cone that the soldier pick up should be a P. brutia, unless there was a plantation of P. halepensis there.

Pine seed, once there are out of the cone, do not last for long (mostly less than a year). However one of the characteristics of both P. halepensis and P. brutia is that they have some serotinous cones (the serotiny level is higher in P. halepensis than P. brutia, but both have a proportion of serotinous cones) [2,3]. Serotinous cones are those that remain closed after maturation, i.e., more than a year [1]. They accumulate for several years, forming a canopy seed bank; these cones open after the tree burns in a wildfire, and thus it is an adaptation to regenerate after fire [1]. At least in the case of P. halepensis, we have evidence that cones remaining close on the tree for many years; most cones open in less than 8 years, but some can last more than 15 years (Fig. 2). In addition we have evidence of cones remaining closed after harvest (at lest 12 years in my experience). This information is for P. halepensis, but could apply to P. brutia as well.

Fig. 2. Left: Frequency distribution of trees in relation to their maximum closed cone age for Pinus halepensis in eastern Spain. The gray pattern corresponds to the proportion of trees in population under high frequency of crown fires, the white to the proportion of trees where crown fires are rare. From [3]. Right: example of long-lived serotinous cones in P. halepensis in eastern Spain.

In conclusion, the Australian soldier may have picked up a serotinous cone, perhaps from a P. brutia. The seed were in the cone for 18 years and then extracted and planted. There are other accounts suggesting that several Australian soldiers took cones of both P. brutia, and P. halepensis (it’s difficult to understand why soldiers would collect pine cones after such a deadly battle, but this is another question …).

Currently most WWI memorials in Australia include a P. halepensis tree, a few a P. brutia. In the memorial cemetery near Gallipoli they planted (in the 1920s) a different pine, a Pinus pinea (stone pine, not native from Turkey, but from Italy and Spain). And in New Zealand (they shared with Australians the Gallipoli drama), the tree in ANZAC memorials includes Pinus radiata (from California) and Pinus canariensis (from Canary Islands, west Africa). That is, any of the ca. 120 pine species may do for a war memorial…

If Gallipoli has not been a fire-prone ecosystem, the pines would not be serotinous, the cones collected by the soldiers would not had kept the seeds, and we would not have pines in the Australian and New Zealand war memorials. So now, when you see a pine in a war memorial, just think about fire adaptations!

References

[1] Lamont BB, Pausas JG, He T, Witkowski, ETF, Hanley ME. 2020. Fire as a selective agent for both serotiny and nonserotiny over space and time. Crit. Rev. Plant Sci. 39:140-172. [doi | pdf | suppl.]  

[2] Pinus brutia jgpausas.blogs.uv.es/2017/04/19/

[3] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. Amer. J. Bot. 100: 2349-2356. [doi | amjbot | pdf | supp.]  

[4] For more about the lone pine puzzle see: Underwood R. 2014  quadrant.org.au | wikipedia

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