Tree root identification saves ancient caves and the forest above them

Barcoding and morphology combined allowed identification and targeted removal of problem trees.

Ancient burial caves dating to approximately 1800 years ago are under threat in Galilee, Israel. The site is the necropolis of Beit She’arim, a UNESCO World Heritage site. Tree roots from the mixed forest growing overhead have begun to penetrate the soft limestone ceiling, causing a risk of structural weakening and collapse. It became necessary to remove the trees with roots damaging the cave, but ideally to do so without needing to indiscriminately fell the entire forested area.

Penetration of plant roots through the cave limestone ceilings of the Beit She’arim necropolis, Galilee, Israel. Photos taken by the Jakoby et al. in January 2018. Image: Jakoby et al. 2020.

A new article published in Plants People Planet describes the steps undertaken to identify the offending trees by their roots alone, allowing for targeted removal and preserving the majority of the overhead forest. Lead author Gilad Jakoby and colleagues used a combination of traditional morphology-anatomy and DNA barcoding to make these identifications. The researchers used the ITS2 region for barcoding and added their data to the current database, in which Mediterranean woody plant species are under-represented.

Though identification at the level of the individual tree for ultra-targeted removal was not possible, trees were identifiable to species. This was still valuable, because characteristic rooting patterns meant that certain species had a high tendency to penetrate the cave, while others did not, so entire species could be removed before causing damage. Two species of genus Pistacia, atlantica and palaestina, were found to be the main culprits. The findings allowed the Parks Authority to save around 75% of the trees atop the cave, including Quercus calliprinos, Rhamnus alaternus, Quercus ithaburensis, Pistacia lentiscus, Punica granatum, Ceratonia siliqua, and Ficus carica.

“The efforts by botanists in combining novel and traditional methods for identification of subterranean roots, disconnected from the plants themselves, enabled the devising of management procedures that served both the antiquities preservation and landscape maintenance,” write the authors, noting that while morpho-anatomical identification alone is more challenging and requires greater knowledge than molecular identification, it is indeed possible and can give satisfactory results.

Erin Zimmerman

Erin Zimmerman is a botanist turned science writer and sometimes botanical illustrator. She did her PhD at the University of Montréal and worked as a post-doctoral fellow with the Canadian Ministry of Agriculture. She was a plant morphologist, but when no one wanted to pay her to do that anymore, she started writing about them instead. Her other plant articles (and occasional essays) appear in Smithsonian Magazine, Undark, New York Magazine, Narratively, and elsewhere. Read her stuff at www.DrErinZimmerman.com.
Erin can also be found talking about plants and being snarky on Twitter @DoctorZedd.

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