New views from old soils

New views from old soils

Many of the colourful layers of volcanic ash seen in road cuttings of the Waikato-Bay of Plenty may hold clues to the past.

Waikato University scientists studying the buried soils on these layers are uncovering not only why they sequester more carbon than any other soil, but have also developed a breakthrough method for extracting possible ancient DNA from these buried soils that could provide clues to past environments and climate change.

Professor David Lowe, who is leading a Marsden-funded study jointly with colleagues at Adelaide University to examine how these soils preserve carbon and whether they offer a new tool for reconstructing palaeoenvironments, says the project has offered serious technical challenges. "The buried soils contain allophane, a clay mineral comprising tiny spherules of aluminium oxide and silica formed from the weathering of glass from volcanic ash. These spherules are only about three to five nanometres (or 30 to 50 atoms) in diameter. 

The mechanisms by which allophane holds and preserves carbon, and possibly ancient DNA, makes it extremely difficult to extract for analysis."

Through a series of experiments using synchrotron radiation at the National Synchrotron Radiation Research Center of Taiwan, and other lab work, Waikato PhD student Yu-Tuan (Doreen) Huang in Professor Lowe's team has shown DNA is not only bound to allophane through phosphate groups but is also physically protected from microbe attack and degradation by filling voids within clusters of tiny allophane spherules (nanoaggregates).

Doreen Huang, working experimentally with Dr Ray Cursons at the University of Waikato, has also discovered no reagants commonly used could break the chemical bond between synthetic allophane and salmon-sperm DNA that had been added to it in the lab. However, through further experimentation they have devised a new method for DNA extraction from the organic matter-rich allophanic soils. Some of these findings have been published in a chapter in a book Soil Carbon (Springer, 2014), and a paper on the new DNA extraction method was presented at the World Congress of Soil Science in 2014.

Professor Lowe's team has also been invited to review the field of palaeoenvironmental DNA research for the Journal of Quaternary Science.