Lichen growth rates over 51 years at Cape Hallett, Northern Victoria Land, support a large (100x) cline across Antarctica

Abstract

Crustose lichens show a very large (roughly 100 times) growth rate cline across Antarctica from some of the lowest known growth rates in the McMurdo Dry Valleys (78° S) to near fastest in the maritime Livingston Island, 63° S. This gradient, which correlates with changes in temperature and precipitation, provides an ideal opportunity to monitor climate-driven change across Antarctica. Although the cline is based on reasonably large sample sizes at its geographic limits, a central site at Cape Hallett (72° S), is represented only by a single data point. Here we report new lichen growth rates for Buellia frigida and Rusavskia elegans from Cape Hallett based on a lichenometry site established in 1966 and rephotographed in 2004 and 2017, thus providing a total span of 51 years. Mean growth rates for B. frigida were almost identical to the previous data point (0.068 mm/yr). Rusavskia elegans had slightly higher, albeit non-significant, growth rates (0.090 mm/yr). Species also had higher growth rates in the latest measurement period, significantly so for B. frigida . However, this did not correlate with mean annual air temperature (which was significantly lower) and, instead, seemed driven by an increase in water availability. We suggest that Cape Hallett is in a microenvironmental zone where vegetation may be driven by local water relations rather than by broadscale temperature clines. Details are provided for a new lichenometry site which has been established at Luther Peak to further aid in long-term monitoring of lichen growth rates in Antarctica.

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