34 september 2004 wwwsfamorguk fig 2: the growth curve of the lichen rhizocarpon geographicum determined by direct measurement a plot of radial growth rate (rgr) versus thallus diameter on rock surfaces in north wales. Through the early 1990s developed lichen dating curves for ﬁve regions in the arctic and subarctic mountain ranges beyond altitudinal and latitudinal treelines although these dating curves are still in use across alaska, little progress has been made in the past decade in updating or extending them or in developing new curves comparison of results from recent moraine-dating. Lichenometry is a fairly new technique a man named of renaud had the idea to use lichens in dating archaeological remains in 1939 a chart can be seen showing the relationship between lichen growth and age produced from an experiment in norway (see figure 4) even so, lichenometry is not widely used and is not always accurate. This paper presents a new lichenometric dating curve for southeast iceland the temporal framework for the curve is based on reliably dated surfaces covering the last 270 years, making it the best constrained study of this nature conducted in iceland the growth of lichen species within rhizocarpon section rhizocarpon is non-linear over.
This decline in growth as the lichen becomes older is illustrated in many growth curves (armstrong, 2004), and supports the trend found on dating curves which shows lichen.
Typical lichen growth curves relating lichen size and age are non-linear (bradwell processes and mortality may enable a more accurate estimate of the time lag to be made and improve the accuracy of dating curves there is also uncertainty regarding the shape of the growth rate–size curve , especially in the rhizocarpon group (trenbirth. Wherebyanumerical relationship (lichenometric dating curve) is established between lichen size andsurface age basedonthe size of lichens growing on surfaces of known historical age (control points) thus, provided glacier history is sufficiently well known to establish a priori the age of enough surfaces for use as control points, lichenometric dating curves.
However, the well-documented recent times in iceland might help building up lichen population monitoring that would give light on population dynamics on features built by geomorphic processes, helping at better understand the influence of mortality on the building of lichen growth ‘curves’ and its potential toward dating curves. In alaska, lichenometry continues to be an important technique for dating late holocene moraines research completed during the 1970s through the early 1990s developed lichen dating curves for five regions in the arctic and subarctic mountain ranges beyond altitudinal and latitudinal treelines although these dating curves are still in use.
Michael g loso æ daniel f doak the biology behind lichenometric dating curves received: 14 march 2005/ accepted: 1 september 2005/published online: 20 october 2005 springer-verlag 2005 abstract lichenometry is used to date late-holocene terminal moraines that record glacier ﬂuctuations tra-ditionally, it relies upon dating curves.
A new approach to lichenometry, based on large samples of the single largest lichen on each boulder, is presented on surfaces of uniform age, lichen sizes measured in this way are near normally distributed, so the mean value can be used in constructing lichenometric-dating curves by combining mean values from several sites. Loso mg, doak df 2006 the biology behind lichenometric dating curves oecologia 147: 223-229 crossref. Traditionally, it relies upon dating curves that relate diameters of the largest lichens in a population to surface ages although widely used, the technique remains controversial, in part because lichen biology is poorly understood.