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Harvard Forest Data Archive
Growth Rates of Xanthoparmelia Lichens in North Cemetery, Petersham MA since 2005Related Publications
- Lead: Anne Pringle
- Contact: Anne Pringle
- Start date: 2005
- End date: 2011
- Status: ongoing
- Location: North Cemetery (Petersham MA)
- Latitude: 42.53
- Longitude: -72.19
- Elevation: 331 meter
- Release date: 2015
- EML file: knb-lter-hfr.217.4
- DOI: digital object identifier
- Related links:
- Study type: long-term measurement, modeling
- Research topic: ecological informatics and modelling; physiological ecology, population dynamics and species interactions
- LTER core area: populations
- Keywords: carbon dioxide, demography, growth, lichens, modeling, population dynamics
Lichens fix carbon dioxide from the air to build biomass. Crustose and foliose lichens grow as nearly flat, circular disks. While smaller lichens grow slowly, but with small, steady increases in radial growth rates, larger lichens grow more quickly, with radial velocities that remain roughly constant over the lifetime of an individual. These basic features follow directly from a novel mathematical model based on the diffusion of carbon dioxide around a lichen, and its absorption by the thallus. Smaller lichens fix carbon dioxide across the entire thallus, but larger lichens fix carbon dioxide disproportionately at edges. Because local edges remain the primary source of carbon as a lichen grows ever larger, radial growth rates remain constant. Predicted growth dynamics depend on four measurable parameters, and tests of the model against data suggest the model provides an accurate, robust, and universal framework for understanding the growth dynamics of lichens in nature.
A group of 55 foliose lichens growing on the French tombstone of the North Cemetery, Petersham, MA, USA was used to measure growth rates of lichens in nature. Target individuals are morphologically uniform and belong to the genus Xanthoparmelia. Inscribed letters and numbers were used to make a map of the entire population and identify individual thalli from year to year. Each thallus was measured each fall for seven years, starting in 2005. A transparent piece of plastic was placed over the thallus and the diameter of the thallus traced with permanent marker. Tracings were digitized and the area calculated from digitized images. New individuals born in 2006, 2007, 2008 and 2009 were added to the survey, and during the survey 32 individuals died. By the end of the survey, in 2011, data had been collected for a total of 72 individuals.
In the data file, the observed values for an individual (alive, merge, size) are coded as NA before a birth is recorded and after a death is recorded. NA may also indicate missing observations. After a merger, the larger individual is coded as alive = 1, merge = 1 for as long as it lives; while the smaller individual is coded as alive = 0, merge = 1 and then as NA. Fragmented individuals (merge = 3) may revert to unmerged (merge = 0) at the next observation. Outlier births are coded as NA.
This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.
Pringle A. 2015. Growth Rates of Xanthoparmelia Lichens in North Cemetery, Petersham MA since 2005. Harvard Forest Data Archive: HF217.
hf217-01: lichen growth rates
- grave: grave identification
- individual: lichen identification
- year: year of measurement
- alive: whether or not lichen was alive
- 0: not alive
- 1: alive
- merge: indicates a merger between two individual lichens
- 0: smaller
- 1: larger
- 3: fragmented
- size: size of lichen (unit: squareCentimeters / missing value: NA)