Figure 1. Repeat photography of a site in the Sibinacocha Watershed where glacial retreat is exposing large tracts of land that are rapidly colonized by microbes (months to years) but only slowly colonized by plants (decades to centuries). The top photograph was taken in 2005 and the bottom in 2010 (the person in each photograph is standing in approximately the same location). The photographer was standing at about
5200 m above sea level near the ‘100-m site’ viewable in an aerial photograph of the site previously published in Schmidt et al. (2009). The distance from the person to the closest edge of the ice is approximately 20 and 200 meters in the top and bottom photos, respectively.
Reprinted from: The Journal of Molecular Ecology, Vol. 23, pg. 254 (2014)
An important observation made during our work on ecosystem succession at the Puca Glacier was that the rate of plant colonization of newly de-glaciated lands in the Sibinacocha Watershed was much slower than it is in recently de-glaciated sites in the Alps and Alaska. At first we hypothesized that the slower rate of succession in the Sibinacocha Watershed was due to the harsher climate (e.g. higher elevation, drier climate etc.) at this site compared to milder climates in the Alps and Alaska. This hypothesis was used to obtain grants from the National Science Foundation and the National Geographic Society to carryout comparative studies of successional processes in Peru, Alaska, Montana and Washington State. The most important finding of this research was that the harsh climate in the Sibinacocha Watershed was not the main factor limiting plant colonization. In fact, evidence is mounting that lack of the nutrient phosphorus is the dominant factor limiting plant colonization in the Sibinacocha watershed. This finding not only contradicted our initial expectations, but also overturned classic theory in the field of ecosystem ecology which posited that nitrogen should be the most limiting nutrient during the initial stages of plant succession. These findings are still being analyzed for final publication, but several papers relating parts of this story have been published (Knelman et al. 2014, Schmidt et al. 2011, 2012, 2014).