Plant succession and the oldest primary succession plots in the world.
Note: This page is being updated - after a second trip to the archives the complete set of photos and stem maps have been collected, as well as substantial other data on historical land cover, bird and mammals through succession, and other quantitative and qualitative data. As it gets processed it'll get posted, email me for more info: bbuma at alaska.edu
100 years ago, William s. cooper founded what is now believed to be the longest running primary succession plot network in the world
William S. Cooper, one of the founding fathers of ecology, is known for many things - presiding over the Ecological Society of America, inspiring one of the most impressive academic family trees in the biological sciences, being a founding father of Glacier Bay National Park. One of his largest contributions to the science of ecology was foundational work on plant succession, inspired in part by his adviser, Cowles, who similarly studied the phenomena of community development with time.
Cooper, in a moment of inspiration, seized upon the opportunity provided by Glacier Bay to establish a network of permanently marked plots on recently deglaciated rock, areas recently devoid of plant life. He had the intention to revisit and chart the development of the plant community from early mosses to gigantic late successional trees in real time. Cooper realized that while chronosequences (studying different locations which are different ages) are useful for inferring change through time, they are less informative then actually observing change through time. He also had the foresight to understand this was a multi-lifetime project, and provided extensive directions to the plots with the express intention of future researchers not yet born continuing the work. Unfortunately, the plots languished after the death of Cooper in the 1970's and his graduate student, Donald Lawrence, in the early 1990's. A combination of isostatic rebound, magnetic declination changes, vegetation change, soil buildup covering the corner markers, and the lack of GPS coordinates (how we rely on them now!) meant the locations were lost.
100 years later...
In 2016, I led an expedition (sponsored by National Geographic and the University of Alaska) to rediscover those plots amongst the now developing woody plant community, bears, and wolves. Using a combination of 1916 maps from the University of Minnesota archives, metal detectors, and compasses (and a variety of other shoestring-type techniques) we found and remeasured the plots, which show substantial change over the last century. By GPS'ing these locations any interested researcher can now access 100 years of permanent plot data, including community composition, maps, diversity indices, and a variety of ancillary data for powerful questions about how communities change, the role of stochastic variability, and rates of change in response to climate warming.
Community development has proceeded in some ways according to theoretical expectations, but in other ways it has diverged from expected timelines. In general, the data highlights the importance of contingency, or random variation in what species established first. The primary player here are willows - if there were willows establishing 100 years ago, they are still around. They form thick nests about 2 meters high, too dense for much tree establishment (the absolute number of willows has decreased as individuals have gotten bigger). In other areas, where competition with mat forming herbs appeared to keep out the willows, there are alders, spruce, and other later successional species.
While richness has gone up overall, meaning more species, the communities are increasingly being dominated by a few number of species - willows or spruce. The small size of the plots established by Cooper means further work is needed to accurately estimate overall diversity, but the patterns in relative diversity are likely real given the data.
Soil development appears to reflect species change and community development - meaning unlike expectations of orderly increase in soil depth, nitrogen and carbon content, etc, we see strong legacies of stochastic species arrival community assemblage. This suggests that on the century timescale, as glaciers recede and as plants push into high latitudes, soil development may be highly heterogeneous.
The latest effort is aimed at expanding Cooper's plots to reflect the reality of a more "mature" (term used loosely!) forest. One m2 plots are not an appropriate size for a more structurally complex forests, with larger individuals, and in 2017 I led another group to put in 15m radius plots around each of the original plots. In those plots, we cored trees, placed 10 additional quadrats, and are looking at community development, yes, but also beta diversity, alpha diversity estimates, and microbial/fungal dynamics - all within a strict, spatially explicit design that will allow us also to explore spatial autocorrelation in these environments. This gets to a fundamental question - how representative are these plots? Results soon!
Thanks to Sarah Bisbing (Cal Poly), John Krapek (UAF), Glenn Wright (UAS), and Glacier Bay National Park for making the re-discovery expedition successful.