How does genetics affect mortality and recruitment in quaking aspen forests? I’m excited to share several years of work with numerous students and collaborators that has just come out in Ecological Applications. You can read the paper at the journal or get a PDF.

The study asks how cytotype (# of chromosome copies), genotype, and environment affect aspen demography. Cytotype variation is common within many species and may have major ecophysiological consequences, that in turn scale up to demography. Aspen is especially interesting because it grows in potentially large clones that can share resources and span environmental gradients.

We set up a network of hundreds of forest plots in southwestern Colorado, spanning riparian areas to mountaintops, and collected genetic data, environmental data, and demographic data from each of them.

We found a mosaic of cytotypes at the regional scale, and also (in gridded sampling within regions) complex patterns of clone interdigitation.

These forests included a range of outcomes, including high mortality and low recruitment to low mortality and high recruitment, as contrasted in the photos below.

We found most interestingly that mortality was higher for triploids, and that mortality and recruitment varied strongly along environmental gradients – with proxies for hotter and drier conditions disproportionately affecting each cytotype.

The study overall suggests that in the near future, climate change will likely have a larger negative effect on triploids. However the strong interactions we found with herbivores, and the differential results for recruitment and mortality, indicate that the story may be more complex. We are now doing additional years of resurvey work, and also trying to scale this up via remote sensing, to get a better handle on the situation.

The work involved several undergraduate students from Arizona State University as well as with some great collaborators. We did the fieldwork originally in 2018 and spent several years processing and understanding all the datasets. There were many long hard days in the forest – randomly located plots take one to some unexpected places, some steep, some wet, all magical. An aspen forest even on a rough day is a beautiful place to work. We hope to have more publications out on this species soon!