A Dendroalsia Mini Quest
Last weekend I was surprised to find Dendroalsia abietina at around 600m elevation on a small mountain at the edge of Comox Lake. It was growing on both rocks and maples alongside its longtime companion, Antitrichia californica. As is often the case when any of us make the mistake of thinking we understand how another organism truly works, this brought me back to square one. D. abietina is endemic to the Western North America, with a range extending from southern California to Campell River area of British Columbia to the north, with herbarium records concentrated around the coast also pockets of occurences into Alberta and Montana.
On southern Vancouver Island, it occurs lavishly on Garry Oaks, but it can also be seen on various street trees. As the native oaks disappear up island, it seems to loiter on Big Leaf Maple, usually about 10' up the trunk. It also finds a home on vertical-ish bedrock, especially with southern exposure. Below are a list of pet theories I've harboured to explain the distribution and needs of this moss. None have held.
Bark chemistry - Thrives on garry oak, but also maple and alder and occasionally conifers.
Loves it warm - Mostly mediterranean habitat, but also Idaho, Montana and Alberta. It must have some extreme cold tolerance.
Loves it dry - Flourishes in hot, mesic, S-facing habitats, but also present in deep understory of coastal forests, plus anomalous population at Looper Canyon.
Rock chemistry - thought it liked basic, limey rocks, but seems to show up on metavolcanic rocks. Perhaps limey veins help?
Aspect - South loving but found in all aspects on understory trunks of maple
Elevation/Winter Cold Typically at low elevations in this region, but also at 600m on rock in central Vancouver Island as well as much higher in Alberta, Idaho, Montana and the Okanagan.
By this logic, there are lots of gaps to fill for the distribution in the PNW. Areas all around Lake Cowichan and north of Alberni inlet should have populations. The northern-most extent is outside the CDF-zone, so why not Sayward and Tsitika. If it can tolerate 1500 east of the rockies, why not 1000m in a drier region west of the rockies? If it grows on limestone and basalt, oak and alder, why not Yellow Cedar or Granite? If you are out and about this summer, please consider joining the bryological side-quest to determine the geographical and ecological limits of Dendroalsia abietina.
