Last week Nathan, Carol, and I met with Ken Holsinger and Brandi Wills from the Uncompahgre Field Office to complete our first monitoring trip of the season. We were investigating a rugged area formed by tributaries of the Gunnison River which has carved the sandstone and shale landscape of the high desert basin into dissected canyons as the river arcs north towards its confluence with the Colorado in the Grand Valley. The Grand Mesa, the world’s largest flat-topped mountain, the snowcapped West Elk, and massive San Juan mountain ranges crown the scene gleaming snowcapped in the hazy distance.
We were looking for cactus. Not just any cactus, we were looking for Sclerocactus glaucus, a small ball-shaped cactus which often doesn’t exceed the size of a tennis ball and has a proclivity to hide out in these shaley areas of hardscrabble amongst pygmy woodlands of pinyon Juniper. A species listed by the US Fish and Wildlife Service as threatened, S. glaucus is a deceiving species, shrouded in a cloud of confusion surrounding its precise taxonomy. I had found out just how contentious views of the species are over the previous six weeks or so while sifting through all of the available literature while compiling a status report for the species.
The genus Sclerocactus consists of approximately 15 distinct species based on systematics. The trouble is that, like other genera of cacti, Sclerocactus’s morphology is highly plastic, making it difficult to classify based on structure alone. Populations of Sclerocactus are isolated in unique environments across the arid west, and most display unique morphological characters. The trouble has been that recent phylogenetic investigation has been beginning to illustrate that the cactus are actual more closely related than previously believed. Some populations which are believed to be genetically pure even possess mixed morphologies, suggesting that the genus may be composed of a large complex of individual ecotypes dictated by geography more-so than effects of genetic drift.
For being a local endemic S. glaucus is notoriously difficult to locate. Known only from four counties on Colorado’s western slope, its patterns of distribution are somewhat confounding in that it is found in a variety of different habitat, soil types, and densities. Plants are small, cryptic, and difficult to locate in the field outside a couple weeks a year when they are flowering; thus making our task to locate new populations to understand the full extent of the range and generate a realistic population estimate based on sound statistical methods a somewhat daunting task.
After a month of in-depth research into the species, seeing it in its native habitat shed light on the difficulties this species presents when trying to get a sense of its abundance and distribution. Miles and miles of potential habitat exist in the form of alluvial river benches and adobe badlands stretching to the horizon. Yet Sclerocactus populations are few and far between, existing in patchy niches where plants are at times locally abundant. Despite this fact, we were able to locate several populations suitable for sampling, and set up several new plots.
The coming weeks are slated to hold more cactus work. We will be setting up new plots on BLM and private land to monitor the trend of specific populations. We are additionally scheduled to search for populations on the large High Lonesome Ranch near Debeque, Colorado. As well as raft a twenty some miles stretch of the Gunnison to clear areas of suspected cactus occupancy in the Dominquez Canyon Wilderness Area.
Phil Krening
Colorado State Office – BLM
Lakewood, CO
The Adobe Badlands of Delta County, CO (Mancos shale formation) ©Phillip Krening http://headwaters.sqsp.com
Sclerocactus glaucus in flower ©Phillip Krening http://headwaters.sqsp.com