BLM New Mexico interns conduct surveying for rare plants

Story and photos by Laura Shriver, Plant Conservation and Restoration Program Specialist; Hannah Millsap, 2019 Botany Intern; and Ashley Taylor, 2019 Botany Intern.

New Mexico’s landscapes give rise to the fourth highest floristic diversity in the country, including 109 species that only grow in New Mexico. However, over 12% of New Mexico’s vascular plants (plants that have true stems, leaves, and roots) are considered at risk. BLM New Mexico is proud to be part of the effort to protect and support rare plants and their unique ways of life.

As part of this effort, BLM New Mexico interns Laura Shriver, Ashley Taylor, and Hannah Millsap surveyed the BLM-managed Ball Ranch Area of Critical Environmental Concern (ACEC) in May 2019 for the rare plants called tufted sand verbena (Abronia bigelovii) and grama grass cactus (Sclerocactus papyracanthus). Tufted sand verbena has been designated a BLM Sensitive Species and is a “gypsum endemic,” which means that it only grows on gypsum outcrops or gypsiferous soils. It is a small wildflower with succulent leaves in the Nyctaginaceae/Four o’ Clock family.

The interns walked around the plants’ suitable habitat in order to update 20-year-old data on occurrences of the plant in the area. Sensitive Species require special management to promote their conservation and reduce the likelihood for future listing under the Endangered Species Act. The BLM also keeps track of Watch Species, which could become Sensitive Species if their populations decline. Ball Ranch ACEC was designated in 1986 to protect natural and cultural resources, including tufted sand verbena (one of the largest populations of tufted sand verbena is in the ACEC) and grama grass cactus, which is a BLM Watch species.

The interns’ primary focus was surveying for tufted sand verbena, so they limited the survey area to Ecological Sites that contained gypsum. They walked transects (a linear feature to keep the surveyor walking in a regular manner so that they can keep track of where they are going) spaced 30m or 10m apart and recorded points of tufted sand verbena or grama grass cactus with a tablet using the FLORA standard. In total, the interns surveyed approximately 1,200 acres, documented 87 tufted sand verbena occurrences (including 6.6 acres of tufted sand verbena polygons), and found 9 occurrences of grama grass cactus.

The interns found that tufted sand verbena was associated with the Sandoval fine sandy loam Ecological Site and the Mancos Shale. This made sense because the Sandoval fine sandy loam Ecological Site has a gypsum profile of up to 10%, and the Mancos Shale in this area is known to have elements of gypsiferous sandstone and shale. Tufted sand verbena primarily grew on hills, ridges, or eroding gullies that are less vegetated than the surrounding landscape. The area where the species was found contains large rock fragments, gypsum fragments, and bio crust. The interns also discovered that tufted sand verbena almost always grew next to tawny Cryptantha, which is a short, hairy wildflower that also grows on gypsum.

The interns could not infer the habitat preferences of grama grass cactus from this survey because they focused on tufted sand verbena habitat, and their transect lines were likely too widely spaced to find many individuals. Grama grass cactus is notoriously difficult to survey. It is short statured, and as the name suggests, grama grass cactus spines look like dried grass blades, so they blend into the surrounding landscape.

Future surveys for tufted sand verbena at Ball Ranch could explore more of the Sandoval fine sandy loam Ecological Site and Mancos Shale that the interns did not survey in 2019. To properly survey for grama grass cactus, a larger crew would need to walk closely spaced transects throughout the entire ACEC. Both plants flower and produce fruit throughout May. Therefore, May is the ideal time to survey for these species because they are easiest to spot when they’re in flower.