Understory Vegetation Inventory: 3 Years After the Hermit’s Peak-Calf Canyon Fire

In 2025, the NMFWRI Ecological Monitoring Department piloted a study to quantify the diversity of understory plants within the HPCC burn scar. Monitoring transects were established within existing projects that received pre-fire mechanical thinning and prescribed burn treatments, and at sites that received no treatments before the fire. To serve as a control, NMFWRI also established plots in adjacent areas that were either unburned or experienced low-severity burning during the HPCC fire. The estimated cover of each species was collected at each plot, and data was analyzed based on certain traits: taxonomic family, growth habit, lifespan, and native or introduced status.  

Monitoring staff identified 216 unique species in the study area, representing 156 genera across 52 families. The most abundant plant families were Asteraceae (daisies) and Poaceae (grasses), which is the norm across the western U.S. A single plot (1/10th of an acre) could contain nearly 60 species. Forbs (wildflowers) were the most species-rich growth habit, but the vegetation cover was dominated by trees, shrubs, and graminoids (grasses and grass-like plants). 

The tree component in this study is restricted to seedlings and saplings in the understory – overstory, mature trees are not included. The tree component was dominated by species that are able to re-sprout from an underground rootstock following disturbance, such as a wildfire: specifically, Gambel oak (Quercus gambelii) and quaking aspen (Populus tremuloides). These trees are crucial for soil stabilization immediately following fire or other disturbances because they do not need to wait for ideal conditions for seed germination. Other tree and shrub species found in the study area can also re-sprout from underground rootstocks, but are not as vigorous as the Gambel oak and quaking aspen.  

Twenty-five introduced plant species were documented across the study areas. Approximately half were annuals or biennials, half were long-lived perennials, and all were either forbs or graminoids. The majority of these species were likely present in the area prior to the HPCC fire, but are more prominent post-fire as they have taken advantage of the major disturbance event. Notable species include kochia (or “burning bush”), Canada thistle, musk thistle, tumbleweed, mullein, and cheatgrass. These plants are especially problematic because they can form dense monocultures, then quickly dry out in drought periods. This presents concerns for fire risk, because they can easily catch and carry flames. Despite the monocultures of introduced species observed in some areas, the vegetation cover of introduced species across the study plots were relatively low, at an average of 3.9% cover. The prominence of annual or biennial species also pales in comparison to that of long-lived (5+ years) perennials. This indicates that the study areas are no longer in an early successional stage.  

Pre-fire treatment history appeared to have mixed effects within the study area. When an area was treated for fuels reductions prior to the HPCC fire, more overstory trees survived, on average. The intensity of pre-fire fuel treatments, as well as HPCC fire intensity, was highly variable, as were its effects. This resulted in a highly variable landscape with many different micro-habitats, that therefore supported highly variable plant communities. Some understory communities were dominated by bunchgrasses, oaks, shrubs, or forbs; depending on elevation, local climate, moisture, microsite variability, and the history of disturbance. Rather than focusing on reference conditions, which range widely, NMFWRI encourages prioritizing ecosystem resilience, as well as adaptations to increasing disturbance as well as conditions such as drought. The productivity and species diversity observed in this inventory is a trend towards resilience of these ecosystems.   

See the the full-length report detailing these results here.