Characterizing Microsite Conditions of the Endangered Wenatchee Mountains Checkermallow (Sidalcea oregana var. calva)

Abstract

To effectively protect and recover rare species, we must understand their ecological niches and habitat requirements. My research focused on Wenatchee Mountains checkermallow (Sidalcea oregana var. calva; “SIORC”), an endangered plant taxon found in central Washington. There are currently only five known populations of SIORC, and these populations are highly vulnerable to extirpation from demographic factors or stochastic events due to the limited abundance and range of remaining populations. Successful conservation of this species requires understanding the conditions this plant needs to survive and reproduce. During 2022 and 2023, I conducted a microsite study on the SIORC population at Camas Meadows and measured a variety of fine-scale characteristics in SIORC habitats throughout the meadow. These microsite characteristics included soil moisture, canopy density, Leaf Area Index (LAI), soil texture, and associated vegetation. I used cluster analyses and PERMANOVAs to relate SIORC presence and abundance to each of these microsite variables. I did not find support for any significant relationships between SIORC and physical microsite variables (soil moisture, canopy density, LAI, soil texture). However, an analysis using more precise, lab-based soil texture data from 2023 found that soil clay vs silt content significantly affected SIORC presence in 2023. Analysis of vegetation characteristics found significant relationships with SIORC presence and SIORC abundance. Species richness, forb cover, and grouping based on overall vegetation characteristics significantly related to SIORC presence. Grouping based on vegetation characteristics did not significantly affect SIORC abundance, but total cover on its own was strongly associated with SIORC abundance. Indicator Species Analyses identified Achillea millefolium as an indicator for SIORC presence. Additionally, I installed 30 continuous soil moisture sensors and measured soil moisture during the growing season. I used a cluster analysis to identify groups of sensors based on soil moisture characteristics and found that, while SIORC abundance was higher for the wettest groups of sensors in July and August, SIORC presence and number of SIORC were the same across all groups. These results suggest that physical microsite characteristics are not driving SIORC distribution, and that other factors such as vegetation characteristics, seed predation, and fire suppression likely play a stronger role in determining SIORC presence and abundance.