Big sagebrush does not root or crown sprout but relies entirely on seed for regeneration. The soil seed bank in sagebrush communities is short-lived, with most seeds germinating within one year of dispersal (Ziegenhagen and Miller 2009). Therefore, recovery following disturbance is dependent on regular replenishment of the seed bank. A better understanding of seed production variability and how that variability regulates seed bank dynamics is needed.
The most widespread and common sagebrush is big sagebrush (Artemisia tridentata) with three prominent subspecies: Wyoming big sagebrush (A. tridentata ssp. wyomingensis), basin big sagebrush (A. tridentata ssp. tridentata), and mountain big sagebrush (A. tridentata ssp. vaseyana).
Our objective was to test the utility of various, easily measured morphological traits for estimating mountain big sagebrush (MBS) seed production potential. We compare the reliability of each trait across multiple sites and consider the practicality of scaling up protocols for making quick, stand-level assessments.
We selected five MBS-dominated sites in central and south-central Utah. Site characteristics included low to moderate livestock use and the presence of a well-developed, native perennial understory where seed production would be representative of a typical intact sagebrush community. Sites had soils ranging from loam to clay-loam in texture. Sample inflorescences (group or cluster of flowers arranged on a stem) were collected in the fall when fruits were partially developed but before full maturation and dispersal had occurred. Samples were then taken to the lab for physical and statistical analyses.
We found the five sites sampled in this study varied significantly among all morphological traits measured. While morphological measures for samples collected from different sites often differed from one another, the strength of the relationship between the independent variables and total number of florets remained strong regardless of site.
Inflorescence weight was the best trait for estimating MBS seed production potential using a simple linear equation. The stability of the equation across sites with clear differences in measured morphological traits and reproductive output suggests that a generalized equation could have broad application; however, a more robust analysis using a more diverse range of sites, years, and environmental conditions is recommended.
We documented an eight-fold range in floret number per inflorescence, suggesting a potential for high site-to-site variability in MBS seed production potential.
The ability to estimate sagebrush seed production potential can be a useful tool for both land managers and researchers to assess recovery potential, predict seed bank establishment and maintenance, and understand succession patterns following disturbance.
This information may also be useful when determining seeding rate following tree removal or other sagebrush improvement treatments in sagebrush steppe communities.