Population survey and trend assessment for Eucephalus vialis at Beatty Creek ACEC
The primary objective of this study is to determine long-term population trends of E. vialis (AKA Aster vialis) at Beatty Creek. In 2009, the Institute for Applied Ecology (IAE) surveyed Beatty Creek
The primary objective of this study is to determine long-term population trends of E. vialis (AKA Aster vialis) at Beatty Creek. In 2009, the Institute for Applied Ecology (IAE) surveyed Beatty Creek ACEC to determine the size of the E. vialis population. We used this information to design a long-term monitoring protocol and conduct population monitoring. This protocol was used to survey the population again in 2010. IAE has conducted studies of this species at multiple sites in the Eugene District, BLM, which will allow us to make comparisons between population size and trends at Beatty Creek and populations elsewhere in the species’ range.
Intuitive Controlled surveys performed in 2009 estimated individuals at 132 points within the Beatty Creek drainage and its tributaries. Subpopulations ranged in size from 1 to greater than 150 individuals and were generally located on the north and east-facing slopes of the Beatty Creek drainage and tributaries. Eucephalus vialis was commonly associated with transitional zones between mesic plant communities dominating the drainages and xeric communities on the adjacent slopes.
In estimating the population size, only the portions of the transects that were within the population boundary established during the Intuitive Controlled surveys were utilized. In 2009, the average number of plants/meter squared was 0.06; the estimated E. vialis population at Beatty Creek is 18,684 ± 7,294 individuals (± 90% C.I.). This population size may be an underestimated as the polygon area does not account for topographical relief. In 2010, we surveyed 3.1% of the population and estimated that total population size was 17,163 ± 6,662 individuals (± 90% C.I.).
In 2009, monitoring along eighteen transects recorded 443 plants with an average of 1.6 stems per plant. Reproductive plants accounted for 38% of the population and, on average, possessed 20 capitula each. In 2010, monitoring of 23 transects recorded 552 plants with an average of 1.5 stems per plant. Reproductive plants accounted for 42% of the population and supported 19 capitula per plant.
These data allow the Beatty Creek population to be compared to E. vialis plants located in the BLM’s Forest Canopy Thinning (FCT) plots as well as unthinned control plots. These FCT plots had longer stems than plants at Beatty Creek. However, a slightly greater percentage of plants flowered at Beatty Creek than in the FCT plots.The most notable difference was that populations with an open canopy (both Beatty Creek and the FCT plots) had much higher flowering rates than the unthinned, control plots.