Assessing management techniques for Lomatium cookii (Cook’s desert-parsley)

EXECUTIVE SUMMARY
This document summarizes results from two studies involving habitat management techniques for L. cookii to support recovery of the species. The studies include 1) an evaluation of herbicide effects at Illinois Forks State Park, in areas occupied and unoccupied with L. cookii and 2) the effects of prescribed fire on L. cookii and the surrounding plant community at French Flat Middle and French Flat South. This information will inform future habitat management activities in sites that may contribute to the recovery of L. cookii and other associated native plant species.

Effects of Herbicide, Illinois Forks State Park
There were no clear differences in survivorship of L. cookii by treatment at Illinois Forks State Park in 2015, 2016, and 2017 (up to 3 years post-treatment). Height differed significantly (P<0.001) between herbicide treatments, where plants in the control treatment were taller than plants treated with herbicide; there were no differences in height between types of herbicide.
In occupied habitat, mean forb cover increased across all treatments from 12% in 2014 to 28% in 2017. Native and introduced graminoid cover decreased across all treatment types from 2014 to 2017 (natives: 26% to 10%; introduced: 30% to 7%). This decrease was due in large part to shifts in hydrology that led to a retreat of Agrostis sp. from pool edges and out of the plots.
In unoccupied habitat, forb cover increased across all plots from 2014 to 2017, from 26% to 44%. Native forbs remained similar in cover from 2014 to 2017, and introduced forbs increased across treatments. Total graminoid cover decreased from 26% to 16% from 2014 to 2017, with decreases occurring in all treatment plots. Native graminoid cover remained low and similar between 2014 and 2017. The diversity of introduced annual graminoids increased from 2014-2017. Continued monitoring will be essential to see if the impacts on introduced graminoids observed in fluazifop and glyphosate treatments continue into the future.

Effects of Fire, French Flat
Density (and population size) of L. cookii at French Flat Middle and French Flat South in 2014 and 2015 were among the lowest recorded at these sites since monitoring began in 1993. While the cause of this decline is unclear, competition with non-native species, increasing litter and thatch, disturbance by off-road vehicles and climatic factors may be playing a role. In the fall of 2015, approximately half of the occupied portion of each meadow was burned under the supervision of BLM staff.
In 2017, density of L. cookii did not differ between burned and unburned plots at French Flat Middle and South. Similarly, number of plants in each size/reproductive class did not differ between burned and unburned plots. Proportion of reproductive plants did not differ significantly between burned and unburned plots, nor were there effects of treatment on grazing of L. cookii.
The plant community responded similarly to the burn treatment at both sites. There was no difference between burned and unburned plots of native forb cover in either meadow. Cover of invasive grasses in both meadows was low (<2%), thus differences between burned and unburned plots were negligible with respect to total cover.