Plant Recruitment Under Beetle-Defoliated Tamarisk in Grand County, Utah: 2009 to 2019
Tim Graham1*, Wright Robinson2, Tim Higgs2
11701 Murphy Lane, Moab, UT 84532, USA; lasius17@gmail.com
2Grand County Weed Dept., 1000 Sand Flats Road, Moab, UT 84532, USA; wwr1018@gmail.com, twhiggs@grandcountyutah.net
Diorhabda carinulata (tamarisk leaf beetles) were first introduced in Grand County in 2004. Regular monitoring of beetle abundance and distribution around the county began in 2007. In 2009 we began exploring responses of other plants to the defoliation of tamarisk. Initially, we simply recorded the presence of plants seen under and adjacent to stands of tamarisk selected to monitor this response, compiling species lists for each site and in total each year; we recorded whether species were native or introduced, and their life history strategy (annual, biennial, or perennial). The number of sites has fluctuated as we’ve dropped and added sites for a variety of reasons. In 2011 we began running a 30 m point-intercept transect at each site; providing cover estimates along the transects as well as the general survey species lists. Results from 2009-2019 will be presented; 111 species have been observed at least once in the general surveys; the number seen at a single site varied from one to 26 species in a single year. There is a trend toward increasing perennial native species, declining perennial introduced species, and increases in non-native annuals across all sites over the years. The total number of vascular plant species increased over time but individual sites behaved very differently, depending on a variety of factors. Average proportional plant cover estimated from point-intercept transects also fluctuated between sites and overtime at individual sites.