Sagebrush steppe vegetation monitoring in Hagerman Fossil Beds National Monument: 2018 annual report

Nicolli, Melissa

As part of the Upper Columbia Basin Network sagebrush steppe vital signs monitoring program, a survey of sagebrush steppe ecological condition was conducted in early June 2018 at Hagerman Fossil Beds National Monument following methods outlined in the Upper Columbia Basin Network monitoring protocol (Yeo et al. 2009). The plot-based surveys occurred within 5 sampling frames that are positioned along the Oregon Trail, the tops of benches, and along the bottomland adjacent to the Snake River. Much of the uplands of the park are inaccessible, consisting of steep and highly unstable unvegetated escarpments. Cover of exposed soil and of principal native and non-native plants or genera were estimated in three-hundred ten 1 m2 quadrats randomly placed throughout the sampling frames (Figure 1). Sample plot locations were drawn using a spatially-balanced random sampling design, the Generalized Random Tessellation Stratified (GRTS) design, which ensures a good representative random sample with good dispersion within each sampling frame. The Monument was surveyed in 2009, reported by Rodhouse (2010), and again in 2012, reported by Stucki and Rodhouse (2012). The Long Butte Fire burned most of the vegetated uplands in HAFO in August 2010 and the 2012 survey provided the first opportunity to evaluate the effects of the fire on vegetation change in the Monument. 6 years later, in 2018, the present survey provided further insight into how the Monument is recovering since the 2010 fire. We provide some preliminary comparisons between conditions encountered in 2009 before the fire and now in 2018. In general, there has been a shift post-fire toward increased annual grass-dominated vegetation. All frames in HAFO had very high frequency and cover estimates of cheatgrass in 2018, much higher than what was recorded in 2009 and fairly similar to the coverage in 2012. Big sagebrush cover was very low compared to 2009 pre-fire levels. Greasewood (Sarcobatus vermiculatus), which resprouts after fire, had the highest cover and frequency of any of the shrubs in 2018, followed by green rabbitbrush (Chrysothamnus viscidiflorus). In 2012, no bluebunch wheatgrass was encountered during monitoring. In 2018, bluebunch wheatgrass was found in 3 of the 5 sampling frames, showing slow recovery of this native bunchgrass species. Sandberg’s bluegrass, a low-stature and very disturbance-resistant native perennial bunchgrass, had the highest bunchgrass frequency and cover estimates for all frames. Other perennial native grasses that were encountered in few plots include squirreltail (Elymus elymoides), indian ricegrass (Achnatherum hymenoides), sand dropseed (Sporobolus cryptandrus) and Great Basin wildrye (Leymus cinereus). Tumbling mustard had a higher frequency and percent cover than any other nonnative invasive forb, occurring in nearly 71% of all plots. This species appears to have greatly increased in abundance in most frames between 2012 to 2018, with a jump of 43%. The noxious weed Russian knapweed (Acroptilon repens) was found within 1 plot in the Upper Bench sampling frame. This area was documented and the location given to park resource management during the field season.

Sagebrush steppe vegetation monitoring in Hagerman Fossil Beds National Monument: 2018 annual report

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