Monitoring of Canyon Grasslands in Craig Mountain WMA, Nez Perce County, Idaho: 21-year results

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Abstract:

In 2015, we resampled 12 permanent vegetation monitoring plots that were established in
bunchgrass steppe communities on Craig Mountain, in Nez Perce County, Idaho. Plots were
established in 1994 when large portions of the mountain became a Wildlife Management Area
(WMA). Plots were sampled again in 2002 to determine if composition within the plots was
changing. Plots were not set up to monitor the effects of wildfire, but seven of the plots burned
in 2000, two years prior to resampling and the same seven plots burned again in 2007 and then
again in 2014, the year before our 2015 sampling; the other five plots have no recorded history
of having burned. Plots were 30 m x 20 m macroplots and represented four grassland habitat
types: bluebunch wheatgrass/pricklypear cactus (Pseudoroegneria spicata/Opuntia
polyacantha), bluebunch wheatgrass/common snowberry (P. spicata/Symphoricarpos albus),
Idaho fescue/common snowberry (Festuca idahoensis/S. albus), and Idaho fescue/prairie
junegrass (F. idahoensis/Koeleria macrantha). Cover is primarily of the bunchgrasses Idaho
fescue and bluebunch wheatgrass. Arrowleaf balsamroot (Balsamorhiza sagittata) provides a
large amount of early cover in some plots. Nested plot frequency was used to measure the
frequency of vascular plants, lichens and mosses. Shrub cover was measured by line
intercepts. Chi-square tests were used to compare frequencies among the three monitoring
years for all native grasses, selected forbs, and three life-form groups: native bunchgrasses,
exotic annual grasses, and mosses. The frequency of native bunchgrasses as a group
increased on two burned plots and none of the unburned. Increases appear to have been driven
by Sandberg’s bluegrass (Poa secunda) which increased in six of the seven burned plots.
Bluebunch wheatgrass did not change after repeated fires, while Idaho fescue decreased
sharply on four burned and one unburned plot. Exotic annual grasses, primarily Japanese
brome (Bromus japonicus) and cheatgrass (Bromus tectorum) increased in four unburned plots
and decreased in another, while among burned plots they either decreased or remained the
same in six plots and only increased in one plot. The aggressive exotic forb yellow starthistle
(Centaurea solstitialis) which has degraded extensive areas of grassland within the WMA,
occurred within or near five plots in 1994, but had not increased in frequency by 2015, and had
decreased in one plot. Moss cover in the burned plots was mostly limited to the surface of rocks.
Many increases in frequency detected 2002 were reversed in 2015, and this was true for native
as well as exotic species. Results are compared to those of several similar studies in our region.

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Shelf Note: Electronic Files - BOTONY: Multiple Species: U21LIC02IDUS

Lichthardt, J., and K. M. Pekas. 2021. Monitoring of Canyon Grasslands in Craig Mountain
WMA: 21-year results. Idaho Natural Heritage Program, Idaho Department of Fish and Game,
Boise, ID. 33 pp. plus appendices