Research Projects
Grassland, Shrubland and Desert
Ecosystem Research Program - Boise
Forb Research
Germination ecology of Great Basin Penstemon
species
Adequate seed supplies of locally adapted populations of
native species are required for revegetation of degraded
sagebrush steppe communities of the Great Basin.
Although native forbs are essential elements of these
communities, seed availability of most forb species is
limited or nonexistent. We are examining intraspecific
variability and developing seed production practices and
seeding technology for three penstemons of the northern
Great Basin. Sand penstemon (Penstemon acuminatus),
hotrock penstemon (P. deustus), and
sagebrush penstemon (P. speciosus) occupy
different habitats and may be valuable for use in
postfire seedings, mixed plantings, roadway revegetation,
and low water use landscaping. Preliminary work
indicated that newly harvested seed of all three species
is dormant, exhibiting less than 15% germination under
favorable conditions. Germination was improved by moist
prechilling for 8 to 12 weeks. The prechilling
requirement for sagebrush penstemon, but not hotrock
penstemon, was reduced by a liquid smoke treatment.
Treatments permitting more rapid and uniform germination
are desirable for production of nursery stock and
establishment of seed production fields for seed
increase or commercial seed production.
Development of Native Forb Plant Materials for the Great
Basin
Select germplasms of common native forb species of the
Great Basin will be released following common garden,
laboratory and genetic studies. About 15 species are
included in this effort.
Seed germination of Lomatium grayi, L.
dissectum, and L. triternatuM
Lomatium
species are among the native forbs considered of high
priority for restoration of Great Basin rangelands.
Research examining germination requirements of members
of this genus is extremely limited and initial efforts
indicate seeds are highly dormant. Research will be
conducted to examine the natural germination ecology of
three species and to develop methods for releasing
germination to facilitate nursery production and seeding
for establishment of seed production fields.
Cultural practices for Lomatium grayi,
L. dissectum, and L. triternatum seed
production
Seed supplies of Lomatium species are currently
not available for use on Great Basin rangelands.
Production of seed fields will require development of
appropriate cultural practices including seeding
techniques, irrigation requirements, and control of
weeds, diseases, and seed predators.
FUELS RESEARCH
Changing Fire Regimes, Increased Fuel Loads, and
Invasive Species: Effects on Sagebrush Steppe and
Pinyon Juniper Ecosystems
We propose to conduct an integrated research program
that addresses each of these information needs. The
first component will evaluate the spatial and temporal
dynamics of the shrublands and woodlands prior to
settlement by using a combination of plant community,
stand structure and dendrochronology data. It also
exam8nes the influence of varying environmental
conditions and invasive species on current shrubland and
woodland dynamics. the second component is closely
aligned with the first. It evaluates the changes that
have occurred in fuel loads since settlement and
provides a comparison of the fuel loading characteristic
for ecosystems that are functional, at risk, or that
have been converted to annual grasses or secondary
weeds, or revegetated. The third component uses
mechanistic studies to examine key factors influencing
community susceptibility to invasion by cheatgrass and
the secondary weeds, squarrose knapweed and rush
skeletonweed. It examines temporal differences in
resources availability among vegetation types and
states. It also evaluates the effects of plant
abundance of existing species and fire on soil resource
availability and cheatgrass establishment and
reproduction, and the effects of fire on secondary weed
establishment and spread. This research will provide
both regional and local information on characteristics
of woodlands and shrublands at greatest risk of
catastrophic fire, most susceptible to cheatgrass
invasion, as well as most suitable for prescribed fire.
It will also provide information on the effects of
resource availability, community condition, and fire on
community susceptibility to cheatgrass and secondary
weed invasion.
Impacts of exotic weeds on fuel loading and fire regimes
in shrub steppe communities and development of
technology and plant resources for their restoration
The cycle of wildfires and annual weed
invasion has altered millions of acres of western
shrublands and grasslands, disrupted ecosystem
functioning, increased wildfire size and frequency,
reduced plant and animal diversity, and set the stage
for invasion by secondary perennial weeds that are even
more difficult to control. Our poor understanding of the
susceptibility of functional and at risk native systems
to weed invasions and the impacts of weeds on fire
regimes and seasonal fuel loading limits our ability to
manage these systems. Criteria are needed to determine
when post-fire seeding to restore native vegetation is
appropriate. Reestablishing native communities
necessitates the use of effective methods for
controlling competitive weeds and the availability of
reliable seed supplies and seed transfer guidelines for
a larger suite of revegetation species, particularly
native forbs.
INVASIVE SPECIES RESEARCH
EMERGENCE AND GROWTH OF WINTERFAT IN RESPONSE TO
CHEATGRASS (BROMUS TECTORUM) DENSITY
Winterfat (Krascheninnikovia lanata [Pursh]
A. D. J. Meeuse & Smit; synonym: Ceratoides lanata
[Pursh] J. T. Howell) is a desired shrub species and an
integral component of salt desert shrublands in the
Intermountain West. On the Snake River Birds of Prey
National Conservation Area (BOP) in southwestern Idaho,
extensive loss of winterfat-dominated communities has
been linked to altered fire regimes associated with
cheatgrass (Bromus tectorum L.) invasions.
Post-fire revegetation efforts are often hampered by the
quick emergence of cheatgrass seedlings with autumn or
spring moisture. We compare the establishment of four
winterfat populations (Birds of Prey; northeastern New
Mexico; Northern Cold Desert Select Germplasm, and Open
Range Tested Germplasm) with and without cheatgrass
competition. Seed of each accession was planted in 15 cm
diameter pots containing four densities of cheatgrass
(0, 2, 4, and 8 plants per pot) in a greenhouse. Plant
measurements were made 4, 5, 7, 9, 11, 13, 15, 17, 19,
and 21 weeks after planting. Measurements included
winterfat survival, height and two canopy diameters and
cheatgrass height and number of leaves and culms per
plant. Initial establishment was greatest for the New
Mexico winterfat source at all cheatgrass levels. Growth
of this source exceeded the others in the absence of
cheatgrass. However, the presence of cheatgrass
depressed growth of all sources by at least 90 percent.
Establishment of winterfat on cheatgrass infested
rangelands necessitates seeding on sites where
cheatgrass densities are low or reduced by site
preparation procedures.
SOIL CARBON MANIPULATION FOR CONTROL OF ANNUAL WEEDS
Annual weeds that proliferate following wildfires
dominate millions of hectares of rangeland in the
western United States. Revegetation with native
perennial plants is not feasible in these areas without
some form of weed control. Carbon application in the
form of sucrose has been shown to suppress annual weeds
by temporary immobilization of nitrogen in the soil
profile. Our objective was to assess the efficacy of
sucrose for annual weed suppression under a wide range
of treatment applications in multiple years. The study
was conducted on an area in the Snake River Birds of
Prey National Conservation Area that burned in 1997.
Sucrose was applied in either early December or in both
December and February at 0, 200, 400, 600, 800, 1000,
1200, 1600, or 2000 total kg-C ha-1. In the first 2
years of this 3-year study, the maximum carbon treatment
resulted in a >75% reduction in biomass production of
the 2 main weed species, cheatgrass (Bromus tectorum)
and tumble mustard (Sisymbrium altissimum). For
the same total amount of sucrose, a single application
in December was more effective than the
December/February application. Application rates
necessary for adequate weed control are probably not
economical for broad-scale application after wildfire.
Use of sucrose as a carbon source may still be feasible
for some high-intensity, small-area applications and in
areas where herbicide use is not acceptable.
Rush Skeletonweed Research
assessment of shrub steppe
communities invaded by rush skeletonweed (chondrilla Juncea L.)
Rush skeletonweed,
an herbaceous Eurasian composite, was first reported in
southern Idaho about 1963. From the original site near
Banks and the South Fork of the Payette River, it
appeared to radiate rapidly, particularly to the south
and east. It is now widespread across southwestern Idaho
and often produces dense stands of wiry, latex-filled
plants that compete with native plant species for water
and nutrients. Initial colonization sites were forest
openings and higher elevation grasslands and shrublands,
and local managers doubted that invasions would occur
widely on lower elevation sites of the Snake River
Plain. But isolated stands of rush skeletonweed are now
found on the western half of the Plain in shrub steppe
communities, abandoned croplands, and disturbed sites.
We are assessing biotic and abiotic parameters of
representative rush skeletonweed stands in a variety of
communities, including those dominated by big sagebrush
(Artemisia tridentata Nutt.), antelope
bitterbrush (Purshia tridentata (Pursh) DC.),
crested wheatgrass (Agropyron cristatum (L.)
Gaertn.), cheatgrass (Bromus tectorum L.), and
medusahead (Taeniatherum caput-medusae (L.)
Nevski). To aid in predicting which communities and
sites may be especially vulnerable to rush skeletonweed
invasion, we plan to combine this assessment with a
region-wide GIS analysis.
Rush skeletonweed demography following wildfire on
Idaho’s Snake River Plain
Rush skeletonweed is a perennial herb native
to Eurasia and northern Africa, and is classified as a
Noxious Weed in the western United States and Canada.
Some reports from our region note possible increases of
rush skeletonweed after fire; others state that the
invader will not persist on very dry sites. On the arid
Snake River Plain of southwestern Idaho, we are
examining rush skeletonweed population demography and
life history following wildfires that burned in summer
2003.
Seed and seedling ecology of rush skeletonweed following
wildfire on Idaho’s Snake River Plain
Rush skeletonweed produces
prolific wind-borne achenes which mature in summer and
fall and are reported to emerge with fall moisture.
These seeds are often targeted for control, but their
actual recruitment role compared to root sprouts has not
been quantified in North America. We are assessing this
role on 11 burned/unburned plot pairs in rush
skeletonweed stands on Idaho’s Snake River Plain. Our
efforts include excavating rosettes to determine their
source from seeds or root buds, measuring the soil seed
bank, assessing seed bank losses to soil microbes,
quantifying seed germination in field-buried bags, and
documenting emergents from field-sown seeds.
Rush skeletonweed seed germination responses
We examined germination
responses of rush skeletonweed seeds that had been
hand-collected from three sites on the Snake River Plain
near Boise, Idaho. In each laboratory trial, replicates
of 50 seeds were tested on saturated blotters in plastic
germination boxes and incubated in germination chambers
at constant temperature with light/dark for 12/12 hr. In
tests from 6 to 34°C, germination averaged >50% of all
seeds at each temperature. The shortest time to 50%
germination of viable seeds occurred at 22ºC. Based on
tetrazolium tests, no seeds were dormant at any
temperature. Germinability by harvest date was <5% of
all seeds for mid-Jul 03 harvest, increasing gradually
to 78% in mid-Sep 03, then declining. Total germination
varied for each of the three harvest sites: 42, 50 and
74%.
|
|