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Factors effecting emergence of 20 Great Basin native forbs when sown at depths typical of rangeland drills

Status: 
Complete
Dates: 
October, 2013 to October, 2015

A precision cone seeder
Installing forb seeding depth trials near Orovada, Nevada using a precision cone seeder.
In the Great Basin, USA, wildfire consumes nearly 400,000 hectares annually (1995-2007) requiring thousands of kilograms of seed to replant impacted areas. Federal policy shifts encouraging the use of native plant materials have resulted in a substantial increase in demand for native seed. While workhorse restoration species remain primarily graminoids, there is considerable interest in diversifying seed mixes with native forbs to better meet multiple use objectives. Consequently, native forbs have become common components of western federal plant materials programs led by the Bureau of Land Management and USDA Forest Service. Many areas of research are unexplored for most forbs, so testing and evaluation to understand germination cues, seedbed ecology requirements, agronomic potential, and species suitability in a restoration context are needed and prevalent in current research. The objectives of this study are to evaluate the effects of species, sowing depth and dormancy status, and the treatment effect of row cover on field emergence of 20 forb species native to the Great Basin. This information is needed to 1) identify species that perform well under common drill seeding practices, 2) identify seeding depth limitations among species of high interest in the regional restoration community, and 3) evaluate the benefit of row cover as a novel technique in rangeland seeding to improve establishment.

Many thousands of forbs are native to the Great Basin, yet relatively few exhibit the morphological, phenological, and ecological characteristics that make them good candidates as workhorse species. These attributes include being locally abundant while having a broad ecological amplitude and demonstrating good establishment and persistence while possessing traits that confer success in cultivated settings. Species selected for this study either have some history of use in restoration plantings like yarrow (Achillea millefolium), globemallows (Sphaeralcea grossulariifolia and S. munroana), and lupines (Lupinus argenteus), or are being screened as candidate species for further development.

Approach

Study sites were selected near Wells and Orovada, Nevada and Fountain Green, Utah. In May of 2013 and 2014 plots were disked to incorporate existing vegetation and summer fallow. In early fall, plots were harrowed and firmed with a Brillion style roller packer to prepare seedbeds for October planting. The study was implemented at three sites in 2013 and 2014 and evaluated 20 native forbs sown at four planting depths and either covered with row cover or left uncovered. Sowing depths were 1.4 cm, 2.6 cm, 3.6 cm, and 4.0 cm. Forb species included in this study were selected from materials being evaluated by the Great Basin Native Plant Program. Species included in this study were categorized as non-dormant (n=4), physically dormant (n=5), physiologically dormant (n=7), or unknown (n=4) based on published literature. Seedling emergence counts were made during late spring and fall the year following planting. 

Improved plant establishment is often observed under plantings covered with NSulate fabric. The fabric helps the seedbed remain moist longer and offers spring frost protection to emerging seedlings.
Improved plant establishment is often observed under plantings covered with NSulate fabric. The fabric helps the seedbed remain moist longer and offers spring frost protection to emerging seedlings.

Key Findings

  • No depth effects were evident, not even between the shallowest seeded depth (1.6 cm) and the deepest (4 cm), for any species or cover treatment. Published recommended seeding depths ranged from 0.32 to 1.9 cm. It may be that critical intervals to observing depth effects are shallower than what were investigated in this study.
  • Mean 2013 emergence counts (4.82 plants from 250 Pure Live Seeds) were an order of magnitude higher than 2014 counts (0.481 plants from 250 PLS). This difference is associated with spring moisture patterns.
  • At Wells, mean emergence (4.70 plants from 250 PLS) across both years was more than twice that observed at Fountain Green (1.89 plants) and Orovada (1.36 plants). The volume and timing of precipitation at Wells along with cooler temperatures likely extended the duration of seedbed moisture availability contributing to better emergence.
  • While emergence was very low regardless of cover treatment, row cover did confer a 3.87 fold increase in establishment compared to uncovered controls.
  • Better emergence was observed among dormant (4.02 physiological dormant plants / 250 PLS, 3.1 physical dormant plants / 250 PLS) than non-dormant (0.98 plants / 250 PLS) species.
  • The most prominent differences in emergence were first due to year then to site, and in both cases spring precipitation patterns appear to be the driving influence. Of factors that are controllable, both the use of row cover and selection of dormant species offered significant improvements over other alternatives. Similarly, a handful of species, namely barestem biscuitroot, hairy bigleaf lupine, silvery lupine, royal penstemon, Hooker's balsamroot, and scarlet gilia emerged at higher rates than other species and are good candidates to include in current restoration activities and further evaluations.

Other

  • Scientific names of study species are listed along with seed weight, dormancy class, recommended sowing depth, duration and mean emergence values across all sites, years, and cover treatments.

 

Scientific Name

Seeds\gram

Dormancy Class

Recommended Sowing Depth (in)

Duration

Mean emergence/250 seeds *

Achillea millefolium

6,450

non-dormant

1/4 or less

perennial

D      0.63

Agoseris grandiflora

460

non-dormant

 

perennial

D      1.48

Agoseris heterophylla

902

non-dormant

 

annual

D      0.89

Arenaria macradenia ssp. ferrisiae

1,026

undiscovered

1/4 - 1/2 deep

perennial

D      0.73

Astragalus filipes

258

physical

1/4 deep

perennial

D      1.61

Balsamorhiza hookeri

222

undiscovered

1/2 deep

perennial

CD   2.38

Enceliopsis nudicaulis

360

undiscovered

 

perennial

D      1.83

Eriogonum umbellatum

460

physiological

1/4 deep

perennial

D     1.53

Heliomeris multiflora var. nevadensis

2,323

undiscovered

1/4 deep

perennial

D      0.5

Ipomopsis aggregata

800

physiological

1/4 - 1/2

biennial

CD    2.28

Lomatium nudicaule

125

physiological

 

perennial

A     17.3

Lupinus argenteus

45

physical

1/2 - 3/4

perennial

BC    5.21

Lupinus prunophilus

53

physical

1/2 - 3/4

perennial

B      5.97

Machaeranthera canescens

2,941

physiological

1/4 or less

perennial

D      0.84

Penstemon acuminatus

1,132

physiological

1/8 - 1/4 deep

perennial

D      1.83

Penstemon pachyphyllus

600

non-dormant

1/8 deep

perennial

D      0.92

Penstemon speciosus

1,141

physiological

1/8 - 1/4 deep

perennial

BCD 3.61

Sphaeralcea grossulariifolia

890

physical

1/4 - 1/2 deep

perennial

D      1.69

Sphaeralcea munroana

1,357

physical

1/4 - 1/2 deep

perennial

D      0.99

Stanleya pinnata var. integrifolia

1,373

physiological

1/4 - 1/2 deep

perennial

D      0.78

* significant differences represented by different letters

         
 

Future research should assess shallower planting depths and other soil types.



Project Contact: 

Principal Investigators:
Co-Investigators:
Val Jo Anderson - Brigham Young University
Bruce Roundy - Brigham Young University
Loreen Allphin - Brigham Young University
William Christensen - Brigham Young University

Collaborators:
Utah Division of Wildlife Resources- Great Basin Research Center staff
OSU- Malheur Experiment Station staff
BFI Native Seeds
Quarter Circle J Seeds

Funding Contributors:
Great Basin Native Plant Project
Great Basin Restoration Initiative
Rocky Mountain Research Station
Bureau of Land Management