Modeling Seedling Root growth
of Great Basin Species
Bruce Roundy and Kert Young
Objectives
1. Develop thermal
accumulation models
for seedling root growth
2. Test the ability of
thermal models to
predict root depth.
3. Predict seedling root
growth and survival for
dry to wet years from
field data.
Soil moisture and temperature stations
• Woodland
– 13 locations in CA, OR, NV, UT
– 90 stations
• Sagebrush/cheatgrass
– 6 locations in OR, WA, NV, UT
– 50 stations
• Soil temperature and water
potential at 1-3, 13-15, 18-20,
and 28-30 cm
Growth chamber study design
• 6 Constant temperatures: 5, 10, 15, 20, 25, 30 C
• 4 Blocks
• 2 soils: Sand,
Borvant gravelly loam
• 13 collections
• 5 replicate tubes
• 3 plants/tube
• Measure deepest root
6 days/week
13 Collections
Forbs
o Eagle Yarrow
o White-VNS Yarrow
o Annual agoseris
o Utah milkvetch
o Appar blue flax
Grasses
o Perennial grasses
– Hycrest crested
– Nordan crested
– Squirreltail – Sanpete Co.,
Utah
– Snake River wheatgrass
– Anatone bluebunch
o Cheatgrass
– Rush Valley, Utah
– Skull Valley, Utah
Status
• All but 10 C
• Heat accumulation
temperature runs done
modeling
• 1 year, 2 sites of field
• Compare predicted and
root studies done
actual in diurnal and
field experiments
• Diurnal growth
chamber studies to
• Predict establishment
conduct
potential using field soil
temperature and
• 1 more year, 2 sites field
moisture data
studies to conduct
Preliminary results
Days to 15 cm root depth
180
160
140
120
Eagle Yarrow
White Yarrow
Annual Agoseris
Utah Milkvetch
Blue Flax
Longspur Lupine
100
80
60
40
20
0
0
5
10
15
20
25
30
Growth chamber temperature (°C)
35
Preliminary results
Days to 15 cm root depth
180
160
Hycrest Crested
Wheatgrass
140
Nordan Crested
Wheatgrass
120
100
Squirreltail
80
Snake River Wheatgrass
60
40
Anatone Bluebunch
Wheatgrass
20
Rush Valley Cheatgrass
0
0
10
20
30
40
Growth chamber temperature (°C)
Skull Valley Cheatgrass
Degree days to 15 cm root depth
Preliminary results
1800
1600
1400
1200
Eagle Yarrow
White Yarrow
Annual Agoseris
Utah Milkvetch
Blue Flax
Longspur Lupine
1000
800
600
400
200
0
0
5
10
15
20
25
30
Growth chamber temperature (°C)
35
Degree days to 15 cm root depth
Preliminary results
900
Hycrest Crested
Wheatgrass
800
700
Nordan Crested
Wheatgrass
600
Squirreltail
500
Snake River Wheatgrass
400
300
Anatone Bluebunch
Wheatgrass
200
Rush Valley Cheatgrass
100
Skull Valley Cheatgrass
0
0
10
20
30
Growth chamber temperature (°C)
40
Preliminary results
Tubes with actively-growing plants
20
18
16
14
12
5
10
15
8
20
25
6
30
4
2
0
Eagle
Yarrow
White
Yarrow
Annual
Utah
Blue Flax Longspur
Agoseris Milkvetch
Lupine
Tubes 0 with actively-growing plants
Preliminary results
20
18
16
14
12
5
10
15
8
20
6
25
30
4
2
0
Hycrest
Nordan Squirreltail Snake River Anatone Rush Valley Skull Valley
Crested
Crested
Wheatgrass Bluebunch Cheatgrass Cheatgrass
Wheatgrass Wheatgrass
Wheatgrass
Coupling root growth and drying rates
Hycrest root growth (cm/day)
1.5
1
0.5
0
0
5
y = 0.1305x - 0.2942
10
15
20
Temperature C
Drying rate (cm/day)
cm/day
cm/day
2
7
6
5
4
3
2
1
0
March-April
May-June
March-June
BM BC DR MC ST
OJ GB
Preliminary conclusions
• Grasses more robust than forbs
• Forbs require more degree hours for root
elongation than grasses
• Some grasses grow nearly as well at cool
temperatures as cheatgrass
• Models to predict root growth are possible
• We should be able to estimate seedling
survival potential