Differences in ecophysiology and climate responses among
subspecies and seed provenances of big sagebrush:
Implications for seed selection
Matt Germino
Supervisory Research Ecologist, Great Basin LCC Scientist
-andJess Vanderveen, Lar Svenson
USGS Forest and Rangeland Ecosystem Science Center, Boise
Bryce Richardson USFS, Rocky Mountain Research Station, Provo
Krista Shellie USDA ARS, Parma ID
Nancy Shaw USFS, Boise
Funding: GBNPSIP, USGS
PROGRESS AND PROSPECTS FROM AUG 2011 to PRESENT
*FINDINGS SHOWN HERE ARE PRELIMINARY; ANALYSES UNDERWAY*
• Rationale-justification
• The ecophysiological approach, how we are using it
• Variation among/within subspecies:
• Climate of origin
• Performance in the cold winter
• Performance in the hot summer
• Correspondence of ecophysiology to taxonomic and genomic
identity
Main questions, linking basic and applied
1. What are the principle changes in ecophysiological performance,
and the main underlying processes (ie. limitation)?
2. How does within-subspecies variation (ie. population level) variation
compare with among-subspecies variation?
3. Does the population variation relate to climate-of-origin? Do local
seed sources perform better? (Wyo&Tri w/ ID= 1 or 2)
4. How do ecophysiological differences relate to establishment
success, considering performance, stress response, & growth
strategies?
5. Does ecophysiological variation compare well with taxonomic and
genomic variation?
Approach: High-throughput (450 to 1300 plants), field-based ecophys.
Big sagebrush (Artemisia tridentata) subspecies:
wyomingensis (Wyoming)
stress, water
tridentata (basin)
growth
vaseyana (mountain)
competition, cold
Physiological performance, balance points, tradeoffs, efficiencies,
thresholds, strategies:
• Survival (80% Vas, 6.5% for Tri,Wyo)
• Growth
• Growth allometrics:
• Root:Shoot, N
• Repro:Vegetative shoot
• Sun-interception efficiency
Crown: STAR (m2 sunlit/m2 total)
Leaf: SLA (cm2/g)
• Leaf type and retention
• Water status (uptake-efflux)
• Photochemical efficiency (FvFm)
• Photosynthesis, transpiration: Water-use efficiency
• Freezing point (supercooling temp)
• Response to drought
• Response to freezing
30
5
10
-5
-10
Sampling all conditions of hot/cold and wet/dry
Precipitation (mm)
15
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Temperature ( C)
Climate diagram for Orchard ID common-garden site (from NRCS
Snowtel): Cold desert!
Soils: 50 cm of loess/silt over a gradient of sand to pebble @ 50-180 cm
(Wet soils at 130 cm depth in late August)
Mean annual temperature = 10.3
Mean annual precipitation = 333 (Rehfeldt’s) or 278 mm/y (Snowtel)
25
50
Temp
Precip mm
Can differences in home-climate explain the results? First, a
glimpse at climate-of-origin shows a high similarity for subspecies:
Grey bars are 4n
Tridentata
T
Vaseyana
V
UT-2V→W
WY-2
AZ-1
UT-1
CO-2
UT-2
ID-2
ID-1
MT-2
WA-1
NV-3
UT-3
NV-2
CA-3W→V
CA-1
ID-5
ID-2
CA-3
CA-2
UT-2
CO-1
OR-2W→T
UT-3
OR-1
MT-1
OR-3W→T
0
ID-2
1000
OR-2
Elevation (m)
2000
Wyomingensis
W
Mean Annual Precipitation (mm)
400
300
200
100
0
Tridentata
Vaseyana
Wyomingensis
0
OR-2V→T
OR-3
OR-2W→T
UT-1
MT-1
CO-1
ID-3
NV-2
OR-3W→T
OR-1
CA-2
NV-1W→T
NV-1
UT-2
CA-1
ID-1
ID-2
WA-1
OR-2
UT-3
MT-1
ID-3
ID-4
NV-1
CA-3W→V
UT-1
CA-2
NV-2
UT-3
NV-3
ID-5
CA-1
OR-1
ID-2
CA-4
CA-3
WY-2
WY-1
MT-3
MT-1
UT-2V→W
CO-2
CO-1
MT-2
OR-1
NM-1T→W
UT-2
AZ-1
NM-2T→W
ID-3
UT-1
ID-1
ID-2
AZ-1T→W
WA-2T→W
WA-1
Mean Annual Temperature (C)
15
10
5
T
Tridentata
V
Vaseyana
W
Wyomingensis
(μmol
CO2m-1s-1)
Photosynth
10
5
% Soil
Moisture
(VWC)
Light-use
efficienc
(FvFm)
Water
Potential
(MPa)
0
0
-1
-2
-3
0.8
0.6
0.4
0.2
30
2"
20
20"
10
Air
Temp (°C)
0
40
20
0
-20
August
Freezing Point
September
October
November
December
January
0.0005
Volts
A look at cold tolerance, freezing points:
Tridentata, local population
0
Tridentata w/ greatest photochemical stress
Tridentata w/ least photochemical stress
-13
-11
-9
-7
-5
-3
-1
TEMPERATURE (C)
1
3
Change in photochemical status
Nov to 16Jan
(cool to freezing)
Subspecies and climate of origin do not influence most mid-winter
parameters, except light-use efficiency (photochemistry):
0
Tridentata
Vaseyana
Wyomingensis
-0.25
all
R² = 0.1046
Linear
(Tridentata)
Slope=-0.033 R² = 0.4761
-0.5
2
6
10
14
Temperature of seed origin (°C)
Δ FvFm in response to deep
freeze
(Control minus frozen to -20C)
Photochemical stress response to deep freezing:
Tridentata
Vaseyana
Wyomingensis
T
V
W
0
-0.05
-0.1
-0.15
-0.2
-0.25
A look at mid-summer limitation:
Tridentata expresses “growthy” traits and
yet maintains higher water status
Water status varies among subspecies, and esp. populations:
Water Potential (MPa),
Tridentata
0
-1
-2
0
T
V
W
a
b
c
-1
-3
-2
-4
-3
Photosynthesis , Tridentata
14
12
10
8
6
4
2
0
Specific leaf area
(cm2/g)
photosynthesis also varies:
60
40
20
a
T
b
V
b
0
W
Mechanisms underlying differences in mid-summer photosynthesis
Point to advantages in water uptake for top-performers:
Tridentata
Vaseyana
Wyomingensis
10
5
0
-1
-2
-3
-4
Water Potential (Mpa)
Water-use efficiency
(photos/transp)
Photosynthesis
umol m-2s-1
15
3
2
1
0
-1.5
-2.5
Water Potential (MPa)
-3.5
Tridentata
Vaseyana
Wyomingensis
4.E+04
2.E+04
0.E+00
0
5
10
Photosynthesis
Vol. cm^3
Vol. cm^3
Relating photosynthesis to growth:
15
4.E+04
2.E+04
0.E+00
-4
-2
Water Potential (MPa)
0
Hierarchical clustering based on taxonomy (Ward’s):
Wintertime:
Summertime:
Total rank score combining all
physiological data
Relationships based on genetic similarity
300
y = 5736x + 159
R² = 0.2953
200
100
0
-0.015
-0.005
0.005
PCA Eigenvector
0.015
Conclusions
- Ecophysiological similarities and differences revealed.
- Wintertime:
- An important growth period, cold stress occurs.
- Diffs in freezing resistance rather than avoidance
- Climate-of-origin affects these
- Min temp is issue for climate change (snowcover, etc)
- Summertime:
- Hydrologic threshholds still need to be determined
- Water limitations to carbon balance are key
- Water uptake, possibly from deep soils, likely important
- Growth vs. efficiency….key issue for selection.
-
Genomic differences are likely
These short-term findings can help glean insight on which seed
sources might perform better on a given site/circumstance
Future plans:
• Determine if patterns hold up in additional years
• Distinguishing perennial VS. ephemeral leaf effects (enabling
scaling our leaf-level data to whole-plant)
• Isotopes to better substantiate the WUE-depth of water uptake
effect
• Evaluate seedlings during critical establishment phase
• Anti-defense compounds – assessing palatability
THE END