Evaluating links between climate change and recent enhanced tree growth at upper altitude sites in the western United States. Presented by Louis Scuderi at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

1. Evaluating links between climate change and recent
enhanced tree growth at upper altitude sites in the
western United States
Louis A. Scuderi and Maria Lohmann,
Department of Earth and Planetary Sciences
University of New Mexico

2. Expected High Altitude Plant Response to
“improving” climate
• “Improving” conditions
– Warmer temperatures
– Increased growing season
length
– Adequate moisture/water
balance
• Response spectrum
– Main stem – Increased
increment growth
– Whole plant – canopy
expansion/densification
– Entire treeline – upward
movement of treeline

3. Recent Results (Salzer et al., 2009)
• Showed that increment growth was increasing for three bristlecone
sites in the western United States
• This increase only was detectable from treeline to 150 meters
below treeline
• The actual elevation of the treeline was not important
Salzer et al., 2009

4. Some Limitations
• Three bristlecone sites
– Are they truly representative of all bristlecones?
• Bristlecone pine only
– Unknown if the response is species specific or extends to other
treeline species
• Focus on the whole stem response (increment growth only)
– What is happening to the entire plant?
– What is happening for all trees at all sites?
• Responding to what factors?
– Temperature, Precipitation, ??? or some combination?

5. Purpose/goals of this research
• To evaluate vegetation cover trends for:
– Many sites
– Many species
– Over an elevation range
• To evaluate vegetation growth trends
– INDEPENDENT OF DENDROCLIMATIC ANALYSIS
• To determine whether dendroclimatic analysis suggesting enhanced
growth is supported by other measures of plant growth

6. Annual NPP (GLOPEM)
g C/m2/year
0 - 213
214 - 425
426 - 638
639 - 850
851 - 1,063
1,064 - 1,275
1,276 - 1,488
1,489 - 1,700
1981
Global Production Efficiency Model
Global Land Cover Facility, www.landcover.org

7. Change in NPP 1981 to 2000
NPPDifference2000-1981
g C/m2/year
High : 2467.93
Pos.
0.0
Neg.
Low : -2190.16

8. Study Area:
Western United
States

9. GIS Based
Processing Steps
Raw and Derived
Data
Extraction of
RAW DATA FROM Analysis Points
AVHRR & MODIS
• Annual NPP (81-00) Output files
CONVERT
• Annual GPP (00-10)
• Land cover
• Species maps Point Data Statistical
ATTRIBUTE
INFORMTION • Annual NPP (81-00) Analysis
TO • Delta NPP (81-00)
• Land cover types
• Point coverages • Precip, Tmax, Tmin ANOVA and
• Tree species
with 6km spacing • Regression Regression by:
• Species attributes
coefficients (a, b, r) • Elevation
• Elevation data
• Land cover types
• PRISM Climate Data
Stratified By • Tree species
• Precipitation
• Land cover type • Species attributes
• Minimum T
• Maximum T • Tree species
• Elevation

10. Analysis Point Extraction
Grid points placed every 6 km
Alternative placements offset every 2 km N,S,E & W
to test whether placement impacted final results
Repeated for each land cover type and species

11. Extractions for each grid cell and point location
• NPP Annual (1981, 1982, 1983 …….., 2000)
• Delta NPP (change in NPP from 1981 to 2000)
• Regression equation (a, b, r)
Each of the above then analyzed by:
• Elevation ranges:
• Divided into 500 meter increments from 0 to 4500 meters
• Land Cover type
• 14 Land Cover Types (Mapped from MODIS: USGS)
• Species
• 17 Species (Little, 1991 - USDA species maps)
• Species characteristics (USDA)
• 28 separate attributes
• drought tolerance
• water use
• growth rate
• etc.

12. Analysis by Land Cover Type
• Between 1981 and 2000 NPP at all elevations increased by an average of
~67 g C/m2 (~7.0 percent) over the entire study area.
Woodland Shrubland Grassland Forest
All 5.5 6.1 11.4 3.1
Elevations
Above 6.3 11.2 8.3 3.4
2000m
Above 1.8 5.4 2.4 4.5
2500m

13. Analysis
By
Tree
Species

14. Species where water availability
is not an issue
Slow growing
Low moisture use
High drought tolerance

15. Species where water availability
is somewhat of an issue
Range of growth rates
Medium moisture use
Low to medium drought tolerance

16. Species where water availability
is an issue (medium to high
water use and/or medium to low
drought tolerance)*
Results:
•Decreasing trends in NPP
or,
•Increase in NPP to a mid-forest
elevation and then a decrease at
higher elevation
*includes subpopulations of
bristlecone and foxtail pines found
in wetter regions

17. ANOVA - NPP and moisture use

18. NPP Change above 2000m
Delta NPP
1981 to 2000
G C/m2
-174 - -150
-149 - -100
-99 - -50
-49 - -1
0 - 50
51 - 100
101 - 150
151 - 200
201 - 250
251 - 300
301 - 350
351 - 400
401 - 450
451 - 500
501 - 550

19. California and Nevada Bristlecone Sites
At Elevations Greater Than 2000m
Pearl
NPP %Change
Peak
1981 to 2000
0-0
1 - 60
61 - 70
71 - 80
81 - 90
91 - 100
101 - 110
111 - 120
121 - 130
131 - 140
Mt 141 - 200
White Washington
Mountains

20. Trends in bristlecone pine NPP
1981-2000
Elevation (m) P. longaeva P. aristata
Mid-point of 500m range
2250 +12.36% -------
2750 + 9.67% + 3.95%
3250 +17.34% + 4.21%
3750 +36.52% + 3.37%
All Elevations +11.67% + 3.82%

21. Bristlecone pine NPP
August
and climate
April
Standardized Coefficients
1981-2000
Bristlecone pine NPP above 2500m
and west of longitude 109
August
April
Standardized Coefficients
Bristlecone pine NPP above 2500m
Annual
and east of longitude 109

22. Conclusions
• Increase in NPP for 11 of the 15 species
– Suggests that some, but not all, species are experiencing higher growth over
the past 30 years
– Pronounced increases at the highest elevations
• Slow growing species with exceptional drought tolerance and low water
usage had the largest increases
– Greater increase for the drier subpopulations of bristlecone and foxtail pine
– Greater increase for arid region Great Basin species
• Supports the argument for enhanced bristlecone pine growth derived
from tree ring analysis
– For NPP this suggests a response to a change in season length and water
availability associated with higher minimum temperatures
• The trend at these sites has continued, albeit at a slower rate, from
2000 to 2010 as indicated from analysis of MODIS GPP and NPP data

23. Questions?