AN UPWARD SHIFT OF
ENGELMANN SPRUCE ON THE
PINALEÑO MOUNTAINS, AZ, USA
Truettner, Charles M.(1, 2, 3); Cole, Ken L. (3); Anderson, R. Scott (3);
Cobb, Neil S. (2,4); D’Andrea, Rob (1, 3); Jarrad, Zach (4); Peters, Michael J. (3)
(1) NatureTrends, LLC, Crested Butte, CO 81224, (2) Merriam-Powell Center for Environmental Research, Flagstaff,
AZ 86001, (3) School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ
86001, (4) Biology Department, Northern Arizona University, Flagstaff, AZ 86001
Four “Proxies” of Vegetation
Change

Lake Sediment Core

Tree-Ring Chronologies

Plot Demographics

Ecological Niche Models
Objective
To understand the climatic factors affecting
vegetation change in the spruce-fir forest on the
Pinaleño Mountains
Overarching Hypothesis
If warming trends continue to increase
throughout the 21st century,
then Engelmann spruce and corkbark fir populations
will no longer persist in the uppermost elevations of desert
mountains in the American Southwest.
Pinaleño Mountains


Tallest mountain range in the
Sky Islands Madrean
Archipelago
Mt. Graham red squirrel
(Tamiasciurus hudsonicus grahamensis)

Southernmost location of
coexisting populations of
Engelmann spruce and corkbark
fir
Image provided by Esri
Soldier Creek Meadow



Cored by Anderson and
Shafer (1991)
Medieval Warming
Period
Possible large crown
fire (1685) or fire
exclusion (1880) from
Grissino-Mayer et al.
1994
1685 or 1880
Study Site Selection
Study Site Selection
Defined Two Different Forest Types with the presence of
Engelmann Spruce and Corkbark Fir
Study Site Selection
Spruce-Fir Forest
(3,130 – 3,270 m)
Transitional Forest
(2,930 m – 3,100 m)
Pinaleño Mountains
Spruce-Fir Forest
(3,130 – 3,270 m)
Transitional Forest
(2,930 m – 3,100 m)
Soldier Creek
Meadow
(2,900 m – 2,800 m)
Photo: Charles Truettner
Two large crowns fires in the last 20 years
(1996 and 2004)
Pinaleño Mountains
2004 Crown Fire
Data provided by LANDFIRE
Plots selected for north and northeastern slopes, no disturbance, and > 75% canopy
Randomly selected 7 plots (0.1) ha with 11-12 trees ≥ 40 cm DBH
Tree-Ring Chronologies
Population
Length
(years)
Estimated
Population
Signal
SFF
162
0.92
TF
57
0.95
SCM
87
0.93
Population
Length
(years)
Estimated
Population
Signal
SFF
129
0.94
TF
74
0.93
SCM
87
0.9
Climate Variables

PRISM resampled to 15 km to match GCMs

Warm-Season Vapor Pressure Deficit (kPa)
August-October
of the previous year
May-June

Cold-Season Precipitation (mm)
November-March
Total Precipitation
Climate Variables

Monsoon Precipitation (mm)


July-September Total Precipitation
Annual Mean Minimum Temperature (°C)

Mean January-December Minimum Temperature
Tree-Ring
Chronologies
Spruce-Fir Forest
Transitional Forest
Soldier Creek
Meadow
Cold-Season PPT
0.55
0.42
0.44
Monsoon PPT
-0.17
0.06
0.07
Annual Mean TMIN
-0.26
-0.15
-0.14
Warm-Season VPD
-0.13
-0.23
-0.3
Spruce-Fir Forest
Transitional Forest
Soldier Creek
Meadow
Cold-Season PPT
0.57
0.6
0.5
Monsoon PPT
-0.12
-0.03
-0.04
Annual Mean TMIN
-0.11
-0.10
-0.05
Warm-Season VPD
-0.24
-0.45
-0.42
Plot Demographics
2012
Plot Demographics
Comparison to Stromberg and Patten (1991)
Plot Demographics
Regeneration 2012
Total Seedling Count
Total Sapling Count
Ecological Niche Models
Caveats for Ecological Niche Models

Only based on the four climatic variables

15 km resolution

Small number of General Circulation
Models
Ecological Niche Models
Extent
Monsoon Index (Romme et al. 2009)
July-September Precipitation/Annual Precipitation
Ecological Niche Models
Extent
Ecological Niche Models
Extent
25% Monsoon Precipitation as Cutoff
Ecological Niche Models
Occurrence Data


Filtered to 15 km grid
cell
Extracted from:
ABLA
n = 51
ABLAvA
n = 36
PIEN
n = 109
1) LANDFIRE Public
Reference Database
2) Southwest
Envionmental
Information Network
3) Global Biodiversity
Index Facility
BIOMOD2
Package in R utilizes multiple modeling algorithms (Thuiller et. al 2012)
1) Generalize Linear Model (GLM)
2) General Additive Model (GAM)
3) Random Forest (RF)
4) Classification Tree Analysis (CTA)
5) Multiple Adaptive Regression Spline (MARS)
20 runs for each modeling algorithm
Examples of Climate Variables
Dynamically Downscaled General
Circulation Models
Data provided by Hosteltler et al. (2012)
15 km resolution
USGS GENMOM
MPI ECHAM5
Ecological Niche Models (1971-1999)
Ensemble Model Evaluation
Species
PRISM
Area Under the Curve Score
True Skill Statistics
ABLA
0.98
0.83
ABLAvA
0.99
0.88
PIEN
0.98
0.87
Species
MPI ECHAM5
Area Under the Curve Score
True Skill Statistics
ABLA
0.97
0.79
ABLAvA
0.96
0.82
PIEN
0.96
0.8
Species
USGS GENMOM
Area Under the Curve Score
True Skill Statistics
ABLA
0.96
0.8
ABLAvA
0.95
0.73
PIEN
0.97
0.82
Variable
ABLA
ABLAvA
PIEN
Cold-Season PPT
0.4
0.54
0.14
Monsoon PPT
0.27
0.19
0.08
Annual Mean TMIN
0.18
0.17
0.15
Variable
Warm-Season VPD
ABLA
0.51
ABLAvA
0.29
PIEN
0.58
Cold-Season PPT
0.05
0.23
0.07
Monsoon PPT
0.05
0.27
0.09
Annual Mean TMIN
0.68
0.33
0.72
Warm-Season VPD
0.2
0.38
0.22
Variable Importance in ENMs
PRISM
MPI ECHAM5
USGS GENMOM
Cold-Season PPT
0.09
0.09
0.07
Monsoon PPT
0.08
0.21
0.10
Annual Mean TMIN
0.72
0.33
0.68
Warm-Season VPD
0.1
0.47
0.18
Ecological Niche Models (2020-2029)
Ecological Niche Models (2030-2039)
Ecological Niche Models (2040-2049)
Ecological Niche Models (2050-2059)
Ecological Niche Models (2060-2069)
Ecological Niche Models (2070-2079)
Ecological Niche Models (2080-2089)
Ecological Niche Models (2090-2099)
Tree-Ring
Chronologies
Spruce-Fir Forest
Transitional Forest
Soldier Creek
Meadow
Cold-Season PPT
0.55
0.42
0.44
Monsoon PPT
-0.17
0.06
0.07
Annual Mean TMIN
-0.26
-0.15
-0.14
Warm-Season VPD
-0.13
-0.23
-0.3
Spruce-Fir Forest
Transitional Forest
Soldier Creek
Meadow
Cold-Season PPT
0.57
0.6
0.5
Monsoon PPT
-0.12
-0.03
-0.04
Annual Mean TMIN
-0.11
-0.10
-0.05
Warm-Season VPD
-0.24
-0.45
-0.42
Let's Bring This All Together
Comparison to Stromberg and Patten (1991)
Variable
ABLA
ABLAvA
PIEN
Cold-Season PPT
0.4
0.54
0.14
Monsoon PPT
0.27
0.19
0.08
Annual Mean TMIN
0.18
0.17
0.15
Variable
Warm-Season VPD
ABLA
0.51
ABLAvA
0.29
PIEN
0.58
Cold-Season PPT
0.05
0.23
0.07
Monsoon PPT
0.05
0.27
0.09
Annual Mean TMIN
0.68
0.33
0.72
Warm-Season VPD
0.2
0.38
0.22
Variable Importance in ENMs
PRISM
MPI ECHAM5
USGS GENMOM
Cold-Season PPT
0.09
0.09
0.07
Monsoon PPT
0.08
0.21
0.10
Annual Mean TMIN
0.72
0.33
0.68
Warm-Season VPD
0.1
0.47
0.18
Let's Bring This All Together
Acknowledgements
Doris-Duke Charitable Foundation
Merriam-Powell Center for Environmental
Research
United States Geological Survey
United States Forest Service
- Coronado National Forests
Questions and
Comments