The Effects of Soil Moisture Stress
on Forest Recovery in the Entiat
River Basin after Stand Replacing
Fire
Marketa M. Elsner
UW Climate Impacts Group
AGU Fall Meeting 2011 (Session GC-34A)
Entiat River Basin
Location:
Columbia River tributary, 20 mi
upstream of Wenatchee, WA
DA:
419 sqmi
Elevation: 751 - 9,150 ft
Dominant species:
Ponderosa pine, Lodgepole pine,
Douglas fir
Experimental watersheds:
Fox Creek (1.9 sqmi)
Burns Creek (2.2 sqmi)
McCree Creek (1.9 sqmi)
Background
Entiat Wildfire History
Entiat Zone Fire (August 24, 1970)
Source: lightning
Burned 188 sqmi (120,000 ac) including
experimental forest
Fox Ck - strong veg recovery
on south-facing slope
Experimental Forest Regrowth
Fox Creek (1.9 sqmi):
control (no seeding or fertilization)
Burns Creek (2.2 sqmi):
aerial seeding & fertilization
McCree Creek (1.9 sqmi):
aerial seeding
Background
Burns Ck - limited veg
recovery on south-facing
slope
Burns Ck - some regions
without forest regeneration
Hydrologic Modeling
(Wigmosta et al. 1994)
DHSVM
 100 meter spatial resolution
 Spatially explicit model intended for
drainage areas typically < 4,000 sqmi
 Input maps include soil depth
Soil depth map typically based on:
 Elevation
 Upstream Source Area
 Slope
Our approach also includes:
 Hillslope curvature
 Relative position on hillslope
(Catani et al. 2010)
Study Approach
Quantify Soil
Moisture Stress
Intensity and duration
of water stress are
important drivers of
vegetation mortality
(Breda et al. 2006; McDowell et al. 2008)
Fig. 3 from McDowell et al. 2008
Computed soil moisture stress:
• Intensity: Percentile of years (1950-2000) where min soil
moisture (top 20cm) is below WP (0.1)
• Duration: Longest continuous duration where minimum soil
moisture (top 20cm) is below WP (0.1)
Study Approach
Quantify observed regions of poor forest
generation
Before 1970 Fire
Photo: 1967
Study Approach
After 1970 Fire
Photo: 2009
Quantify observed regions of poor forest
generation
Before 1970 Fire
Photo: 1967
Study Approach
After 1970 Fire
Photo: 2009
Temperature
Column Soil Moisture
Precipitation
Day 1 SWE
Study Approach
Comparison of Pre - Fire (‘50-’69)
and Post-Fire (‘70-’00) Periods
Comparison of Simulated Soil Moisture Stress
and Lack of Forest Regeneration
REGEN
NO-REGEN
STRESS
44% of STRESS had
NO-REGEN
64% NO-REGEN
had STRESS
NO-STRESS
56% of NO-STRESS
had NOREGEN
17% of NO-REGEN
had
NOSTRESS
9% of STRESS had
REGEN
91% of NO-STRESS
had REGEN
36% of REGEN had
STRESS
82% of REGEN had
NO-STRESS
Preliminary Results
*Simulated moisture stress based on
1950-2000 time period
Simulated Intensity vs. Duration Relationship
0.10
0.08
Fig. 3 from McDowell et al. 2008
0.06
Results for Entiat Watershed
suggest hydraulic limitation
over carbon limitation
Preliminary Results
Entire Entiat Watershed
*Min Soil Moisture vs. Stress Duration for
each year 1950-2000
Simulated Intensity vs. Duration Relationship
0.10
0.08
Fig. 3 from McDowell et al. 2008
Results for Experimental
Results
for Entiat
Watershed
Watersheds
suggest
other
suggest
factors hydraulic
contributelimitation
to veg
over carbon
limitation
limitation
Preliminary Results
0.06
Experimental
Entire Entiat Watersheds
Watershed
*Min Soil Moisture vs. Stress Duration for
each year 1950-2000
Conclusions
Observed
regeneration
Simulated NO
Moisture Stress
Observed NO
regeneration
Simulated
Moisture Stress
However,
 > 50% cells with NO-STRESS had NO-REGEN indicating other
drivers of poor recruitment
 Watershed treatment (seeding & fertilization) did not influence
recruitment
Marketa M. Elsner
mmcguire@uw.edu
Coauthors:
Alan F. Hamlet
Richard Woodsmith
Jeremy S. Littell
Erkan Istanbulluoglu
▪ UW CIG, UW Civil & Environmental Engineering
▪ formerly with USFS Research Station, Wenatchee, WA
▪ UW CIG
▪ UW Civil & Environmental Engineering
Acknowledgements:
Rob Norheim (CIG)
Pam Wilkins (USFS)
Pablo Carrasco
▪ map figures
▪ digitizing aerial photos and data collection
▪ development of baseline DHSVM models
Future Application
Soil moisture stress is projected
to increase in the future due to:
 loss of snowpack
 increased evaporation
 projected drier summers
Maps of areas of poor
recruitment may help guide
vegetation recovery strategies
under a changing climate
Medium Climate Change Scenario
Historical (1950-2000) to
2040s (2030-2059)
Entiat Vegetation Classes
Source: National
Landcover
Database 2001
(30m resolution)
Entiat River Basin
Fine Scale Projections (100m)
2030-2059 A1B
In collaboration with the USFS PNW Research Station
SWE
ET
Flow Depth
Streamflow
units: cfs
Units:mm
unless
otherwise
noted