geog presentation for_web
TRANSCRIPT
Postglacial dynamics of
Olympic Peninsula forests: comparing
simulations and observations
A Master’s Thesis presented to the
Department of Geography University of Oregon
byDavid Fisher
Thanks toDan Gavin
Bart BartleinJed Kaplan
Olympic Mountains, WA
• How does knowledge of the life history of tree species -- regeneration, growth, competition, mortality -- as well as the relationship between species and climate at important life stages, improve our explanation of the dynamic changes in forest composition since the Late Glacial period, 15,000 years ago?
Research Questions
• Paleoecology & Biogeography of Olympic Peninsula forests
• Methods -- quantifying important bioclimatic variables and simulating paleoecological records with a process-based vegetation model
• Results -- Simulations compared to present and paleo records
• What did we learn?
Outline of this talk
Paleoecological Records
Yahoo Lake - Pollen Percentage Diagram
Figure by D. G. Gavin
Cold, Dry? Warm, Dry Cool, Wet
(Gavin, D.G. 2013)
Limiting factors for tree growth: On the west side: energy On the east side: moisture
¯0 40 8020 Kilometers
¯0 40 8020 Kilometers
¯0 40 8020 Kilometers
0
2 deg C
-4
-2
4
6 meters
2
3
Alpinemountain hemlocksubalpine fir
Pacific silver fir
Douglas-firwestern hemlockSitka spruce
Minimum Jan Temp Mean Annual Precip Potential Natural Forest Zones
50km
(Henderson et al. 2011)
PRISM (Daly et al. 2008)
PRISM (Daly et al. 2008)
lodgepole pinePinus contorta
subalpine firAbies lasciocarpa
mountain hemlockTsuga mertensiana
Pacific silver firAbies amabilis
Douglas-firPseudotsuga menziesii
western redcedarThuja plicata
western hemlockTsuga heterophylla
Sitka sprucePicea sitchensis
red alderAlnus rubra
grass
Methods: Considering the seedling, how should we measure energy and moisture requirements?
Growing Degree Days
FJ M A M J J A S O N D
5
-5
10
15Average Daily Temperature
(Deg C)
Post-Snow Growing Degree Days
0
1000
2000Size of Snowpack
(Snow-Water equivalent)
Methods: Considering the seedlings, how do we measure energy?
(mm)
Local Measurements of Post-Snow GDD
(two SNOTEL stations)
Year SW NE2006 6492007 4322008 4932009 6702010 487 4732011 373 3842012 650 563
Post-Snow GDD Measurements
SW = BuckinghorseNE = Waterhole http://www.wcc.nrcs.usda.gov/snotel/SNOTEL-brochure.pdf
−60 −30 0 30 60
w. hemlockS. sprucew. redcedarr. alder
P. silver firDoug-fir
m. hemlock l. pinesubalpine fir
1600
1400
800
300
1890 1920 1950 1980 2010
Post-Snow GDD Simulations
Low - Dry
High - Dry
High - Wet
Mid - Wet
Low - Wet
Five Locations
Year
# Post-Snow GDDs
annual PS-GDD required for each species to establish
Cohorts of trees grow on patches of land (15m x 15m).
Each species is unique in its ability to establish, grow, and die.
Continuous Climate (temperature, precipitation, cloudiness) is the main driver.
LPJ-GUESS: a process-based vegetation model
http://www.nateko.lu.se/lpj-guess/education/html/guess.pdf
Process Parameters
title Title for runnyear_spinup Number of simulation years to spinup forvegmode Vegetation mode ("INDIVIDUAL", "COHORT", "POPULATION")ifdailynpp Whether photosynthesis calculated daily (alt monthly)ifdailydecomp Whether soil decomposition calculated daily (alt monthly)ifbgestab Whether background establishment enabled (0,1)ifsme Whether spatial mass effect enabled for establishment (0,1)ifstochmort Whether mortality stochastic (0,1)ifstochestab Whether establishment stochastic (0,1)estinterval Interval for establishment of new cohorts (years)distinterval Generic patch-destroying disturbance interval (years)iffire Whether fire enabled (0,1)ifdisturb Whether generic patch-destroying disturbance enabled (0,1)ifcalcsla Whether SLA calculated from leaf longevityifcdebt Whether to allow C storagenpatch Number of patches simulatedpatcharea Patch area (m2)outputdirectory Directory for the output filesifsmoothgreffmort Whether to vary mort_greff smoothly with growth efficiency (0,ifdroughtlimitedestab Whether establishment drought limited (0,1)ifrainonwetdaysonly Whether it rains on wet days only (1), or a little every day (0)ifspeciesspecificwateruptake Whether or not there is species specific soil water uptake (0,1)
Global PFT Parameters:
lambda_max Non-water-stressed ratio of intercellular to ambient CO2 ppemax Maximum evapotranspiration rate (mm/day)reprfrac Fraction of NPP allocated to reproductionwscal_min Water stress threshold for leaf abscission (raingreen PFTs)
Lifeform Parameters (Tree, Grass):
crownarea_max Maximum tree crown area (m2)ltor_max Non-water-stressed leaf:fine root mass ratiok_allom2 Constant in allometry equationsk_allom3 Constant in allometry equationsk_rp Constant in allometry equationscton_leaf Leaf C:N mass ratiocton_root Fine root C:N mass ratiocton_sap Sapwood C:N mass ratiopathway Biochemical pathway ("C3" or "C4")kest_repr Constant in equation for tree estab ratekest_bg Constant in equation for tree estab ratekest_pres Constant in equation for tree estab ratelitterme Litter moisture flammability threshold (fraction of AWC)respcoeff Respiration coefficient (0-1)k_chilla Constant in equation for budburst chilling time requirementk_chillb Coefficient in equation for budburst chilling time requirementk_chillk Exponent in equation for budburst chilling time requirement
Climate Group Parameters (Boreal, Temperate):
pstemp_min Approximate low temp limit for photosynthesis (deg C)pstemp_low Approx lower range of temp optimum for photosynthesis (deg C)pstemp_high Approx higher range of temp optimum for photosynthesis (deg C)pstemp_max Maximum temperature limit for photosynthesis (deg C)
Leaf Group Parameters (Broadleaf, Needleleaf):
gmin Canopy conductance not assoc with photosynthesis (mm/s)phenology Phenology ("EVERGREEN", "SUMMERGREEN", "RAINGREEN" or "ANY")turnover_root Fine root turnover (fraction/year)intc Interception coefficient
Shade Group Parameters (shadevintol, shadeintol, shadetol, shadevtol):
turnover_sap Sapwood turnover (fraction/year)greff_min Threshold for growth suppression mortality (kgC/m2 leaf/yr)est_max Max sapling establishment rate (indiv/m2/year)alphar Shape parameter for recruitment-juv growth rate relationshipparff_min Min forest floor PAR for grass growth/tree estab (J/m2/day)
PFT (or species) specific parameters:
include ! Include PFT in analysisphengdd5ramp ! GDD on 5 deg C base to attain full leaf coverrootdist ! Fraction of roots in each soil layer (first value=upper layer)turnover_leaf ! Leaf turnover (fraction/year)wooddens ! Sapwood and heartwood density (kgC/m3)k_allom1 ! Constant in allometry equationsk_latosa ! Tree leaf to sapwood xs area ratiosla ! Specific leaf area (m2/kgC)fireresist ! Fire resistance (0-1)tcmin_surv ! Min 20-year coldest month mean temp for survival (deg C)tcmin_est ! Min 20-year coldest month mean temp for establishment (deg C)tcmax_est ! Max 20-year coldest month mean temp for establishment (deg C)twmin_est ! Min warmest month mean temp for establishment (deg C)twminusc ! Stupid larch parametergdd5min_est ! Min GDD on 5 deg C base for establishmentlongevity ! Expected longevity under lifetime non-stressed conditions (yr)leaflong ! Leaf longevity (years)drought_tolerance!Drought tolerance level (0 = very -> 1 = not at all) (unitless)
Output Files:
file_cmass ! ! C biomass output filefile_anpp ! ! Annual NPP output filefile_lai ! ! LAI output filefile_cflux ! ! C fluxes output filefile_dens ! ! Tree density output filefile_cpool ! ! Soil C output filefile_runoff ! ! Runoff output filefile_firert ! ! Fire retrun time output filefile_mnpp ! ! Monthly NPP output filefile_mlai ! ! Monthly LAI output filefile_mgpp ! ! Monthly GPP-LeafResp output filefile_mra ! ! Monthly autotrophic respiration output filefile_maet ! ! Monthly AET output filefile_mpet ! ! Monthly PET output filefile_mevap ! ! Monthly Evap output filefile_mrunoff ! ! Monthly runoff output filefile_mintercep ! ! Monthly intercep output filefile_mrh ! ! Monthly heterotrphic respiration outputfile_mnee ! ! Monthly NEE output filefile_mwcont_upper Monthly wcont_upper output filefile_mwcont_lower Monthly wcont_lower output filefile_speciesheights Mean species heights in 2000
Parameters of LPJ-GUESS(Smith et al. 2001)
Parameterizing LPJ-GUESS, 9 different tree species
Shade&ToleranceMin&Annual&Post4Snow&
GDD%&available&soil4water
Maximum&Age
lodgepole'pine Very&Intolerant 300 0.15 250
subalpine'fir Very&Tolerant 300 0.5 250
mountain'hemlock Very&Tolerant 300 0.68 400
Pacific'silver'fir Very&Tolerant 800 0.7 400
Douglas8fir Intolerant 800 0.2 750
western'hemlock Very&Tolerant 1400 0.6 400
western'redcedar Tolerant 1400 0.5 1000
red'alder Very&Intolerant 1400 0.5 80
Sitka'spruce Tolerant 1600 0.7 500
-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0Age (-ka)
-8
-6
-4
-2
0
2
Temperature(C)
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
Temperature(C)
Annual
DJF
JJA
SON
MAM
[-120.0, 46.389]
[decadal averages every 10 years]
Figure by P.J. Bartlein
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0 25 50 75 0 25 50 75% Cover in field plots (gray); Simulated biomass x 10 (black)
elev
atio
n (m
eter
s)
lodgepole pine
subalpine fir
mountain hemlock
Pacific silver fir
Douglas-fir
western hemlock
western redcedar
Sitka spruce
red alder
West Side East SidePercent cover of tree species in 639 ecological plots in the Olympic National Forest (downloaded from Ecoshare.info)
Simulated biomass of tree species averaged overthe last 1000 years at each site
0
1500
0
1500
Elev
atio
n (m
eter
s)
Results: present-day
< 0.5 50-10010-502-100.5-2
−15000 −10000 −5000 0−15000 −10000 −5000 0
Grass
lodgepole pine
subalpine fir
mountain hemlock
Pacific silver fir
Douglas-fir
western hemlock
western redcedar
Sitka spruce
red alder
grass
lodgepole pine
subalpine fir
mountain hemlock
Pacific silver fir
Douglas-fir
western hemlock
western redcedar
Sitka spruce
red alder
Low Elevation, Wet Side Low Elevation, Dry Side
Percent of Total
15,000 10,000 5000 0 15,000 10,000 5000 0
Years before present
MD
MD
M = Model ResultsD = Pollen Data
−15000 −10000 −5000 0−15000 −10000 −5000 0
grass
lodgepole pine
subalpine fir
mountain hemlock
Douglas-fir
western hemlock
western redcedar
Sitka spruce
grass
lodgepole pine
subalpine fir
mountain hemlock
Pacific silver fir
Douglas-fir
western hemlock
Sitka spruce
High Elevation, Wet Side High Elevation, Dry Side
15,000 10,000 5000 0 15,000 10,000 5000 0
< 0.5 50-10010-502-100.5-2
Percent of Total
Years before present
MD
MD
M = Model ResultsD = Pollen Data
−15000 −10000 −5000 0
grass
lodgepole pine
subalpine fir
mountain hemlock
Pacific silver fir
Douglas-fir
western hemlock
western redcedar
Sitka spruce
red alder
Mid Elevation, Wet Side
Late Glacial to late Holocenetransition is captured.....
But what about the abundant Douglas-fir and alder pollen in the early Holocene
15,000 10,000 5000 0
Years before present
MD
MD
M = Model ResultsD = Pollen Data
0
200
400
600
−15000 −10000 −5000 0
−10−8−6−4−20246810121416182022
−15000 −10000 −5000 0
Deg C mm
Jan & July Temperature Jan & July Precipitation
Years before present Years before present
At the Mid elevation, Wet Side site
−20000 −15000 −10000 −5000 0−20000 −15000 −10000 −5000 0
−20000 −15000 −10000 −5000 0−20000 −15000 −10000 −5000 0
S. spruce
w. hemlockw. redcedar r. alder
P. silver firDoug-fir
m. hemlockl. pine
subalpine fir
S. spruce
w. hemlock
m. hemlockP. silver fir
subalpine fir w. redcedar r. alder
Doug-firl. pine
1600
1400
800
300
0.7
0.6
0.5
0.20.15
900
600
300
Low - Dry
High - Dry
High - Wet
Mid - Wet
Low - Wet
15
10
5
0
20
Post-snow GDD
Simulated Biomass
Kg C per square meter
Fraction available
soil-water
Fire Return Time (years)
15,000 10,000 5000 020,000 15,000 10,000 5000 020,000
+2
-2
-1
0
+1More Snow
Less Snow
Rain-Snow Temp
• The two climate variables that are controlling species composition across the Peninsula are both influenced by snowpack
The influence of snow
−20000 −15000 −10000 −5000 0
−20000 −15000 −10000 −5000 0−20000 −15000 −10000 −5000 0
15,000 10,000 5000 020,000
900
600
300
Fire Return Time (years)
0.7
0.6
0.5
0.20.15
Fraction available
soil-water
1600
1400
800
300
Post-snow GDD
15,000 10,000 5000 020,000
+2
-2
-1
0
+1More Snow
Less Snow
Scenarios with varying Rain-Snow temp threshold at the high elevation wet site
°C
0.0
2.5
5.0
7.5
10.0
−2 −1 0 1 2
variable
Pacific silver firsubalpine firlodgepole pineDouglas-firmountain hemlockgrass
Simulated Biomass
Kg C per square meter
Rain-Snow Temp°C
More SnowLess Snow
Thresholds crossed
0°C to 1°Cenough snow to favor mountain hemlock (by limiting others)
1°C to 2°Ctoo much snow for consistent forest cover, open canopy plants thrive (grass and pine)
Scenarios with varying Rain-Snow temp threshold at the high elevation wet site
• Supported the theory that energy requirements control species composition on the west side, and moisture controls composition on the east side
• Quantified the climatic tolerance of seedlings in terms of one specific energy-related climate variable (Post-snow GDD) and one moisture-related variable (fraction available soil-water)
• Provided the first species-level test against the paleoecological record of the influence of these climate variables
What did we learn?
Thank You!References
Daly, C., M. Halbleib, J. I. Smith, W. P. Gibson, M. K. Doggett, G. H. Taylor, J. Curtis, and P. P. Pasteris. 2008. “Physiographically Sensitive Mapping of Climatological Temperature and Precipitation Across the Conterminous United States.” International Journal of Climatology 28 (15) (December): 2031–2064. doi:10.1002/joc.1688.
Gavin, D. G., L. B. Brubaker, and D. N. Greenwald. 2013. “Postglacial Climate and Fire- Mediated Vegetation Change on the Western Olympic Peninsula, Washington.” Ecological Monographs (April 18). doi:10.1890/12-1742.1.
Henderson, J.A., R.D. Lesher, D.H. Peter, and C.D. Ringo. 2011. “A Landscape Model for Predicting Potential Natural Vegetation of the Olympic Peninsula USA Using Boundary Equations and Newly Developed Environmental Variables”. USDA General Technical Report: PNW-GTR-941. USDA Forest Service.
Liu, Z., B. L. Otto-Bliesner, F. He, E. C. Brady, R. Tomas, P. U. Clark, A. E. Carlson, et al. 2009. “Transient Simulation of Last Deglaciation with a New Mechanism for Bolling-Allerod Warming.” Science 325 (5938) (July 16): 310–314. doi:10.1126/science.1171041.
Smith, B., Prentice, I.C. & Sykes, M.T. 2001. Representation of vegetation dynamics in modelling of terrestrial ecosystems: comparing two contrasting approaches within European climate space. Global Ecology and Biogeography 10: 621-637.