changes in vegetation dynamics in alaska: implications for arctic herbivores eugénie euskirchen
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Changes in Vegetation Dynamics in Alaska: Implications for Arctic Herbivores Eugénie Euskirchen Wildlife Response to Environmental Arctic Change Workshop Nov. 17 -18, 2008. Pan-Arctic Detection of Recent Land Surface Changes. ≤ -3.0.TRANSCRIPT
Changes in Vegetation Dynamics in Alaska: Implications for Arctic Herbivores
Eugénie Euskirchen
Wildlife Response to Environmental Arctic Change Workshop
Nov. 17 -18, 2008
Growing Season Change 1988 - 2000
Change in Gross Primary Productivity
1982 - 2003
Change in Snow Cover Duration
1970 - 2000
Bunn & Goetz, Earth Interactions, 2006
McDonald et al., Earth Interactions, 2004
Euskirchen et al., Global Ch. Biol., 2007
<-0.4-0.4 -0.3-0.2-0.05 0.1
>0.1
Days shorter
yr-1
Days longer yr-1
Pan-Arctic Detection of Recent Land Surface Changes
≤-3.0-2.0 -1.0 0.0 1.0 2.0
≥3.0
Days shorter
yr-1
Days longer yr-1
Studies have also documented changes in plant community composition at high-
latitudes
Increased shrubiness
Sturm et al., 2001; 2005
Changes in fire regimesIncreases in insect outbreaks
Treeline advance
Suarez, 1999; Lloyd & Fastie, 2003
•Changes in the length of the snow & growing seasons impact vegetation. •How well can we predict these changes in vegetation? (TEM-DVM)
•What is the magnitude of climate-related changes in the productivity of the major ecosystem types (including their dominant plant functional types, PFTs) in northern Alaska?
•How can we use predictions in vegetation changes to gain an understanding of how herbivores may be impacted by predicted changes in vegetation? (TEM-DVM linked to CARMODEL)
•What types of processes / dynamics and habitats do vegetation models need to consider?
Spruce forest
Tussock tundra
Willow-birch tundra
Spruce, Salix spp., other deciduous shrubs, evergreen shrubs not including spruce, sedges, forbs, lichens, and feathermoss
Betula spp., other deciduous shrubs, evergreen shrubs, sedges, forbs, lichens, feathermoss and Sphagnum moss
Salix spp., Betula spp., other deciduous shrubs evergreen shrubs, sedges, forbs, lichens, & feathermoss
TERRESTRIAL ECOSYSTEM MODEL WITH DYNAMIC VEGETATION
AND LEAF, WOOD, AND ROOT COMPONENTS (TEM-DVM)
Linked to other submodels including a soil thermal model (permafrost dynamics; Zhuang et al., 2001) and hydrology model (snow dynamics; Euskirchen et al., 2007)
RH
NETNMINCS NS NLOST
NINPUT
SOIL
LightNAV
LightNAV
Atmospheric Carbon Dioxide (CO2)
NAV
Euskirchen et al., in press, Ecol. Applications
• The study region in northern Alaska is classified as 77% sedge tundra, 13% shrub tundra, and 8% evergreen needleleaf forest, with each of these ecosystems comprised of 8 or 9 PFTs.
• The model is parameterized based on field data collected in the study region.
Ch
an
ge in
air
te
mp
era
ture
(°C
year-
1)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
MAM
SON
Mean annual
JJA
DJF
A2 C
SIR
O
A2
Had
. C
M3
A2 P
CM
B1 C
SIR
O
B1
Had
. C
M3
B1 P
CM
B2
CS
IRO
B2
Had
. C
M3
B2
PC
M Mea
n
We used a wide range of future climate scenarios, based on the IPCC SRES scenarios and three global climate models (GCMs). Shown below is input air
temperature data.
230
155
115
75
35
-5
(Sed
ge
)
Forb
Salix
Gra
ss
Salix
Feath
er
Betu
la Sp
ruce
Sed
ge
Decid
.
Fea
ther
Forb
Decid
. Sed
ge
Dec
id.
Sed
ge
E.g
ree
nForb
Lic
hen
E.g
ree
n Feath
er
E.g
ree
nSp
hag
.G
rass
Betu
laLic
he
nLic
hen
(Fore
st)
(S
hru
b)
(Sh
rub
)
ForestShrub tundraSedge tundra
Ch
an
ge in
NP
P,
2003-2
100 (
g C
m-
2)
Change in NPP (2003 – 2100) across all ecosystem types and PFTs,
arranged in descending order.
Euskirchen et al., in press, Ecol. Applications
Salix
0100
200
300
400
Betu
la
Decid
.
Everg
r.
Sed
ges
Forb
s
Gra
sses
Lic
hen
s
Feath
er.
01
23
45
6
Betu
la
Decid
.
Everg
r.
Sed
ges
Forb
s
Gra
sses
Lic
hen
s
Feath
er.
Salix
Change in Vegetation Carbon Change in Vegetation Nitrogen
Shrub Tundra 2003 - 2100V
eg
eta
tion
C c
han
ge (
g C
m-2)
Veg
eta
tion
N c
han
ge (
g N
m-2)
Increases in NPP resulted in increases in biomass, and consequently, decreases in
summer albedo.
0.1
0.12
0.14
0.16
0.18
0.2
2003 2023 2043 2063 2083
Su
mm
er
Alb
ed
o
Forest
Shrub tundra
Regional
Sedgetundra
The albedo of the shrub tundra is approaching that of the forest at the end of the simulation. Can the shrub tundra ecosystem still be a considered shrub tundra ecosystem?
How can TEM-DVM be used to relate vegetation changes to herbivores?
•Arctic calving caribou provide an example of a species that is likely to be affected by climate change, but with long annual migrations and a circumpolar distribution the effects on populations will not be uniform.
• An explicit energetics model (CARMODEL) is available that allows assessment of projected climate induced changes in potential forage intake on fat and protein dynamics.
CARMODEL (Russell et al., 2005)
En
erg
etic
s M
od
el
Energy Submodel
Daily forage intake
Hourly digestion
Rumen contentsNext hour
Cow weight
Growth Submodel
Daily Growth of Cow & Calf
• Maintenance• Activity• Gestation• Lactation
Daily Energy Allocation
Next day
Forage
• Biomass of a PFT• Digestibility• Cell wall content• Nitrogen content• Diet
Snow depth
Activity budgets
Reproductive strategy
• Conception date• Gestation period• Wean date
Future climate:• Air temperature • Precipitation • Solar radiation
Daily
Daily
Daily
Yearly
• Compare and contrast the implications of climate induced changes in forage biomass and quality on fat and protein dynamics in two groups of caribou with characteristically different diets at calving: a) caribou that calve in the wetter portions of the coastal plain (Central Arctic, Teshekpuk), and b) caribou that calve in uplands and drier portions of the coastal plain (Western Arctic, Porcupine).
• Analyses based on a range of climate scenarios will allow managers and subsistence users to more effectively understand the range of possible future conditions and to plan adaptation strategies.
1 kmX 1 km
Integration of the model presented here (TEM-DVM) with other land cover maps / habitat classification schemes:
• Finer scale representation of the ecosystem types within a landscape or region is possible.
• It is also possible to incorporate other ecosystem/habitat types than the three presented earlier.
• Some parameterization data for PFTs in a given habitat type is necessary.
• One recent model development is a dynamic soil layer module (Yi et al., manuscript in prep.) that incorporates different types of soil layers (e.g., live moss, humic, fibric) and drainage classes (e.g., moderately well-drained, poorly drained).
Future Work & Challenges:
• Incorporating shifts from one ecosystem type to another
• Incorporating changes in vegetation (at the ecosystem & PFT level) under changes in the fire regime and insect outbreaks
• Understanding how the phenology of the various PFTs responds to changes in growing season length in terms of both budburst in the spring and leaf senescence in the fall
• Incorporating water competition among the PFTs
• Increased levels of herbivory may lead to increases in productivity of ecosystems under climate change. How then does this increased herbivory feed back on the ecosystem? Field experiments suggest that the increased herbivory will ultimately modulate this increased productivity (e.g., Sjögersten et al., 2008).