Transcript Impact of Climate Change on W Forests

Impact of Climate Change
on Western Forests
Mortality and Distribution Changes
Western Forests and Woodlands
Cobb, 2007, EESI
Western Forests and Woodlands
Woodlands=open stands
of trees spaced far
enough apart so that
their canopies do not
touch
Aerial view of Pinyon-Juniper
Woodland in Central New Mexico
Pinyon-Juniper Woodland in
Central New Mexico
Predicted Changes to Terrestrial Ecosystems
as a result of Climate Change (IPCC 2007)
 Warm temperatures, in the long-run, will strain water
resources producing drought-induced stress and
broad-scale die-offs of vegetation
 Beginning trends are already being observed
Mortality is wide-spread
throughout Western
Forests
Observed & Predicted Changes to Terrestrial
Ecosystems as a result of Climate Change
(IPCC 2007)
Modern Vegetation Zones
Eleva
tion
Rang
e
(feet)
Annu
al
Preci
pitati
on
ArcticAlpine
Alpine Tundra
11,50
012,70
0
35"40"
Hudsonian
Spruce-Fir or Subalpine
Conifer Forest
9,50011,50
0
30"40"
Canadian
Mixed Conifer Forest
8,0009500
25"30"
Transition
Ponderosa Pine Forest
60008500
18"26"
Upper
Sonoran
Pinyon-Juniper Woodland,
Semi-Arid Grasslands,
Semi-Arid Scrub
35006500
10"20"
Mojave, Sonoran, or
Chihuahuan Desert
1003500
Merriam's
Life Zones
1891
Lower
Sonoran
Reduction in available
habitat for alpine and
arctic species
Alpine Tundra
Spruce-fir
Mixed Conifer Forest
Ponderosa Pine Forest
3"12"
Pinyon-Juniper Woodland
Juniper-Savanna Woodland
Ecotone shifts
Ecotone=zone of
transition between two
plant communities
In Northern New
Mexico, the
ecotone between
pinyon-juniper
woodland &
Ponderosa pine
forest is moving
to higher
elevation
Cobb, 2007, EESI
Pinyon Mortality
Mortality extends
across an area of
12,000 km2 in the
Southwest
Breshears et al. 2005, PNAS
NOTE:
P-J is now
Juniper Savanna
Upward
movement of
biomes
Extent of Pinyon Mortality
Cobb, 2007, EESI
Mortality due to high temperatures
combined with drought
Cobb, 2007, EESI
Causes of Pinyon Mortality
 Three primary
causes:



Temperature
Drought
Insect Infestation
(bark beetle)
 In most trees, the
bark beetle was the
ultimate cause of
death
 Trees weakened by
global change-type
drought are
susceptible
 Bark beetles
populations are
greater due to
warmer winters
Cobb, 2007, EESI
Effect of temperature on pinyon pine
growth
Newberry, 2009
Summer temperatures reduce growth in pinyon pines. Indicating the
influence of temperature as well as drought in pinyon mortality.
Mechanisms of mortality

Tree mortality due to high temperatures can happen
in three ways
1.
2.
3.



Carbon starvation
Cavitation
Insect infestation (i.e., bark beetle)
The first two are direct consequences of
environmental (abiotic) changes
The third one is due to a biotic agent
More recently, forest mortality due to high
temperatures alone (1& 2) are being observed
throughout Western forests
Projected shifts in piñon
distribution
Cole & Ironside, in prep.
So why do we care about tree
mortality?
 Looking at effects the P-J
ecosystem….



Pinyon jays will lose their home
Loss of an important food source for
humans and animals (pine nuts)
Loss of understory plants
 What else will happen?
 Increased soil erosion
 Increased soil temperature and
evaporation
 Increase fuel load for fires
 Forests become source not sink for
carbon dioxide
Forest-Climate Connection: Carbon Cycle
Why the
up and
down
pattern?
Annual
fluctuations
reflect
differences in
photosynthesis
and respiration
between
summer and
winter
Cunningham/Cunningham 2002 text
Draft criteria for Sustainable Forests
1. Conservation of biological diversity
2. Maintenance of production capacity of
forests
3. Maintenance of soil and water resources
4. Maintenance of forest contribution to global
carbon cycle
5. Maintenance and enhancement of long-term
socioeconomic benefits to meet the needs of
legal, institutional, and economic framework
for forest conservation and management
Source: Data from USFS, 2002