Transcript Alpine Plants - University of Colorado Boulder

Alpine Vegetation- patterns of biodiversity
and response to environmental change
Bill Bowman- Ecology and Evolutionary Biology
Mountain Research Station, INSTAAR
([email protected])
reference: Körner, Ch. 1999. Alpine Plant Life. Springer Verlag, Berlin
What is the alpine?
Is it tundra?
Nival
Alpine
treeline
Subalpine
Montane
elevation of treeline corresponds
with:
1) minimum growing season
temperature around 6 °C
2) wind
3) geomorphic disturbance- avalanches
krummholz- "twisted wood"
Global distribution of treeline
from Körner, 1999
large variation in
altitude at midlatitudes
associated with continentalitytreelines lower in moist, maritime
locations
Alpine is a globally distributed biomeplants have similar
"growth forms:"
graminoids
(grasses, sedges)
forbs
(broad leaved
herbaceous plants)
prostrate shrubs
Alpine environmental conditions:
 cold
 temperatures may change rapidly
 windy (mainly temperate zone)
 soils often poorly weathered
 low water and nutrient availability
 high UV irradiance (although offset
by cloud cover)
 low p(CO2) - dependent on elevation
Adaptations to the alpine environment include:
 being short
high investment into
belowground biomass (high
root:shoot ratio)
 low growth rates
 tolerance to low temperatures
(= intolerance of high
temperatures)
Alpine is an extensive biome- globally distributed
How has
Pleistocene
glaciation
influenced alpine
diversity and
plant
distribution?
Continuous and isolated alpine habitat: Colorado
interglacial (present)
Glacial (ca. 20K BP)
Biogeographic trends in Rocky Mountain alpine plant diversity
% of flora circumpolar
species
n.s.
200
100
~ same number species
0
35
40
45
50
2
r =0.49
P< 0.01
40
30
more Arctic species to north
20
35
50
40
45
6
% of flora endemic
number of species
300
2
r =0.46, P< 0.01
4
more endemic species to south
2
0
35
40
45
Latitude (degrees)
50
50
Biogeographic similarities (after Hadley 1987)
Sørenson’s index
Beartooth
(50-83)
Absoroka
Gros Ventre
51
Teton
Big Horn
Wind River
58
51
54
Uintah
Medicine Bow
48
59
Indian Peaks
44
50
Needles
San Fransisco Peaks
34
Sangre de Cristos
Global Plant Diversity
Regional scale plant diversity in S. Rockies; the influence of
mountains:
Weld County: ~600 species
Boulder County: 1550 species
(50% of flora of Colorado)
MOUNTAINS
• Have the highest plant species diversity
• High mountain environments have a high
percentage of endemic plants
• Alpine areas have a much high plant
diversity than forested areas
Alpine Mesotopographic Gradient
(After Billings)
Prevailing wind
Fellfield Fellfield
snow
Snowbed
Snowbed
Moist
Meadow
Wet
Meadow
Similarity of flora among communities
(Sørenson’s index): 25-77%
Dry
Meadow
What controls variation in diversity across the landscape?
soil resources?
Diversity
1.0
0.5
0.0
0.0
Decreasing belowground
competition; more spp. coexist
Increasing aboveground
competition; competitive
exclusion
Increasing stress
and belowground
competition
0.2
0.4
0.6
0.8
Soil Resource Availability
1.0
Alpine plant diversity relationship to soil N+P availability on
Niwot Ridge
other factors:
 disturbance (climate &
animal)
 water availability
Diversity (H')
3
2
1
0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
N and P supply (proportion of
maximum)
0.7
Environmental change in alpine - primarily “indirect:”
climate, N deposition, stratospheric ozone degredation (↑UV)
locally most immediate threat is N deposition
Colorado ranks 3rd in U.S. population growth, with most of the increase in the
Front Range urban corridor:
source: William Travis
CU Geography
Where in the alpine landscape is change most probable?
Snow is an effective reservoir of
atmospheric N inputs
Moist meadows- elevated N
inputs due to topographic location
15N
Moist meadow plant N uptake from snow
(% growth demand)
750
c (13)
500
b
(6)
b (5)
250
b
15
-1
N uptake (g N g tissue)
labeling experiment:
(1)
a
al
th
a
C
Bi
st
or
ta
ia
em
is
A
rt
as
t
m
A
co
D
es
ch
am
ps
i
a
(g
ra
ss
)
yl
is
0
+ responder to N
non responders
(10)
Implications of differential N uptake by alpine vegetation:
 change in plant species composition ("weedy" native
species)- may already be occurring

change in ecosystem properties:
> enhancement of N cycling (net N mineralization
and nitrification) rates- loss of N from terrestrial to
aquatic ecosystems
> greater climatic control (lower biological control)
over variation in primary production