Upload
tovi
View
33
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Interactions between herbivory by snowshoe hare ( Lepus americanus ) and the establishment of white spruce ( Picea glauca ) on the Tanana River floodplain, AK. Proposed research by Justin Olnes M.S. Biological Sciences University of Alaska-Fairbanks 2/14/2014. Outline. - PowerPoint PPT Presentation
Citation preview
Interactions between herbivory by snowshoe hare (Lepus americanus) and the establishment of white spruce (Picea
glauca) on the Tanana River floodplain, AK
Proposed research byJustin Olnes
M.S. Biological Sciences University of Alaska-Fairbanks
2/14/2014
Outline
Theoretical framework-Plant-herbivore interactions
Background-Snowshoe hares-White spruce
Preliminary data and hypothesesSignificance
Plant-herbivore interactionsThe impact of herbivory on dominant vegetation
• Density of the herbivore
• Density of the plant species—is it dominant or rare?
• Secondary compounds and forage selection
Plant-herbivore interactionsThe impact of herbivory on dominant vegetation
22-year record of changes in species composition (indexed by leaf litter biomass) in LTER FP1 sites
Snowshoe hares (Lepus americanus)
• Dominant herbivore of the boreal forest• Total biomass can exceed that of all other vertebrate
herbivores during population peaks(Krebs et al. 2001, Rexstad and Kielland 2006)
Krebs et al. 2013
White spruce (Picea glauca)
• Dominant conifer of the boreal forest• Reproduces via masting events
Ohse et al. 2009
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
2002
2005
2008
2011
0
1000
2000
3000
4000
5000
6000
7000
Year
Aver
age
# of
see
d/sq
uare
met
er
Observations at BNZ-LTER
BNZ LTER
Question 1:How does herbivory by snowshoe hares alter the survival and growth of white
spruce seedlings within the floodplain at BNZ-LTER?
Question 2:Does a relationship exist between white spruce age structure along the floodplain and the population cycle of snowshoe hares at BNZ-LTER?
Question 1:How does herbivory by snowshoe hares alter the survival and growth of white
spruce seedlings within the floodplain at BNZ-LTER?
0 2 4 6 8 10 12 14 160
20
40
60
80
100
f(x) = 2.77396192581361 x + 3.10956538917369R² = 0.345214579288559
f(x) = 7.87403492138888 x − 15.7716936498736R² = 0.61753541661666
dm (mm)
Heig
ht (c
m)
Question 1: Preliminary Data
Planted spruce
All sites, 2010
Inside
Outside
Question 1: Preliminary Data
Natural spruce
Hypothesis: The survival and growth rate of white spruce within floodplains is significantly reduced by snowshoe hare herbivory when mast seeding events coincide with a peak in the hare cycle.
Question 2:Does a relationship exist between white spruce age structure along the floodplain and the population cycle of snowshoe hares at BNZ-LTER?
Question 2: Theoretical Concept Hypothesis: Age structure of floodplain white spruce influenced by:• Mast event history• Snowshoe hare population abundance• Flood event history
𝑌 𝑡=𝑀 𝑡−𝐻𝑡−𝐻𝑡+1…−𝐻𝑡+𝑛−𝐹 𝑡…𝐹 𝑡+𝑚
: number trees established for year t: magnitude of cone production for year t: Abundance of snowshoe hares for year t: Flood level of Tanana River for year t n is the number of years it takes for a white spruce to outgrow risk of browsing by snowshoe haresm is the number of years it takes for a white spruce to outgrow risk of damage or burial by flooding
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
2013
0
1000
2000
3000
4000
5000
6000
7000
Year
Aver
age
# of
see
d/sq
uare
met
er
Hare Peak
Question 2: Preliminary Data White spruce seedfall data at BNZ-LTER
19851986198719881989 19901991 199219931994199519961997 19981999200020012002200320042005 2006200720082009201020110
10
20
30
40
50
60
70
80
90
FP1FP2FP3FP4FP5
Aver
age
# ha
re p
elle
ts p
er tr
ay
Question 2: Preliminary Data
hare pellet data (from litter traps)
FP1 FP2 FP3 FP4 FP50
1
2
3
4
5
6
19982002
Floodplain successional stage
Aver
age
Hare
Pel
let C
ount
per
tray
Question 2: Hypothesis Age structure of floodplain white spruce influenced by:• Mast event history• Snowshoe hare population abundance• Flood event history
Significance
Projected climate change and polar amplification
• Increased drought stress reducing annual growth in white spruce (Barber et al. 2000)
• Reduced seed production and seed viability (Roland et al. 2013)
• Snowshoe hares may benefit from increased fire frequency(Bryant 1994)
No retrospective study on white spruce age structure has been conducted for floodplains of interior Alaska
No research has investigated the impact of snowshoe hare herbivory on conifers, like white spruce, in interior Alaska
Reduced presence of white spruce on the landscape
“Indeed, it is all too clear that every surviving oak is the product either of rabbit negligence or of rabbit scarcity. Some day some patient botanist will draw a frequency curve of oak birth years, and show that the curve humps every ten years, each hump originating from a low in the ten year rabbit cycle.”
- Aldo Leopold, A Sand County Almanac