shoestring2014 10-light
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Hungry and neglected seedlings: Does light matter more than nutrients? Shinjini Goswami, UM OhioTRANSCRIPT
I mean a lot more than I
look….
Hungry and neglected seedlings: Does light matter more than
nutrients?
Presented by: Shinjini Goswami
Contact: [email protected]
Why do we care about seedlings in a forest?
Reproductive adult density &
distribution
Seed density & distribution
Seedling density &
distribution
Forest regeneration
potential
Seed production per adult (timing)
Seed dispersal in space
Seed to seedling transition stage (time & space)
Survival, persistence and growth
Possible limiting factors
Why do we care about seedlings in a forest?
Reproductive adult density &
distribution
Seed density & distribution
Seedling density &
distribution
Forest regeneration
potential
Seed production per adult (timing)
Seed dispersal in space
Seed to seedling transition stage (time & space)
Survival, persistence and growth
Possible limiting factors
Light?Nutrients?Moisture?
• Seedlings- Rapid response to fertilization- Whole plant allocation patterns (variable among species)- survivorship future regeneration potential
Sugar MapleBeech
• Seedlings- Rapid response to fertilization- Whole plant allocation patterns (variable among species)- survivorship future regeneration potential
• Sugar maple and American beech masted in most of MELNHE mature forest stands in 2011; same year we started fertilization
Sugar MapleBeech
Questions:
• Does seedling allocation respond to nutrient, light, or water resources?
• Which resources most influence survivorship?
All seedlings (<50 cm): identified to species and surveyed from 2012
Studying allocation response to nutrients, moisture and light:
• Harvested 20 beech and sugar maple seedlings/treatment plot in 3 mature stands
• Root:Shoot was calculated on mass basis
• Soil moisture and canopy cover was measured for each seedling subplot
Study design and methods
0.00
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0.30
C N NP P
See
dlin
g b
iom
ass
(g)
Beech
Sugar maple
Biomass growth was not nutrient limited in the first 2 years (p= 0.14)
R² = 0.2114
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0.35
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20 22 24 26 28 30
see
dlin
g b
iom
ass
(g)
Soil moisture
Beech
Sugar maple
Seedling biomass differed significantly between the two species (p< 0.00)
Sugar maple biomass growth increased with soil moisture (p= 0.12)
Shallow rooting by sugar maple may cause moisture sensitivity
P increased relative allocation to roots in sugar maple (p= 0.02)
0
0.1
0.2
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0.5
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0.7
C N NP P
Ro
ot:
Sh
oo
t
Beech
Sugar maple
0
5
10
15
20
25
30
35
C N NP P
See
dlin
g su
rviv
ors
hip
(%
)
Beech
Sugar maple
N decreased sugar maple survivorship (p= 0.07)
0
10
20
30
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50
60
70
80% 82% 84% 86% 88% 90% 92% 94%
See
dlin
g su
rviv
ors
hip
(%
)
Canopy cover
Sugar maple
Beech
Survivorship of beech (p= 0.09) and sugar maple (p= 0.03) decreased with increasing canopy cover
Response to light availability
Conclusions
• Beech seedlings are relatively non-plastic with respect to the variables measured
• Seedling survivorship depends on light availability but not strongly
• It is unclear why fertilizing with N reduces survivorship.
• Seedling mortality at earlier life stages might be mostly stochastic; possibly under the canopy environmental variables are not important at this life stage