Upload
others
View
17
Download
0
Embed Size (px)
Citation preview
Correlations between functional traits, environmental gradients, and distributional
patterns of vascular epiphytes within tropical canopies in Costa Rica
Carrie L. Woods, Ph.D candidate
Clemson University
ATBC 2013
1
• A central question in community ecology concerns the number of species able to coexist at small spatial scales (a diversity)
• High in tropical forests
Diversity
2
Introduction Methods Results Conclusion
Valencia et al. 1994, Woods et al. in prep
• Habitat heterogeneity promotes species diversity
• Structurally complex environments enable habitat partitioning
Diversity
3
Introduction Methods Results Conclusion
(Hutchinson 1959, MacArthur 1958, MacArthur and MacArthur 1961, Ricklefs 1977, Huston 1979, Tilman 1986, Rosenzweig 1995)
“Heterogeneity matters”, Deborah Clark, ATBC 2013
• Relates the function of a plant to the environment
– Resource allocation
– Trade offs
– e.g. leaf thickness
• Enables a better prediction and understanding of the distribution and coexistence of species
Functional traits
4
Introduction Methods Results Conclusion
Westoby et al. 2002, Wright et al. 2004
Questions
• Do epiphytes partition the canopy along habitat and resource gradients?
• Do functional leaf traits explain the distribution of epiphytes within tree canopies?
5
Introduction Methods Results Conclusion
Habitat diversity in the canopy
• Structurally complex
• Habitat gradients (temperature, RH wind speed, branch diameter)
• Resource gradients (canopy soil, atmosphere, light)
6
Resource diversity
Light Canopy soil
Habitat diversity
temperature, wind
RH Branch diameter
Atmosphere
(Parker 1995, Nadkarni 2004)
• Multiple adaptations to take up water and nutrients
Vascular epiphytes: Functional complexity
7
Canopy soil Water from tanks
Aerial roots Atmospheric uptake
Soil ferns Aroids, Orchids Tank bromeliads Atmospheric bromeliads Bark Ferns?
Introduction Methods Results Conclusion
Vascular epiphytes: Functional complexity
8
Introduction Methods Results Conclusion
Habitat partitioning of canopy by epiphytes
9
Introduction Methods Results Conclusion
• Habitat partitioning
– Pittendrigh 1948
– Benzing and Renfrow 1971
– Johansson 1974
– Hietz and Briones 1998
– Zotz et al 2007
– Reyes-García 2012
• Habitat specialization?
Field site
• La Selva Biological Research Station in Costa Rica
• Wet tropical forest
• 4000 mm of annual precipitation
• Average monthly temperature is 25.8°C ± 0.2, and varies little throughout the year
10
Introduction Methods Results Conclusion
• 5 emergent Virola koschnyi trees
– 90° branches and no trunk epiphytes
• Spatial distribution of epiphytes every meter (m)
Data collection methods
11
Introduction Methods Results Conclusion
• Habitat gradients
– T, RH, vapor pressure deficit (VPD)
– Branch diameter
• Resource gradients
– % canopy openness (light)
– % canopy soil cover
Data collection methods
12
T/RH datalogger
Introduction Methods Results Conclusion
13
Inner canopy 0-2 m from trunk
Canopy zones: Inner (0-2 m) Introduction Methods Results Conclusion
Canopy zones: Mid (2-5 m)
14
Mid canopy 2-5 m from the trunk
Introduction Methods Results Conclusion
15
Canopy zones: Outer (> 5 m)
Outer canopy > 5 m from the trunk
Introduction Methods Results Conclusion
16
Habitat associations Introduction Methods Results Conclusion
• Conservative randomization tests for epiphyte species associations for each canopy zone
• Compared the ObsRelDen of each species to the ExpRelDen generated by 1000 iterations of random shuffling the 3 canopy zones (two tailed test, a = 0.05)
• Obs > Exp 97.5% = positive
• Obs < Exp 97.5% = negative DeWalt et al. 2006
Functional leaf traits
17
• Functional leaf traits of abundant epiphyte species within Virola koschnyi trees
– 10 individual leaves per species
– No orchids or atmospheric bromeliads
– Soil ferns, Aroids, Tank bromeliads, and Bark ferns
• Examined relationships between habitat and resource gradients and functional leaf traits
Introduction Methods Results Conclusion
Functional leaf traits
18
Introduction Methods Results Conclusion
• Environmental conditions – Air VPD
– Substrate temperature
– % canopy openness
• Functional leaf traits – Specific leaf area (SLA)
– Leaf dry matter content (LDMC)
– Succulence
– Sclerophylly
– Leaf toughness (LTo)
– Rate of epidermal water loss (EWL)
T/RH datalogger
Leaf penetrometer
19
Habitat and Resource gradients: canopy zones Introduction Methods Results Conclusion
Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)
% c
an
op
y s
oil
co
ve
r
0
20
40
60
80
100
Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)
Bra
nch d
iam
ete
r (c
m)
0
5
10
15
20
25
30 a
b
c
a
b
c
Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)
% c
anopy o
penn
ess
0
10
20
30
40
50
60
a
b
c
Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)
VP
D (
kP
a)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
a ab
b
Are different species associated with these diverse habitats?
Woods et al. in prep
20
Habitat partitioning of canopy zones
Soil ferns Aroids
Tank bromeliads
Orchids
Atmospheric bromeliads
Bark ferns
Inner + Mid Outer
All zones Low VPD, low % CO, soil
Introduction Methods Results Conclusion
Woods et al. in prep
21
Soil ferns Aroids
Tank bromeliads
Orchids
Atmospheric bromeliads
Bark ferns
Inner + Mid Outer
All zones
Habitat partitioning of canopy zones
Low VPD, low % CO, soil High VPD, high % CO, bark
Introduction Methods Results Conclusion
Woods et al. in prep
22
Soil ferns Aroids
Tank bromeliads
Orchids
Atmospheric bromeliads
Bark ferns
Inner + Mid Outer
All zones
Habitat partitioning of canopy zones Introduction Methods Results Conclusion
Low VPD, low % CO, soil High VPD, high % CO, bark
What mechanisms underlie this pattern?
Woods et al. in prep
23
Trait-Environment Relationships Introduction Methods Results Conclusion
PCA1-4 -2 0 2 4
PC
A2
-4
-2
0
2
4
substrate
temperature
CO
RH
air temperature
VPD
SLA
Sclerophylly
LDMC
Leaf thickness
Succulence
L
eaf
tou
gh
ne
ss
Le
af
res
ista
nc
e t
o f
rac
ture
R
ate
of
EW
L
PC
A2
-4
-2
0
2
4
ElaLatElaLat
AntUpa GuzLinGuzLin
GuzLinGuzLin
AntUpa
GuzLin
GuzLin
TilAnc
TilAnc
TilAncTilAnc
TilAnc
TilAnc
TilAnc
AecNud
GuzMonGuzMon
AecNud GuzLinGuzLin
TilAnc
TilAncTilAnc
AntUpaElaLat
GuzLinGuzLin
ElaHerElaHer
AntUpa
AntRam
TilMonTilMonTilMon
TilMon
TilMon
TilMon
ElaHer
GuzMonGuzMon
AntUpaAntUpa
TilMon
TilMonTilMon
MicRep
MicRep
MicRep
MicRep
MicRep
MicRepMicRepMicRep
MicRep
MicRep
ElaLat
AntRam
ElaLat
ElaHer
ElaHerElaHer
ElaHer
ElaHer
AntRamAntRam
ElaHer
ElaHer
AecNudAecNud
AecNudAecNud
AecNudAecNud
AecNud
AntRam
AntRamAntUpa
AntUpa
ElaLat
AntUpa
ElaLat GuzMon
GuzMon
substrate
temperature
CO
RH
air temperature
VPD
(A)
(B)
Soil ferns Aroids Tank bromeliads Bark ferns
PCA1 (39.9%)
PC
A2
(2
3.0
%)
24
Functional leaf traits of functional groups Introduction Methods Results Conclusion
SL
A (
mm
2 m
g-1
)
0
4
8
12
16
20
aa
b
b
Scle
roph
ylly
(g m
-2)
40
80
120
160
200
240
a
a
b
b
Soil fern
Aroid
Tank bromeliad
Bark fern
LD
MC
(m
g g
-1)
100
150
200
250
300
350 a
b
cc
Soil fern
Aroid
Tank bromeliad
Bark fern
Su
ccu
len
ce
(g m
m-2
)
300
400
500
600
700
a
b
a
a
25
Habitat partitioning based on functional traits
PCA1
-4 -2 0 2 4
Soil fern
Aroid
Tank bromeliad
Bark fern
PCA1
-4 -2 0 2 4
ElaHer
ElaLat
AntUpa
AntRam
AecNud
TilAnc
GuzMon
GuzLin
TilMon
MicRep
(A)
(C)
-4 -2 0 2 4
PCA2
-4 -2 0 2 4
(B)
(D)
Bark ferns
Tank bromeliads
Aroids
Soil ferns
PCA1
Soil ferns and aroids
– shady sites with high RH and low VPD
– Large investment in leaf structure
Most tank bromeliads and bark ferns
– More open and hot sites with high VPD
– Low investment in leaf structure
Introduction Methods Results Conclusion
PCA1-4 -2 0 2 4
PC
A2
-4
-2
0
2
4
substrate
temperature
CO
RH
air temperature
VPD
SLA
Sclerophylly
LDMC
Leaf thickness
Succulence
L
eaf
tou
gh
ne
ss
Le
af
res
ista
nc
e t
o f
rac
ture
R
ate
of
EW
L
PC
A2
-4
-2
0
2
4
ElaLatElaLat
AntUpa GuzLinGuzLin
GuzLinGuzLin
AntUpa
GuzLin
GuzLin
TilAnc
TilAnc
TilAncTilAnc
TilAnc
TilAnc
TilAnc
AecNud
GuzMonGuzMon
AecNud GuzLinGuzLin
TilAnc
TilAncTilAnc
AntUpaElaLat
GuzLinGuzLin
ElaHerElaHer
AntUpa
AntRam
TilMonTilMonTilMon
TilMon
TilMon
TilMon
ElaHer
GuzMonGuzMon
AntUpaAntUpa
TilMon
TilMonTilMon
MicRep
MicRep
MicRep
MicRep
MicRep
MicRepMicRepMicRep
MicRep
MicRep
ElaLat
AntRam
ElaLat
ElaHer
ElaHerElaHer
ElaHer
ElaHer
AntRamAntRam
ElaHer
ElaHer
AecNudAecNud
AecNudAecNud
AecNudAecNud
AecNud
AntRam
AntRamAntUpa
AntUpa
ElaLat
AntUpa
ElaLat GuzMon
GuzMon
substrate
temperature
CO
RH
air temperature
VPD
(A)
(B)
Functional strategies explain partitioning
26
• Specialization to particular habitats based on functional leaf traits (niche partitioning)
• Different species and functional groups converged on a similar strategy when in a similar habitat
• Functional leaf traits explained the distribution of epiphytes within tree canopies
Introduction Methods Results Conclusion
Acknowledgements
Ralph Garcia, Minor Hidalgo, Angie Amesquita (REU), Sarah Callan, and Dr. Saara J. DeWalt (advisor)
Dr. Catherine Cardelús Rigoberto Vargas Carly Phillips Lindsay Martin
27