[PPT] - environmental gradients, and distributional patterns of vascular PowerPoint Presentation

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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

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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

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Introduction Methods Results Conclusion Valencia et al. 1994, Woods et al. in prep

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Habitat heterogeneity promotes species diversity
Structurally complex environments enable habitat

partitioning

Diversity

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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

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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

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Introduction Methods Results Conclusion Westoby et al. 2002, Wright et al. 2004

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Questions

Do epiphytes partition the canopy along

habitat and resource gradients?

Do functional leaf traits explain the

distribution of epiphytes within tree canopies?

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Introduction Methods Results Conclusion

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Habitat diversity in the canopy

Structurally

complex

Habitat gradients

(temperature, RH wind speed, branch diameter)

Resource gradients

(canopy soil, atmosphere, light)

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Resource diversity Light Canopy soil Habitat diversity temperature, wind RH Branch diameter Atmosphere

(Parker 1995, Nadkarni 2004)

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Multiple adaptations to take up water and nutrients

Vascular epiphytes: Functional complexity

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Canopy soil Water from tanks Aerial roots Atmospheric uptake Soil ferns Aroids, Orchids Tank bromeliads Atmospheric bromeliads Bark Ferns? Introduction Methods Results Conclusion

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Vascular epiphytes: Functional complexity

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Introduction Methods Results Conclusion

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Habitat partitioning of canopy by epiphytes

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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?

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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

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Introduction Methods Results Conclusion

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5 emergent Virola

koschnyi trees

– 90° branches and no trunk epiphytes

Spatial distribution of

epiphytes every meter (m)

Data collection methods

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Introduction Methods Results Conclusion

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Habitat gradients

– T, RH, vapor pressure deficit (VPD) – Branch diameter

Resource gradients

– % canopy openness (light) – % canopy soil cover

Data collection methods

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T/RH datalogger Introduction Methods Results Conclusion

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Inner canopy 0-2 m from trunk

Canopy zones: Inner (0-2 m)

Introduction Methods Results Conclusion

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Canopy zones: Mid (2-5 m)

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Mid canopy 2-5 m from the trunk Introduction Methods Results Conclusion

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Canopy zones: Outer (> 5 m)

Outer canopy > 5 m from the trunk Introduction Methods Results Conclusion

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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

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Functional leaf traits

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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

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Functional leaf traits

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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

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Habitat and Resource gradients: canopy zones

Introduction Methods Results Conclusion

Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)

% canopy soil cover

20 40 60 80 100

Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)

Branch diameter (cm)

5 10 15 20 25 30

a b c a b c

Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)

% canopy openness

10 20 30 40 50 60

a b c

Inner (0-2 m) Mid (2-5 m) Outer (> 5 m)

VPD (kPa)

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

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Habitat partitioning

f 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

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Soil ferns Aroids Tank bromeliads Orchids Atmospheric bromeliads Bark ferns Inner + Mid Outer All zones

Habitat partitioning

f canopy zones

Low VPD, low % CO, soil High VPD, high % CO, bark Introduction Methods Results Conclusion Woods et al. in prep

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Soil ferns Aroids Tank bromeliads Orchids Atmospheric bromeliads Bark ferns Inner + Mid Outer All zones

Habitat partitioning

f 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

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Trait-Environment Relationships

Introduction Methods Results Conclusion

PCA1

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2

2 4

PCA2

4
2

2 4

substrate temperature CO RH air temperature VPD

SLA

(B) Soil ferns Aroids Tank bromeliads Bark ferns PCA1 (39.9%) PCA2 (23.0%)

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Functional leaf traits of functional groups

Introduction Methods Results Conclusion

SLA (mm2 mg-1)

4 8 12 16 20

a a b b

Sclerophylly (g m-2)

40 80 120 160 200 240

a a b b Soil fern Aroid Tank bromeliad Bark fern

LDMC (mg g-1)

100 150 200 250 300 350

a b c c Soil fern Aroid Tank bromeliad Bark fern

Succulence (g mm-2)

300 400 500 600 700

a b a a

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Habitat partitioning based

n functional traits
4
2

2 4

Soil fern Aroid Tank bromeliad Bark fern

(A)

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 SLA Sclerophylly LDMC Leaf thickness Succulence

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Functional strategies explain partitioning

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Specialization to particular habitats based on

functional leaf traits (niche partitioning)

Different species and functional groups converged
n a similar strategy when in a similar habitat
Functional leaf traits explained the distribution of

epiphytes within tree canopies

Introduction Methods Results Conclusion

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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

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