Using Urban Forests to Predict the Success of Western Red Cedar during

Global Change

Anna O’Brien

University of Washington

Global Change

• Ecosystems are changing in their basic characteristics, to which organisms are often finely adapted

• Temperatures, CO2, & nitrogen deposition (nutrients)

Global Change

Melting sea ice

&

Animals Plants

• How will our local conifers respond to global change?

• Pacific Northwest forests are almost entirely made up of conifer trees, they provide the ecosystem structure on which countless other organisms depend, and are economically important

• Conifers will respond to global change variables1, and predicting this response is critical to conservation and management efforts

• I focus on Thuja plicata, Western Red Cedar

Research Question

1. Handa, Korner, Hattenschwiler 2006; Yin, Liu, Lai 2008

Modeling Global Change

Temperature Nitrogen deposition

CO2 levels

Future vs Current

Urban vs Rural Areas

• Urban areas resemble global change effects2

• Can therefore use the effects of urban areas on species and ecosystems to predict the effects of global change

2.Carreiro and Tripler 2005

Hypotheses

Thuja plicata recent germinant.

1. Edges of forest with urban influence will have higher temperatures and soil nitrogen levels than urban forest centers and rural areas

2. Reproduction of trees will be reduced at urban forest edges compared to urban forest centers and rural areas.

3. Growth of trees will be increased at urban forest edges compared to urban forest centers and rural areas.

• Seattle has forested parks in urban neighborhoods.• Rural area sites included to account for edge effects unrelated

to the urban influence.

Study Site

IButton

R

R

R

UU

U

UU

Growth: Take core with increment borer

Environment: Measure temperature with iButton, and take soil sample from two locations

Reproduction: Count seedlings

Measurements

Environment-N• Urban nitrogen levels > Rural nitrogen levels (P=.005)• Urban park edge nitrogen levels may not be significantly greater

than park center levels

0

5

10

15

20

25

Rural edge Rural center Urban edge Urban center

mg NO3/kg dry soil

Soil Nitrogen (NO3) Levels

-5

0

5

10

15

20

25

30

Environment-Temperature• Preliminary Temperature Data• Edge Temperatures > Center Temperatures

Temperature

(°C)

Feb 2009 Jun 2009

CENTER

EDGE

Schmitz Park – Temperatures

Reproduction• Low germination totals• Urban Center > Urban Edge• Rural Edge > Rural Center

Thuja plicata germination at edges and centers

00.05

0.10.15

0.20.25

0.30.35

Rural EdgePlots

Rural CenterPlots

Urban EdgePlots

Urban CenterPlots

Total germinants per number of plots

Growth

1. Obtain yearly growth data from tree cores

2. Obtain yearly temperature data for region & modify to local sites

3. Compare temperatures by year to tree growth

Directions

• Why so low germination?– Lack of viability – Herbivory– Fungi3

3.Weber, Karst, Gilbert & Kimmins, 2005

Thuja plicata seed, USDA plants, 2009

Conclusions

1. Environment – Urban edges show influence consistent with global change

2. Reproduction – Urban edges have a significant negative effect; low germination totals concerning

3. Growth – Hypothesize that growth will be increased at edges compared to other areas

• What is the likely future success of Thuja plicata?

• What does this mean for conservation and management?

Acknowledgements

• Howard Hughes Medical Institute• Janneke Hille Ris Lambers• Brian Buchwitz• Ailene Kane• Irene Weber and Melissa Winstanley• Seattle Parks, Cedar River Watershed, King County Parks, &

Washington State Parks

Questions?