Response to Physical Environment -Tundra

Robert D. Hollister

Atqasuk

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What is ITEX?• International Network of experiments• Focus on climate change impacts on tundra vegetation of Arctic and

Alpine (recently Antarctic)• Formalized 1990, earliest sites initiated 1992• Primary experiment: passive warming (1-2 ºC) with Open Top

Chambers (OTCs), non-destructive measurements.

• Networking (16 workshops)• Standard protocols (ITEX manual)• Outputs

– Phenology (synth. workshop 1996, publ. 1997, 1999)– Community (synth. workshop 2001, publ. 2005, 2006)– Ecosystem (synth. publ. 2007)

13 Barrow

The original 26 International Tundra Experiment study sites.

Data Collection

• Abiotic

• Plant

• Community

• Ecosystem

Abiotic Measures• Screen Height Temperature• Canopy Temperature• Soil Temperature• Precipitation• Canopy Relative Humidity• Soil Moisture• Light Intensity• Wind Speed Near the Ground• Thaw Depth

Plant Measures• Phenology (first visible: leaf, bud, flower, fruit)

• Growth (leaf number, leaf length)

• Reproduction (number and size of flowers)

Inflo

resc

en

ce le

ng

th (

cm)

Inflo

resc

en

ce le

ng

th (

cm) Julian day

TDDsm

160 180 200 2200

5

10

15

20

25

0 200 400 6000

5

10

15

20

25

Luzula confusa

control warmed

ADAWBDBW

1998

20001999

Symbol - site

Line - year

Fill/Color - treatment

Community Measures• Species Composition (measured using a point frame):

Atqasuk Wet MeadowWarmed (OTC) plot

Ecosystem Measures• Carbon Exchange (measured using a LiCOR)

• Nutrient Changes (soil samples and resin membranes)

Atqasuk Dry HeathWarmed (OTC) plot