Is the spring flush of nutrients in the Is the spring flush of nutrients in the tundra controlled by snow depth?tundra controlled by snow depth?

Kate Buckeridge and Paul GroganDepartment of Biology, Queen’s University

Kingston, ON, Canada

Is there a spring nutrient flush in arctic tundra?

Chapin, 1980, The Mineral Nutrition of Wild Plants, Annual Review of Ecology and Systematics 11: 233-60

Whalen & Cornwell, 1985, Can. J. Fish. Aquat. Sci 42: 797-808

• Ecosystem controls on vegetation patterns• Climate change predictions: deeper snow• Spatial and temporal variability in snow depth

Soil Temp

Litter and SOM

WINTER

microbial community dynamics ?, soil

water, soil C

Snow depth and quality

Soil solution (N)

Microbial Biomass (N)

THAW

DEEPENED SNOW EFFECTS

Is there a nutrient flush?

Is it ecologically significant?

Is it larger with deepened snow?

What triggers the flush?

Denitrification

?

Plant uptake

Leaching ?SPRING

Daring Lake, NWT, Canada (64o 52’N, 111o 35’W)

• ~25 km N of treeline• Continuous permafrost• Birch hummock tundra • Mesic organic soil

Circumpolar distribution

25% of total arctic soil carbon

DOY 129 (May 9)

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(o C)control soil temperature, 5 cmair temperature DOY 147 (May 27)

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(g m

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100200300400500600700800900

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02468

101214161820

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B-PO

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MBC

:N

100200300400500600700800900

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(o C)

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Soil

wat

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H2O

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Control

02468

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Mic

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(g M

B-PO

4 m

-2)

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Julian Day

MBC

:N

Control & snow fence soils:

• No N pulse

• DOC and PO43- pulse may be

important for nutrient transfer from terrestrial to aquatic

• Microbial C:N:P variation suggests microbial community succession

Snow fence soils only:

• DIN + DON pulse ~75% of annual aboveground plant N requirement for this ecosystem

• A second substantial DOC and PO4

3- pulse

• Microbial C:N:P variation suggests microbial community succession

Period 1 Period 2

Moderate fluctuations

Soil Temp

Litter and SOM

WINTER

microbial community dynamics ?, soil

water, soil C

Snow depth and quality

Period 1

Small fluctuations

THAW

DEEPENED SNOW EFFECTSRising air T:

Soil: -7 to -2 oC

Decomposition & leaching ↑

Large fluctuations

Deep snow melt:Soil: -2 to +2 oC

Period 2

Large fluctuations

PredationImmobilization/ mineralization

Soil solution (N)

Microbial Biomass (N)

Denitrification

?Leaching ?

Plant uptake

SPRING

• Yes, there is a spring nutrient flush

• The early thaw flush is C and P• The snow melt flush is C, N and P, under deepened

snow only

• Microbial community succession and SOM quality affected by temperature change, osmotic pressure changes, before snow thaw is complete

• Ecologically significant? Spring flush may contribute to vegetation patchiness across landscape

• Loss or retention of flush depends on plant and microbial uptake before snow thaw is complete

ACKNOWLEDGEMENTS

Field, lab and data:Linda CameronElyn HumphriesPeter LafleurMeghan LaidlawBob ReidMike TrebergMathew Vankoughnett

Logistics:Steve Matthews, GNWT

Funding:Natural Sciences and

Engineering Research Council of Canada (NSERC)

International Polar YearW. Garfield Weston Foundation

(via CNST (ACUNS))Indian and Northern Affairs

Canada (INAC-NSTP)Canadian Tundra Ecosystem

Carbon Study (CTECS) Queen’s University