Winter Soil Respiration Near Dead and Living Lodgepole Pines at Niwot Ridge, CO

Justin D’AtriWinter Ecology Spring 2010

Mountain Research Station – University of Colorado, Boulder

INTRODUCTION

• According to United States Geographical Survey scientist Craig D. Allen, “many forest and woodlands today are at an increasing risk of climate-induced dieback (Allen 2009).”

Mountain Pine BeetleNative InsectOutbreaks have happened in the past but never at the

current scale.

Current Situation Caused By:Alteration of Temporal & Spatial disturbances (Seastedt 2010)

-More Benign Winters-Decades of Fire

Suppression

Current Situation• Social Effects (Allen 2009)

-Pose Fire Risk (1.5 million acres in CO)-Potential Loss of Tourism (hiking, skiing, fishing)-Loss of Timber Resource-Expensive Management Techniques (Thinning,

Burning, Pesticides)• Environmental Effects

-Change in Carbon source/sink? Global Implications-Change in ecosystem services? Local Implications

• Research is Necessary for Sucessful Forest Management

What We KnowSoil Respiration increases with Snow Depth

Soil Respiration increases with Soil Temp

Dead root decay

Fungal-dominatedMicrobes

Soil faunaexcretion

Inorganic N

CO2

Bacteria and fungi co-dominate

Rhizodeposition

Soil fauna

Watertranspiration

excretion

N uptake

DOCSOM

Response to Tree Death

Current Research • Seastedt T, Xiong Y, D’Atri J. Rapid Soil Organic Matter (SOM) Loss from

Forest Dieback in a Subalpine Coniferous Ecosystem. INSTAAR, University of Colorado Boulder, CO. [In Press 2010]

RESULTS• -Forest dieback results in rapid C

emissions from surface soil• -Total Carbon (C) decreased 38–49 % • -Total Nitrogen (N) decreased

26–45 %• -Increased soil pH near dead trees caused by

an accumulation of soil NH4+ and K+.

• A rapid reduction in surface soil SOM suggests that forest dieback caused the ecosystem to be a large C source.

Where did over 38% of the surface carbon go?

1. Lost through microbial respiration as CO2

2. Leaching of Dissolved organic Carbon (Runoff)

The increased loss of Carbon near dead lodgepole pines suggests an increase in soil respiration.

Question:Is there more soil respiration

occurring near dead lodgepole pines than living lodgepoles during the winter?

If there is more respiration occurring under a dead tree then we should measure an increase in CO2 being emitted from the soil.

Hypothesis There will be a difference in the rate of

respiration between the soil near living lodgepole pines compared with the soil near dead lodgepole pines because of the amount of dead tree material in the soil.

Null: There is no difference in soil respiration

Methods Choosing a site:

In order to minimize variation in geology and topography and I chose one micro site consisting of a matrix of living and dead trees in the same small forest area.

Criteria for Comparison: Controls-Deep snowpack ~50cm-Mature Tree-Not too close to other trees of different treatment-All from same micro site-Same Organic Matter Quality

MethodsCO2 Flux Measurements– Measured by CO2

analyzerTemperature Measurements- Thermometers

Data collection-Dig snowpit

-Record concentrations at 0s, 30s, 60s, 90s, & 120s

-Calculate Flux (120s –0s)-2 collection trails per tree-Average the two fluxes-Compare fluxes in excel-10 trees total

ResultsAverage Living CO2 Flux = 39.1Average Dead CO2 Flux = 32.9

Living Dead

P-value = 0.517195994

Discussion• Reject alternative hypothesis • Accept Null

–There is no difference in soil respiration• Study suggests that winter respiration is

not influenced by tree type. • Temperature seems to be the largest

control influencing under snowpack soil respiration.

If the loss of Carbon doesn’t happen during winter then when does it happen and where does the carbon go?

Further Research:-CO2 flux measured year round-full soil profile-stream chemistry

Problems with Project• CO2 analyzer battery• Breathing near snow pit• Finding a “controlled” site• Not enough samples• Maybe could find significant results

with more trials

Summary• Study suggests that winter

respiration is NOT influenced by tree type.

• For this site, temperature seems to be the largest control influencing under snowpack soil respiration.

Thanks to:Derek

Sarah

Chris

References•Seastedt T, Xiong Y, D’Atri J. Rapid Soil Organic Matter(SOM) Loss from Forest Dieback in a Subalpine Coniferous Ecosystem. INSTAAR, University of Colorado Boulder, CO. [In Press 2010]

Allen, C. D. "Climate-induced forest dieback: an escalating global phenomenon?" Unasylva 60 (2009): 43-49.

Kurz, W. A et al. "Mountain pine beetle and forest carbon feedback to climate change." Nature 452 (2008): 987-90.