Winter Soil Respiration Near Dead and Living Lodgepole Pines at Niwot Ridge, CO Justin D’Atri Winter 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 Beetle Native Insect Outbreaks 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 Know Soil Respiration increases with Snow Depth Soil Respiration increases with Soil Temp

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 NH 4 + 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

Methods CO2 Flux Measurements– Measured by CO2 analyzer Temperature 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

Results Average Living CO2 Flux = 39.1 Average Dead CO2 Flux = 32.9 LivingDead P-value =

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