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

1. Winter Soil Respiration Near Dead and Living Lodgepole Pines at Niwot Ridge, CO Justin D�Atri Winter Ecology Spring 2010

2. 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).� Since 1996, the Rocky Mountain Pine Beetle has killed 1.5 million acres of Northern Colorado forest, ultimately posing a serious threat to Colorado�s sub-alpine ecosystems. This widespread epidemic is primarily a result of global climate change and overall forest mismanagement�from strict fire suppression policy to a failure in ensuring age and size diversity among the trees (Kurz et al. 2008). As a result, the pine beetle is proving to be detrimental to Colorado�s recreational economics, water quality, fire safety and overall forest aesthetic as a result of the overwhelming number of dead lodgepole pines. The associated ecosystem changes caused by the epidemic must be documented in order to have any chance of coming with successful management plans. Since 1996, the Rocky Mountain Pine Beetle has killed 1.5 million acres of Northern Colorado forest, ultimately posing a serious threat to Colorado�s sub-alpine ecosystems. This widespread epidemic is primarily a result of global climate change and overall forest mismanagement�from strict fire suppression policy to a failure in ensuring age and size diversity among the trees (Kurz et al. 2008). As a result, the pine beetle is proving to be detrimental to Colorado�s recreational economics, water quality, fire safety and overall forest aesthetic as a result of the overwhelming number of dead lodgepole pines. The associated ecosystem changes caused by the epidemic must be documented in order to have any chance of coming with successful management plans.

3. 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

4. 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 any chance of coming with successful management plans. It is easy to see the visual changes caused by the mountain pine beetle epidemic by just looking at the vast swaths of brown dead forests. While these macro-changes are easily observed, any change to the underlying ecosystem processes will need a closer look. The dead trees are predicted to have an effect on the local ecosystem cycling of the dying forests, but the extent of the ecological changes are currently unknown. In order to understand the changes in ecosystem functioning more scientific study is required. any chance of coming with successful management plans. It is easy to see the visual changes caused by the mountain pine beetle epidemic by just looking at the vast swaths of brown dead forests. While these macro-changes are easily observed, any change to the underlying ecosystem processes will need a closer look. The dead trees are predicted to have an effect on the local ecosystem cycling of the dying forests, but the extent of the ecological changes are currently unknown. In order to understand the changes in ecosystem functioning more scientific study is required.

6. Soil pH is expected to change in response to the cessation of root exudates causing a change in the cation concentrations of the soil. Plant-derived carbon input to soil in forms of leaf- and root-litter and root rhizodeposits are the most important C resources fueling soil decomposer food web (Ruf and others 2006; Pollierer and others 2007), which drive soil biogeochemical processes. One of the first things that changes in a dying tree, is the termination of root exudates. Properly working root exudation secretes organic compounds (usually sugars, amino acids, and enzymes) into the soil as an exchange with symbiotic fungi for nutrients. It is believed that when the tree is dying, normal root exudation ceases and evidence suggests that soil biota populations change and small roots began to decompose 2 months after treatment (Edwards, Ross-Todd 1979, & Zeller et al. 2008). � Soil pH is expected to change in response to the cessation of root exudates causing a change in the cation concentrations of the soil. Plant-derived carbon input to soil in forms of leaf- and root-litter and root rhizodeposits are the most important C resources fueling soil decomposer food web (Ruf and others 2006; Pollierer and others 2007), which drive soil biogeochemical processes. One of the first things that changes in a dying tree, is the termination of root exudates. Properly working root exudation secretes organic compounds (usually sugars, amino acids, and enzymes) into the soil as an exchange with symbiotic fungi for nutrients. It is believed that when the tree is dying, normal root exudation ceases and evidence suggests that soil biota populations change and small roots began to decompose 2 months after treatment (Edwards, Ross-Todd 1979, & Zeller et al. 2008). �

7. 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. Increased amounts of inorganic nitrogen have been documented near dead lodgepole pines when compared to living trees. This extra NH4+ is assumed to be due to the amount of dying roots and associated fungi that are decomposing around the dead trees. Soil biota communities changed to a more bacterial based community under dead trees This study suggests that the ecosystem change caused by the mountain pine beetle is yet another carbon source and another manifestation of global change. Increased amounts of inorganic nitrogen have been documented near dead lodgepole pines when compared to living trees. This extra NH4+ is assumed to be due to the amount of dying roots and associated fungi that are decomposing around the dead trees. Soil biota communities changed to a more bacterial based community under dead trees This study suggests that the ecosystem change caused by the mountain pine beetle is yet another carbon source and another manifestation of global change.

8. 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. Respiration: Everybody breathes, even bacteria! The lost C and N exited the system either through gaseous emissions (respiration and denitrification, respectively) or through the leaching of inorganic N and even dissolved organic C and N. The increase in inorganic N observed here was small relative to the loss observed in total N. Our study can only speculate that both gaseous and leaching losses occurred, but their contributions to the ~40 % loss measured here cannot be quantified. (Seastedt 2010) Respiration: Everybody breathes, even bacteria! The lost C and N exited the system either through gaseous emissions (respiration and denitrification, respectively) or through the leaching of inorganic N and even dissolved organic C and N. The increase in inorganic N observed here was small relative to the loss observed in total N. Our study can only speculate that both gaseous and leaching losses occurred, but their contributions to the ~40 % loss measured here cannot be quantified. (Seastedt 2010)

9. 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. In subalpine forest ecosystems the most amount of soil respiration occurs during the winter under the snow pack. This study will focus on the rate of soil respiration under the snow pack for a lodgepole forest. � In subalpine forest ecosystems the most amount of soil respiration occurs during the winter under the snow pack. This study will focus on the rate of soil respiration under the snow pack for a lodgepole forest. �

10. 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

11. 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

12. Methods CO2 Flux Measurements� Measured by CO2 analyzer Temperature Measurements- Thermometers

13. 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 Concentration at 120s minus the concentration at 0s equals flux.Concentration at 120s minus the concentration at 0s equals flux.

14. Results

15. 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.

17. 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

18. 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

19. 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.