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Influence of Aspen Tree Wells on Microbial Respiration in Winter Ecology

This study explores the impact of aspen tree wells on microbial respiration during winter months, affecting nutrient availability in spring. Findings suggest no significant difference in microbial respiration rates in vs. out of tree wells. Future research areas include tree species "microenvironments" and canopy effects on microbes.

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Influence of Aspen Tree Wells on Microbial Respiration in Winter Ecology

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  1. Aspen Tree Well Influence on Microbial Respiration Chloe Sommer // Winter ecology, Spring 2018 Mountain research station, university of Colorado at boulder

  2. Introduction • Tree wells = depressions in snow around tree trunks, formed by a tree’s reemitted longwave radiation • Microbial communities (bacteria, fungi) found underground flourish during winter months due to more stable conditions (Žifčáková, Větrovský, Howe, & Baldrian, 2016) BRINGING THEM TOGETHER • Deeper snow means more ground insulation, leading to more microbial activity (Lipson et al, 2006)

  3. So what? • Decomposition affects nutrient availability come spring growing season (Laganiere, Pare, & Bradley, 2009) • Affects distribution, composition of spring/summer vegetation • Are tree wells creating microenvironments for microbes? • Microbial CO2 output contributes to atmospheric CO2 levels • Climate change implications?

  4. Background • Organic material (litter) affects distribution and survival of microbial communities (Laganiere, Pare, & Bradley, 2009) • Insulation, moisture, nutrient (N) availability = happy microbes • Quaking aspens produced fastest decaying, most nutrient-rich litter of trees studied (subalpine region) (Laganiere, Pare, & Bradley, 2010) • Highest likelihood of observing noticeable difference in & out of tree well Question: Are there different rates of microbial respiration in vs. out of aspen tree wells?

  5. Methods • Plot out 25 x 25m aspen grove near MRS • Select trees via randomly generated coordinates • Measure: • snow depth • soil surface temperature • soil respiration over 2 minutes in & out of tree well at each site • 5 replications

  6. Methods • Additionally, measure: • DBH • Tree well diameter • Find possible trends relating size of tree & tree well to microbial respiration differences inside vs. outside of well

  7. Results p-value: 0.0321  SIGNIFICANT!

  8. Results p-value: 0.9269  NOT significant

  9. Results

  10. Results

  11. Discussion: Methodology • All observations in one grove at one point in time • Subjective selection for most prominent tree wells • Insufficient amount of replications • Difficult to measure litter depth • Willows spotted nearby aspen grove • Accidentally in a riparian zone? Soil moisture implications? • Struggle to seal CO2 monitor due to hard, frozen soil  gas escape? Inaccurate readings?

  12. Discussion • No significant difference in microbial respiration in vs. out of wells • Aspens had generally small and shallow tree wells; not large enough to make a real difference? • Snow depth in vs. out of wells may not be influencing microbial respiration...but other factors might • Wind exposure (transport of aspen litter) • Tree density / canopy cover • Nutrient availability / ground litter depth

  13. Future Research • Tree well “microenvironments” surrounding different tree species? • Tree density / canopy cover effect on microbial respiration? • Wind exposure & litter depth/distribution? • How deep underneath snow will you find photosynthesizing plants?

  14. Summary • Deeper snow depth = greater soil temperature trend supported • No significant difference found in microbial respiration rates in vs. out of quaking aspen tree wells  other factors at play • No trend in aspen tree size & its tree well’s effects on microbes • Photosynthesis occurring near aspens & underneath snow • Ample opportunity for future research

  15. Acknowledgements • Huge thanks to: • Tim Kittel, instruction & guidance • Derek Sweeney, CO2 monitor whiz • Cloe Dickson, data recorder & deep snow survivor • Tyler Piehl, glorified manual labor “The real significant finding was the friendships we made along the way”

  16. Literature Cited • Laganière, J., Paré, D., & Bradley, R. L. (2009). Linking the abundance of aspen with soil faunal communities and rates of belowground processes within single stands of mixed aspen–black spruce. Applied Soil Ecology, 41(1), 19-28. 10.1016/j.apsoil.2008.08.005 • Laganiere, J., Pare, D., & Bradley, R. L. (2010). How does a tree species influence litter decomposition? separating the relative contribution of litter quality, litter mixing, and forest floor conditions. Canadian Journal of Forest Research, 40(3), 465-475. 10.1139/X09-208 • Lipson, D. L., Schmidt, S. K., Williams, M. W., Delany, A. C., Monson, R. K., Burns, S. P., & Turnipseed, A. A. (2006). Winter forest soil respiration controlled by climate and microbial community composition. Nature, 439(7077), 711-714. 10.1038/nature04555 • White, C. Variables Affecting Tree Well Formation. Winter Ecology. University of Colorado at Boulder, 2012. • Žifčáková, L., Větrovský, T., Howe, A. and Baldrian, P. (2016), Microbial activity in forest soil reflects the changes in ecosystem properties between summer and winter. Environ Microbiol, 18: 288–301. doi:10.1111/1462-2920.13026

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