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Bark Beetle’s Affect on Winter Soil Respiration and Soil Moisture

Bark Beetle’s Affect on Winter Soil Respiration and Soil Moisture. Presented By: Andrew Carroll Winter Ecology: Spring Semester 2013 Mountain Research Station, University of Colorado, Boulder. Bark Beetle Background.

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Bark Beetle’s Affect on Winter Soil Respiration and Soil Moisture

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  1. Bark Beetle’s Affect on Winter Soil Respiration and Soil Moisture Presented By: Andrew Carroll Winter Ecology: Spring Semester 2013 Mountain Research Station, University of Colorado, Boulder

  2. Bark Beetle Background • Bark beetle has affected over 6.6 million acres affected in Colorado (USDA, 2011) • As of 2011 has affected 3.3 million acres of pine species (USDA, 2011)

  3. Question • Does bark beetle kill significantly affect soil repiration and/or soil moisture in lodgepole/limber pine forests?

  4. Hypothesis • Soil respiration will be significantly different between soils with healthy trees and bark beetle infested trees • Specifically, soil under healthy trees will have higher rates of soil respiration. • Soil Moisture will not be significantly different since trees are not particularly active in winter.

  5. Methods • Measured out two 24 by 30 ft rectangles that encompassed an area of healthy trees and an area of dead/bark beetle trees. • Each rectangle was facing north east, had very similar slopes, and similar soil temperatures When I say “reproducible” you say “results”

  6. Bark Beetle Rectangle • Seven bark beetle killed trees within.

  7. Healthy Tree Rectangle • Five large healthy trees with 6 smaller lodgepole

  8. Methods Cont. • Dug 5 pits within each rectangle • Took CO2 reading for each of the 5 pits (10 pits total) along with snow depth and soil temperature at 10 cm for each pit • Took soil samples from 2 of the 5 pits within each rectangle (4 soil samples total) and measured soil moisture before and after drying

  9. Data Analysis • For soil respiration- Found the flux of all 5 pits within each rectangle and utilized a T test to compare the two ecosystems. • For soil moisture content- Calculated the difference between wet and dry soil and divided that by the wet weight to get a percent moisture content. Utilized a T test to compare the two means

  10. Results: Soil Respiration • Average CO2 flux for Bark Beetle=.0253 • Average CO2 flux for Healthy= .18308

  11. Results: Soil Respiration cont. • T test soil Respiration • P value=.158 (not significant) • I could only use 3 pit values since there were only 3 legitimate CO2 fluxes for the bark beetle rectangle.

  12. Results: Soil Moisture • Soil moisture for Bark Beetle: .2403 or 24.03 % water • Soil moisture for Healthy: .2571 or 25.71 % water

  13. Results: Moisture Content cont. • T test • P value=.9071 • Not significant

  14. Discussion • Reject alternative hypothesis for soil respiration • Accept null hypothesis that there is no significant difference between soil respiration for bark beetle strands and healthy strands during the winter. • Same conclusion for a very similar study done in summer. (Morehouse, 2008) • Accept original hypothesis for soil moisture content (i.e. there is no significant difference between the two strands.)

  15. Discussion cont. • Interesting that it conflicts with Xiong, et al.’s results • Why does the decrease in microbial biomass they found not correlate to results of this study? • Winter • Different ages of bark beetle infection • Different microbe species • Problems with CO2 data • Future Research • Go back and re-run experiment • Measure both microbial biomass and soil respiration

  16. Problems • Data collected was very sporadic and did not seem to follow the normal trend of soil respiration well • Could be due to “wobble” of CO2 canister during measurement • Problems with the machine itself, i.e. not calibrated correctly, water damage, etc • Deeper snow would have been very helpful • More legitimate data to use for statistical tests • Data was “edited” because of possible leakage of CO2 canister, in that only parts of the readings that made sense were used.

  17. Summary • No significant difference between soil respiration in bark beetle infested strands and healthy strands of trees • No significant difference between moisture content in bark beetle infested strands and healthy strands of trees

  18. References • Kelting DL, Burger JA & Edwards GS (1998) Estimating root repiration, microbial respiration in the rhizosphere, and root-free soil respiration in forest soils. Soil Biol. Biochem. 30: 961–968 • Morehouse K, Johns T, Kaye J, Kaye A (2008) Carbon and nitrogen cycling immediately following bark beetle outbreaks in southwestern ponderosa pine forests. Forest Ecology and Management, 255, 2698–2708. • Neumann G (2007) Root exudates and nutrient cycling. In: Marschner P, Rengel Z (eds) Nutrient cycling in terrestrical ecosystems. Springer, Berlin • "Region 2 - Forest & Grassland Health." USDA Forest Service. N.p., n.d. Web. 22 Feb. 2013. <http://www.fs.usda.gov/detail/r2/forest-grasslandhealth/?cid=stelprdb5348787>. • Xiong, Y. M., D'Atri, J. J., Fu, S. L., Xia, H. P. & Seastedt, T. R. (2011) Rapid soil organic matter loss from forest dieback in a subalpine coniferous ecosystem. Soil Biol. Biochem. 43, 2450–2456

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