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’s Affect on Winter Soil Respiration and Soil

Moisture

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)

Question

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

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.

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”

Bark Beetle Rectangle

Seven bark beetle killed trees within.

Healthy Tree Rectangle

Five large healthy trees with 6 smaller lodgepole

Methods Cont.

Dug 5 pits within each rectangleTook 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

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

Results: Soil Respiration

Average CO2 flux for Bark Beetle=.0253 Average CO2 flux for Healthy= .18308

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.

Results: Soil Moisture

Soil moisture for Bark Beetle: .2403 or 24.03 % water

Soil moisture for Healthy: .2571 or 25.71 % water

Results: Moisture Content cont.

T test P value=.9071

Not significant

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.)

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

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, etcDeeper snow would have been very helpfulMore legitimate data to use for statistical

testsData was “edited” because of possible

leakage of CO2 canister, in that only parts of the readings that made sense were used.

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

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