Burning Effects onSoil Temperature in Subalpine

EnvironmentsEthan Larson

MRS, University of Colorado-BoulderSpring 2013

IntroductionFire effects on soil

Changes the soil chemistry More C in soil (Knicker, 2007) Increases in inorganic N

Soil retains less water (Iverson, 2002) In the same experiment, soil temperatures in

burned areas were on average, higher than that of unburned soils during summer months (may be different for winter).

Why?Subnivean Residents

Soil temperature can affect the animals that live under the snow (Coulson et. al, 1995).

Insects usually use soil for insulation so change in soil temperatures can lead to high mortalities (Mail, 1930).

Soil temperature can also affect the rate of decomposition that occurs under the snowpack (Schmidt & Lipson, 2003).

Snow accumulation/durationSoil temperatures can affect the accumulation of snow,

and snowpack can, in return, affect soil temperatures.Snow pack features, such as depth hoars, can only occur

when the soil is at a certain temperature (there is a certain temperature gradient).

The QuestionDo recent burns have an effect on how well

the soil retains heat?

Hypothesis: Burned soils will be less efficient at retaining heat than healthy (unburned) soils.

Methods1. Pick a random location2. Measure:

1. Snow depth (if applicable)2. Air Temperature3. Sunlight?4. Soil Temperature

3. N=10 (per site)4. Repeat at corresponding

location

Fourmile Canyon FireStarted September 6, 2010Lasted for 11 daysApproximately 10 square miles burned

Image of Fourmile

Fire. Courtesy of Nasa’s

Aqua Satellite

Where I Was in Fourmile

Mostly moderate burns; (severe=completely burnt soil, low=no burning at the base, moderate=partial burning at the base)

Fourmile ResultsSunshine Road Site:

Average Air Temp= 0.8°CAverage Healthy Forest

Snow Depth=3.5cmAverage Burned Forest

Snow Depth=2.5cmAverage Healthy Soil

Temp= 0.8°cAverage Burned Soil

Temp=0.2 °CP-value of unpaired, two-

tailed t-test=0.6774 Much greater than 0.05 Not significant Healthy Burned

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.8

0.2

Average Soil Tempera-tures in Sunshine Road

Location

Avera

ge S

oil

Tem

pera

ture

s (°

C)

Fourmile Results Cont.Fourmile Road Site

Average Air Temp= 1.8°CAverage Healthy Forest

Snow Depth=3.6cmAverage Burned Forest

Snow Depth=3.7cmAverage Healthy Soil

Temp= 0.5°cAverage Burned Soil

Temp=0.6 °CP-value of unpaired, two-

tailed t-test=0.8569 Much greater than 0.05 Not significant Healthy Burned

0.44

0.46

0.48

0.5

0.52

0.54

0.56

0.58

0.6

0.62

Average Soil Temper-atures in Fourmile

Canyon Road Location

Avera

ge S

oil

Tem

pera

ture

s (°

C)

Flagstaff FireStarted June 26, 2012Lasted 7 daysBurned approximately 300 acresCaused by lightning strike

Where I was on Flagstaff

Flagstaff ResultsAverage Air Temp= -

3.3°CAverage Healthy Forest

Snow Depth=4.3cmAverage Burned Forest

Snow Depth=3.9cmAverage Healthy Soil

Temp= -2.9°cAverage Burned Soil

Temp=-2.2°CP-value of unpaired, two-

tailed t-test=0.2731 Much greater than 0.05 Not significant

Healthy Burned

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

Average Soil Tempera-tures in Flagstaff Burn

Area

Avera

ge S

oil

Tem

pera

ture

s (°

C)

Overarching Results/ConclusionsThere doesn’t

appear to be any correlation between recent burning and winter soil temperatures.P-values were all

really high, indicating no significance

Accepting null hypothesis of no effect.

But…Temperatures under

“deep” snow are more significantP-value of 0.0955

Not quite below 0.05 but much closer (more significant).

Could justify doing more research on snowier years.

Healthy Burned

-2.5

-2

-1.5

-1

-0.5

0

Average Soil Tempera-tures in "Deep" Snow on

Flagstaff

Avera

ge S

oil

Tem

pera

ture

s

Questions?

ReferencesBaker, Malchus B. “Hydrologic and Water Quality Effects of Fire.” 31-42.

Coulson, Hodkinson, Strathdee, Block, Webb, Bale and Worland. 1995. “Thermal Environments of Arctic Soil Organisms During the Winter.” Arctic and Alpine Research, 27, 364-370.

Iverson, Louis R. 2002. “Soil Temperature and Moisture Fluctuations During and After Prescribed Fire in Mixed-Oak Forests, USA.” Natural Areas Journal, 22, 296-304.

Knicker, Heike. 2007. “How does fire affect the nature and stability of soil organic nitrogen and carbon? A review.” Biogeochemistry, 85, 91-118.

Mail, G. A. 1930. “Winter Soil Temperatures and their Relation to subterranean Insect Survival.” Journal of Agricultural Research, 41, 571-592.

Schmidt, S. K. & D. A. Lipson. 2003. “Microbial growth under the snow: Implications for nutrient and allelochemical availability in temperate soils.” Plant and Soil, 259, 1-7.