j march fire project

7/31/2019 J March Fire Project

1/23

Hypothesis

Six years following catastrophic fire, soilnitrogen will be at low levels due to lack of litter and duff that sequester nitrogen.

Nitrogen levels will be only slightly reducedfollowing salvage logging due to lack of nitrogen in cellulose.


2/23

Function of Nitrogen

Ammonia (NH 4 -) preferred by late seralforests

Litter, duff, detritus, urine

Nitrite (NO 3-) intermediate step betweenammonia and nitrate

Toxic

Nitrate (NO 2-) preferred by early seralpioneers

Fixed and bound by bacteriaConverted to ammonia at biota deathMineralized from ammonia as

bacterial byproduct


3/23

Comparison of Nitrogen Levels inForest Soils

0.74

0.47

0.02 0.08 0.050.02

0.4

0.010.03

0

0.2

0.4

0.6

0.8

1

NH4- NO2-N NO3-N c o n c e n t r a t i o n ( p p m )

Unburned

Burned

Burned Salvage


4/23

Burned vs. Unburned

Decreasing factors AmmoniaNitrate

Increasing factorsPhosphorusPotassium

No changeNitrite

> t Significant? .018 yes.05 yes

.049 yes

.95 no

.33 no


5/23

Burned vs. Burned Salvage

Decreasing factors AmmoniaNitrateNitritePhosphatePotassium

> t Significant? .257 no.201 no.15 no.71 no.63 no


6/23

Function of OtherMacronutrients

Phosphate (PO 4 ) from mineral soilMakes up phospholipid bilayer of cell

membrane

Responsible for energy (ATP)

Potassium (K) from potash, a volcanic ash Aids in diffusing nutrients into roots -turgor pressure Aids in fruit sizing Aids in nerve transmission


7/23


8/23

Soil Chemistry Statistics

Unburned vs. Burned Forest Soils Statistically significant results includedammonia, nitrate, phosphorus

Burned vs. Burned Salvaged Forest SoilsNone of the parameters compared werestatistically significant.


9/23

Importance of Soil Depth

Soil depth is indicative of plant size,density, and source of topsoil.


10/23

Importance of Duff and Litter

Litter comes from deciduous trees whichhas LNE (low nitrogen efficiency)Duff comes from conifers which hasHNE (high nitrogen efficiency)

Litter and duff:Hold soil moistureBlock sun and cool soilSequester Ammonia


11/23

Importance of Rhizome Depth

Rhizomes occupy the root zones wheremost: Water is diffusedMicronutrients are captured

Nitrogen cycling occurs

Rhizomes are the most active part of theroot. The symbiotic relationship betweenmicrobes and plants allow Nitrogencycling. Microbes consume humusreleasing NO 3- as a byproduct.


12/23

Comparison of Depth inForest Soils

5 3 . 4

2 .5

3 7 .8

0 .1

4 2 . 4

6 6 . 90

7 .1

0

20

40

60

80

Soil Duff Rhizome

d e p t

h ( c m

)Unburned

BurnedBurned Sa lvage


13/23


14/23

Comparison of Moisture in ForestSoils

4 .8

1 8

3 .6

0

5

10

15

20

25

Moisture

p e r c e n t m o i s t u r e

Unburned

Burned

Burned Sa lvage


15/23

Importance of Temperature

High temperature is caused by lack of canopy,shrubs, and exposed soils and:Lowers soil moistureIncreases soil biota activity

Cycles Nitrogen irregularly

Low temperature is the result of high shade, thick litter and:Raise soil moistureDecrease soil biota activity Cycles Nitrogen evenly


16/23

Comparison of Temperature inForest Soils

1 7 . 619.9

21.9

0

5

1 0

1 5

20

25

30

Temperature d e g r e e s c e n t i g r a d e

Unburned

Burned

Burned Sa lvage


17/23

Importance of Compaction

Soil peds are made up of sand/silt/clay particlesSoil texture determines how much airand water space existsLow compaction indicates peds withgood air and water capacity High compaction indicates soils with low

water capacity and infiltration.


18/23


19/23

Burned vs. Unburned

Decreasing factorsSoil depthPercent moistureCompaction

Increasing factorsDuff depthRhizome depthTemperature

> t Significant? .0001 yes.0001 yes.358 no

.0001 yes

.041 yes

.0001 yes


20/23

Burned vs. Burned Salvage

Duff depth was similar and mostly absent

Decreasing factorsCompaction

Increasing factorsSoil depthRhizome depthPercent moistureTemperature

> t Significant? .524 no

.167 no

.716 no

.016 no

.0001 yes


21/23

Soil Characteristics Statistics

Unburned vs. Burned Forest SoilsStatistically significant results included soil

depth, litter depth, rhizome depth, percentmoisture, and temperature.

Burned vs. Burned Salvaged Forest SoilsThe only statistical significant

difference was temperature.


22/23

Interpretations

6 years following fire, nitrogen decreases due toDenitrification converted to N 2 (78% of atmosphere)

Potassium and Phosphate increase due toMineralization

Following salvage, nitrogen decreased slightly

Incineration of nitrogen-rich leavesoccurred during fire previously Dead trunks contain little nitrogen

(cellulose)


23/23

Implications for Treatment

Treat soils immediately following fire tomaintain high nitrogenEspecially in the form of Ammonia

Supports perennials and late seral

succession

Encourage nitrogen fixing plants Ex. Silver Lupine ( Lupinus argentius )

Seed within first year to sequesterreleased nitrogen

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