Nitrogen Utilization by Saprophytic Fungi in a Managed

Forest Ecosystem

Brian Strahm

IntroductionIntroduction“Under the silent , relentless chemical jaws of the fungi, the debris of the

forest quickly disappears…”-A. Forsyth and K. Miyata, Tropical Nature

NITROGENlimiting nutrient

for plant and

microbial growth

FUNGIdecomposers

of soil

organic matter

DECOMPOSITIONreleases nutrients

back into the

environment

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Fall River LTSP StudyFall River LTSP Study

• Pacific County, WA

• Weyerhaeuser -

McDonald Tree Farm

• Treatments:

Conventional Bole Only

Total Tree Plus

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TreatmentsTreatments

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2nd Generation Douglas-fir Forest (~ 47 years old)

Bole Only

Total Tree Plus

MethodsMethods

Malt Extract

Nitrogen Substrates

Nitrogen SubstratesNitrogen SubstratesOrganic Nitrogen:

• Aspartate - chain structure; single N

• Arginine - chain structure; multiple N

• Proline - ring compound; single N

Inorganic Nitrogen:

• Sodium nitrate - Na+ NO3-

• Ammonium chloride - NH4+ Cl-

•Ammonium nitrate - NH4+ NO3

-

Amino acids

Ions in solution

Organic SubstratesOrganic Substrates

Aspartate

Arginine

Proline

Inorganic SubstratesInorganic Substrates

nitrogen

oxygen

Nitrate (NO3-)

nitrogen

hydrogen

Ammonium (NH4+)

ResultsResults

Forest Fungal Growth per N Substrate

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0 1 2 3 4 5 6

Days

Relative Growth (cm)

KNO3NH4ClNH4NO3AspartateArginineProline

ResultsResults

Bole Only Fungal Growth per N Substrate

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0 1 2 3 4 5 6

Days

Relative Growth (cm)

KNO3NH4ClNH4NO3AspartateArginineProline

ResultsResults

Total Tree Plus Fungal Growth per N Substrate

-2

-1.5

-1

-0.5

0

0.5

1

0 1 2 3 4 5 6

Days

Relative Growth (cm)

KNO3NH4ClNH4NO3AspartateArginineProline

ResultsResults

Average Relative Growth per Treatment

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

Forest Bole Only Total Tree Plus

Average Relative Growth (cm)

Organic N Inorganic N

ConclusionsConclusionsEnvironmental Homogeneity and Specialization

Forest Stand:

• Heterogeneous environment

• No particular substrate specialization

Bole Only:

• Increasingly homogeneous environment

• Trend toward utilization of inorganic nitrogen

Total Tree Plus:

• Homogenous environment

• Strongest prevalence for inorganic nitrogen

• Proline / Pathogenic fungi?

ThanksThanks

Tina Jensen

Marianne Elliott 

ReferencesReferences• Edmonds, R.L., Thomas, T.B, Rhodes, J.J. 1991. Canopy and soil

modification of precipitation chemistry in a temperate rain forest.Soil Science Society of America Journal 55: 1685-1693.

• Gebauer, G., Taylor, A.F.S. 1999. 15N natural abundance in fruitbodies of different functional groups of fungi in relation to substrate utilization. New Phytology 142: 93-101.

• Osono, T., Takeda, H. 2001. Organic chemical and nutrient dynamics in decomposing beech leaf litter in relation to fungal ingrowth and succession during 3-year decomposition processes in a cool temperate deciduous forest in Japan. Ecological Research 16: 649-670.

• Sharples, J.M., Cairney, J.W.C. 1997. Organic nitrogen utilization by an unidentified mycobiant isolated from mycorrhizas of Pisonia grandis. Mycol. Res. 101: 315-318.

• Yamanaka, T. 1999. Utilization of inorganic and organic nitrogen in pure cultures by saprophytic and ectomycorrhizal fungi producing sporophores on urea-treated forest floor. Mycol. Res. 7: 811-816.