NREM 301Forest Ecology & SoilsDay 24 – Nov 12, 2009

Lubrecht Forest, Montana

Nutrient Cycling (Chapters 16-18)

Lab Next Week – Field Quiz Exercise

IADOT & Story County Conservation Board (SCCB)

New rest area - signs identifying trail to the Skunk River Greenbelt

Enhance wildlife habitat for the traveling public.

Your job –• develop a plan to identify

the kinds of habitat that arepresent for specific wildlifespecies

• determine whatmanagement if any couldbe used to enhance thepresent habitat.

Rest Area Project Site

2008 I-35 Rest Area/Skunk River Greenbelt Site

Abandoned Grazed Forest

Old Field Forest

Grassland Area

Clarion loam 2-5%

Hayden loam 2-5%

Hayden loam 2-5%

Hayden loam 9-18%

1930

1950

19501930

1970

1930 2008

Page 525 Textbook

Geochemical

Biogeochemical

Biochemical

General NutrientCycle

How much nitrate, ammonia, calcium and sulfate does Ames get each year fromwet fall (with rain)? kg/ha/yr ~ lbs/ac/yr

What is total N per year?Does that meet corn needs? What about forest needs?

Group Activity

Geochemical Cycle – Wet Deposition

Group Activity

Which nutrients have the largest atmospheric inputs, the largest leaching losses?

Nutrient CycleSubcycles

Why does P notoften limit plantgrowth?

Why does the biochemical cyclenot contribute to annual Ca needs?

Surface Runoff

Fertilization

Group ActivityLeaching & tiles

Be prepared to describe each of the words (phrases) on the diagram

1. Decomposition2. Ammonification3. Nitrification4. Assimilation5. Drainage Loss 6. Denitrification7. Nitrogen Fixation

Are there any processes that are missing – especially in agricultural landscapes?

Nitrogen Cycle

NitrosomonasBacteria

NitrobacterBacteria

Mineralization

Uptake

Let’s look in detail at the N cycle

Anaerobic

Free Living Bacteria - AzotobactorSymbiotic N-fixersRhizobium – Woody LegumesFrankia – Woody Non-legume

AmmoniumAmmonia (NH3)Ammonium (NH4)

Lightening

23% N-fixers

90% N-fixers

97% N-fixers

Actinorhizal woody plants22 genera of woody plants are non-leguminous N fixers with FrankiaExamples: (see Table 17.2 in text)AlnusCasuarina CeanothusCerocarpusElaeagnaceae

Black LocustWoody – leguminous N-fixer

with Rhizobium2 important in temperate forestsBlack locust & MesquiteThe rest are tropical or sub-tropical

Acid soils – fewer bacteria & actinomycetes– slower decomposition –most available N for plant uptake is NH4

Basic soils – most diverse – faster decomposition – more NO3 – taken up

Neutral

How does pH influence the Nitrogen Cycle?

Acid

Surface Runoff

Fertilization

Group Activity

Uptake

Leaching & tiles

No N from Weathering/All from Atmosphere

Geochemical = 16%

Biogeochemical = 45%

Biochemical = 39%

Identify sub-cycles as annual sources

AmmoniumAmmonia (NH3)Ammonium (NH4)

Surface Runoff

Fertilization

Uptake

Leaching No N from Weathering/All from Atmosphere

What happens to N Cycle when

going from prairie to corn?

• Fixation• Plant loss• OM added to soil• Decomposition rate• Ammonification• Nitrification• Denitrification• Leaching• Plant uptake

downup

downup

upup

Down (tile)

upup

AmmoniumAmmonia (NH3)Ammonium (NH4)

What Happens to N Cycle When -

Land is Drained?

AmmoniumAmmonia (NH3)Ammonium (NH4)

Results of Drainage

Ammonium

Ammonia (NH3)Ammonium (NH4)

Nitrate Loads to Mississippi River

Surface Runoff

Fertilization

Uptake

Leaching No N from Weathering/All from Atmosphere

N Cycle Process ChangesWhen Forest Burns

• Plant loss – up (but rapidreplacement)

• OM FF lost – N volatilized• Decomposition of what is

left – up• Ash left raises pH • Ammonification – up• Nitrification – up in conifers• Plant uptake – down & shifts

to understory• Leaching loss – up for a

short time• Fixation - up• Denitrification up some if

plants dead less Tr• Surface runoff – up short time

AmmoniumAmmonia (NH3)Ammonium (NH4)