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)