NRES 701C Topics and Methods in Soil Biogeochemistry Miscellaneous Topics

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NRES 701CTopics and Methods in Soil
BiogeochemistryMiscellaneous Topics
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Rhizosphere and Roots

• Measurement of root biomass is tedious (ask Ben)
• Measurement of root production and turnover is
  very problematic (Vogt et al., 1998)

Vogt, K.A, D.J. Vogt, and J. Bloomfield. 1998.
Analysis of some direct and indirect methods for
estimating root biomass and production of forests
at an ecosystem level. Plant Soil 200 71-89
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Rhizosphere and Roots

• Measurement of root production and turnover by
  sequential coring
• High variability
• May miss peaks and valleys, therefore
  underestimating production

Corings
Biomass
Jan Apr Jul Oct Jan Apr Jul
Oct Jan Apr Jul Oct
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Rhizosphere and Roots

• Minirhizotrons
• Can be measured daily
• Do not easily convert to biomass (units are in
  counts per slide)
• Very tedious to process data (images)

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Rhizosphere and Roots

• Ingrowth cores
• Cores of root-free soil imbedded into profile
• Remove cores and obtain root mass
• Will disturbance cause nutrient release from soil
  and attract roots?
• Will lack of roots initially allow greater
  production than would normally occur?

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Rhizosphere and Roots

• Ingrowth cores
• Cores of root-free soil imbedded into profile
• Remove cores and obtain root mass
• Will disturbance cause nutrient release from soil
  and attract roots?
• Will lack of roots initially allow greater
  production than would normally occur?

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Rhizosphere and Roots

• N Budget Approach
• (N input mineralization) - output uptake in
  biomass
• Assumes
• No N translocation from roots
• Steady-state condition
• Mineralizeable N can be measured and it totally
  taken up by plants
• N limits plant growth

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Rhizosphere and Roots

• C Budget Approach
• All C fluxes measured aside from roots
• Assumes
• C fluxes can be measured
• Steady-state condition

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Rhizosphere and Roots

• C Budget Approach (Raich and Nadelhoffer Agren_
• All C fluxes measured aside from roots
• Assumes
• C fluxes can be measured
• Steady-state condition

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Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient
mineralization (W. Cheng and colleagues) using
13C natural abundance in soils (C-4 soils, C-3
plants)
Cheng, W., D.W. Johnson, and S. Fu. 2003.
Rhizosphere effects on decomposition controls of
plant species, phenology, and fertilization
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Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient
mineralization (W. Cheng and colleagues) using
PRS probe (resin stakes) in soils with and
without plants (soybean and sunflower)
Grassland Soil
Organic Farm Soil
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Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient
mineralization (W. Cheng and colleagues) using
PRS probe (resin stakes) in soils with and
without plants
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Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient
mineralization (W. Cheng and colleagues) using
PRS probe (resin stakes) in soils with and
without plants
Grassland Soil
Organic Farm Soil
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Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient
mineralization (W. Cheng and colleagues) using
PRS probe (resin stakes) in soils with and
without plants
Grassland Soil
Organic Farm Soil
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Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient
mineralization (W. Cheng and colleagues) using
PRS probe (resin stakes) in soils with and
without plants Summary Plants caused lower
mineral N and K Plants caused greater ortho-P,
SO42-, Fe, Mn, Zn, Cu Plants caused no change in
Ca, Mg, B Effects were generally greater in
organic farm soil and sunflower
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Rhizosphere and Roots
Rock-eating mycorrhizae (Jongmans, et al. 1997)
Jongmans, A.G., N. van Breemen, U. Lundstrom,
P.A.W. van Hees, R.D. Finlay, M. Srinivasan, T.
Unestam. R. Geiser, P.A. Melkerud, and M. Olsson.
1997. Rock-eating fungi. Nature 389
682-683 Blum, J.D., A. Klaue, C.A. Nezat, C.T.
Driscoll, C.E. Johnson, T.G. Siccama, C. Eagar,
T.J. Fahey, and G.E. Likens. 2002. Mycorrhizal
weathering of apatite as an important calcium
source in base-poor forest ecosystems. Nature
417 729-731. Van Breemen, N., U.S. Lundstrom,
and A.G. Jongmans. 2000. Do plants drive
podzolization via rock-eating mycorrhizal fungi?
Geoderma 94 163-171.
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Statistics Pseudoreplication (Hurlburt, 1984)
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Statistics Pseudoreplication (Hurlburt, 1984)
Pseudoreplication is defined as the use of
inferential statistics. with data from
experiments that are not replicated (though
samples may be)
Plot 1
Plot 2
Sample replicate
Hurlburt, S.H. 1984. Pseudoreplication and the
design of ecological field experiments.
Ecological Monographs 54 187-211
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Statistics Pseudoreplication (Hurlburt, 1984)

• The problem is that true replication is
  frequently not possible in ecological research
  because
• Old plots resampled were not replicated
• Some treatments (fires, tornados, hurricanes,
  global warming) cannot be replicated
• So what do we do, throw out all those studies?
• Do we eliminate planetary science from all
  further research?

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Statistics Regression vs ANOVA (Cottingham et
al., 2005)
They argue that more info and statistical power
is usually gained with fewer reps and more spread
of data points using regression
Cottingham, K.L., J.T. Lennon, and B.L. Brown.
2005. Knowing when to draw the line designing
more informative ecological experiments.
Frontiers in Ecology 3 145-152.
www.frontiersinecology.org
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Statistics Regression vs ANOVA (Cottingham et
al., 2005)
Cottingham, K.L., J.T. Lennon, and B.L. Brown.
2005. Knowing when to draw the line designing
more informative ecological experiments.
Frontiers in Ecology 3 145-152.
www.frontiersinecology.org
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Statistics A method for analyzing unreplicated
experiments Basically, uses variation already
known or upper possible bound of variation
between plots
Perrett, J.J., and J.J. Higgins. 2005. A method
for analyzing unreplicated agricultural
experiments. Unpubl. ms, Univ. of Northern
Colorado.