701C NRES Topics and Methods in Soil Biogeochemistry Miscellaneous Topics
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
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
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)
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?
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?
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
Rhizosphere and Roots
C Budget Approach All C fluxes measured aside from roots Assumes: C fluxes can be measured Steady-state condition
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
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
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)
600.00
Resin Stake N
500.00
400.00
300.00
200.00
1 00.00
0.00
N o ne
So ybean
Sunflo wer
N o ne
So ybean
Sunflo wer
Grassland Soil
Organic Farm Soil
Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient mineralization (W. Cheng and colleagues) using PRS probe (resin stakes) in soils with and without plants
1 6.00
Resin Stake P
1 4.00
1 2.00
1 0.00
8.00
6.00
4.00
2.00
0.00
N o ne
So ybean
Sunflo wer
N o ne
So ybean
Sunflo wer
Grassland Soil
Organic Farm Soil
Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient mineralization (W. Cheng and colleagues) using PRS probe (resin stakes) in soils with and without plants
25.00
Resin Stake Fe
20.00
1 5.00
1 0.00
5.00
0.00
N ne
So o ybean
Sunflo wer
N o ne
So ybean
Sunflo wer
Grassland Soil
Organic Farm Soil
Rhizosphere and Roots
Rhizosphere-induced decomposition and nutrient mineralization (W. Cheng and colleagues) using PRS probe (resin stakes) in soils with and without plants
3000.00
Resin Stake Ca
2500.00
2000.00
1 500.00
1 000.00
500.00
0.00
N o ne
So ybean
Sunflo wer
N o ne
So ybean
Sunflo wer
Grassland Soil
Organic Farm Soil
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
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.
Statistics Pseudoreplication (Hurlburt, 1984)
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
Statistics Pseudoreplication (Hurlburt...