Hello , everyone. I measured the rhizospheric fungal community by ITS2 sequencing and found greater within site dissimilarity in rhizospheric compartment than thoes in bulk soil. I wonder of priority effects could be operating in rhizospheric compartment? How can I directly test the priority effects? Can I take the bulk soil as the initial state and the rhizospheric as the final state and then compare the difference between these two state? Thank you for your consideration!
To understand the rhizosphere effect you must compare with the bulk soil microbial community. The best way to prepare Plexiglas compartment box where the compatmation may be done with the nylon net through which root can not penetrate to the next compartment in the same box. In that way you may differentiate rhizosphere effect, please see the publication by Tarafdar & Marschner (1994) Soil Biology & Biochemistry 26, 387-395. In the rhizosphere compartment you get the effect of root as well as bulk soil. Then,you have to substrate the value you are getting only in the bulk soil. Therefore, you have to take the value of rhizosphere at the initial stage and substrate the bulk soil value from that to get rhizosphere effect. In general, rhizosphere effect depends on the availability of substrate, rhizosphere microbial community , plant growth promoting microbes and analysis used to examine overall microbial community. For more details you may consult the attached files.
The other things you may priorities under field conditions are :
- Root location
-Differences in microbial community
- Seasonal changes in the rhizospheric microorganisms
- Influence of transgenic plants
- Stability and dynamics of microbial community
- Rhizospheric enzyme production and activity
Dear Apple,
You can compare the bulk soil and the rhizosphere zones. They are two different environments.
-The dynamic of the soil zone is under several biochemical reactions driven by the organic matter decomposition by soil microorganisms.
-The dynamic of the rhizosphere zone is governed by the presence of living roots with soluble and available exudates. You can even subdivide the rhizosphere into the inner and outer rhizosphere (adjacent soil).
Have a look to some pictures of the root colonization process over time (ex. : Beauchamp and Kloepper, 2003). This process depends of the plant species and age.
May be you should determine which fungi are there? Try a rapid identification of your fungi (using your ITS2). Are they mycorhizes? Are they plant pathogens? Then you could examine priority effects.
Sincerely,
Chantal Beauchamp
Dear Chantal,
Thank you for your ardent reply. In this study, I have divided the rhizosphere into two parts and foud the fungal community different in these two part when compared with the bulk soil.
By ITS2 sequencing, I can predict the throphic mode of the fungi community, most of them belong to saprotroph. But I feel confused how can I examine the priority effects as I did not know a taxon's final abundance and its starting abundance (lack time series experiment in the same environment)?
I wonder if it is possible for you to give me an example how to examine priority effects? Can we take the bulk soil as the staring stage and the inner rhizosphere as the final stage?
Best,
Zhang
Dr. Apple, you may divide rhizosphere into two parts, one is rhizoplane ( root surface area) and other is true rhizosphere (soil adhering to the root surface), then you may compare with the bulk soil. You may compare rhizosphere and the rhizoplane with the bulk soil to get the variation and diversity effect.
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