Im going to measure soil respiration efflux with a portable, closed chamber for soil respiration system (EGM-4 with SRC-1, PP-Systems, Hitchin, UK) with a measurement time of 120s.
So, according to the literature, I should put some PVC collars (10 cm inner diameter and 10 cm long, with perforated walls in the first 5 cm) in the soil and the machine on top of it.
Now, in order to estimate heterotrophic respiration I need to place a root exclusion PVC cylinder (40 cm diameter, 40 cm high).
So, my question is: how will a 40cm high PVC cylinder block roots (for example on a alfa alfa crop field?) Should I remove all the roots? And how?
Thank you in advance
You should also consider using no collar insert. See our paper: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2389.2010.01331.x/abstract
I would recommend considering the system you have and finding a solution to ensure a good seal of the collar base without cutting any roots etc.
As to how to determine no root respiration. It sounds like a good idea to do an experiment of cutting to different depth instead of inserting a fixed collar depth as the roots are very deep. However, I suspect most (>90) of active fine roots contributing most to respiration are in the top 30 cm (also see above paper). Therefore, why not use 3-5 different cutting depth (repeat cutting throughout the year) and measure the decline in respiration. From this you should be able to derive a model (regression) on lost flux over depth unit, which should give you a total root respiration estimate.
Good luck!
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2389.2010.01331.x/abstract
Dear Matteo Francioni
If you are going to observe the heterotrophic soil respiration exclusively, then you have to exclude the roots from the soil. You can go through the following link it may be helpful to you.
http://nature.berkeley.edu/ahg/pubs/microbial.pdf
Good Luck
Thank you Rama, especially for the paper provided.
Now the question is: what if I have to exclude alfa alfa roots (5 m long)? I should place the exclusion pvc collars on a 5 years old alfa-alfa field. Could it be a solution a systemic herbicide?
Dear Francioni,
It vary with the type and objective of the study,you can also establishes the microcosm experiment or lab incubation study.
You should also consider using no collar insert. See our paper: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2389.2010.01331.x/abstract
I would recommend considering the system you have and finding a solution to ensure a good seal of the collar base without cutting any roots etc.
As to how to determine no root respiration. It sounds like a good idea to do an experiment of cutting to different depth instead of inserting a fixed collar depth as the roots are very deep. However, I suspect most (>90) of active fine roots contributing most to respiration are in the top 30 cm (also see above paper). Therefore, why not use 3-5 different cutting depth (repeat cutting throughout the year) and measure the decline in respiration. From this you should be able to derive a model (regression) on lost flux over depth unit, which should give you a total root respiration estimate.
Good luck!
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2389.2010.01331.x/abstract
Some similar experiments have been done by our group in grassland. PE collars (20 cm inner diameter and more than 50 cm long) were pushed into the ground in autumn, and we cut down the above-ground plants, then heterotrophic soil respiration will be measured in next year. Because we think the roots are dead in the cylinder. The PE collars can prevent disturbance from the lateral roots.
Good luck!
Thanks Mao! Any suggestion regarding herbicides? I mean, could it be a solution if I can't wait more than one month?
Dear Matteo,
to avoid significant changes on soil water content, induced by the PVC collar, you should use fine net (or permeable geo-tissues) to exclude the roots growth but not the water (and dissolved compounds) movement.
You should also consider that with the root exclusion you are also reducing the roots inputs (exudates) to the soil microbial community, so affecting the heterotrophic respiration.
Finally you can’t exclude the lateral CO2 diffusion from outside the collars (but could be minimal under certain circumstances).
An option is to use an ex-situ approach on intact soil cores (the comparison with the field efflux measurement is maintained), to avoid the artefact of field exclusion (see our paper, attached).
Attached you will find also a recent example of in situ measurement of SRh.
Good luck
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