My research aims at understanding Experimental warming impacts on CO2 fluxes in alpine region of Himalaya. We use open top chambers (OTCs) to simulate climate warming. As these OTCs are long-term monitoring permanent plots, we restrict our sampling (soil, plant and CO2 flux) so as to avoid any disturbance. However, it is necessary to evaluate root response to warming to understand how below-ground is affected. Hence, I am looking for a non-destructive but robust and widely used method to evaluate root biomass. Notably, the roots in the region go down to a depth of approximately 40-70 cm.
Use the relationship of leaf area index and root biomass. You can peruse through this paper.
Article Correlation of Leaf Area Index to Root Biomass in Populus tr...
The most widely used method is using allometric equation which relates above ground biomass to below round biomass.
Cairns, M. A., Brown, S., Helmer, E. H., & Baumgardner, G. A. (1997). Root biomass allocation in the world's upland forests. Oecologia, 111(1), 1-11.
Dear all,
I believe that if you use allometric equations to relate above- and belowground biomass, you are making a strong, implicit assumpion, which is that the root/shoot ratio remains constant.
If you aim assessing also this ratio, and you cannot dig your plots, I would recommend the use of rhizotrons and scanners taking pictures of the root system.
It is a lot of work, some uncertainty exists particularly in silty soils, but I do not know anything else if you want to assess the root growth along the time.
Regards
Leonardo
I fully agree with Leonardo, that use of empirical equations to 'estimate' root biomass is inadequate. Other known direct solutions like rhizotrons and rhizoscopes are also not ideal for natural soil. The reason is some belowground disturbance (much smaller than destructive root extraction procedure but anyway not a zero) and heterogeneity of soil making difficult the extrapolation of visible root abundance to the whole soil profile as g root mass/m2. Rhizotron works better for the planted soil pots experiments. My biased opinion is that indirect methods work better, specifically, respirometry can be used to explore the contribution of belowground activity to the whole C-balance. You install permanent gas-probes at series of soil depths inside OTC and record CO2 profiles in soil. Then use a math model with diffusion terms to compute CO2 sources at each soil layer. It gives you respiration rates of the belowground system: roots+microbes. I published such research in Soil Biol Biochem, 2007
Hi Nicolai, thank you for this detail.
This sounds interesting. Can you please share your research?
Pankaj, welcome to read my paper, pdf attached. Do not hesitate to contact me for explanations. Let me know what else do you imply by the 'share' request.
Root biomass is dominated by coarse roots and I am not sure if it depends on soil fertility as implied in some answers. Biomass equations exist for some species. Rhizotrons are in forests, not valid tools to estimate coarse root biomass.
Carbon fluxes are dominated by fine roots and most of the reservation on allometric equations in the answers apply to them.
I believe that there are ways of doing this with Ground Penetrating Radar - something I have been hoping to try for a long time in African savannas.
I suppose the allometric functions may give you a god estimate if you can´t sample the roots in the field. I used allometric functions for pine and spruce in boreal forests (Petersson and Ståhl 2007), however, these functions wee based on a large sample. Do you know whether anyone has done the digging part and constructed some functions for the region/species over there that you could use?
Good luck!
Cheers,
Robert