I used a Li-COR Flux system to measure respiration in different soil types. The question is, my data is mostly positive values but on a small scale (0 < x < 1). However, there are a couple of days where I got negative values.. VERY negative (-43, -32...). They are not outliers since I did triplicates per day.
I don't want to delete this data, I think maybe something was happening in the microbial communities those days. But the difference in scale doesn't allow me to visualize the data in scatter plots.
I was thinking about some type of standardization? But I don't want to alter the dC/dt values.
Thank you!
Did you check the condition of the instrument and try to measure the same plots in other days? It is strange to get so big negative observation values. I suggest you to consult to an experienced engineer of the instrument. Moreover, try to find answers by considering multiple factors such as climate, soil type, vegetation, and land use, although I did not get negative values in my two-year-period investigation (in subtropical forests using Licor 8100) or read papers which report a negative soil CO2 efflux as high as yours.
Cheers,
Hui
Check this out- (CO2 uptake was already observed in drylands)
Article Soil CO2 influx in drylands: A conceptual framework and empi...
Laura Alejandra Manchola Rojas , potentially there are numerous soil organisms consuming CO2. Two major types are I) photorophic (green plant parts, algae, cyanobacteria), and ii) chemoorganotrophic microorganisms (nitrifying, Fe/Mn/H2... oxidizers, methanogens, etc.). I observed the 'negative soil respiration' with LiCor in the lab incubation of peat soil cores containing very active methanogenic communities. Having said that, I agree with other researchers above that you should first check the instrumental issues and clarify the phenomenology (under which specific conditions, the negative fluxes occur)
In my 6 years of research on soil respiration, I didn't find any negative result. But theoretically, it can happen by CO2 consumption by microorganisms. I would recommend the answers of Nicolai S Panikov. Bestw ishes
Khairul Md Alam Nicolai S Panikov Boaz Hilman Hui Wei Simon Weldon
I want to thank all the community for your contributions and recommendations.
I used peat, peat mineral mix, and forest floor mineral mix. No vegetation; conditions like moisture and temperature were controlled since this was an incubation study. The treatment was adding different amounts of wood shavings, but these negative values are not associated with the wood application or soil type.
I consider there definitely must be an instrumental issue. However, I will take all the factors you mention into consideration. Thanks for the literature provided.
Laura, my advice is to pay attention to the chemistry of the 'mineral mix' that you have used. It is enough to have a minor pH shift up to get a negative CO2 flux. There are diverse mineral CO2 absorbers, and even the water addition can cause temporal removal of CO2 as a result of redistribution between gaseous and liquid phases (as you probably know, the Henry constant for CO2 is very high).
We got negative emissions of CO2 right after wood ash spreading due to chemical consumption of CO2. That was the only case.