Dear,
We know DOC in soils could be originated from litter and SOM decomposition, leached from litter, or from root exudations. Meanwhile, it provides C substrate to soil microorganisms for growth and respiration. Does anybody have literatures to directly determine DOC as one of the sources of respired CO2 from soils.
Moreover, I will appreciate you if anybody has a literature studying on the relationship between DOC and extractable OC (K2SO4 extracted in my case but other EOC such as water-extracted OC is OK) in forest soils.
Many thanks,
Hui
Few years back, we tried to quantify DOC in soils from cultivated grassland. We monitored soil respiration in incubated soil using respirometer (RESPICOND VI). However, we didn't look into the relationship between those two. There should be lots of paper by Blagodatskaya E, Kabiltz K and by Marschner B on DOC. Check our paper 'grassland carbon sequestration and emissions following cultivation in a mixed crop rotation". That may provide you some insights.
Dear Bharat,
Thanks for your response. Yes several researchers observed significant relationship between DOC concentration and CO2 efflux while some others did not. Per Bengtson and G. Bengtsson (2007, Ecology Letters) found that although DOC concentration was not significantly related to CO2 flux, respired C mainly originated from DOC. I read some articles published by the K. K.'s research group. I remember that they ever observed respiration rate decreased as DOC was consumed (or results likewise). It will be perfect in case that more studies using isotope technique to explore relationship between DOC and respiration are recommended.
I observed significant positive relationship between DOC and microbial biomass by phospholipid fatty acid (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103901). I also attempted to discuss their relationship with respirable carbon (fig. 6). Based on my experience, these pools (dissolved and respirable carbon) are balanced by available N in the system and microbial biomass/community composition.
I don't know if this paper can help you. The paper relates to the stoichiometry of nutrient (C:N:P) in litter and in microbes that participate to litter decomposition. They demonstrated that the proportion of C:N:P in the soluble fraction of leaf litter was closed to the proportion of C:N:P in microbes as in aquatic ecosystem. I think this indicates, somehow, C metabolism related to DOC that may be easily to uptake by microbes. For more informations, please contact the author or coauthors. They are working on C mineralisation in litter and in underlying soil.
Dear Hui,
You might be interested in the answer to a very similar question here https://www.researchgate.net/post/How_can_i_determine_the_most_labile_fraction_of_soil_organic_matter_content_of_soil Please, pay attention to the answer of Dr. Pere Rovira
I think, that this article will be useful information for you.
F. Hagedorn et al., 2004 suggest that dissolved organic C is produced during incomplete decomposition of recalcitrant soil C, while easily degradable components are rapidly consumed by soil microbes and thus make minor contributions to the dissolved organic C.
With respect/
Dear Rüdiger,
Thanks for the recomended papers. I have read the two papers by Iqbal et al. and Fang et al.and they observed significant correlations between DOC and Rs, indicating that there was a linkage between DOC and Rs. van Hees's paper is helpful on my questions here.
And dear Hamkalo, thank you very much to provide this important literature to me. The observations in Frank's study tell us the main origin of DOC in soils.
Thank you all for your help.
Regards
It's an interesting question! Yet back to your question, biogeochemically, you have to use the 13C or 14 isotopic tracers to differentiate CO2 respired between the DOC and other SOC sources, such as MBC, organic matter. I never see people have done this……otherwise, you never know whether the microbes use DOC or other SOC sources for respiration.
Dear Dr. Xiao-Jun Allen Liu,
You may be interested in the study of Hagedorn et al. (2004) "A 13C tracer study to identify the origin of dissolved organic carbon in forested mineral soils" The authors have foud that about 90–95% of DOC sampled from forest soil with suction cups at 5–10 cm depth was older than 4 years. Thus, if microbes use DOC - they do it slow :)
Hi Tymur:
Yes, the DOC seems only made minor contribution to microbial decomposition or respiration, based on the Hagedorn et al. (2004) paper.
Dear Tymur and Xiaojun,
Thanks for your discussions. Whether respired CO2-C originates from DOC is still under debate, based on previous studies. While Hagedorn et al. (2004) found that DOC contains C older than 4 years, which indicates that DOC contributes minor to respiraton, Bengtson and Bengtsson (2007, Ecology Letters 10, 783-390) observed that respired soil C was sourced from DOC. Hope someone have stronger literatures which can clearly answer this question.
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