Carbon Mineralization during Decomposition of Switchgrass: Effect of Pore Size Distribution and Residue Type on the Source of Carbon Dioxide Emission
Abstract
Decomposition of plant residues is a major source of carbon dioxide (CO2) emission from agricultural land. Net change of carbon during the decomposition depends on two sources; accumulation/mineralization of C from plant organic matter (OM), and increased mineralization of C from native soil OM. The latter referred to as "Priming Effect", is one of the keys to understand and predict the change of soil carbon stock. However, mechanisms and regulating factors of priming effect are still not understood comprehensively, because most of the studies on the priming effect focused on OMs which are readily available (e.g., glucose). There can be different mechanisms and regulating factors during the plant decomposition. For instance, transport of mineralized C can be regulated by pore size and residue chemistry can stimulate microbes of different functions leading to various patterns of the priming effect.
In this study, we evaluated the effect of the pore size distribution (prevalent pore size as >30 mm and < 10 mm) and residue type on the different sources of CO2 emission and priming effect. We used 13C labeled Switchgrass (Panicum virgatum L. var. Cave-In-Rock) leaves and roots to track the C from switchgrass residues. Soil microcosms with incorporated switchgrass residues were incubated for 22 days, and 13CO2 and CO2 emission was measured at days 1, 3, 5, 8, 15, 22. To understand the linkage between microbial activity and source of CO2, we measured the distribution of b-glucosidase using zymography. Preliminary results showed that total CO2 emission is regulated by pore size distribution and residue type. CO2 emission from residue was not affected by pore sizes, but the peak CO2 emission reached earlier in soil with prevalent pore size > 30 mm (day 3 - 8) compared to the soil with prevalent pore size < 10 mm (day 8-15). CO2 from residue was greater in leaves rather than roots as expected. Surprisingly, CO2 from soil was also greater in leaves compared to roots, suggesting that microbial activity stimulated by leaf residues led to the greater soil OM decomposition. Priming effect was greater in the soil with prevalent pore size < 10 mm, showing the highest rate at day 8. In contrast, the soil with prevalent pore size > 30 mm showed the highest priming effect rate on day 1, and gradually decreased. We expect that the pattern observed in CO2 emission is related to b-glucosidase enzyme activities.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B21J2315K
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0463 Microbe/mineral interactions;
- BIOGEOSCIENCES;
- 0486 Soils/pedology;
- BIOGEOSCIENCES