Progress has been made in the study of the evolution law and driving mechanism of the active bank of black soil organic matter in Nanjing

Dissolved organic matter is the most active functional component of soil organic matter, which affects the formation of soil stable carbon pool, biogeochemical processes, and soil response and feedback
to climate change.
The content and output flux of soil dissolved organic matter in ecosystems have been reported a lot, but the formation and transformation mechanism still needs to be revealed
.
Northeast melanin is known for its high organic matter, but it is in a state of continuous decay, showing a "double decline"
in content and activity.

The team of Ding Weixin, a researcher at Nanjing Institute of Soil Science, took the 100-year cultivation time series of black soil farmland as the research object, and explored the evolution law and driving mechanism
of dissolved organic matter content and quality.
It is found that the dissolved organic matter and total organic matter of black soil decrease simultaneously with the increase of cultivation years, but the bioavailability and content have a negative exponential relationship
.
Spectral analysis showed that the decrease of complex macromolecular compounds and the increase of small aromatic substances and protein-like components were the main reasons for
the improvement of bioavailability of dissolved organic matter.
Although soil organic matter is the main source of dissolved organic matter, there is a decoupling relationship
between the two in terms of component composition.
Soil oxygen availability drives the composition and availability of dissolved organic matter
.
With the improvement of soil oxygen availability, three types of reactions are induced: first, the enhanced oxidase activity catalyzes the decomposition of polymer humus substances into small aromatic components; Second, the reduction of the dosing ratio of carbon-nitrogen hydrolase promotes the formation of protein-like components; Third, the oxidation of ferric iron to ferric iron promotes the precipitation of complex polymers in dissolved organic matter
.
Therefore, in the process of reducing the organic matter content of black soil, the increase of oxygen availability improves the bioavailability of dissolved organic matter and accelerates the transformation and loss
of activated carbon pool.
This finding deepens the understanding of the mechanism of black soil organic matter decay and productivity decline, and provides a theoretical basis
for farmland carbon management and soil carbon mechanism model improvement.

The relevant research results were published in Global Change Biology, with doctoral student Ye Li as the first author and associate researcher Chen Zengming as the corresponding author
.
The research was supported
by the National Natural Science Foundation of China, the "Black Earth Granary" Pilot Project of the Chinese Academy of Sciences, the Youth Trust Project of the China Association for Science and Technology, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Paper link

Conceptual diagram of oxygen-induced dynamics of dissolved organic masses and their main mechanisms