The study found a nitrogen-mediated mechanism of phosphorus supply regulating soil organic carbon pool

Recently, researchers from the Phosphorus Biogeochemistry Research Group of the South China Botanical Garden of the Chinese Academy of Sciences, with the joint funding of the National Natural Science Foundation of China and the Guangdong Basic and Applied Basic Research Fund, discovered the nitrogen-mediated mechanism of phosphorus supply regulating soil organic carbon pool. The results were published in Soil Biology and Biochemistry. Luo Xianzhen is the first author of the paper, and Hou Enqing is the corresponding author.

The effect of phosphorus addition on soil organic carbon pool depends on nitrogen availability. Photo courtesy of the research team

In (near) natural terrestrial ecosystems, the total soil phosphorus content can span about 4 orders of magnitude, ranging from about 1 mg kg-1 to about 10,000 mg kg-1. How this large spatial difference affects plant and soil microbial activity, and thus shapes the structure, function and processes of terrestrial ecosystems, is an important scientific question.

Field nutrient addition experiments are an important means of studying this scientific problem. Previous studies have shown that phosphorus addition boosts terrestrial vegetation productivity, leading the researchers to hypothesize that phosphorus addition also promotes soil organic carbon pools. In order to test this scientific hypothesis, the researchers conducted a comprehensive analysis based on 536 related studies in terrestrial ecosystems to explore the relationship between phosphorus supply and soil carbon storage, and found that the increase of phosphorus supply promoted soil organic carbon storage, and increased with the increase of soil nitrogen availability.

According to reports, in the case of low soil nitrogen availability (C:N ratio > 16), phosphorus addition promotes vegetation productivity and thus promotes plant carbon input, but also promotes microbial activity (that is, increases microbial biomass), promotes soil respiration, and increases soil carbon loss, which will offset the increase in plant carbon input, so that the impact of phosphorus addition on soil organic carbon may have no change or negative effect.

Under the condition of high soil nitrogen availability (C:N ratio ≤ 16), phosphorus addition greatly promoted vegetation productivity, increased plant carbon input, and had no effect on microbial activity, reduced soil respiration and soil carbon loss, thereby increasing soil carbon storage. The possible cause of the above phenomenon is that under the addition of phosphorus, the high nitrogen availability of the soil provides more nitrogen to the microorganisms, and reduces the carbon mineralization of the microorganisms to obtain nitrogen.

This study reveals the nitrogen-mediated mechanism of phosphorus regulating soil organic carbon pools, and emphasizes the importance of considering elemental interactions in terrestrial process models. (Source: China Science News Zhu Hanbin)

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