The effects of wildfires on soil carbon and nutrient cycling and their extracellular enzyme mechanisms are revealed

Coniferous and broad mixed forests in China’s subtropical-warm temperate climate transition zone are particularly sensitive to climate change, soil microorganisms have high sensitivity to wildfires, and the impact of wildfires on soil microbial community structure and function has attracted more and more attention. Soil extracellular enzymes play a key role in biogeochemical processes, such as regulating carbon and nutrient cycling. However, the effect of changes in soil physicochemical properties and microbial community composition on soil extracellular enzyme activity after fire is unclear. Therefore, the response and regulatory factors of extracellular enzyme activity after fire are of great significance for elucidating the effect of fire on nutrient-microbial enzymes in microbial processes.

A conceptual framework for changes in soil properties, microbial communities, and extracellular enzyme activity after fire. The dotted line reflects the denaturation of fire-induced extracellular enzymes immediately after fire. Solid lines show the indirect effects of fire on soil properties and microbial communities. The red path reflects the main factors controlling the influence of fire on the activity of C, N, and P to obtain extracellular enzymes. (Photo courtesy of the paper team)

Based on this, Chen Ji’s team from the Institute of Earth Environment, Chinese Academy of Sciences, took the subtropical-warm temperate forests of central China as the research object, and explored the response of carbon (C), nitrogen (N) and phosphorus (P) to extracellular enzyme activities and their regulatory factors at 1, 6, 13 and 50 years after forest fires. The enzymatic activity of C-(β-glucosidase), N-(N-acetylglucosaminidase) and P- (acid phosphatase) decreases with the increase of time after fire, reaching its highest value 1 year after fire. The response of carbon-harvesting enzyme activity to fire was positively correlated with bacterial biomass, indicating that post-fire microbial composition was associated with changes in extracellular enzyme decomposition. Soil acquired phosphatase activity was positively correlated with soil phosphorus availability, while acquired phosphoase activity was positively correlated with soil nitrogen availability. As a result, soil extracellular enzyme activity decreased with the passage of time after the fire, suggesting that wildfires may reduce microbial nutrient requirements.

The results have been published in the journal Land Degradation & Development, and the work has been jointly funded by the National Natural Science Foundation of China and other projects. (Source: Yan Tao, China Science News)

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