The food web represents the intricate feeding relationships among organisms in an ecosystem that are almost ubiquitous. In soil, small food webs of bacteria, fungi, and nematodes are called soil micro-food webs. In general, agricultural activities, such as tillage, weeding, and fertilization, can severely disrupt soil micro-food web communities. To protect soil health and improve crop yields, soil micro-food webs need to maintain high complexity, biomass, and absorb more energy.

In a study published in Soil Biology and Biochemistry, researchers led by Prof. WANG Kelin from the Institute of Subtropical Agriculture of the Chinese Academy of Sciences conducted a seven-year observation and control experiment in a karst region in southern China. To reduce random error, they used new methods to study how synchronized land-use change (starting at the same time and place) affects soil ecological processes and functions were used. They revealed the complex process of changes in community composition and energy flow in soil micro-food webs under different intensities of agricultural disturbance.

According to the researchers, clearing and planting maize (e.g., frequent tillage and weeding) on natural scrubland simplifies the soil micro-food web and reduces the energy passing through the food chain. While planting forage (no-tillage) increases the soil microbial biomass and complexity of the micro-food web.

In addition, high trophic level organisms (omnivores) help maintain the structure of the soil food web structure and promote energy absorption.

"This study improves our understanding of the mechanisms that maintain the complexity of soil micro-food webs and energy flow," said Prof. ZHAO Jie, corresponding author of the study. "These findings also have implications for rational land use planning."

The main food crop in the karst drylands of southern China is maize. (Image by LING Jiangnan)

The energetic structures of soil micro-food web in different land use. CL, cropland (maize); FG, forage grassland (tall-pasture); EL, economic forest land (walnut); NS, natural shrubland. (Image by LONG Xianwen)

Soil micro-food web co-occurrence network in different land uses. CL, cropland (maize); FG, forage grassland (tall-pasture); EL, economic forest land (walnut); NS, natural shrubland. (Image by LONG Xianwen)