Effect of intercropping medicinal herbs in Pinus elliottii plantation on soil properties and microbial community...

Pinus elliottii is an important afforestation species in the hilly regions of southern China, but long-term monoculture may lead to soil nutrient depletion and microbial community imbalance.

This study aimed to evaluate the effects of different understory medicinal plant intercropping patterns on soil properties, enzyme activities, and soil microbial communities in P. elliottii plantations, and to identify suitable intercropping patterns for forest-medicinal plant compound management.

Three intercropping patterns were tested: P. elliottii-Ficus simplicissima-Spatholobus suberectus (PHS), P. elliottii-Alpinia oxyphylla-S. suberectus (PAS), P. elliottii-Alpinia hainanensis-S. suberectus (PSA), with a pure P. elliottii forest serving as control (CK). Soil nutrient dynamics and enzyme activities were determined, and soil microbial communities were analyzed using high-throughput sequencing.

Under the same intercropping pattern, soil nutrients in the 0-20 cm layer were higher than those in the 20-40 cm layer. In the 0-20 cm layer, all three intercropping patterns significantly reduced amylase activity compared to CK (P < 0.05). In the PAS pattern, acid phosphatase, neutral protease, and urease activities were significantly enhanced, with urease activity significantly higher in 0-20 cm than in the 20-40 cm layer. High-throughput sequencing revealed interactions among intercropping patterns, soil properties, and microbial communities. Intercropping significantly affected the structure, composition, and diversity of both soil bacterial and fungal communities. PSA showed pronounced effects on soil nutrient status and exhibited the highest bacterial and fungal ASV richness. Redundancy analysis (RDA) identified organic carbon (SOC) and total nitrogen (TN) as key drivers of microbial variation. Random forest and LEfSe analyses further identified key taxa, such as Acidibacillus and Thermosporothrix, as significantly associated with the intercropping effects. Functional prediction suggested that microorganisms may improve soil quality by regulating gene responses in "Metabolism of terpenoids and polyketides" and "Urea Cycle" pathways, as well as by secreting enzymes such as ferredoxin hydrogenase and β-mannosidase.

Forest-medicinal plant intercropping improved soil quality and reshaped microbial communities in P. elliottii plantations. The PSA pattern showed the greatest potential for enhancing soil microecological functions and may serve as a suitable intercropping model for sustainable plantation management.