A research team led by Prof. WANG Kelin from the Institute of Subtropical Agriculture of the Chinese Academy of Sciences, has uncovered how multitrophic organisms adapt to phosphorus (P) limitation in subtropical ecosystems. Their findings, published in Journal of Advanced Research, shed light on strategies to alleviate P limitation in fragile subtropical ecosystems.

Phosphorus limitation severely constrains agricultural sustainability and the stability of forest ecosystem structure and function in subtropical regions. Although plants and phosphate-mobilizing bacteria are key essential for soil P mobilization, their effectiveness is influenced by climate, land use, lithology, and higher trophic levels. Previous research has focused on single abiotic or biotic factors, leaving a gap in understanding how multitrophic organisms adapt to P limitation under varying lithological conditions.

In this study, the researchers established a north-south transect in subtropical Southwest China across contrasting lithologies – carbonate (karst) rocks versus clastic (non-karst) rocks. They investigated how multitrophic biodiversity and interactions influence soil P mobilization during the transition from cropland to forest succession. 

Results show that long-term fertilization in both karst and non-karst croplands increases the accumulation of moderately labile and stable P pools while weakening biological P mobilization capacity. After the conversion of cropland to forest, the labile P fraction in karst soils increases by 43.8%, while the moderately labile P and stable P fractions decrease by 79.1% and 36.6%, respectively. 

In non-karst soils, the moderately labile P and stable P fractions decreased by 62.6% and 34.8%, respectively. Multitrophic biodiversity and P activation capacity were significantly higher in karst regions than in non-karst regions. Forest restoration in the karst regions enhanced the cascade interactions among phosphate-mobilizing bacteria, mycorrhizal plants, and nematodes. This synergy enhanced biological P mobilization and uptake, which reduced P precipitation by calcium/magnesium and consequently alleviated P limitation. 

This study emphasizes the vulnerability of karst ecosystems to human disturbances such as tillage and deforestation, which readily cause species loss and disrupt critical multitrophic interdependencies.

"Reducing mineral P inputs and enhancing legacy P mobilization through biological pathways are critical to promoting agricultural sustainability and supporting the recovery of degraded ecosystems under global change," said Prof. ZHAO Jie, corresponding author of the study. 

Sampling sites in the karst and non-karst regions of southwest China. (Image by LIAO Xionghui)

Conceptual diagram illustrating how multitrophic organisms adapt to P limitation under different lithological conditions. (Image by LIAO Xionghui)