Karst regions in southwestern China are among the most fragile agricultural landscapes worldwide. Rocky desertification threatens both ecosystems and local farm livelihoods. Multifunctional agroforestry systems (AFSs) have been promoted as a way to restore degraded soils while sustaining crop production. However, few studies have focused on their functional performance in karst environments.

In a study published in Agroforestry Systems on August 22, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators found that intercropping fruit trees with medicinal plants can fundamentally reshape the multi-element nutrient network across soil, roots, and leaves in fragile karst landscapes. Their findings suggest that well-designed agroforestry can improve nutrient coordination and resilience in one of the world's most fragile agricultural landscapes.

The researchers examined how multifunctional AFSs regulate multi-element stoichiometric relationships in soil-plant systems in the karst region of Southwest China, and what these effects imply for sustainable management. They compared a Prunus salicina monoculture (Pm) with several AFSs. The understory species included Hypericum monogynum, Polygala fallax, Rubus suavissimus, and Semiliquidambar cathayensis + Illicium difengpi. They measured the concentrations and stoichiometric relationships of macroelements and metallic elements in soil, roots, and leaves. They then assessed nutrient acquisition efficiency, root-to-leaf translocation capacity, and elemental coupling.

They found that, compared with monoculture cultivation of plum trees (Prunus salicina), AFSs incorporating different medicinal plants significantly restructured nutrient element composition and stoichiometric balances. The Prunus salicina and Rubus suavissimus system exhibited the most substantial increases in nutrient bioaccumulation and translocation factors. Notably, plant nutrient acquisition efficiency was more strongly linked to soil elemental ratios, especially phosphorus-based ratios, than to the absolute concentration of any single element.

Species selection mattered more than species richness alone. Network analysis identified calcium and manganese as key integrators that link nutrient dynamics across soil, root, and leaf compartments. This suggests that these elements act as hubs in the plant–soil nutrient network.

These results suggest that nutrient management in karst orchards should shift from the traditional supplementation of nitrogen and phosphorus to the coordinated regulation of multiple elements. In particular, the calcium-to-magnesium ratio and iron- and manganese-related ratios should be optimized.

"When selecting understory medicinal plants, managers should prioritize functional matching rather than simply pursuing species abundance," said LIU Chenggang of XTBG.