Legumes (the plant family that includes beans and peas) play an important role in nutrient cycling and ecosystem functioning, known for their ability to fix nitrogen from the air. However, it remains unclear how phosphorus (P, a key nutrient plants need to grow) availability influences intraspecific and interspecific interactions among tropical legumes.

In a study published in Plant and Soil, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences showed that interspecific interactions significantly enhance plant performance of tropical legumes, particularly under phosphorus-limited conditions.

Through greenhouse experiments, the researchers conducted systematic analyses on the responses of four legume species (Crotalaria assamica, Crotalaria pallida, Flemingia macrophylla, and Ototropis multiflora) under low, medium, and high phosphorus conditions. They also compared growth under three neighbour regimes: intraspecific (same species), interspecific (different species), and no competition (isolated plants).

They found that legumes grown with interspecific neighbors produced significantly greater aboveground and total biomass compared to those grown with intraspecific neighbors or in isolation. In contrast, intraspecific interactions led to increased belowground biomass and enhanced resource-acquisition traits, such as root length and nodule formation, suggesting stronger competition for soil resources among individuals of the same species.

They also found that legumes have species-specific responses to competition and phosphorus availability. Crotalaria pallida shifted from facilitative interactions at low P to competitive ones at high P, while Crotalaria assamica consistently facilitated neighboring plants across all P levels. Flemingia macrophylla and Ototropis multiflora showed weaker overall responses but still benefited from interspecific interactions.

The researchers then analyzed physiological traits and found that mixed-species groups had higher levels of nutrients in their leaves and stronger natural defense systems. These defenses help the plants cope with stress caused by nutrient-poor soils.

The findings underscore that neighbour identity is a key driver of both individual performance and community dynamics in tropical ecosystems.

“Our work points to a practical strategy: mixed-species planting could boost productivity and resilience in phosphorus-limited soils," said ZHANG Jiaolin of XTBG. “That has direct implications for tropical forest restoration, agroforestry systems, and sustainable farming practices.”

A tropical legume species. (Image by ZHU Renbin)

Published: 04 August 2026