Researchers from the South China Botanical Garden of the Chinese Academy of Sciences, working with international collaborators, have confirmed that soil microorganisms in tropical forests are widely limited by phosphorus (P) availability, with this constraint intensifying significantly with increasing elevation. The findings were recently published in Soil Ecology Letters.

The research was conducted along three representative tropical forest elevational gradients in Guangdong and Hainan provinces, spanning an elevation range of approximately 100 to 1,400 meters. By combining measurements of soil extracellular enzyme activities with ecological stoichiometry analyses, the team quantitatively evaluated microbial metabolic limitations involving carbon (C), nitrogen (N), and phosphorus under contrasting climatic and vegetation conditions.

Results revealed that microbial metabolism was consistently characterized by strong phosphorus limitation across all study sites. The severity of phosphorus limitation increased markedly at higher elevations where temperatures are lower. By contrast, microbial carbon limitation was generally weak and showed no consistent elevational trend.

Further analyses identified temperature as the dominant environmental factor governing microbial nutrient limitation. Lower temperatures at higher elevations reduced phosphorus release via organic matter mineralization and mineral weathering, while simultaneously promoting microbial investment in phosphorus-acquiring enzymes. These patterns suggest a trade-off in microbial resource allocation between carbon and phosphorus acquisition.

Elevational gradients provide an effective spatial proxy for evaluating climate change impacts. The findings imply that future warming may partially alleviate phosphorus limitation in tropical forest soils, but could also intensify microbial carbon limitation—with potential consequences for soil organic carbon turnover and long-term carbon stability.

This study advances understanding of belowground microbial processes in tropical forests and their sensitivity to climate change, offering important implications for terrestrial carbon-cycle modeling and tropical forest management under global change.

The study was supported by the National Natural Science Foundation of China.