Forests are vital components of global biogeochemical cycles. Previous studies have focused on the effects of environmental factors like climate and topography on soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry. However, it remains unclear how plant diversity modulates soil nutrient limitations across different environmental contexts.

In a study published in Forest Ecology and Management, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences revealed how plant species diversity dynamically regulates the relative limitations of soil N and P nutrients on C processes by altering soil C:N:P stoichiometric relationships in natural forest ecosystems.

The researchers established a large-scale sampling framework across six 20-hectare forest dynamics plots along the 101°E longitudinal transect spanning southwest China to Southeast Asia. By integrating vegetation and topographic data, they systematically analyzed spatial variations in soil C, N, and P concentrations and their stoichiometric ratios.

The results showed that plant diversity alleviated nutrient limitations in natural forest ecosystems. Within individual forest sites, higher species diversity was strongly correlated with increased soil P concentrations. These diverse areas also exhibited lower C:N, C:P, and N:P ratios, indicating a shift toward a more balanced soil nutrient environment.

Notably, the relationship between plant diversity and soil nutrients was heavily dependent on the background level of soil P. In P-poor forests, high plant diversity primarily enhanced soil P content, thereby mitigating P limitation. In P-rich forests, however, high diversity promoted the accumulation of C and N, potentially boosting C sequestration capacity.

“This systematic shift demonstrated that the diversity-stoichiometry relationship is especially sensitive to soil P status,” said XIA Shangwen from XTBG, one corresponding author of the study. “Where P is limited, plant diversity helps mobilize or retain this critical nutrient; where P is abundant, diversity appears to drive organic matter buildup.”

Moreover, researchers confirmed that climatic factors such as temperature and precipitation primarily shaped the large-scale geographical patterns of soil C, N, and P stoichiometry, and that topographical heterogeneity (e.g., terrain ruggedness) further modulated local nutrient retention capacity by influencing microenvironments and plant diversity.

The study suggests that maintaining or restoring species diversity is not just about conservation, but about ensuring ecosystem functionality and resilience.