Carbon (C), nitrogen (N) and phosphorus (P) are fundamental elements of plants and ecosystems. Investigation on stoichiometric relationships between soil C, N, and P could improve our understanding on nutrient cycling and provide valuable information for forest management.

To advance the spatial and vertical variations of soil C, N, and P stoichiometry in tropical forests on Hainan Island, Professor REN Hai from South China Botanical Garden of Chinese Academy of Sciences, collaborated with Professor HUI Dafeng from Tennessee State University, and scholars from Hainan University and Hainan Normal University initiated a research on the influence of environmental factors on the soil C, N and P variations of tropical forests on Hainan Island, South China.

The researchers collected soil samples (0-100 cm depth) from 100 plots in different forest types including tropical natural rain forest, Eucalyptus plantation, rubber plantation, Casuarina plantation, coniferous plantation and orchard, and measured total C, N and P concentrations (Fig 1).

Results showed that soil C and N concentrations, and soil C:P and N:P ratios declined from the surface soil layer to the deeper soil layers, due to soil C and N were mostly controlled by biological processes such as photosynthesis and N2-fixation, while soil P was more influenced by bedrock. Additionally, soil C and N concentrations were significantly influenced by longitude and vegetation cover, while soil P concentration and C:P and N:P ratios were significantly controlled by latitude (Fig 2).

This study produced a comprehensive data set of soil C, N, and P stoichiometry, and their variation patterns and controls in the tropical forests. The generated information could help improve ecosystem models for better understanding of forest element stoichiometry, ecosystem productivity, and plant-environment relationships.

The relevant research entitled “Soil C:N:P stoichiometry in tropical forest s on Hainan Island of China : Spatial and vertical variations” has been published in Catena.

For further reading, please refer to : https://doi.org/10.1016/j.catena.2021.105228.

Fig 1. Study sample plot distribution

Fig 2. Relationships between soil C, N, P concentrations and latitude, longitude, elevation, vegetation cover, and tree height. Sample size is 100