Controls over foliar n:p ratios in tropical rain forests

Summary

This paper examined controls over foliar N:P ratios in tropical rain forests by analysing original data from 150 canopy tree species in Costa Rica and Brazil, combined with a comprehensive literature synthesis. The authors challenge the common generalisation that tropical forests are uniformly N-rich and P-poor, finding instead that species-level variability is the dominant influence on foliar N:P stoichiometry, with only modest constraints from soil P availability, soil order, or seasonal effects. The findings suggest that tropical forest N:P stoichiometry is substantially less well-constrained than in marine systems or many other terrestrial biomes.

Regional applicability

This study focuses on tropical forest ecosystems (Costa Rica and Brazil) and is not directly applicable to United Kingdom farming or land management systems. However, the methodological approach to understanding species-level nutrient stoichiometry and the critique of broad generalisations based on coarse environmental categories may inform temperate forest and agroforestry research in the UK.

Key measures

Foliar nitrogen and phosphorus concentrations; foliar N:P ratios; soil phosphorus availability; soil order; latitude; mean annual precipitation; seasonal variation

Outcomes reported

The study examined foliar N and P concentrations from 150 canopy tree species across tropical sites to identify major sources of variation in foliar N:P ratios. Key findings revealed that species variability is the dominant influence on foliar N:P ratios in tropics, with seasonal, soil P availability, and soil order effects but substantial overlap across soil types.

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