Potential Hypotheses Predicting Leaf Litter Nitrogen and Phosphorus Patterns at the Global Scale

Area of Science:

• Ecology
• Biogeochemistry
• Plant Physiology

Background:

• Climate influences leaf nutrient patterns via direct physiological effects, soil nutrients, or species composition.
• Understanding these influences on leaf litter stoichiometry is crucial but remains unresolved.

Purpose of the Study:

• To evaluate the effectiveness of different hypotheses in predicting leaf litter nitrogen and phosphorus patterns globally.
• To determine the relative importance of environmental and biological factors on leaf litter stoichiometry.

Main Methods:

• Analysis of 4657 global observations of leaf litter nitrogen (N) and phosphorus (P) concentrations and N/P ratios.
• Evaluation of the Temperature-Plant Physiology, Soil Substrate Age, and Species Composition hypotheses for predicting latitudinal patterns.

Main Results:

• Leaf litter stoichiometries varied significantly among plant functional types.
• Litter N and N/P ratios decreased with latitude, while P increased.
• The Species Composition hypothesis best predicted latitudinal P patterns, but no hypothesis accurately predicted litter N.
• Plant functional type, soil pH, and climate were key drivers of litter N, P, and N/P ratios, respectively.

Conclusions:

• Mechanisms controlling litter stoichiometry differ fundamentally from those of green leaves.
• Existing biogeochemical models and plant nutrition paradigms require revision to account for these differences.