Widespread controls of leaf nutrient resorption by nutrient limitation and stoichiometry

Leaf nutrient resorption is a key process in nutrient cycles, but
fundamental knowledge regarding its control mechanisms remains limited.
Among the three proposed basic control mechanisms on leaf nutrient
resorption, namely nutrient concentration control, nutrient limitation
control, and stoichiometry control, only the first has been demonstrated
to exist globally, while the latter two have not been systematically
evaluated. Here, we conducted a global data synthesis to explore nutrient
limitation and stoichiometry control on leaf resorption of carbon,
nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium, based on
3,395 data points from 109 peer-reviewed studies.  Results showed
that the nutrient limitation control existed globally, but was only
applicable for the resorption of nitrogen, phosphorus, and potassium. The
stoichiometry control existed globally for carbon and all studied
nutrients, and coexisted with nutrient limitation control. Conifers’
resorption relied primarily on stoichiometry control rather than nutrient
limitation control. Nutrient limitation control was stronger in evergreen
angiosperms than in deciduous angiosperms. Our findings support the
ubiquity of both nutrient limitation and stoichiometry in controlling leaf
resorption for multiple nutrients, such that these controls should be
considered in Earth system models to better predict biogeochemical cycles
in terrestrial ecosystems.