Climate and soil properties regulate the initial concentrations of potassium, calcium and magnesium in plant litter on a global scale

The initial concentration of litter nutrient not only affects the following decomposition process but also determines the quantities of nutrients returned to the soil. The aim of this study is to assess the global patterns and driving factors of three macronutrients, namely potassium (K), calcium (Ca) and magnesium (Mg), in freshly fallen litter. By synthesizing 5861 data points extracted from 584 publications, we quantitatively evaluated the concentrations of litter K, Ca and Mg in different litter types, life forms, taxonomic divisions and mycorrhizal associations. Also, using the machine learning method, we predicted their global patterns in forests, grasslands and shrublands. We found that (1) mean K, Ca and Mg concentrations ranged from 2.63 to 6.23, 1.05 to 11.50 and 0.20 to 2.74 g/kg, respectively, across different litter types; (2) the initial nutrients of the litter were significantly affected by plant functional types (e.g. life form, taxonomic division and mycorrhizal association), climate (e.g. isothermality, mean diurnal range, annual evapotranspiration and precipitation seasonality) and soil properties (e.g. pH, exchangeable Ca concentration and water content), with a higher litter K concentration of herbaceous plants, higher K, Ca and Mg concentrations from angiosperms and higher K and Mg concentrations from plants associated with arbuscular mycorrhiza (AM) fungi; and (3) the predicted leaf litter K, Ca and Mg concentrations were lower in high-latitude regions compared with those in low- and/or mid-latitude regions. Our study provides a globally comprehensive analysis on the patterns and driving factors of three important macronutrients in freshly fallen litter, contributing to a better understanding of their role in the decomposition process of litter, as well as the associated biogeochemical cycles under the future climate change scenario.Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.image