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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. [ABSTRACT FROM AUTHOR]

Forest microclimates can contrast substantially from the macroclimate outside forests. These microclimates regulate understory biodiversity and ecosystem functions. Studies have quantified the global patterns and driving factors of forest understory temperature offsets, but data from China were almost missing, making the global assessment incomplete. To fill this knowledge gap, we quantitatively synthesized 494 paired observations from China extracted from 91 publications to quantify mean (Tmean), maximum (Tmax) and minimum temperature offsets (Tmin). Results showed that (1) forest canopies significantly buffered understory Tmean and Tmax against macroclimatic temperature, with average offsets of 1.0 and 1.5°C, respectively, while understory Tmin offsets were not significantly different from zero; (2) forest type (broadleaved, mixed, vs. coniferous) and forest location (rural vs. urban) did not affect Tmean, Tmax or Tmin offsets, but climate zone and season showed significant impacts; and (3) macroclimatic temperature, wind speed, tree height and canopy density also impacted temperature offsets, although their effects varied among Tmean, Tmax and Tmin. Our results complement the global assessment of forest buffering capacity, and reiterate the necessity for incorporating microclimatic variability into future bioclimatic modelling of species demography and distributions. [ABSTRACT FROM AUTHOR]

Litter decomposition is a key ecological process that determines carbon (C) and nutrient cycling in terrestrial ecosystems. The initial concentrations of C and nutrients in litter play a critical role in this process, yet the global patterns of litter initial concentrations of C, nitrogen (N) and phosphorus (P) are poorly understood.We employed machine learning with a global database to quantitatively assess the global patterns and drivers of leaf litter initial C, N and P concentrations, as well as their returning amounts (i.e. amounts returned to soils).The medians of litter C, N and P concentrations were 46.7, 1.1, and 0.1%, respectively, and the medians of litter C, N and P returning amounts were 1.436, 0.038 and 0.004 Mg ha−1 year−1, respectively. Soil and climate emerged as the key predictors of leaf litter C, N and P concentrations. Predicted global maps showed that leaf litter N and P concentrations decreased with latitude, while C concentration exhibited an opposite pattern. Additionally, the returning amounts of leaf litter C, N and P all declined from the equator to the poles in both hemispheres.Synthesis: Our results provide a quantitative assessment of the global concentrations and returning amounts of leaf litter C, N and P, which showed new light on the role of leaf litter in global C and nutrients cycling. [ABSTRACT FROM AUTHOR]