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The forest headwater streams are important hubs for connecting terrestrial and aquatic ecosystems, with plant litter and sediments as the major carriers for material migrations; however, until now we knew little about the dynamics of trace elements such as iron (Fe) and aluminum (Al) in forest headwater streams. Here, we quantitatively identified the spatiotemporal dynamics of Fe and Al storages in plant litter and sediments and their influencing factors in a subtropical forest headwater stream, and assessed the potential pollution risk. The results showed that: (1) the mean concentrations of Fe and Al in plant litter (sediments) were 5.48 and 8.46 (7.39 and 47.47) g·kg−1, and the mean storages of Fe and Al in plant litter (sediments) were 0.26 and 0.43 (749.04 and 5030.90) g·m−2, respectively; (2) the storages of Fe and Al in plant litter and sediments significantly fluctuated from January to December, and showed a decreasing pattern from the source to mouth; and (3) storages of Fe and Al had no significant correlation with riparian forest type and the present of tributary and the Fe and Al storages in plant litter were mainly affected by water temperature and water alkalinity, and their storages in sediments were mainly affected by water temperature and frequency of rainfall; and (4) there were no anthropogenic pollution in Fe and Al in the forest headwater stream. Our study revealed the primary factors of concentrations and storages of Fe and Al in plant litter and sediments in a forest headwater stream, which will improve our understanding of the role of headwater streams in forest nutrient storage and cycling along with hydrological processes. [ABSTRACT FROM AUTHOR]

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]

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]

Soluble components leach rapidly during the early stage of litter decomposition and represent the earliest nutrient input to the soils after leaf fall, which have significant importance for the material cycle in ecosystems. However, the concentration characteristics and primary drivers of litter soluble components at the global scale remain unclear. Therefore, 303 observations of water soluble compounds (WSCs), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) and auxiliary plant functional traits (mycorrhizal association, taxon division, plant life form, and leaf type) were collected worldwide. Linear mixed-effect models were used to examine the relative effects of climate, soil, topography, and plant functional traits on the concentration of different soluble components of litter. The average concentrations of leaf litter WSCs, DOC, and DON were 22.50, 4.15, and 0.01%, respectively. The concentration of WSCs in leaf litter was regulated by plant functional traits and soil properties, with mycorrhizal association and soil microbial biomass carbon to nitrogen ratio as the primary drivers. The concentration of DOC in leaf litter was influenced by climate and topography, with elevation being the most important factor. Our study reveals the global patterns and drivers of different soluble components in leaf litter, which is crucial for predicting litter decomposition under future climate change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Termites enhanced litter decomposition by an average of 41.2% globally. • Termites displayed much stronger effects in forests than in grassland. • Termites played a greater role in decomposing woody litter than foliar litter. • MAP primarily dominated the termite-drived litter decomposition. Termites play a vital role in litter decomposition, yet a comprehensive global-scale quantitative analysis of their effects and key drivers still needs to be developed. Here, we conducted a meta -analysis using 187 observations to evaluate the impacts and drivers of termite influence on litter decomposition. Our findings revealed that termites enhanced litter decomposition by an average of 41.2% globally, with mean annual precipitation (MAP) being the primary factor driving termite effects. Moreover, termites exert a more substantial influence on woody litter decomposition compared to foliar litter, whereas they play a more influential role in forests than in grasslands, showing a more significant impact on litter placed on the soil surface than underground. Additionally, MAP acts as the sole dominant driver of decomposition in woody litter, while both MAP and mean annual temperature (MAT) are the key factors affecting the termite-drived litter decomposition in the forest. MAP, MAT and elevation were also detected as the dominant factors in regulating the degradation of plant debris when litter is placed on the soil surface or using meshbag to exclude termites. Our results indicated that termites could significantly contribute to litter decomposition, and MAP mainly derives these material recycling processes globally and regionally. [ABSTRACT FROM AUTHOR]