Quantifying the variation patterns and environmental controls of forest litterfall: A regional synthesis of...

Enhancing the strength of forest carbon sinks is critical in the wake of the accelerating global climate change and intensifying greenhouse effect. However, the regional patterns and environmental controls of forest litter, a major carbon pool and entry pathway from tree-to-soil systems, remain uncertain. Herein, we consolidated up to a decade of data from six ecological studies (totaling 28 stands) conducted across South Korea between 1999 and 2022 (spanning 23 years) to examine variations in total and component-based litterfall with geo-topography and climate. Linear mixed-effects models for leaf, non-leaf, and total litterfall were further developed to understand mechanistic litter-environment relationships and identify key abiotic factors controlling regional litterfall. Our analysis reveals a pronounced latitudinal pattern in total litterfall, with >37°N zones generating up to 54 % less litter than areas of lower range (p < 0.001). Leaf and non-leaf fractions varied significantly with slope (p < 0.01 for leaf; p < 0.001 for non-leaf), while only non-leaf litter responded substantially to elevation (p < 0.001). Total litterfall increased with rising growth season temperature but decreased with increasing precipitation. Our top-performing models adequately captured litterfall variation, as evidenced by conditional R² values of 0.77 (RMSE = 39.2 g m^-2), 0.93 (28.9 g m^-2), and 0.98 (7.4 g m^-2) for non-leaf, leaf, and total litter, respectively. Climate emerged as the main regulating factor for coarse-scale litterfall, with evapotranspiration largely explaining total and non-leaf litter and temperature strongly relating to leaf litter. Large-scale conservation strategies should therefore consider regional abiotic variations to ensure stable plant-soil-atmosphere feedbacks and improve the preparedness of natural systems against the detrimental impacts of climate change.