Variability and drivers of litter water-holding parameters in subtropical China based on field experiments and meta-analysis

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Study region This study examined litter water-holding characteristics at local and regional scales in subtropical China. Field experiments were conducted in the upper Pi River basin, while regional patterns were assessed using published data across subtropical China. Study focus This study quantified variation in litter water-holding characteristics and identified their controlling factors. Field experiments measured the maximum water-holding rate (MWHR) of different forest types and litter components. The effects of litter properties and decomposition on MWHR were evaluated. A meta-analysis assessed regional variation in natural water-holding rate (NWHR), MWHR, and effective water-retention rate (EWRR), and their responses to environmental gradients. New hydrological insights for the region MWHR reached 249.24% in deciduous broadleaf forests and 223.56% in bamboo forests. It differed among litter components in the order leaves > roots > stems > fruits. Litter chemical and optical properties explained 54%–88% of MWHR variation, with total carbon, lignin content, and color tone coefficient as key predictors. MWHR initially increased and then decreased during decomposition. Across subtropical China, mean NWHR, MWHR, and EWRR were 40.7%, 232.2%, and 146.5%, respectively. NWHR and MWHR decreased with increasing temperature but increased with elevation (p < 0.001). These results show that litter water retention is controlled by litter traits, decomposition, and environmental gradients. The quantified parameters can improve the representation of litter water storage in forest hydrological models.