Water's path from moss to soil Vol. 2: how soil-moss combinations affect soil water fluxes and soil loss in a temperate forest

Mosses are key components of many ecosystems and particularly related to water cycling. In principle, the importance of mosses for water-related processes is known; however, their influence is rarely quantified in scientific studies. To fill this research gap, this study concentrates on the influence of mosses of different species on surface runoff, the amount of percolated water, soil loss, and the temporal dynamics of soil water content. For this purpose, an experimental approach consisting of an ex situ rainfall simulation (45 mm h- 1 for 30 min) with infiltration boxes equipped with biocrust wetness probes was applied. On average, mosses significantly reduced surface runoff by 91% and soil loss by almost 100%, while the amount of percolated water was increased by 85% compared with bare soils. These processes were superimposed by desiccation cracks, and partly water repellency, with the result that the respective influences could not be quantified individually. However, by simultaneously measuring the water content in the substrates during rainfall simulations, we were able to achieve a better understanding of the water flows in the substrates. For instance, water content at 3 cm substrate depth was higher under mosses than in bare soils, implying that mosses facilitated infiltration. In this study, we were able to demonstrate that mosses play an important role in soil hydrology and in protecting the soil from erosion, and it is imperative that further experiments will be conducted to elucidate the apparently underestimated effects of mosses and their specific traits on soil water fluxes and sediment transport.