Animals & nature · 2026
Is the soil beneath established moss on stream banks wetter or drier than bare soil?
It was generally drier. In a two-year field experiment along streams in Illinois and Virginia, soil beneath established moss mats held less moisture than bare soil at most sites and sampling times. Newly introduced moss did not show a clear moisture difference from bare soil, so the finding does not apply to every moss covering.
Details
Researchers studied 56 stream-bank sites, comparing naturally moss-covered soil, naturally bare soil, soil where moss was added and soil where moss was removed. They measured moisture at depths of 4, 6 and 8 centimeters during several seasonal sampling periods.
Soil beneath established moss mats was drier than bare soil, and removing established mats increased soil moisture relative to plots that remained moss-covered. Newly introduced mats, however, had soil moisture similar to bare plots. This suggests that how established and structurally intact a moss mat is matters, rather than moss presence alone. Moisture responses also differed between the regions, most noticeably during rainy periods.
The authors propose that established mats catch rainfall and likely lose more water through evaporation from their surfaces, leaving less water to enter the soil below. That mechanism is an explanation for the findings, not a separately demonstrated result in the abstract. The evidence concerns shallow soil along the studied temperate streams, not all mosses or environments.
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