Establishing a moss cover inhibits the germination of Typha latifolia, an invasive species, in restored peatlands.
Invasion of Typha latifolia L. into man-made pools in restored North American peatlands may represent a serious barrier to the establishment of a plant community typical of natural pool edges. As no classical method of population management appears applicable in the context of peatlands, our aim was to determine the ability of three environmental factors to inhibit T. latifolia germination, namely peat type, shade level and moss cover. A split-plot experiment conducted in a growth chamber investigated the effects of three substrates (fibric peat, mesic peat and filter paper) and six shade levels (including total obscurity) on germination rates of T. latifolia. In a second, greenhouse experiment, the effect of three increments of moss cover (null, fragmented and full) growing on two peat types (fibric and mesic) was examined for six corresponding seedbeds. Our results show that peat type was the major factor affecting germination, as almost none occurred on fibric peat while germination rates reached 84% on mesic peat. However, germination on mesic peat decreased with increasing moss cover: the germination rate dropped from 36±3% on bare peat to 1±0% in full moss carpets. Germination of T. latifolia was initiated by very low light levels (as low as 6%) but was inhibited by total obscurity. The low pH of fibric peat as well as the modification of environmental factors (e.g. light or substrate access) by moss carpets appear to be factors explaining the results. Establishing a dense moss cover and digging pools to a depth that prevents the exposure of peat with a pH favorable to seed germination (above 4) might be efficient methods to reduce Typha latifolia invasions in restored peatland pools.