Toronto | Earthworms may be a threat to plant diversity in natural ecosystems, according to a new study that found a link between the presence of the invertebrates and reductions in the abundance of trees and other plant species.
Researchers visited 40 parcels in 5 sugar maple forests in the understory of sugar maple forests in southern Quebec in Canada, finding earthworms in half of all the sites.
Their analysis uncovered a correlation between the number of earthworms and the abundance and diversity of certain understory species. New shoots of red maple, striped maple, American beech, and two fern species became rarer as earthworm populations increased.
The presence of earthworms does however seem to be good for ash trees and grasses. The most likely explanation is that the earthworms consume organic matter in forest litter, said Line Lapointe from Laval University in Canada.
This results in soils that can’t hold as much moisture, and that in turn interferes with seed germination and the ability of some species’ plantlets to survive, Lapointe said.
Earthworms have started to change plant composition in sugar maple forests. If nothing is done, these changes could become more pronounced and spread to other forest communities, she said.
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