Do invasive jumping worms impact sugar maple (Acer saccharum) water-use dynamics in a Central Hardwoods forest?

Abstract

Although non-native earthworms are known to drastically change forest soils and understory plant communities, comparatively little is known about how the introduction of different earthworm groups may alter perennial plant functioning (i.e., physiological, morphological, and/or anatomical traits), or how these dynamics may vary between different earthworm groups. Our objective was to assess whether a recent replacement of European earthworms by Amynthas spp. (i.e., Asian “jumping worms”) in a Central Hardwoods forest of the Upper Midwest impacts patterns of water use in dominant overstory Acer saccharum Marshall (sugar maple). We found that (1) soil water content was often greater in Amynthas sites, (2) compared to those growing in sites with only European earthworms, A. saccharum growing with Amynthas had higher midday leaf water potential values (a measure of greater plant water status) early in 2017 but lower midday leaf water potential by the end of 2018, and (3) A. saccharum from Amynthas sites had fewer, but wider xylem conduits than trees from European sites, but this trend was not significant and was not associated with differences in stem hydraulic functioning between the two groups. Overall, these results suggest that Amynthas invasions may not impact the overstory of A. saccharum—dominated forests within the Upper Midwest, at least early during invasions of forests colonized by existing earthworms or during growing seasons with above-average precipitation. Future work should investigate the impacts of different earthworm groups on tree water and nutrient relations over longer periods of colonization and in different tree age classes.