Invasive earthworms unlock arctic plant nitrogen limitation

Abstract

Arctic plant growth is predominantly nitrogen (N) limited. This limitation is generally attributed to slow soil microbial processes due to low temperatures. Here, we show that arctic plant-soil N cycling is also substantially constrained by the lack of larger detritivores (earthworms) able to mineralize and physically translocate litter and soil organic matter. These new functions provided by earthworms increased shrub and grass N concentration in our common garden experiment. Earthworm activity also increased either the height or number of floral shoots, while enhancing fine root production and vegetation greenness in heath and meadow communities to a level that exceeded the inherent differences between these two common arctic plant communities. Moreover, these worming effects on plant N and greening exceeded reported effects of warming, herbivory and nutrient addition, suggesting that human spreading of earthworms may lead to substantial changes in the structure and function of arctic ecosystems.

Animal soil food web complexity triggers shifts in microbial communities, including PAH degraders, but without clear effects on phenanthrene phytoremediation

“…A field study looking at higher concentrations of mixed contaminants also showed significant decreases of the willow biomass in contaminated plots compared to controls (Brereton et al, 2016). Our results are also in line with the reported positive effects of earthworms on plant productivity (Blume-Werry et al, 2020;Van Groenigen et al, 2014), including during phytoremediation of lead (Jusselme et al, 2015). This effect has been previously attributed to the bioturbation (burrowing) activity of earthworms, that results in many beneficial effects for plants, such as improved soil porosity (Shipitalo and Le Bayon, 2004) leading to increased soil water infiltration (Bouché and Al-Addan, 1997) and aeration (Bartlett et al, 2010), organic matter degradation and increased nutrient cycling (Edwards, 1997).…”

Do Invasive Earthworms Affect the Functional Traits of Native Plants?

“…Surprisingly, although earthworms are known to decrease the spatial homogeneity of soil resource distribution (Shuster et al, 2001), we did not observe a strong modification of the plant belowground traits at the species and community level, which differed from what was shown in previous studies. Blume-Werry et al (2020) showed that fine root growth of the plant community was higher in the presence of exotic earthworms in meadows after 55 days and after 103 days of experiment independent of the vegetation type (meadows vs. heath, with plant communities mainly composed of forbs or shrubs, respectively, and grasses) than in the absence of earthworms. Cameron et al (2014) showed that the proportion of A. millefolium roots present in exotic earthworms burrows was important during the first month of growth, but root growth in soil cracks became similarly important after 2 and 3 months.…”

“…a meta-analysis showed that native earthworm effects become weak to non-significant the more fertile the soil is and with a high proportion of sand in the soil (van Groenigen et al, 2014). However, so far, few studies showed a modification of plant functional traits other than biomass-related traits with native or exotic earthworm presence (e.g., Wurst et al, 2003;Hale et al, 2008;Eisenhauer et al, 2009a;Laossi et al, 2009;Dávalos et al, 2013Dávalos et al, , 2015Cameron et al, 2014;Dobson et al, 2017;Agapit et al, 2018;Blume-Werry et al, 2020;Liu et al, 2020). With four of the studied traits that responded significantly to earthworms presence, our study partly confirmed our hypothesis that earthworms affect the traits related to plant resource uptake and development (hypothesis ii).…”

The Cold Region Critical Zone in Transition: Responses to Climate Warming and Land Use Change

“…The resulting soil biological responses alter the soil food web structure, net soil respiration, and provision of ecosystem services. For example, the establishment of humandispersed burrowing earthworms in subarctic Sweden, although currently still sparse, is expected to have potentially far-reaching consequences for soil hydrology, nutrient cycling, and carbon emissions if continued (103,104).…”