Climate change alters slug abundance but not herbivory in a temperate grassland

abundance through changes in plant community dynamics and forage quality. However, it is important to note that there was a significant effect of slug herbivory in the heated plots during the spring of 2013 when the differences in plant community and forage quality were minimal (unpublished data), suggesting that climate treatments were also directly influencing slug activity. Increasing temperatures have been reported to increase the herbivory of D. reticulum by reducing the presence of D. reticulum’s nematode parasite, Phasmarhabditis hermaphrodita [51]. Phasmarhabditis hermaphrodita is not common in the United States, but it is possible that temperature impacts on slug predator species could result in changes in slug herbivory patterns, such as that found in this study. Conclusions Slugs did not have an impact on plant biomass production and community dynamics in this hay-managed pasture of central Kentucky under current climatic conditions or the imposed climate treatments (e.g., increased temperatures and additional precipitation), except in the early growing season when slug herbivory and abundance were directly stimulated by increased temperatures. Later in the season abundance appeared to be related to both direct and indirect effects of the imposed climate treatments. Increased precipitation buffered the negative impacts of hot and dry conditions in late summer and early fall on slug abundance, but differences at this time of the year between heated and non-heated plots may have been

related to a direct negative effect of heat on slugs and/or a decrease in plant %N and forage quality associated with heat-driven changes in the plant community. Although slug abundance was sensitive to abiotic and biotic changes resulting from the climate change treatments, the limited effect of slug herbivory measured with exclosures warrants greater study. Impacts of climate change on slug herbivory were not observed in this study, likely due to low slug abun- dance, as others have found changes in slug herbivory with climate [12, 15, 27]. In areas where slugs are more abundant or in grasslands dominated by annual species where seedlings are abundant each year [45], the effect of climate change on slug herbivory may be more pro- nounced and important for continued ecosystem function. Supporting information S1 Table. Pairwise comparisons of the plant species cover estimates for the climate treat- ments done with MRPP analysis in the ordination, showing that the plant community of all heated plots differed significantly from that of the non-heated plots. Bolding indicates significance. (PDF) S1 Fig. Paired slug control (left) and exclosure (right) rings within an experimental climate treatment plot (photo by D. Weber). (TIF) S2 Fig. Relationship between slug length and mass developed from Deroceras reticulatum caught on-site and used to convert slug abundance data from trapping in the treatments to mass estimates. (TIF) S3 Fig. Histogram of the number of slugs of each size that were trapped during the 2013 season. Sizes range from 2.5 mm to 35 mm. (TIF) PLOS ONE

Slug herbivory & climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0283128 March 14, 2023 14 / 17