Effects of Microplastic Fibers and Drought on Plant Communities

Abstract

Microplastics in soils can affect plant performance, as shown in studies using individual plants. However, we currently have no information about potential effects on plant community productivity and structure. In a plant community consisting of seven plant species that co-occur in temperate grassland ecosystems, we thus investigated the effect of microplastics (i.e., microfibers) and drought, a factor with which microfibers might interact, on plant productivity and community structure. Our results showed that at the community level, shoot and root mass decreased with drought but increased with microfibers, an effect likely linked to reduced soil bulk density, improved aeration, and better penetration of roots in the soil. Additionally, we observed that microfibers affected plant community structure. Species such as Calamagrostis , invasive in Europe, and the allelophatic Hieracium , became more dominant with microfibers, while species that potentially have the ability to facilitate the establishment of other plant species (e.g., Holcus ), decreased in biomass. As microfibers affect plant species dominance, the examination of cascade effects on ecosystem functions should be a high priority for future research.

Effects of Microplastics and Drought on Ecosystem Functions and Multifunctionality

“…Soil was mixed in all experimental units in order to provide the same level of disturbance. For additional details see Lozano and Rillig (2020).…”

“…To calculate ecosystem multifunctionality we followed the ecosystem function multifunctionality method proposed by Manning et al (2018). Briefly, we identified the clusters of 12 ecosystem functions ( Figure S1), which included the soil functions measured in this study and total shoot mass (raw data obtained from Lozano and Rillig (2020)). This cluster analysis allowed us to give more even weights to the ecosystem functions as they are interrelated and shared drivers.…”

“…Microplastic fibers promoted soil aggregation either under well-watered or drought conditions, likely due to positive effects of fibers on soil bulk density, aeration and water retention (de Souza Machado et al, 2019), which may promote root growth (Lozano & Rillig, 2020) and hyphal extension (Elliot & Coleman, 1988;Wang et al, 2017). Therefore, roots, hyphae and microplastic fibers might together have helped entangle soil particles, thus promoting soil aggregation.…”

“…For instance, microplastic fibers can enhance soil water holding capacity and so lead to the retention of water for longer periods (de Souza Machado et al, 2019), thus altering soil water conditions, and potentially influencing ecosystem functions. Indeed, microplastic fibers may promote plant growth and other processes (de Souza Machado et al, 2019), and this could alleviate drought conditions promoting plant productivity at the community level (Lozano and Rillig, 2020). All of this suggests that microplastic effects on ecosystem functionality may be exacerbated when other global change drivers, such as drought, come into play.…”

“…Results from linear models on eleven ecosystems functions and multifunctionality response to microplastic fibers (M), drought (D) and their interaction (M x D).Multifunctionality also included shoot mass (data extracted fromLozano and Rillig, 2020).Degrees of freedom of each factor (df =1). F values and p-values (in parentheses) are shown; p values <0.1 in bold.…”