DOI: 10.5061/dryad.nvx0k6drc
title: EFFECTS OF MICROPLASTICS AND DROUGHT ON SOIL ECOSYSTEM FUNCTIONS AND MULTIFUNCTIONALITY

description:   Microplastics in soils have become an important threat for
 terrestrial systems as they may potentially alter the
 geochemical/biophysical soil environment and can interact with drought. As
 microplastics may affect soil water content, this could exacerbate the
 well-known negative effects of drought on ecosystem functionality. Thus,
 functions including litter decomposition, soil aggregation or those
 related with nutrient cycling can be altered. Despite this potential
 interaction, we know relatively little about how microplastics, under
 different soil water conditions, affect ecosystem functions and
 multifunctionality. To address this gap, we performed an experiment using
 grassland plant communities growing in microcosms. Microplastic fibers
 (absent, present) and soil water conditions (well-watered, drought), were
 applied in a fully factorial design. At harvest, we measured soil
 ecosystem functions related to nutrient cycling (ß-glucosaminidase,
 ß-D-cellobiosidase, phosphatase, ß-glucosidase enzymes), respiration,
 nutrient retention, pH, litter decomposition and soil aggregation (water
 stable aggregates). As terrestrial systems provide these functions
 simultaneously, we also assessed ecosystem multifunctionality, an index
 that encompasses the array of ecosystem functions measured here. We found
 that the interaction between microplastic fibers and drought affected
 ecosystem functions and multifunctionality. Drought had negatively
 affected nutrient cycling by decreasing enzymatic activities by up to ~39
 %, while microplastics increased soil aggregation by ~18 %, soil pH by ~4
 %, and nutrient retention by up to ~70 % by diminishing nutrient leaching.
 Microplastic fibers also impacted soil enzymes, respiration and ecosystem
 multifunctionality, but importantly, the direction of these effects
 depended on soil water status. That is, under well-watered conditions,
 these functions decreased with microplastic fibers by up to ~34 % while
 under drought they had similar values irrespective of the microplastic
 presence, or tended to increase with microplastics. Litter decomposition
 had a contrary pattern increasing with microplastics by ~6 % under
 well-watered conditions while decreasing to a similar percentage under
 drought. Synthesis and applications. Single ecosystem functions can be
 positively or negatively affected by microplastics fibers depending on
 soil water status. However, our results suggest that microplastic fibers
 may cause negative effects on ecosystem soil multifunctionality of a
 similar magnitude as drought. Thus, strategies to counteract this new
 global change factor are necessary
description: An experiment in the greenhouse was established. A plant
 community (7 plant species) grew in pots in a factorial design that
 included drought and microplastics in the soil as treatments. At harvest,
 different soil ecosystem functions were measured. 
description: shootmass = g WSA = water stable aggregates
 (%) soilrespiration = net_Co2_ppm
 Enzymes = umol g-1 h-1 decomposition = litter
 decomposition ( %) Nutrients =  mg/l