Artificial light at night (ALAN) causes shifts in soil communities and functions

Abstract

Artificial light at night (ALAN) is increasing worldwide, but its effects on the soil system have not yet been investigated. We tested the influence of experimental manipulation of ALAN on two taxa of soil communities (microorganisms and soil nematodes) and three aspects of soil functioning (soil basal respiration, soil microbial biomass and carbon use efficiency) over four and a half months in a highly controlled Ecotron facility. We show that during peak plant biomass, increasing ALAN reduced plant biomass and was also associated with decreased soil water content. This further reduced soil respiration under high ALAN at peak plant biomass, but microbial communities maintained stable biomass across different levels of ALAN and times, demonstrating higher microbial carbon use efficiency under high ALAN. While ALAN did not affect microbial community structure, the abundance of plant-feeding nematodes increased and there was homogenization of nematode communities under higher levels of ALAN, indicating that soil communities may be more vulnerable to additional disturbances at high ALAN. In summary, the effects of ALAN reach into the soil system by altering soil communities and ecosystem functions, and these effects are mediated by changes in plant productivity and soil water content at peak plant biomass. This article is part of the theme issue ‘Light pollution in complex ecological systems’.

Light pollution in complex ecological systems

“…In this experiment, Dyer et al [35] report an increase in invertebrate movement activity at night, which is linked to higher predation rates. Cesarz et al [36] also report significant effects on soil communities and functioning (in this case, soil basal respiration and carbon use efficiency). However, Grenis et al [37] reveal contrasting effects on community composition of moths in response to skyglow and point-light sources.…”

“…R. Soc. B 378: 20220351 [52], plant production [34], soil respiration [36] and movement activity and space use [35,38]. Such changes in processes and functions can have strong consequences for species interactions and ecological networks that constitute entire communities [53].…”

“…Cesarz et al . [ 36 ] also report significant effects on soil communities and functioning (in this case, soil basal respiration and carbon use efficiency). However, Grenis et al .…”

“…However, there is still much work to be done to systematically understand community-level responses to light pollution across ecosystem types. Research in this issue demonstrates significant effects of ALAN on community composition of grassland plant communities [ 34 ], terrestrial above- [ 29 , 37 ] and belowground [ 36 ] as well as freshwater invertebrate communities [ 51 ]. Going beyond such ecosystem boundaries, Parkinson & Tiegs [ 28 ] conducted their research at the intersection of aquatic and terrestrial systems.…”

“…Notably, alterations in both physiology and behaviour can exert significant influence on fundamental ecological processes and functions [ 39 ]. Research in this issue reveals significant effects on growth and development of marine invertebrates [ 52 ], plant production [ 34 ], soil respiration [ 36 ] and movement activity and space use [ 35 , 38 ]. Such changes in processes and functions can have strong consequences for species interactions and ecological networks that constitute entire communities [ 53 ].…”