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Soil mesofauna, such as Collembola and mites, are important decomposers in many ecosystems. In lawns, soil mesofauna have been implicated in the decomposition of thatch, an unsightly and problematic by-product of management found in many urban grasslands. In this study, we utilized a model lawn mesocosm experiment and ubiquitous soil mesofauna (Collembola: Isotomidae) to understand their role in thatch decomposition under a variety of simulated lawn management conditions. Our results showed that Collembola enhanced thatch decomposition by 6–8% over Collembola-absent treatments, with clipping additions moderating, and in some cases diminishing the role of Collembola in thatch decomposition. This finding was likely caused by substrate switching in the presence of clippings, and Collembola and clipping additions favoring unique aspects of microbial decomposition: Collembola enhanced oxidative enzymes, enhanced microbial biomass carbon, and marginally reduced microbial respiration, which are associated with oligotrophic microbes. Clipping additions generally increased hydrolytic enzymes, had little effect on microbial biomass, and enhanced respiration, which are associated with copiotrophic microbes. These contrasting results highlight the nuanced effects of soil mesofauna in enhancing thatch decomposition and suggest that management decisions related to lawn mowing may be equally important in mitigating thatch in lawns. • Thatch lost 4‐10% mass over 180 days. Collembola presence enhanced thatch decay by 6‐8%. • Collembola enhance enzyme production, microbial C, which are linked to microbial life history shifts. • Clippings reduce the Collembola effect on thatch decay, by stimulating hydrolytic enzymes and microbial respiration. [ABSTRACT FROM AUTHOR]

Abstract: Shifts in the density and composition of arthropod communities can alter soil carbon and nitrogen cycling dynamics. However, it is uncertain how factors such as land use intensity, litter chemical composition, and climate structure arthropod communities during decomposition. During a 730-day study, we characterized temporal changes in litter-colonizing arthropod communities in two litter types (corn, Zea mays, and grass, predominantly Bromus inermis) decomposing in three ecosystems representing an agricultural management intensity gradient (conventionally tilled, no-till, and old field). Further, to assess the relationships between litter chemistry and arthropod communities, we also correlated changes in arthropod densities and community composition with shifts in litter molecular chemical characteristics. Arthropod densities were greater in decomposing grass litter than in corn litter for seven out of thirteen taxa collected and all but two taxa increased in litter with management intensity (spiders – negative, Entomobryidae – no response). In contrast, total arthropod densities in soil decreased with management intensity. Temporal variation in arthropod density and community composition in litter corresponded with precipitation events and changes in litter chemistry during decomposition. For example, collembolan, oribatid, and mesostigmatid mite densities were negatively correlated with the relative abundance of lignin and positively correlated with nitrogen containing compounds. Our study demonstrates that the influence of agricultural management intensity on arthropods in litter is strikingly different from that in bulk soil, and suggests that management intensity interacts with litter chemistry and climate over the course of decomposition to determine both the density and composition of arthropod communities inhabiting litter at the soil surface. [Copyright &y& Elsevier]

The chemical complexity of decomposing plant litter is a central feature shaping the terrestrial carbon ( C) cycle, but explanations of the origin of this complexity remain contentious. Here, we ask: How does litter chemistry change during decomposition, and what roles do decomposers play in these changes? During a long-term (730 days) litter decomposition experiment, we tracked concurrent changes in decomposer community structure and function and litter chemistry using high-resolution molecular techniques. Contrary to the current paradigm, we found that the chemistry of different litter types diverged, rather than converged, during decomposition due to the activities of decomposers. Furthermore, the same litter type exposed to different decomposer communities exhibited striking differences in chemistry, even after > 90% mass loss. Our results show that during decomposition, decomposer community characteristics regulate changes in litter chemistry, which could influence the functionality of litter-derived soil organic matter ( SOM) and the turnover and stabilisation of soil C. [ABSTRACT FROM AUTHOR]

Highlights: [•] N fertilization reduced potentially mineralizable C by as much as 58%. [•] Total, light fraction, and permanganate oxidizable C were not influenced by N. [•] Soil and litter enzymes showed small, temporally variable responses to N. [•] Results do not support N fertilization as a contributor to depletion of C stocks. [Copyright &y& Elsevier]