Despite decades of research, our understanding of the importance of invertebrates for soil biogeochemical processes remains incomplete. This is especially true when considering soil invertebrate effects mediated through their interactions with soil microbes. The aim of this study was to elucidate how soil macroinvertebrates affect soil microbial community composition and function within the root zone of a managed grass system. We conducted a 2-year field mesocosm study in which soil macroinvertebrate communities were manipulated through size-based exclusion and tracked changes in microbial community composition, diversity, biomass and activity to quantify macroinvertebrate-driven effects on microbial communities and their functions within the rhizosphere. The presence of soil macroinvertebrates created distinct microbial communities and altered both microbial biomass and function. Soil macroinvertebrates increased bacterial diversity and fungal biomass, as well as increased phenol oxidase and glucosidase activities, which are important in the degradation of organic matter. Macroinvertebrates also caused distinct shifts in the relative abundance of different bacterial phyla. Our findings indicate that within the rhizosphere, macroinvertebrates have a stimulatory effect on microbial communities and processes, possibly due to low-intensity microbial grazing or through the dispersal of microbial cells and spores by mobile invertebrates. Our results suggest that macroinvertebrate activity can be an important control on microbially-mediated processes in the rhizosphere such as nitrogen mineralization and soil organic matter formation.

Urban soils differ from those in other managed ecosystems in many ways, including their heterogeneity, unique organic matter inputs and exposure to past and present anthropogenic activities. Soil processes in urban systems are influenced by the microbiome, specifically bacterial and fungal communities that are currently recognized as the primary drivers of soil organic matter dynamics. However, our understanding of biotic controls on microbial communities is incomplete, particularly in regard to the roles of invertebrates. We aim to highlight how invertebrates and their interactions with microbial communities may shape ecosystem processes in urban systems. We discuss three primary pathways through which invertebrates are known to influence the soil microbiome: dispersal of microorganisms throughout soils, grazing on microbial biomass, and mixing of organic inputs within soils and subsequently altering microbial resource accessibility. These invertebrate-mediated pathways may be particularly important because of their influence on soil microbiomes of urban systems. We also propose future research directions aimed at quantifying the influence of invertebrates on soil microbial processes to gain a more comprehensive understanding of urban microbiome function. Understanding the impact of invertebrates on the microbiome of urban systems can potentially lead to better management of microbiomes and enhance microbe-driven ecosystem services.

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Land-use change is highly dynamic globally and there is great uncertainty about the effects of land-use legacies on contemporary environmental performance. We used a chronosequence of urban grasslands (lawns) that were converted from agricultural and forested lands from 10 to over 130 years prior to determine if land-use legacy influences components of soil biodiversity and composition over time. We used historical aerial imagery to identify sites in Baltimore County, MD (USA) with agricultural versus forest land-use history. Soil samples were taken from these sites as well as from existing well-studied agricultural and forest sites used as historical references by the National Science Foundation Long-Term Ecological Research Baltimore Ecosystem Study program. We found that the microbiomes in lawns of agricultural origin were similar to those in agricultural reference sites, which suggests that the ecological parameters on lawns and reference agricultural systems are similar in how they influence soil microbial community dynamics. In contrast, lawns that were previously forest showed distinct shifts in soil bacterial composition upon recent conversion but reverted back in composition similar to forest soils as the lawns aged over decades. Soil fungal communities shifted after forested land was converted to lawns, but unlike bacterial communities, did not revert in composition over time. Our results show that components of bacterial biodiversity and composition are resistant to change in previously forested lawns despite urbanization processes. Therefore land-use legacy, depending on the prior use, is an important factor to consider when examining urban ecological homogenization.

Because of public concern about exposing children to pesticides, legislation restricting its use on school playing fields has increased. One way to manage weeds without chemical herbicides is overseeding or the practice of repetitively seeding with a rapidly germinating turfgrass species. Overseeding for broadleaf weed control was tested on eight fields in Central New York (CNY) for three seasons and 40 fields across the northeastern United States for two seasons. Half of each field was treated each season by overseeding Lolium perenne L. (perennial ryegrass) three to five times each season for a total of 731 kg seed/ha (15 lb per 1000 ft2). Changes in the percent broadleaf weeds, grass, bare ground, soil moisture, Dark Green Color Index (DGCI) of grass cover, depth to soil compaction, and shear strength were measured after each treatment. The percent broadleaf weeds decreased and the percent grass cover increased due to overseeding in the Northeast fields, but not in CNY fields. Depth to compaction, percent soil moisture, and shear strength varied over time in the Northeast fields, and the percent bare ground, DGCI, and soil moisture varied over time in CNY fields. DGCI in the Northeast and soil compaction in CNY were affected by the interaction of overseeding × time. Although overseeding can be a beneficial weed management tool and affect other turf and soil traits in an integrated turf management program, monitoring environmental conditions and supporting field maintenance routines are critical weed management strategies for maintaining healthy turfgrass.

Land-use change is highly dynamic globally and there is great uncertainty about the effects of land-use legacies on contemporary environmental performance. We used a chronosequence of urban grasslands (lawns) that were converted from agricultural and forested lands from 10 to over 130 years prior to determine if land-use legacy influences components of soil biodiversity and composition over time. We used historical aerial imagery to identify sites in Baltimore County, MD (USA) with agricultural versus forest land-use history. Soil samples were taken from these sites as well as from existing well-studied agricultural and forest sites used as historical references by the National Science Foundation Long-Term Ecological Research (NSF-LTER) Baltimore Ecosystem Study program. We found that the microbiomes in lawns of agricultural origin were similar to those in agricultural reference sites, which suggests that the ecological parameters on lawns and reference agricultural systems are similar in how they influence soil microbial community dynamics. In contrast, lawns that were previously forest showed distinct shifts in soil bacterial composition upon recent conversion but reverted back in composition similar to forest soils as the lawns aged over decades. Soil fungi did not follow similar trends as the bacteria in the previously forested lawns. Our results show that components of bacterial biodiversity and composition are resistant to change in previously forested lawns despite urbanization processes. Therefore land-use legacy, depending on the prior use, is an important factor to consider when examining urban ecological homogenization.

With increasing urbanization and critical issues of food insecurity emerging globally, urban agriculture is expanding as an agroecosystem with a distinct soil type. Growing food in cities is challenged by legacy contaminants in soils, which necessitates the use of imported, safe soils and composts. To promote the long-term sustainability of urban agriculture, we examined the agronomic potential of constructing safe, locally sourced soils to support food production. We collected composts from four municipal composting facilities in New York City: Big Reuse, Long Island City, Queens (BRL), New York Department of Sanitation, Fresh Kills, Staten Island (DNY), Lower Eastside Ecology Center (LES) and Queens Botanic Garden (QBG). We then created two types of constructed soils using each compost: 100% pure compost and a 50:50 blend of compost and clean excavated sediments from the New York City Clean Soil Bank. We then assessed the growth of tomato, pepper and kale in the constructed soils within a plant growth chamber facility. We found Clean Soil Bank sediments enhanced tomato aboveground biomass production by 98%, kale aboveground biomass production by 50% and pepper plant height by 52% when mixed with compost from BRL. At the same time, Clean Soil Bank Sediments decreased tomato plant height by 16% and aboveground biomass production by 29% in LES compost and tomato plant height by 18% in QBG compost, likely due to compost properties. The addition of Clean Soil Bank sediments showed no decline in the symbiosis of arbuscular mycorrhizal fungi across all composts, which is an important beneficial plant–microbe interaction in agroecosystems. A positive ecosystem service was found when Clean Soil Bank sediments were added to municipal composts, with up to a 74% decrease in greenhouse gas emissions of soil CO2 in BRL compost. The results indicate that urban agricultural soils can be constructed using clean, locally sourced materials, such as composted organic waste and excavated sediments from city development sites to support sustainable urban agriculture while enhancing ecosystem services.