The soils of streets, urban parks and suburban areas were examined for yeasts in the summer of 2020 on the territory of the southern cities of Russia and the Republic of Crimea: Krasnodar, Maykop, Sochi and Simferopol. The results of this study are compared with the results of a previous study carried out in these cities in 2019. This study was conducted three months after the lockdown due to the COVID-19 pandemic, which led to a sustained decline in household waste deposition in these areas. The number of tourists visiting these southern cities decreased significantly, and the number of walkers and visitors to urban parks fell sharply. In 2020, after the decline of household waste loads, the yeast abundance was slightly but reliably higher than in 2019. A total of 30 yeast species were observed - 11 ascomycetes and 19 basidiomycetes. This was more than in 2019 and was caused by twice as many autochthonous basidiomycetous yeast species (natural core community), which were found in urban soils only after the reduction in household waste in the environment - , And at the same time, the proportion of clinically significant (opportunistic) yeasts, and , was much lower in 2020 than in 2019. Thus, the observed changes in yeast communities in urban soils could be a short-time response of the microbial community to a reduction in household waste.

A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with detritivore diversity are key to advancing our understanding of litter mass loss in nature.

Soil microorganisms are the main primary decomposers of plant material and drive biogeochemical processes like carbon and nitrogen cycles. Hence, knowledge of their nutritional demands and limitations for activity and growth is of particular importance. However, potential effects of the stoichiometry of soil and plant species on soil microbial activity and carbon use efficiency are poorly understood. Soil properties and plant traits are assumed to drive microbial carbon and community structure. We investigated the associations between C and N concentrations of leaf, root, and soil as well as their ratios and soil microbial biomass C and activity (microbial basal respiration and specific respiratory quotient) across 32 young native angiosperm tree species at two locations in Central Germany. Correlations between C:N ratios of leaves, roots, and soil were positive but overall weak. Only regressions between root and leaf C:N ratios as well as between root and soil C:N ratios were significant at one site. Soil microbial properties differed significantly between the two sites and were significantly correlated with soil C:N ratio across sites. Soil C concentrations rather than N concentrations drove significant effects of soil C:N ratio on soil microbial properties. No significant correlations between soil microbial properties and leaf as well as root C:N ratios were found. We found weak correlations of C:N ratios between plant aboveground and belowground tissues. Furthermore, microorganisms were not affected by the stoichiometry of plant tissues in the investigated young trees. The results suggest that soil stoichiometry represents a consistent determinant of soil microbial biomass and respiration. Our study indicates that stoichiometric relationships among tree organs can be weak and poor predictors of soil microbial properties in young tree stands. Further research in controlled experimental settings with a wide range of tree species is needed to study the role of plant chemical traits like the composition and stoichiometry of root exudates in determining interactions between above- and belowground compartments.

Global change alters the composition and functioning of ecosystems by creating novel environmental conditions and thereby selecting for specific traits of organisms. Thus, trait-based approaches are promising tools to more mechanistically understand compositional and functional shifts in ecological communities as well as the dependency of response and effect traits upon global change. Such approaches have been particularly successful for the study of plant communities in terrestrial ecosystems. However, given the intimate linkages between aboveground and belowground compartments as well as the significance of plants as integrating organisms across those compartments, the role of plant traits in affecting soils communities has been understudied. This special issue contains empirical studies and reviews of plant trait effects on soil organisms and functions. Based on those contributions, we discuss here plasticity in trait expression, the context-dependency of plant trait effects, time lags in soil biotic responses to trait expression, and limitations of measured plant traits. We conclude that plant trait-based approaches are an important tool to advance soil ecological research, but also identify critical limitations and next steps.

Soil respiration is an essential component of carbon (C) cycling in terrestrial ecosystems. Despite increasing awareness of the significance of aboveground-belowground interactions, little is known about tree diversity effects on soil respiration and the underlying mechanisms. Here, we conducted a 105-days microcosm experiment in a climate chamber to test the effects of tree diversity (1, 2, and 4 species) on soil respiration. We expected tree diversity to affect soil respiration through changes in tree growth and surface litter decomposition (indicated by the litter mass loss). Our results show that soil respiration varied among the four focal tree species and increased with tree species richness. Path analysis revealed tree growth as the main mechanism driving soil respiration and explaining the tree diversity effect in this short-term experiment. Our results indicate that tree diversity and particular tree traits regulate C dynamics through balancing C storage (plant productivity) and C release (soil respiration).

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decades ago, and we have gained important insights into the functioning of soils, there still are fundamental aspects that need to be better understood to ensure that the ecosystem services that soils provide are not lost and that soils can be used in a sustainable way. In this perspectives paper, we highlight some of the major knowledge gaps that should be prioritized in soil ecological research. These research priorities were compiled based on an online survey of 32 editors of Pedobiologia - Journal of Soil Ecology. These editors work at universities and research centers in Europe, North America, Asia, and Australia.The questions were categorized into four themes: (1) soil biodiversity and biogeography, (2) interactions and the functioning of ecosystems, (3) global change and soil management, and (4) new directions. The respondents identified priorities that may be achievable in the near future, as well as several that are currently achievable but remain open. While some of the identified barriers to progress were technological in nature, many respondents cited a need for substantial leadership and goodwill among members of the soil ecology research community, including the need for multi-institutional partnerships, and had substantial concerns regarding the loss of taxonomic expertise.

Earthworms (Oligochaeta: Lumbricidae) have substantial effects on the structure and fertility of soils with consequences for the diversity of plant communities and associated ecosystem functions. However, we still lack a clear understanding of the functional role earthworms play in terrestrial ecosystems, partly because easy-to-use methods to quantify their activities are missing. In this study, we tested whether earthworms and their casts can be dual-labelled with N and C stable isotopes by cultivating them in soil substrate amended with N ammonium nitrate and C-glucose. Additionally, we also wanted to know whether (i) earthworms from different functional groups (soil-feeders vs. litter-feeders) and their casts would differ in their incorporation of stable isotopes, (ii) if enrichment levels are higher if the same amount of isotopes is applied in one dose or in staggered doses, and (iii) if isotopic enrichment in casts changes when they are stored in a conditioning cabinet or in a pot filled with soil placed in a greenhouse. Our findings show the feasibility of dual-labelling tissues and casts of both litter-feeding () and soil-feeding () earthworms using the same method. The advantage of this method is that earthworms and their casts can be labelled under realistic conditions by cultivating them for only four days in soil that received a one-time addition of commercially available stable isotopes instead of offering labelled plant material. In earthworms, the isotopic enrichment remained at a stable level for at least 21 days; labelled casts could be stored for at least 105 days without significantly decreasing their isotopic signals. This simple and efficient method opens new avenues for studying the role of these important ecosystem engineers in nutrient cycling and their functional relationships with other organisms.