Cascading effects of moth outbreaks on subarctic soil food webs

The increasing severity and frequency of natural disturbances requires a better understanding of their effects on all compartments of biodiversity. In Northern Fennoscandia, recent large-scale moth outbreaks have led to an abrupt change in plant communities from birch forests dominated by dwarf shrubs to grass-dominated systems. However, the indirect effects on the belowground compartment remained unclear. Here, we combined eDNA surveys of multiple trophic groups with network analyses to demonstrate that moth defoliation has far-reaching consequences on soil food webs. Following this disturbance, diversity and relative abundance of certain trophic groups declined (e.g., ectomycorrhizal fungi), while many others expanded (e.g., bacterivores and omnivores) making soil food webs more diverse and structurally different. Overall, the direct and indirect consequences of moth outbreaks increased belowground diversity at different trophic levels. Our results highlight that a holistic view of ecosystems improves our understanding of cascading effects of major disturbances on soil food webs.

Contrasting responses of above- and belowground diversity to multiple components of land-use intensity

Land-use intensification is a major driver of biodiversity loss. However, understanding how different components of land use drive biodiversity loss requires the investigation of multiple trophic levels across spatial scales. Using data from 150 agricultural grasslands in central Europe, we assess the influence of multiple components of local- and landscape-level land use on more than 4,000 above- and belowground taxa, spanning 20 trophic groups. Plot-level land-use intensity is strongly and negatively associated with aboveground trophic groups, but positively or not associated with belowground trophic groups. Meanwhile, both above- and belowground trophic groups respond to landscape-level land use, but to different drivers: aboveground diversity of grasslands is promoted by diverse surrounding land-cover, while belowground diversity is positively related to a high permanent forest cover in the surrounding landscape. These results highlight a role of landscape-level land use in shaping belowground communities, and suggest that revised agroecosystem management strategies are needed to conserve whole-ecosystem biodiversity.

Plant diversity enhanced soil fungal diversity and microbial resistance to plant invasion

Interactions and feedbacks between aboveground and belowground biomes are fundamental in controlling ecosystem functions and stability. However, the relationship between plant diversity and soil microbial diversity is elusive. Moreover, it remains unknown whether plant diversity loss will deteriorate the stability of soil microbial communities. To shed light on these questions, we conducted a pot-based experiment to manipulate the plant richness gradient (1, 2, 4, 8 species) and plant (Symphyotrichum subulatum (Michx.) G.L.Nesom) invasion status. We found that, in the non-invasion treatment, soil fungal diversity significantly and positively correlated with plant diversity, while the relationship between bacterial and plant diversity was not significant. Under plant invasion, the coupling of plant-fungal alpha diversity relationship was enhanced, but the plant-fungal beta diversity relationship was decoupled. We also found significant positive relationships between plant diversity and soil microbial resistance. The observed positive relationships were determined by turnover (species substitution) and nestedness (species loss) processes for bacterial and fungal communities, respectively. Our study demonstrated that plant diversity enhanced soil fungal diversity and microbial resistance in response to plant invasion. This study expands our knowledge about the aboveground–belowground diversity relationship and diversity-stability relationship. Importance Our study newly showed plant invasion significantly altered relationships between aboveground and belowground diversity. Specifically, plant richness indirectly promoted soil fungal richness through the increase of soil TC without plant invasion, while plant richness had a direct positive effect on soil fungal richness under plant invasion. Our study highlights the plant diversity effect on soil fungal diversity especially under plant invasion, and the plant diversity effect on microbial resistance in response to plant invasion. These novel findings will add important knowledge about the aboveground–belowground diversity relationship and diversity-stability relationship.

Cascading Effects of Moth Outbreaks on Subarctic Soil Food Webs

The increasing severity and frequency of natural disturbances requires a better understanding of their effects on all compartments of biodiversity. In Northern Fennoscandia, recent large-scale moth outbreaks have led to an abrupt change in plant communities from birch forests dominated by dwarf shrubs to grass-dominated systems. However, the indirect effects on the belowground compartment remained unclear. Here, we combined eDNA survey of multiple trophic groups with network analyses to demonstrate that moth defoliation has far-reaching consequences on soil food webs. Following this disturbance, diversity and relative abundance of certain trophic groups declined (e.g. ectomycorrhizal fungi) while many others profited (e.g. bacterivores, omnivores) making soil food webs more diverse and structurally different. Overall, the direct and indirect consequences of moth outbreaks increased belowground diversity at different trophic levels. Our results highlight that a holistic view of ecosystems improves our understanding of cascading effects of major disturbances on soil food webs.

BioLink: Linking belowground biodiversity and ecosystem function in European forests

<p>Biodiversity of ecosystems is an important driver for the supply of ecosystem services to people. Soils often have a larger biodiversity per unit surface area than what can be observed aboveground. Here, we present what is to our knowledge, the most extensive literature-based key-word assessment of the existing information about the relationships between belowground biodiversity and ecosystem services in European forests. The belowground diversity of plant roots, fungi, prokaryota, soil fauna, and protists was evaluated in relation to the supply of Provisioning, Regulating, Cultural, and Supporting Services. The soil biota were divided into 14 subgroups and the ecosystem services into 37 separate services. Out of the 518 possible combinations of biotic groups and ecosystem services, no published study was found for 374 combinations (72%). Of the remaining 144 combinations (28%) where relationships were found, the large majority (87%) showed a positive relationship between biodiversity of a belowground biotic group and an associated ecosystem service. We concluded that (1) soil biodiversity is generally positively related to ecosystem services in European forests; (2) the links between soil biodiversity and Cultural or Supporting services are better documented than those relating to Provisioning and Regulating services; (3) there is a huge knowledge gap for most possible combinations of soil biota and ecosystem services regarding how a more biodiverse soil biota is associated with a given ecosystem service. Given the drastically increasing societal demand for knowledge of the role of biodiversity in the functioning of ecosystems and the supply of ecosystem services, we strongly encourage the scientific community to conduct well-designed studies incorporating the belowground diversity and the functions and services associated with this diversity.</p>

Effect of legume-cereal mixtures on the diversity of bacterial communities in the rhizosphere

Aboveground plant diversity is known to influence belowground diversity and ecosystem processes. However, there is little knowledge of soil microbial succession in legume-grass mixtures. Therefore, this study was designed to determine the effect of oat and common vetch binary mixtures at three seeding rates on soil bacterial communities. Denaturing gradient gel electrophoresis (DGGE) of 16S rDNA fragments was used to profile the structure of the bacterial community in the rhizosphere. Compared with a monoculture of common vetch and oat, the Shannon-Weaver index and species richness of the mixtures were increased. Thirteen cloned monocultures and mixtures of oat and common vetch soil 16S rDNA sequences were deposited to NCBI. Based on the sequencing results, the bands could be identified as related to Proteobacteria, Bacteroidetes and Cyanobacteria. Common vetch did not have some bacteria relatives to Sphingomonas spp. Some bacterial taxa could be detected in the ratio of 1:1 and 1:2, but not in the ratio of 1:3, e.g. Myxococcales. The results suggested that the belowground diversity could be promoted by mixed cropping systems.