A Polyphasic Approach for Assessing Eco-System Connectivity Demonstrates that Perturbation Remodels Network Architecture in Soil Microcosms

Abstract

2019). A polyphasic approach for assessing eco-system connectivity demonstrates that perturbation remodels network architecture in soil microcosms. Microbial Ecology. https://doi. Abstract 22Network analysis was used to show changes in network attributes by analyzing the relations 23 among the main soil microbial groups in a potted tomato soil inoculated with arbuscular 24 mycorrhizal fungus, treated with low doses of Mentha spicata essential oil, or both, and then 25 exposed to ten-fold higher oil addition (stress pulse). Pretreatments were chosen since they 26 can induce changes in the composition of the microbial community. Cellular phospholipid 27 fatty acids (PLFAs) and the activity of six soil enzymes, mainly involved in the N-cycle were 28 measured. Networks were constructed based on correlated changes in PLFA abundances. The 29 values of all parameters were significantly different from those of random networks 30 indicating modular architecture. Networks ranked from the lowest to highest modularity: 31 control, non-pretreated and stressed, inoculated and stressed, oil treated and stressed, 32 inoculated and treated with oil and stressed. The high values of network density and 1 st /2 nd 33 eigenvalues ratio are related to arylamidase activity while N-acetyl-glucosaminidase, acid 34 phosphomoesterase and asparaginase activities related to high values of the clustering 35 coefficient index. We concluded that modularity may be an efficient indicator of changes in 36 the network of interactions among the members of the soil microbial community and the 37 modular structure of the network may be related to the activity of specific enzymes. 38Communities that were stressed without a pretreatment were relatively resistant but prone to 39 sudden transition towards instability, while oil or inoculation pretreatments gave networks 40 which could be considered adaptable and susceptible to gradual change. 41 42 43

Spatial heterogeneity of <i>Cladonia rangiformis</i> and <i>Erica</i> spp. induces variable effects on soil microbial communities which are most robust in bare-soil microhabitats

“…The last distance in crust-covered areas was covered by crust, while in uncrusted areas it was represented by bare soil. The nodes of the valued network represented PLFA biomarkers, while ties stood for the significant correlations between them (Stamou et al, 2019). The networks were analyzed with the Cytoscape and Ucinet packages and results visualized with an attribute circle layout.…”

“…Finally, the small-worldness index (SW) indicates whether a network exhibits small-world properties. This happens if the estimated length of shortest path (L real ) is more or less equal to the shortest path (L rand ) estimated for an equivalent random network (L real ≈ L rand ), while the clustering coefficient of the network (Cl real ) is much higher than that for the random counterpart (Cl real >>Cl rand ), i.e., if SW= (Cl real /Cl rand )/(L real /L rand ) > 1 (Humphries and Gurney, 2008;Stamou et al, 2019). For testing departure from randomness the outputs of each experimental network were tested against those provided by 999 corresponding Erdős-Rényi random networks with the same number of nodes and density by using Student's t test for a single sample and N > 30.…”

A Case Study of Nematode Communities’ Dynamics along Successional Paths in the Reclaimed Landfill

“…Proulx et al [16] observed that the structure of the assemblages of coexisting biota is effectively modeled as a network of nodes, representing taxonomic units, while linkages represent the interactions among them. In particular, by applying network analysis, we aimed to highlight the usefulness of small-world properties that facilitate the evaluation at the level of the entire network and local clusters simultaneously [17]. Few studies have used network analysis to explore the relationships between nematode genera.…”

Recurring heavy rainfall resulting in degraded-upgraded phases in soil microbial networks that are reflected in soil functioning

“…Changes in environmental variables condition the structure, dynamics, and interactions between living organisms as well as the functioning of ecosystems both directly, by affecting the rates of related processes, and indirectly, by affecting diversity (Hong et al, 2021). Stamou et al (2019) stated that the structure of soil microbial communities is constantly in a state of imbalance and therefore particularly prone to disturbances. Rillig et al (2015) argued that the response of biocommunities to disturbances is driven by the idiosyncratic responses of the individuals and the energy costs associated with these responses.…”

“…A merit of network analysis is that it reveals global and local aspects of the interactions' configuration simultaneously (Glo-cal analysis; Stamou and Papatheodorou, 2016). This Glo-cal approach was applied successfully to assess ecosystem connectivity in perturbated soil mesocosms (Stamou et al, 2019), to describe the associative patterns of soil nematode communities in reclaimed landfills (Stamou et al, 2020), and to depict changes in microbial co-occurrence patterns in cultivated areas inoculated with Plant Growth Rhizobacteria (Papatheodorou et al, 2021). Further, such an approach helped us to analyze the interplay between the deterministic and stochastic processes that are thought to modulate the structure of a community and control its resistance and resilience (Stamou et al, 2020).…”