Ramesha H Jayaramaiah

Litter decomposition is a key ecosystem process that governs nutrient release and organic matter turnover in terrestrial ecosystems. While plants are known to influence rhizosphere microbiome, their role in shaping microbial colonization of litter, and further regulating decomposition remains less understood. Here, we employed a field-based Tea Bag Index (TBI) experiment to investigate how living plant functional groups (PFGs), including C3, C4, forb, and N2-fixing legumes affect decomposition of standardized tea substrates (Green tea = labile; Rooibos tea = recalcitrant) and the associated microbial communities. Our results demonstrate that PFG type exerted a stronger influence on decomposition rate than species richness. The PFG impacts on decomposition were linked directly with shifts in substrate-colonizing communities, and indirectly with higher soil nitrate, N mineralization, and favourable moisture conditions. Microbial assemblages on Green vs Rooibos tea were distinct, indicating strong substrate filtering with PFG-mediated selection of decomposer communities. Across both substrates, PFGs and soil properties jointly explained most of the variance in decomposition rate, with additional, context-dependent contributions from bacterial and faunal (protist and metazoan) diversity reflecting their functional roles in litter breakdown. These findings underscore the central role of PFGs in structuring decomposer communities and regulating key soil processes. Preserving plant functional diversity is therefore essential for preserving microbial-mediated soil processes and ensuring grassland ecosystem resilience.

Soil microfauna are recognised as key regulators of nitrogen (N) transformations, primarily through grazing and translocation mechanisms. The interactions between soil microorganisms and their microfaunal grazers play a crucial role in controlling N mineralisation and immobilisation processes. Despite the well‐established role of bacterivore nematodes and other microbial grazers in enhancing N mineralisation, the extent to which these organisms contribute to overall nutrient cycling within fungal‐dominated systems remains unclear. In a non‐amended soil microcosm experiment, we investigated microorganisms‐microfauna interaction using morphological observations, quantitative polymerase chain reaction and high‐fthroughput sequencing. Our findings indicate that microbial grazing by microfauna did not enhance N mineralisation contrary to our hypothesis, despite an increase in bacterial grazers and bacterial abundance compared to the defaunated control. Instead, we observed a dominant fungal‐driven N immobilisation process, as evidenced by the increased presence of saprophytic fungi, fungivore nematodes, and a high nematode channel index. The absolute abundance of fungal communities, particularly members of the Sordariomycetes class, further supports the hypothesis that fungi play a central role in regulating N transformations. These results challenge the conventional assumption that microfauna‐driven bacterial turnover leads to enhanced N availability and highlight the significant role of fungal networks in N retention.

Omnivore nematodes within the order Dorylaimida are among the largest free-living soil-dwelling nematodes, suggesting a significant role in soil biomass and carbon cycling. However, their contribution to these soil processes remains underexplored. Estimating biomass based on nematode morphological traits provides a practical and reliable approach for assessing their contribution in carbon dynamics. This study provides estimated individual biomass and the daily carbon budget of dorylaimids, utilizing a database of taxon-specific body-size measurements sourced from publicly available literature. We calculated biomass and potential carbon budgets for 618 reported populations worldwide, encompassing 464 species, 127 genera, 47 subfamilies, and 19 families. Biomass estimates derived using body diameter as a sole predictor, based on two recently published formulae and two adjusted formulae developed in this study, were compared with Andrássy's original formula, which incorporates both body length and diameter. The adjusted formulae proposed in this study demonstrated a superior fit compared to the recently published models. Overall, we found an estimated average individual omnivore nematode biomass (fresh weight) of 3.33 μg for females and 3.55 μg for males, and the corresponding daily carbon budgets of 0.03903 μg and 0.04163 μg for females and males, respectively. The considerable variability in biomass data across the taxonomic ranks, highlight the need for robust taxonomic resolution for ecological studies. This study offers a comprehensive dataset and improved formulae for estimating biomass and potential carbon budget in omnivore nematodes, enhancing our understanding of their functional roles in carbon dynamics and other ecosystem processes.

Understanding the interactions between plant and soil microbial diversity is crucial for predicting ecosystem responses to environmental changes. While the individual roles of plant and microbial diversity in driving ecosystem functions have been widely investigated, their interplay especially under stress conditions remains largely underexplored. This study investigated how interactions between plant and microbial diversity affect key soil functions during and after drought. We simultaneously manipulated soil microbial diversity and plant species richness, while also considering the influence of plant functional groups (PFGs), to investigate their interactions and effects on key soil functions. Our results revealed independent and interactive effects of plant and microbial diversity in shaping soil functions. Microbial diversity loss significantly altered microbial community structure and impacted microbially-driven soil N and P pools and processes such as N-mineralization. These effects were modulated by plant species richness and varied across different PFGs. The relative influence of plant and microbial diversity on soil functions was context-dependent. Microbial diversity showed stronger effects on specific functions, such as phosphatase activity, and under the drought condition. Plant diversity, particularly through PFGs (e.g. legumes), played an independent role in shaping the microbial-driven soil functions. These findings advance mechanistic insights and highlight the importance of considering both above- and belowground biodiversity, along with their interactions, in shaping soil functions and ecosystem resilience, particularly under environmental stress. Further, it emphasizes the need to explicitly consider PFGs, along with above- and belowground biodiversity, as a strategy for preserving essential belowground functions in the face of ongoing environmental changes.

Nematodes are versatile bioindicators of the soil food web in both agricultural and natural ecosystems. Multiple nematode‐based indices (NBIs), derived from morphological, life history and community traits, provide invaluable information on various aspects of soil health. However, a standardised approach is required to explicitly link NBIs to the soil health concept. Moreover, unifying all NBIs into a single quantitative index could offer a more comprehensive and straightforward bioindicator for soil health. The ecological foundations for individual NBIs have been well established, but a single standardised bioindicator for soil microfaunal communities including nematodes, remains absent. Here, we integrated existing knowledge on NBIs into an innovative framework for quantitatively assessing soil health and ecosystem functions. Moreover, we propose a new Nematode Soil Health (NSH) index which summarises all NBIs into a single quantitative bioindicator. The framework was tested with five case datasets covering different soil types, depths, land uses and seasonal variations. Results for Datasets 1 and 2 indicated no significant difference in NSH values among soil types (Ferrosol, Chromosol and Vertosol) but significantly greater NSH in topsoil compared to subsoil layers. Dataset 3 revealed that soil amendments with fauna significantly increased the NSH index compared to defaunated soils, supporting the role of soil faunal communities in maintaining soil health. The NSH index (in Dataset 4) was also significantly higher in perennial pastures than annual croplands and exhibited (in Dataset 5) seasonal variation, with higher values in spring compared to autumn. Although this framework requires further calibration, testing and standardisation on more nematode community datasets, it could be combined with quantitative estimations or graphical representations of NBIs to provide additional information relevant to soil health conditions. The NSH index has the potential to foster the practical application of NBIs in soil health assessment programs, enhancing their adoption by practitioners and farmers.

Soil biota play a pivotal role in shaping various ecosystem functions, ultimately contributing to soil health and human well-being. In this study, soil samples from four depths were collected from a remnant vegetation site and used as donor soil to assess whether soil fauna could transfer ecosystem functions, such as nitrogen (N) and phosphorus (P) cycling and nematode pest suppression, to a homogenised agricultural soil (receptive soil) in three incubation experiments. Ammonium, nitrate and plant-available phosphorus concentrations were measured as proxies for nutrient cycling, while the abundance of the two key plant-parasitic nematodes, Pratylenchus neglectus and Merlinius brevidens, served as proxies for plant-parasitic nematode suppression. Results revealed that soil fauna facilitated the transfer of up to 26 % more nitrogen from donor to receptive soil, but phosphorus levels remained unaffected. Nematode suppression effects were depth-specific and species-specific. The organic layer showed the highest nematode suppression, but depth 0–10 cm yielded the highest plant growth, suggesting physicochemical constraints in the organic layer. Nematode-based indices shifted towards a more mature and structured soil food web in the receptive soil. This study demonstrates the significant role of soil fauna in performing ecosystem functions particularly N cycling and plant-parasitic nematode suppression. These findings highlight the potential for using targeted soil amendments to enhance soil health, ultimately contributing to sustainable plant growth.

Biodiversity is an essential component for ecosystem functioning and stability, with numerous biotic interactions and complementarity playing important roles. The complexity of these relationships can be seen in both above- and belowground ecosystems and understanding these intricate relationships between biodiversity and ecosystem functioning (BEF) is critical to ecological research, especially in the context of rapidly changing global environments. This review synthesizes contemporary research and fundamental insights into BEF linkages, with a particular emphasis on the function of plant-microbial biotic interactions in shaping aboveground biodiversity and their cascading effects on ecosystem processes. One of the most significant developments is the discovery that microbial communities responsible for a variety of soil functions are inextricably linked to plant communities and ecosystem processes. However, BEF studies rarely explore the relationships between above- and belowground biodiversity components, as well as how global change affects them. In light of this, we propose emerging paths for future study, emphasizing the necessity of global-scale networks and collaborative efforts to address difficult ecological challenges. Addressing these crucial knowledge gaps might help to improve our understanding of the interplay between biodiversity, biotic interactions and ecosystem functions, thereby improving primary productivity as well as ecosystem resilience and sustainability in the face of projected global change.