Search for: All records

Abstract Interactions between plants and soil microbes can influence plant population dynamics and diversity in plant communities. Traditional theoretical paradigms view the microbial community as a black box with net effects described by phenomenological models.This approach struggles to quantify the importance of plant–microbe interactions relative to other competition and coexistence mechanisms and to explain context dependence in microbe effects.We argue that a mechanistic framework focused on microbial functional groups will lead to conceptual and empirical advances, as demonstrated by extending resource ratio theory to plant–microbe interactions. We review the diverse pathways by which different microbial functional groups can influence plant resource competition. Finally, we suggest approaches to link theory with observations to measure the key parameters of our framework.Synthesis: Our review highlights recent experimental advancements for uncovering microbial mechanisms that alter plant host resource competition and coexistence. We synthesize these mechanisms into a conceptual model that provides a framework for future experiments to investigate the importance of plant–microbe interactions in structuring plant populations and communities. 

1. Climate change is projected to cause shifts in precipitation regimes globally, leading to intensified periods of precipitation and droughts. Most studies that have explored the influence of changing precipitation regimes on ecosystems have focused on changes in mean annual precipitation, rather than the variance around the mean. Soil fungi are ubiquitous organisms that drive ecosystem processes, but it is unknown how they respond to long-term increased interannual precipitation variability. 2. Here, we investigated the influence of long-term increased precipitation variability and host type on soil fungal diversity and community composition in a dryland ecosystem. We collected 300 soil samples from two time points and different host type substrate types at a long-term precipitation variability experiment at the Jornada Long Term Ecological Research site. Next, we used amplicon sequencing to characterize soil fungal communities. 3. Soil fungal alpha diversity and community composition were strongly affected by host type and sampling year, and increased precipitation variability caused a modest, statistically insignificant, decrease in soil fungal evenness. Furthermore, results from our structural equational model showed that the decrease in grass-associated soil fungal richness was likely an indirect result of host decline in response to increased precipitation variability. 4. Synthesis. Our work demonstrates effects of increase in interannual precipitation variability on soil fungi, and that plant hosts play a key role in mediating soil fungal responses. 

Aim: Roots and rhizospheres host diverse microbial communities that can influence the fitness, phenotypes, and environmental tolerances of host plants. Documenting the biogeography of microbiomes can detect the potential for a changing environment to disrupt host-microbe interactions, particularly in cases where microbes, such as root-associated Ascomycota, buffer hosts against abiotic stressors. We evaluated whether root-associated fungi had poleward declines in diversity as occur for many animals and plants, tested whether microbial communities shifted near host plant range edges, and determined the relative importance of latitude, climate, edaphic factors, and host plant traits as predictors of fungal community structure. Location: North American plains grasslands Taxon: Foundation North American grass species ⎯ Andropogon gerardii, Bouteloua eriopoda, B. gracilis, B. dactyloides, and Schizachyrium scoparium and their root-associated fungi Methods: At each of 24 sites representing three replicate latitudinal gradients spanning 17° latitude, we collected roots from 12 individual plants per species along five transects spaced 10 m apart (40 m × 40 m grid). We used next-generation sequencing of the fungal ITS2 region, direct fungal culturing from roots, and microscopy to survey fungi associated with grass roots. Results: Root-associated fungi did not follow the poleward declines in diversity documented for many animals and plants. Instead, host plant identity had the largest influence on fungal community structure. Edaphic factors outranked climate or host plant traits as correlates of fungal community structure; however, the relative importance of these environmental predictors differed among plant species. As sampling approached host species range edges, fungal composition converged among individual plants of each grass species. Main conclusions: Environmental predictors of root-associated fungi depended strongly on host plant species identity. Biogeographic patterns in fungal composition suggested a homogenizing influence of stressors at host plant range limits. Results predict that communities of non-mycorrhizal, root-associated fungi in the North American plains will be more sensitive to future changes in host plant ranges and edaphic factors than to the direct effects of climate. 

Interactions between plants and microbes have important influences on evolutionary processes, population dynamics, community structure, and ecosystem function. We review the literature to document how climate change may disrupt these ecological interactions and develop a conceptual framework to integrate the pathways of plant-microbe responses to climate over different scales in space and time. We then create a blueprint to aid generalization that categorizes climate effects into changes in the context dependency of plant-microbe pairs, temporal mismatches and altered feedbacks over time, or spatial mismatches that accompany species range shifts. We pair a new graphical model of how plant-microbe interactions influence resistance to climate change with a statistical approach to predictthe consequences of increasing variability in climate. Finally, we suggest pathways through which plant-microbe interactions can affect resilience during recovery from climate disruption. Throughout, we take a forward-looking perspective, highlighting knowledge gaps and directions for future research.