Fine Root and Mycorrhizal Trait Adjustments to the Environment

Trait-based plant ecology, which has mostly focused on above-ground traits, is increasingly placing an emphasis below-ground. Despite recent syntheses of large-scale fine-root trait datasets and the compilation of the Fine-Root Ecology Database, we still need to bridge the gap between fine-root and mycorrhizal traits and investigate below-ground trait adjustments to the environment. We will present results of an observational study in western Canada, where we tested whether fine-root and mycorrhizal traits relate to the abiotic environment at the intraspecific level. We also examined relationships between fine-root traits and mycorrhizal fungal exploration types (i.e., differentiation of extraradical hyphae). We quantified the variation in fungal exploration type abundance and in root morphological, chemical, and architectural traits among the first three fine-root orders (i.e., absorptive fine roots) of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and across biogeographic gradients in climate and soil factors. We then combined root and fungal trait measurements with next-generation sequencing. First, we show that intraspecific fine-root adjustments do not fit along a single axis of root economic strategy and are concordant with a potential increase in fine-root acquisitive capacity with environmental limitations. Second, we did not find evidence for a functional connection between root traits and fungal exploration types within Douglas-fir populations. We found temperature, precipitation and soil C:N ratio affected ectomycorrhizal community similarities and exploration type abundance but had no effect on fungal richness and diversity. Finally, we will touch on preliminary results from a separate experimental study undertaken at the SPRUCE (Spruce and Peatland Responses Under Changing Environments) experimental manipulation in a bog in northern Minnesota. We analyzed a time series of minirhizotron images collected using new, high-resolution automated minirhizotron technology to better understand the effects of warming and elevated [CO₂] on long-term mycorrhizal hyphal phenology, morphology and fine-root/hyphae interactions. We are finding interesting, species-specific differences in hyphal associations throughout the peat profile and over time.