OOS 9-4 - Connections and disconnections between soil fungal and tree communities over space and time

“Scaling up” microbial ecology over spatial and temporal scales is a persistent challenge to building effective and reliable predictive frameworks. Non-linear relationships in microbial community turnover at increasing spatial scales make it difficult to find generalizable patterns in microbial biogeography. Further, understanding the temporal aspects of these dynamics is hindered by the paucity of long-term microbial survey data. Given that plant-microbial relationships are key drivers of microbial community structure, investigating the broader spatial and temporal dynamics of plant-microbial relationships may lead to an improved understanding of the rules governing these relationships and their functions, as well as their sensitivity to future global change.
To better understand spatial and temporal patterns for plant-microbial relationships, we used tree census and soil microbiome data from the US Forest Service’s Forest Inventory and Analyses (FIA) archive. We collected data from 114 plots in Indiana, USA over the years 2000-2005 and 2012-2019. Tree community data was obtained from the FIA Datamart and fungal communities were assessed by extracting DNA from organic and mineral soil samples in the FIA archive via high-throughput sequencing (Illumina MiSeq). We found tree community ordinations significantly corresponded to soil fungal community ordinations when the tree community dominance were determined based on basal area, as opposed to species counts. Tree species richness was correlated to fungal richness in upper surface soils (organic horizons), whereas tree-mycorrhizal dominance was correlated to fungal richness in mineral horizons. Over time, fungal community turnover did not correlate with tree community turnover, however, fungal community change was greater at lower latitudes. Overall, we show that above- and below-ground biodiversity are linked, that these relationships manifest differently based on soil horizon, and that the processes influencing how these communities change over time do not necessarily coincide.