Long-term warming inverts the relationship between ecosystem function and microbial resource acquisition

Soil microbial traits drive ecosystem functions, which can explain the positive correlation between microbial functional diversity and ecosystem function. However, microbial adaptation to climate change related warming stress can shift microbial traits with direct implications for soil carbon cycling. Here, we investigated how long-term warming affects the relationship between microbial trait diversity and ecosystem function. Soils were sampled after 24 years of +5°C warming alongside unheated control soils from the Harvard Forest Long-Term Ecological Research site. Ecosystem function was estimated from six different enzyme activities and microbial biomass. Functional diversity was calculated from metatranscriptomics sequencing, where reads were assigned to yield, acquisition, or stress trait categories. We found that in organic horizon soils, warming decreased the richness of acquisition-related traits. In the mineral soils, we observed that heated soils exhibited a negative relationship with the richness of acquisition-related traits. These results suggest that microbial communities exposed to long-term warming are shifting away from a resource acquisition life history strategy.