Deciphering the Complex Interactions between Litter Inputs and Microbial Responses in Modulating Long-Term Soil...

Natural climate solutions that focus on increasing carbon in forests rely on the potential for additional carbon that may be incorporated into soil organic matter (SOM). The fate of soil carbon in temperate forests remains uncertain due to the complex role of microbes and their regulation of carbon flows in soils, especially with the addition of extra litter. We identified comprehensive molecular-level evidence that revealed shifts in SOM composition and microbial communities after 30 years of added litter in a temperate deciduous forest. Chronic litter addition failed to add new soil carbon after 30 years and correlated with reorganization in microbial community composition and altered carbon use. Excluding detrital inputs decreased soil carbon content, resulting in enhanced SOM decomposition and shifts toward specific bacterial groups (such as oligotrophs) that can utilize less energetically favorable carbon substrates that are typically more recalcitrant. Collectively, we found that microbial communities shifted in composition and altered carbon use strategies and traits, which aligned with changes to the molecular composition of SOM. Finally, this work demonstrates that in mesic temperate forests, decadal increases in litterfall, resulting from increased ecosystem productivity or management, may not offset soil carbon losses from climate change nor enhance carbon sequestration.