Biology subjects

Sorensen, P. O.

Publications and source records attributed to Sorensen, P. O..

3 recordsLinked to original sources

bioRxiv2025

Warming winter disrupts mycorrhizal phenology and plant-fungal nutrient cycling.

Climate change is reshaping the timing of ecological processes in montane ecosystems, where short, snowpack-dependent growing seasons tightly constrain plant-microbe interactions. Arbuscular mycorrhizal (AM) fungi regulate plant acquisition of nitrogen (N) and phosphorus (P) during nutrient pulses triggered by melting snowpack. Yet the extent and consequences of warming-induced phenological asynchrony between AM fungi and host plants remains unknown. We experimentally advanced snowmelt in a subalpine meadow and monitored plant and AM fungal growth, soil nutrients, and AM fungal community composition throughout the growing season. Early snowmelt advanced plant greenness and root standing stock but suppressed AM fungal hyphal production, reducing available NH{square}{square} and PO43-. Hyphal allocation strategies shaped AM fungal temporal niches and species-specific responses to warming. Nutrient-foraging, edaphophilic AM fungi dominated early in the season, while rhizophilic AM fungi dominated later, following peak root growth. Our results reveal that fungal functional traits and nutrient dynamics govern the temporal niche partitioning of mycorrhizal fungi. By decoupling AM fungal activity from plant demand and nutrient mineralization windows, early snowmelt drives plant-fungal asynchrony. This decoupling weakens mycorrhizal symbioses and threatens nutrient retention and ecosystem stability under future warming. Such belowground temporal mismatches may determine the resilience of seasonally temperature-dependent ecosystems under warming.

ecology↗

bioRxiv2023

Virus diversity and activity is driven by snowmelt and host dynamics in a high-altitude watershed soil ecosystem

Viruses, including phages, impact nearly all organisms on Earth, including microbial communities and their associated biogeochemical processes. In soils, highly diverse viral communities have been identified, with a global distribution seemingly driven by multiple biotic and abiotic factors, especially soil temperature and moisture. However, our current understanding of the stability of soil viral communities across time, and their response to strong seasonal change in environmental parameters remains limited. Here, we investigated the diversity and activity of environmental DNA and RNA viruses, including phages, across dynamics seasonal changes in a snow-dominated mountainous watershed by examining paired metagenomes and metatranscriptomes. We identified a large number of DNA and RNA viruses taxonomically divergent from existing environmental viruses, including a significant proportion of RNA viruses target fungal hosts and a large and unsuspected diversity of positive single-stranded RNA phages (Leviviricetes), highlighting the under-characterization of the global soil virosphere. Among these, we were able to distinguish subsets of active phages which changed across seasons, consistent with a "seed-bank" viral community structure in which new phage activity, for example replication and host lysis, is sequentially triggered by changes in environmental conditions. Zooming in at the population level, we further identified virus-host dynamics matching two existing ecological models: "Kill-The-Winner" which proposes that lytic phages are actively infecting abundant bacteria, and "Piggyback-The-Persistent" which argues that when the host is growing slowly it is more beneficial to remain in a lysogenic state. The former was associated with summer months of high and rapid microbial activity, and the latter to winter months of limited and slow host growth. Taken together, these results suggest that the high diversity of viruses in soils is likely associated with a broad range of host interaction types each adapted to specific host ecological strategies and environmental conditions. Moving forward, while as our understanding of how environmental and host factors drive viral activity in soil ecosystems progresses, integrating these viral impacts in complex natural microbiome models will be key to accurately predict ecosystem biogeochemistry.

microbiology↗

bioRxiv2021

Measurement of Volatile Compounds for Real-time Analysis of Soil Microbial Metabolic Response to Simulated Snowmelt

Snowmelt dynamics are a significant determinant of microbial metabolism in soil and regulate global biogeochemical cycles of carbon and nutrients by creating seasonal variations in soil redox and nutrient pools. With an increasing concern that climate change accelerates both snowmelt timing and rate, obtaining an accurate characterization of microbial response to snowmelt is important for understanding biogeochemical cycles intertwined with soil. However, observing microbial metabolism and its dynamics non-destructively remains a major challenge for systems such as soil. Microbial volatile compounds (mVCs) emitted from soil represent information-dense signatures and when assayed non-destructively using state-of-the-art instrumentation such as Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-TOF-MS) provide time resolved insights into the metabolism of active microbiomes. In this study, we used PTR-TOF-MS to investigate the metabolic trajectory of microbiomes from a subalpine forest soil, and their response to a simulated wet-up event akin to snowmelt. Using an information theory approach based on the partitioning of mutual information, we identified mVC metabolite pairs with robust interactions, including those that were non-linear and with time lags. The biological context for these mVC interactions was evaluated by projecting the connections onto the Kyoto Encyclopedia of Genes and Genomes (KEGG) network of known metabolic pathways. Simulated snowmelt resulted in a rapid increase in the production of trimethylamine (TMA) suggesting that anaerobic degradation of quaternary amine osmo/cryoprotectants, such as glycine betaine, may be important contributors to this resource pulse. Unique and synergistic connections between intermediates of methylotrophic pathways such as dimethylamine, formaldehyde and methanol were observed upon wet-up and indicate that the initial pulse of TMA was likely transformed into these intermediates by methylotrophs. Increases in ammonia oxidation signatures (transformation of hydroxylamine to nitrite) were observed in parallel, and while the relative role of nitrifiers or methylotrophs cannot be confirmed, the inferred connection to TMA oxidation suggests either a direct or indirect coupling between these processes. Overall, it appears that such mVC time-series from PTR-TOF-MS combined with causal inference represents an attractive approach to non-destructively observe soil microbial metabolism and its response to environmental perturbation.

microbiology↗