Biology subjects

Kennedy, P. G.

Publications and source records attributed to Kennedy, P. G..

4 recordsLinked to original sources

bioRxiv2025

Temporal dynamics of ectomycorrhizal fungi: Leaf habit and exploration strategy explain seasonal variation in community abundance and composition

Ectomycorrhizal (EcM) fungi are well-recognized symbionts impacting tree health and ecosystem functioning globally, yet understanding of their timing of proliferation in soils across seasons and years remains limited. We analyzed monthly patterns of EcM fungal abundance and community structure over two years in five temperate monodominant forest plots via quantitative PCR and Illumina sequencing. We found that the phenological dynamics of EcM fungi differed significantly by host tree leaf habit, fungal exploration type, fungal genus, and soil moisture. Overall, total EcM fungal abundances based on qPCR consistently peaked in autumn, and were more dynamic in evergreen than deciduous plots, supporting ideas of surplus carbon and asymmetric above-belowground dynamics. Longer-distance exploration types peaked earlier and were more stable than shorter-distance types, suggesting an independent and supportive role in releasing spring nutrients. About half of 20 focal taxa consistently peaked in either autumn, summer, or spring, while others were either host- and/or year-dependent. Our findings highlight that phenology is a key EcM fungal trait best explained by both host and fungal contributions, and future studies across biomes should consider seasonal shifts and sampling to elucidate phenological traits. Summary- The timing of belowground production and seasonal community dynamics remain poorly understood for ectomycorrhizal (EcM) fungi. - We collected soils monthly for two years from five temperate monodominant forest plots. - Fungal production peaked in autumn, shorter-distance and evergreen-associated spanned wider ranges, and half of focal fungal genera showed seasonal preference, emphasizing autumn surplus carbon and spring nutrients from long-distance types. - Future studies should consider seasonal shifts when sampling EcM fungal communities, and forest carbon models should include asymmetric above-belowground phenology. Translated Summary (Spanish)- La fenologia de la produccion y composicion de comunidades de hongos ectomicorrizicos (EcM) es poco estudiada. - Recolectamos suelos mensualmente por dos anos de cinco parcelas mono-dominantes templados. - Produccion maxima de hongos ocurrio en otono, hongos asociados con arboles siempreverdes y de exploracion de corta-distancia observaron rangos mas amplios, y la mitad de generos de hongos focales observaron preferencia estacional, enfatizando extra carbono en otono y nutrientes en primavera de tipos larga-distancia. - Estudios deben considerar cambios estacionales para el muestreo de hongos EcM, y modelos de carbono deben incluir fenologia asimetrica entre hojas y hongos. Plain language summaryEctomycorrhizal fungi are critical for the global carbon cycle, but their seasonal and inter-annual growth patterns remain unclear. We sample soil DNA monthly over two years across five different monodominant temperate forest stands. We find an overall belowground peak in autumn, with significantly later growth under wetter conditions, more dynamism with evergreen trees, and distinct spring growth by longer-distance fungi.

ecology↗

bioRxiv2025

Warming and reduced rainfall alter fungal necromass decomposition rates and associated microbial community composition and functioning at a temperate-boreal forest ecotone

Changes in temperature and rainfall regimes will have significant yet potentially contrasting impacts on rates of soil organic matter (SOM) decomposition. To assess how a combined stress treatment of warming and drought impacts the decomposition of fungal necromass--a fast-cycling soil organic matter (SOM) pool--we incubated Hyaloscypha bicolor necromass under both ambient and altered conditions (air and soil warming +3.3{degrees}C and [~]40% reduced rainfall) at the B4Warmed experiment in Minnesota, USA. We conducted two multi-week incubations, one assessing mass loss and microbial community composition on decaying necromass after 1, 2, 7, and 14 weeks and the second characterizing the substrate utilization capacities of necromass- associated microbial communities after weeks 1 and 7. Warming and reduced rainfall significantly accelerated the initial rate of necromass decay by [~]20%, but overall mass loss was not different between treatments at the end of the 14-week incubation. The accelerated initial rate of decay paralleled shifts in microbial community composition and activity in the altered plots, demonstrating a higher metabolic capability to utilize C and N substrates early in decomposition but a lower capability later in decay. These findings highlight the dynamic, stage-dependent response of fungal necromass decomposition to altered climate regimes, underscoring the importance of considering both temporal dynamics and the functional capacity of microbial communities when assessing the impacts of climate change on soil carbon and nutrient cycling in forest ecosystems.

ecology↗

bioRxiv2024

Necromass chemistry interacts with soil mineral and microbial properties to determine fungal carbon and nitrogen persistence in soils

Despite the importance of mineral-associated organic matter (MAOM) in long-term soil carbon (C) and nitrogen (N) persistence, and the significant contribution of fungal necromass to this pool, the factors controlling the formation of fungal-derived MAOM remain unclear. This study investigated how fungal necromass chemistry, specifically melanin, interacts with soil mineral properties and microbial communities to influence MAOM formation and persistence. We cultured the fungus Hyaloscypha bicolor to produce {superscript 1}3C- and {superscript 1}{square}N-labeled necromass with varying melanin content (high or low) and incubated it in both live and sterile soils collected from six Indiana forests that differed in their clay and iron oxide (FeOx) content. After 38 days, we found that seven times more fungal-derived N was incorporated into MAOM than fungal-derived C, with fungal N comprising 20% of the MAOM-N pool. Low melanin necromass formed more MAOM-C than high melanin necromass, although site-level differences in overall MAOM formation were substantial. Soil clay and FeOx content were strong predictors of MAOM formation, explaining [~]60% and [~]68% of the variation in MAOM-C and MAOM-N, respectively. However, microbial communities significantly influenced MAOM formation, with MAOM-C formation enhanced and MAOM-N formation reduced in sterile soils. Furthermore, the relative abundance of fungal saprotrophs was negatively correlated, and bacterial richness was positively correlated with MAOM formation, and these relationships were influenced by necromass melanin content. This study reveals that microbial communities and soil properties interactively mediate the incorporation of fungal necromass C and N into MAOM, with microbes differentially influencing C and N incorporation, and these processes being further modulated by necromass melanization.

ecology↗

bioRxiv2019

Decelerated carbon cycling by ectomycorrhizal fungi is controlled by substrate quality and community composition

Interactions between symbiotic ectomycorrhizal (EM) and free-living saprotrophs can result in significant deceleration of leaf litter decomposition. While this phenomenon is widely cited, its generality remains unclear, as both the direction and magnitude of EM fungal effects on leaf litter decomposition have been shown to vary among studies. Here we explicitly examine how contrasting leaf litter types and EM fungal communities may lead to differential effects on C and N cycling. Specifically, we measured the response of soil nutrient cycling, litter decay rates, litter chemistry and fungal community structure to the reduction of EM fungi (via trenching) with a reciprocal litter transplant experiment in adjacent Pinus- or Quercus-dominated sites. We found clear evidence of EM fungal suppression of C and N cycling in the Pinus-dominated site, but no suppression in the Quercus-dominated site. Additionally, in the Pinus-dominated site, only the Pinus litter decay rates were decelerated by EM fungi and were associated with decoupling of litter C and N cycling. Our results support the hypothesis that EM fungi can decelerate C cycling via N competition, but strongly suggest that the Gadgil effect is dependent on both substrate quality and EM fungal community composition. We argue that understanding tree host traits as well as EM fungal functional diversity is critical to a more mechanistic understanding of how EM fungi mediate forest soil biogeochemical cycling.

ecology↗