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1. Native megafauna ( Bison bison ) act as a surprising inhibitor of cedar tree expansion in a Great Plains grassland

   https://doi.org/10.1002/eap.70108  

   Noble, Sidney; Ratajczak, Zak; Noble, Brynn (October 2025, Ecological Applications)

   Abstract In the Central Great Plains of North America, fire suppression is causing transitions from grasslands to shrublands and woodlands. This woody encroachment alters plant community composition, decreases grassland biodiversity, undermines key ecosystem services, and is difficult to reverse. How native grazers affect woody encroachment is largely unknown, especially compared to domesticated grazers. Bison were once the most widespread megafauna in North America and are typically categorized as grazers, with negative effects on grasses that indirectly benefit woody plants. However, bison can negatively impact woody plants through occasional browsing and mechanical disturbance. This study reports on a 30‐year experiment at Konza Prairie Biological Station, a mesic grassland in the Central Great Plains of North America, under fire suppression and experimental presence/absence of bison. Based on remote sensing, deciduous tree canopy cover was lower with bison (6% grazed vs. 16% ungrazed). Shrub land cover showed no difference (42% grazed vs. 41% ungrazed), while herbaceous land cover was higher with bison (51% grazed vs. 40% ungrazed). Evergreen tree canopy cover (Juniperus virginianaL.), which decreases biodiversity and increases wildfire risk, was approximately 0% with bison compared to 4% without bison. In the survival trial ofJ. virginianaseedlings, we found a 40% overwinter mortality with bison, compared to 5% mortality without bison. Compared to ungrazed areas, native plant species richness was 97% and 38% higher in bison‐grazed uplands and lowlands, respectively. Species evenness and Shannon's index were higher in the bison treatment in uplands, but not in lowlands. Bison affected community composition, resulting in higher cover of short grass species and lower tree cover. While grazers are generally assumed to favor woody plants, we found that bison had the opposite effect at low fire frequencies. We argue that the large size of bison and their behaviors account for this pattern, including trampling, horning, and occasional browsing. From a conservation perspective, bison might hamper tree expansion and increase plant diversity in tallgrass prairies and similar grasslands. 

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2. Grassland woody plant management rapidly changes woody vegetation persistence and abiotic habitat conditions but not herbaceous community composition

   https://doi.org/10.1111/1365-2664.14716  

   Charton, Katherine T; Damschen, Ellen I (September 2024, Journal of Applied Ecology)

   Abstract Grasslands are among the most imperilled ecosystems worldwide, and many have experienced degradation due to the loss of historical disturbance regimes and subsequent woody encroachment. Management practitioners often use physical and chemical management interventions in combination with fire to counter encroachment, altering aboveground structure and belowground function, respectively. This may disrupt the feedbacks that perpetuate encroachment and restore the herbaceous community.We use a large‐scale field experiment to assess the initial effects of different management interventions on woody vegetation persistence, abiotic habitat conditions, and herbaceous community composition. We evaluate these effects across seven sites spanning a natural soil moisture gradient to capture one aspect of environmental heterogeneity with which managers regularly contend.We found that chemical intervention, both with and without the addition of physical intervention, was most effective at reducing woody plant cover and abundance, and a second application reduced woody plant abundance by more than one application alone. We also found that any management intervention increased light availability and air temperature and decreased soil moisture, with the combination of physical and chemical interventions having the greatest effects. Finally, none of the management interventions affected herbaceous richness and functional group cover within the study period, indicating delayed or nonexistent effects on herbaceous community composition.Synthesis and application. Our findings suggest that management should focus on chemical intervention for the greatest effects on woody plant persistence and abiotic habitat conditions. Changes to herbaceous community composition may occur in the long term and seem likely since short‐term effects of management were successful in altering processes related to encroachment feedbacks. 

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3. Litter Decomposition in Pacific Northwest Prairies Depends on Fire, with Differential Responses of Saprotrophic and Pyrophilous Fungi

   https://doi.org/10.3390/microorganisms13081834  

   Burrill, Haley M; Ralston, Ellen B; Dawson, Heather A; Roy, Bitty A (August 2025, Microorganisms)

   Fungi contribute to ecosystem function through nutrient cycling and decomposition but may be affected by major disturbances such as fire. Some ecosystems are fire-adapted, such as prairies which require cyclical burning to mitigate woody plant encroachment and reduce litter. While fire suppresses fire-sensitive fungi, pyrophilous fungi may continue providing ecosystem functions. Using litter bags, we measured the litter decomposition at three prairies with unburned and burned sections, and we used Illumina sequencing to examine litter communities. We hypothesized that (H1) decomposition would be higher at unburned sites than burned, (H2) increased decomposition at unburned sites would be correlated with higher overall saprotroph diversity, with a lower diversity in autoclaved samples, and (H3) pyrophilous fungal diversity would be higher at burned sites and overall higher in autoclaved samples. H1 was not supported; decomposition was unaffected by burn treatments. H2 and H3 were somewhat supported; saprotroph diversity was lowest in autoclaved litter at burned sites, but pyrophilous fungal diversity was the highest. Pyrophilous fungal diversity significantly contributed to litter decomposition rates, while saprotroph diversity did not. Our findings indicate that fire-adapted prairies host a suite of pyrophilous saprotrophic fungi, and that these fungi play a primary role in litter decomposition post-fire when other fire-sensitive fungal saprotrophs are less abundant. 

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4. Experimental warming has limited impacts on post‐fire succession across a burn severity gradient

   https://doi.org/10.1111/jvs.13248  

   Taber, Ethan M; Mitchell, Rachel M (February 2024, Journal of Vegetation Science)

   Abstract QuestionsAnthropogenic climate change is causing increases in the severity of wildland fire in many parts of the world. At the same time, post‐fire succession is occurring under new, warmer temperatures that are projected to continue increasing. Despite this, the combined effects of uncharacteristically high burn severity and increased ambient temperature on post‐fire community composition remain poorly understood. We ask how post‐fire forest understorey community composition and species richness are influenced by (1) burn severity, (2) experimental warming, and (3) years since fire. LocationMuseum Fire Scar,Pinus ponderosaforest, Arizona, United States. MethodsWe established 120 1‐m²quadrats in unburned, low‐ and high‐severity locations nine months after a mixed‐severity fire. Half of the plots were subject to experimental warming via open‐top warming chambers that elevated daytime temperatures by 1.079°C, simulating near‐term anthropogenic warming. Plant composition data were collected annually for three years. Relationships between community composition, burn severity, and experimental warming were analyzed using repeated‐measures PERMANOVA and linear mixed‐effects models. ResultsComposition differed significantly according to burn severity, time since fire, and their interaction, while experimental warming did not significantly influence composition. Species richness significantly increased in burned areas compared to unburned control within two years of fire. ConclusionsOur results suggest that near‐term temperature increases, driven by anthropogenic climate change, will have little effect on community composition relative to fire severity. High‐severity fire drove large, rapid changes in plant composition compared to unburned controls, favoring exotic annuals in a historically perennial‐dominated plant community. 

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5. Fire Frequency Driven Increases in Burn Heterogeneity Promote Microbial Beta Diversity: A Test of the Pyrodiversity‐Biodiversity Hypothesis

   https://doi.org/10.1111/mec.17756  

   Hopkins, Jacob R; Bennett, Alison E; McKenna, Thomas P (May 2025, Molecular Ecology)

   ABSTRACT Fire is a common ecological disturbance that structures terrestrial ecosystems and biological communities. The ability of fires to contribute to ecosystem heterogeneity has been termed pyrodiversity and has been directly linked to biodiversity (i.e., the pyrodiversity–biodiversity hypothesis). Since climate change models predict increases in fire frequency, understanding how fire pyrodiversity influences soil microbes is important for predicting how ecosystems will respond to fire regime changes. Here we tested how fire frequency‐driven changes in burn patterns (i.e., pyrodiversity) influenced soil microbial communities and diversity. We assessed pyrodiversity effects on soil microbes by manipulating fire frequency (annual vs. biennial fires) in a tallgrass prairie restoration and evaluating how changes in burn patterns influenced microbial communities (bacteria and fungi). Annual burns produced more heterogeneous burn patterns (higher pyrodiversity) that were linked to shifts in fungal and bacterial community composition. While fire frequency did not influence microbial (bacteria and fungi) alpha diversity, beta diversity did increase with pyrodiversity. Changes in fungal community composition were not linked to burn patterns, suggesting that pyrodiversity effects on other ecosystem components (e.g., plants and soil characteristics) influenced fungal community dynamics and the greater beta diversity observed in the annually burned plots. Shifts in bacterial community composition were linked to variation in higher severity burn pattern components (grey and white ash), suggesting that thermotolerance contributed to the observed changes in bacterial community composition and lower beta diversity in the biennially burned plots. This demonstrates that fire frequency‐driven increases in pyrodiversity augment biodiversity and may influence productivity in fire‐prone ecosystems. 

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