An official website of the United States government
Summary Pyrogenic savannas with a tree–grassland ‘matrix’ experience frequent fires (i.e. every 1–3 yr). Aboveground responses to frequent fires have been well studied, but responses of fungal litter decomposers, which directly affect fuels, remain poorly known. We hypothesized that each fire reorganizes belowground communities and slows litter decomposition, thereby influencing savanna fuel dynamics.In a pine savanna, we established patches near and away from pines that were either burned or unburned in that year. Within patches, we assessed fungal communities and microbial decomposition of newly deposited litter. Soil variables and plant communities were also assessed as proximate drivers of fungal communities.Fungal communities, but not soil variables or vegetation, differed substantially between burned and unburned patches. Saprotrophic fungi dominated in unburned patches but decreased in richness and relative abundance after fire. Differences in fungal communities with fire were greater in litter than in soils, but unaffected by pine proximity. Litter decomposed more slowly in burned than in unburned patches.Fires drive shifts between fire‐adapted and sensitive fungal taxa in pine savannas. Slower fuel decomposition in accordance with saprotroph declines should enhance fuel accumulation and could impact future fire characteristics. Thus, fire reorganization of fungal communities may enhance persistence of these fire‐adapted ecosystems.
more »
« less
This content will become publicly available on August 1, 2026
Litter Decomposition in Pacific Northwest Prairies Depends on Fire, with Differential Responses of Saprotrophic and Pyrophilous Fungi
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.
more »
« less
- Award ID(s):
- 2106130
- PAR ID:
- 10657034
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Microorganisms
- Volume:
- 13
- Issue:
- 8
- ISSN:
- 2076-2607
- Page Range / eLocation ID:
- 1834
- Subject(s) / Keyword(s):
- decomposition fire fungi grasslands litter bags prairie pyrophilous saprotrophic
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Following disturbances such as wildfires, oak seedlings must form a symbiotic association with mycorrhizal fungi to survive. Wildfires, however, reduce available mycorrhizal fungal propagules in the soil. Ectomycorrhizal (ECM) fungi on oak seedlings sampled in severely burned (7 sites), moderately burned (7 sites), and unburned areas (8 sites) in the Great Smoky Mountains National Park were evaluated 21 months after the 2016 Chimney Tops 2 Wildfire by Sanger sequencing of the nuclear ribosomal DNA internal transcribed spacer region (nrITS; fungal barcode). Sequences were aligned and grouped into Operational Taxonomic Units (OTUs) based on well-supported phylogenetic clades and 98–100% nrITS sequence homology with sequences in GenBank. One hundred seventy-nine root-associated fungi comprising 124 OTUs were recovered after removing duplicates (the same fungus on two or more roots of the same plant). The ECM genusRussulawas the most diverse genus (25 OTUs), followed by theThelephora/Tomentellaclade (18 OTUs),Lactifluus(8 OTUs),Lactarius(4 OTUs), and Laccariaaff.laccata(2 OTUs).RussulaOTUs were identified more frequently on oak roots from burned areas and in burned soils, suggesting that someRussulataxa may have a selective advantage in burned areas. High alpha diversity occurred within each of the burn categories, but little overlap of taxa occurred between burn categories (high beta diversity). Approximately half of the recovered OTUs (100/179 total root-associated fungi = 55.9%) were found on a single plant. Oak seedlings growing in moderately and severely burned areas 21 months after a fire were capable of forming root associations with available fungi. In contrast to the expectation that root-associated fungal diversity would be reduced after a wildfire, diversity 1 year after the Chimney Tops 2 Fire was high with ectomycorrhizalLaccaria,Russulaceae, andThelephoraceaedominating. This study suggests that the availability of ECM fungi post-fire is not a barrier to oak re-establishment.more » « less
-
Abstract. African elephants (Loxodonta africana) are the largest extant terrestrial mammals, with bodies containing enormous quantities of nutrients. Yet, we know little about how these nutrients move through the ecosystem after an elephant dies. Here, we investigated the initial effects (1–26 months postmortem) of elephant megacarcasses on savanna soil and plant nutrient pools in the Kruger National Park, South Africa. We hypothesized that (H1) elephant megacarcass decomposition would release nutrients into soil, resulting in higher concentrations of soil nitrogen (N), phosphorus (P), and micronutrients near the center of carcass sites; (H2) carbon (C) inputs into the soil would stimulate microbial activity, resulting in increased soil respiration potential near the center of carcass sites; and (H3) carcass-derived nutrients would be absorbed by plants, resulting in higher foliar nutrient concentrations near the center of carcass sites. To test our hypotheses, we identified 10 elephant carcass sites split evenly between nutrient-poor granitic and nutrient-rich basaltic soils. At each site, we ran transects in the four cardinal directions from the center of the carcass site, collecting soil and grass (Urochloa trichopus, formerly U. mosambicensis) samples at 0, 2.5, 5, 10, and 15 m. We then analyzed samples for C, N, P, and micronutrient concentrations and quantified soil microbial respiration potential. We found that concentrations of soil nitrate, ammonium, δ15N, phosphate, and sodium were elevated closer to the center of carcass sites (H1). Microbial respiration potentials were positively correlated with soil organic C, and both respiration and organic C decreased with distance from the carcass (H2). Finally, we found evidence that plants were readily absorbing carcass-derived nutrients from the soil, with foliar %N, δ15N, iron, potassium, magnesium, and sodium significantly elevated closer to the center of carcass sites (H3). Together, these results indicate that elephant megacarcasses release ecologically consequential pulses of nutrients into the soil which stimulate soil microbial activity and are absorbed by plants into the above-ground nutrient pools. These localized nutrient pulses may drive spatiotemporal heterogeneity in plant diversity, herbivore behavior, and ecosystem processes.more » « less
-
Abstract Ectomycorrhizal (ECM) fungi have long been thought to reduce litter decomposition in nitrogen (N)‐limited ecosystems by outcompeting saprotrophs for litter N (a phenomenon known as the ‘Gadgil effect’). However, recent research has called the generality of this effect into question, by demonstrating that ECM fungi can increase or decrease organic matter decomposition in different forests. The ecological factors driving such variation in the size and direction of ECM fungal effects on decomposition remain unclear.Here, we tested the hypothesis that ECM fungi would suppress decomposition of N‐poor, recalcitrant litter more in forests with lower N‐availability by exacerbating saprotrophic N limitation. We conducted an in situ ECM fungal and root reduction experiment (via soil trenching) in nine pine forests across three US states, which varied in soil and litter N content, climate and pine host (Pinus muricatain California,P. elliottiiin Florida and P.resinosain Minnesota). In each site, we decomposed needle litter from (1) a pine species native to that site and (2) a common litter,P. strobus, for 1 year.Contrary to our expectations, ECM fungi either stimulated (California) or had no effect on (Florida and Minnesota) pine needle decomposition. Across sites, ECM fungal stimulation of decomposition did increase with total soil N content, but was unrelated to inorganic N availability. Furthermore, despite previous work suggesting that competition for N structures ECM fungal–saprotroph interactions, trenching effects on decomposition did not differ between pine litter types, despite large differences in initial litter C:N ratios, recalcitrance and net litter N immobilization.Synthesis. Taken together, our results add to a growing body of evidence that the ‘Gadgil effect’ is not universal, even in the N‐poor litter of temperate pine forests where it was first described and is often invoked. Furthermore, the inconsistency of relationships between trenching effects with different metrics of decomposer N supply and demand calls into question the central role of N in structuring fungal interguild interactions.more » « less
-
Abstract Litter decomposition facilitates the recycling of often limiting resources, which may promote plant productivity responses to diversity, that is, overyielding. However, the direct relationship between decomposition,k, and overyielding remains underexplored in grassland diversity manipulations.We test whether local adaptation of microbes, that is, home‐field advantage (HFA), N‐priming from plant inputs or precipitation drive decomposition and whether decomposition generates overyielding. Within a grassland diversity‐manipulation, altering plant richness (1, 2, 3 and 6 species), composition (communities composed of plants from a single‐family or multiple‐families) and precipitation (50% and 150% ambient growing season precipitation), we conducted a litter decomposition experiment. In spring 2020, we deployed four replicate switchgrass,Panicum virgatum, litter bags (1.59 mm mesh opening), collecting them over 7 months to estimate litterk.Precipitation was a strong, independent driver of decomposition. Switchgrass decomposition accelerated with grass richness and decelerated as phylogenetic dissimilarity from switchgrass increased, suggesting decomposition is fastest at ‘home’. However, decomposition slowed with switchgrass density. In plots that contained switchgrass, we observed no relationship between decomposition and fungal saprotroph dissimilarity from switchgrass. However, in plots without switchgrass, decomposition slowed with increasing saprotroph dissimilarity from switchgrass. Combined these findings suggest that HFA is strongest when closely related neighbours, that is, heterospecific neighbours, are present in the community, rather than other individuals of the same species, that is, conspecifics. Legumes accelerated decomposition with more litter N remaining in those plots, suggesting that N‐inputs from planted legumes are priming decomposition of litter C. However, decomposition and overyielding were unrelated in legume communities. While in grass communities, overyielding and decomposition were positively related and the relationship was strongest in plots with low densities of switchgrass, that is, with heterospecific neighbours.Combined these findings suggest that plant species richness and community composition stimulate litter decomposition through multiple mechanisms, including N‐priming, but only HFA from local adaptation of microbes on closely related species correlates with overyielding, likely through resource recycling. Our results link diversity with ecosystem processes facilitating above‐ground productivity. Whether diversity loss will affect litter decomposition, productivity or both is contingent on resident plant traits and whether a locally adapted soil microbiome is maintained. Read the freePlain Language Summaryfor this article on the Journal blog.more » « less
