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1. Decadal survival of tropical pioneer seeds in the soil seed bank is accompanied by fungal infection and dormancy release

   https://doi.org/10.1111/1365-2435.14476  

   Zalamea, Paul‐Camilo ; Sarmiento, Carolina ; Arnold, A. Elizabeth ; Kuo, Venus ; Delevich, Carolyn ; Davis, Adam S. ; Brown, Thomas A. ; Dalling, James W. ( December 2023 , Functional Ecology)

   Pioneer trees require high‐light environments for successful seedling establishment. Consequently, seeds of these species often persist in the soil seed bank (SSB) for periods ranging from several weeks to decades. How they survive despite extensive pressure from seed predators and soil‐borne pathogens remains an intriguing question.

   This study aims to test the hypotheses that decades‐old seeds collected from the SSB in a lowland tropical forest remain viable by (i) escaping infection by fungi, which are major drivers of seed mortality in tropical soils, and/or (ii) maintaining high levels of seed dormancy and seed coat integrity when compared to inviable seeds.

   We collected seeds ofTrema micranthaandZanthoxylum ekmaniiat Barro Colorado Island, Panama, from sites where adult trees previously occurred in the past 30 years. We used carbon dating to measure seed age and characterized seed coat integrity, seed dormancy and fungal communities.

   Viable seeds from the SSB ranged in age from 9 to 30 years forT. micrantha, and 5 to 33 years forZ. ekmanii. We found no evidence that decades‐old seeds maintain high levels of seed dormancy or seed coat integrity. Fungi were rarely detected in fresh seeds (no soil contact), but phylogenetically diverse fungi were detected often in seeds from the SSB. Although fungal infections were more commonly detected in inviable seeds than in viable seeds, a lack of differences in fungal diversity and community composition between viable and inviable seeds suggested that viable seeds are not simply excluding fungal species to survive long periods in the SSB.

   Synthesis.Our findings reveal the importance of a previously understudied aspect of seed survival, where the impact of seed–microbial interactions may be critical to understand long‐term persistence in the SSB.

   Read the freePlain Language Summaryfor this article on the Journal blog.

    

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2. Long‐term ecological legacies in western Amazonia

   https://doi.org/10.1111/1365-2745.13501  

   Åkesson, Christine_M ; McMichael, Crystal_N_H ; Raczka, Marco_F ; Huisman, Seringe_N ; Palmeira, Mona ; Vogel, Johnny ; Neill, David ; Veizaj, Jason ; Bush, Mark_B ; de_Lafontaine, ed., Guillaume ( October 2020 , Journal of Ecology)

   Modifications of Amazonian forests by pre‐Columbian peoples are thought to have left ecological legacies that have persisted to the modern day. Most Amazonian palaeoecological records do not, however, provide the required temporal resolution to document the nuanced changes of pre‐Columbian disturbance or post‐disturbance succession and recovery, making it difficult to detect any direct, or indirect, ecological legacies on tree species.

   Here, we investigate the fossil pollen, phytolith and charcoal history of Lake Kumpak^a, Ecuador, during the last 2,415 years inc. 3–50 year time intervals to assess ecological legacies resulting from pre‐Columbian forest modification, disturbance, cultivation and fire usage.

   Two cycles of pre‐Columbian cultivation (one including slash‐and‐burn cultivation, the other including slash‐and‐mulch cultivation) were documented in the record around 2150–1430 cal. year BP and 1250–680 cal. year BP, with following post‐disturbance succession dynamics. Modern disturbance was documented afterc. 10 cal. year BP. The modern disturbance produced a plant composition unlike those of the two past disturbances, as fire frequencies reached their peak in the 2,415‐year record. The disturbance periods varied in intensity and duration, while the overturn of taxa following a disturbance lasted for hundreds of years. The recovery periods following pre‐Columbian disturbance shared some similar patterns of early succession, but the longer‐term recovery patterns differed.

   Synthesis. The trajectories of change after a cessation of cultivation can be anticipated to differ depending on the intensity, scale, duration and manner of the past disturbance. In the Kumpak^arecord, no evidence of persistent enrichment or depletion of intentionally altered taxa (i.e. direct legacy effects) was found but indirect legacy effects, however, were documented and have persisted to the modern day. These findings highlight the strengths of using empirical data to reconstruct past change rather than relying solely on modern plant populations to infer past human management and ecological legacies, and challenge some of the current hypotheses involving the persistence of pre‐Columbian legacies on modern plant populations.

    

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3. Fire influences reproductive outcomes by modifying flowering phenology and mate‐availability

   https://doi.org/10.1111/nph.17923  

   Richardson, Lea K. ; Wagenius, Stuart ( January 2022 , New Phytologist)

   A recent study posited that fire in grasslands promotes persistence of plant species by improving mating opportunities and reproductive outcomes. We devised an investigation to test these predicted mechanisms in two widespread, long‐lived perennials. We expect fire to synchronize flowering, increase mating and boost seed set.

   We quantified individual flowering phenology and seed set ofLiatris asperaandSolidago speciosafor 3 yr on a preserve in Minnesota, USA. The preserve comprises two management units burned on alternating years, allowing for comparisons between plants in burned and unburned areas within the same year, and plants in the same area across years with and without burns.

   Fire increased flowering synchrony and increased time between start date and peak flowering. Individuals of both species that initiated flowering later in the season had higher seed set. Fire was associated with substantially higher flowering rates and seed set inL.asperabut notS.speciosa. InL.aspera, greater synchrony was associated with increased mean seed set.

   Although fire affected flowering phenology in both species, reproductive success improved only in the species in which fire also synchronized among‐year flowering. Our results support the hypothesis that reproduction in some grassland species benefits from fire.

    

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4. Transient effects of corridors on polygyne fire ants over a decade

   https://doi.org/10.1111/een.13214  

   Resasco, Julian ; Burt, Melissa A. ; Orrock, John L. ; Haddad, Nick M. ; Shoemaker, DeWayne ; Levey, Douglas J. ( December 2022 , Ecological Entomology)

   Although corridors are frequently regarded as a way to mitigate the negative effects of habitat fragmentation, concerns persist that corridors may facilitate the spread of invasive species to the detriment of native species.

   The invasive fire ant,Solenopsis invicta,has two social forms. The polygyne form has limited dispersal abilities relative to the monogyne form. Our previous work in a large‐scale corridor experiment showed that in landscapes dominated by the polygyne form, fire ant density was higher and native ant species richness was lower in habitat patches connected by corridors than in unconnected patches.

   We expected that these observed corridor effects would be transient, that is, that fire ant density and native ant species richness differences between connected and unconnected patches would diminish over time as fire ants eventually fully established within patches. We tested this prediction by resampling the three landscapes dominated by polygyne fire ants 6 to 11 years after our original study.

   Differences in fire ant density between connected and unconnected habitat patches in these landscapes decreased, as expected. Differences in native ant species richness were variable but lowest in the last 2 years of sampling.

   These findings support our prediction of transient corridor effects on this invasive ant and stress the importance of temporal dynamics in assessing population and community impacts of habitat connectivity.

    

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5. Microbiome‐mediated response to pulse fire disturbance outweighs the effects of fire legacy on plant performance

   https://doi.org/10.1111/nph.17689  

   Revillini, Daniel ; David, Aaron S. ; Menges, Eric S. ; Main, Kevin N. ; Afkhami, Michelle E. ; Searcy, Christopher A. ( September 2021 , New Phytologist)

   Fire plays a major role in structuring plant communities across the globe. Interactions with soil microbes impact plant fitness, scaling up to influence plant populations and distributions. Here we present the first factorial manipulation of both fire and soil microbiome presence to investigate their interactive effects on plant performance across a suite of plant species with varying life history traits.

   We conducted fully factorial experiments on 11 species from the Florida scrub ecosystem to test plant performance responses to soils with varying fire histories (36 soil sources), the presence/absence of a microbiome, and exposure to an experimental burn.

   Results revealed interactive ‘pulse’ effects between fire and the soil microbiome on plant performance. On average, post‐fire soil microbiomes strongly reduced plant productivity compared to unburned or sterilized soils. Interestingly, longer‐term fire ‘legacy’ effects had minor impacts on plant performance and were unrelated to soil microbiomes.

   While pulse fire effects on plant–microbiome interactions are short‐term, they could have long‐term consequences for plant communities by establishing differential microbiome‐mediated priority effects during post‐disturbance succession. The prominence of pulse fire effects on plant–microbe interactions has even greater import due to expected increases in fire disturbances resulting from anthropogenic climate change.

    

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