American Journal of Botany最新文献

{"title":"Toward a functional understanding of novel fire regimes in tropical forests.","authors":"David Pacuk, Peter van der Sleen, Frank J Sterck, Masha T van der Sande","doi":"10.1002/ajb2.70112","DOIUrl":"https://doi.org/10.1002/ajb2.70112","url":null,"abstract":"<p><p>Climate change and land-use alterations are driving forest fires to unprecedented frequencies and intensities worldwide. Even wet tropical forests-historically rarely subjected to fire-are increasingly experiencing fire disturbances. The impact of wildfires on these forests is likely large, since many of their tree species are not adapted to fire. The extent of the consequences depends on complex feedback mechanisms between fire and vegetation, with plant functional traits playing a critical role. However, how different traits may drive fire-vegetation dynamics in such ecosystems is poorly understood due to limited consolidation of relevant data. This uncertainty leaves the future of tropical forests in question. In this review, we explore how functional traits influence the feedback between fire and vegetation. Specifically, we examine how functional traits of species shape (1) fire regimes (here considered in terms of fire frequency and intensity) through fuel characteristics, (2) their resistance to fire, and (3) their recovery after fire. Resilience is conceptualized as resistance to biomass loss and capacity for post-disturbance biomass recovery. We provide a comprehensive overview of these traits and 12 mechanisms involved. Since the relative importance of these traits and mechanisms for fire dynamics and species' fire resilience remains unknown, we conclude by outlining possible scenarios for how novel fire regimes might affect tropical forest resilience. We also identify knowledge gaps and avenues for future research to improve our understanding of fire-vegetation dynamics in tropical forests.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70112"},"PeriodicalIF":2.7,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145285380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Changes in plant flammability-related traits to fire regime characteristics and biomass conditions in the Cerrado.","authors":"Vagner Zanzarini, Davi R Rossatto, Alessandra Fidelis","doi":"10.1002/ajb2.70110","DOIUrl":"https://doi.org/10.1002/ajb2.70110","url":null,"abstract":"<p><strong>Premise: </strong>Flammability-related traits in open savanna plant communities may shift in response to fire frequency (high vs. low) and history (recently vs. fire exclusion). Dead biomass accumulation and moisture content are expected to drive flammability components (combustibility and consumability). We hypothesized that in low fire frequency and fire exclusion areas, dead biomass accumulates, prolonging combustion duration with higher maximum temperatures and biomass consumption. Conversely, greater biomass should enhance combustibility, while higher moisture should dampen it.</p><p><strong>Methods: </strong>In Cerrado open savannas, we selected areas with high or low fire frequency and areas that were recently burned or excluded from fire for the last 21 years. For grasses, forbs, and shrubs, we measured the following flammability-related traits: moisture content, dead biomass, burn rate, maximum fire temperature, and burned biomass.</p><p><strong>Results: </strong>Dead biomass remained similar between fire frequencies and histories. Plants burned slowly (~0.5 cm s^-1) in areas where fire frequency was low or excluded. In all areas, ca 60% of the plant biomass was consumed by fire. The percentage of initial dead biomass increased the flammability components until 75% dead biomass, but beyond this threshold, burn rate, temperature, and burned biomass declined. Moisture content consistently reduced temperature and amount of biomass burned.</p><p><strong>Conclusions: </strong>Areas with fire excluded had slower fire spread but the amount of plant biomass consumed was not substantially lower. The amount of dead biomass has nonlinear relationships with combustibility and consumability, indicating that areas with more biomass accumulation may have lower flammability. Thus, we need to investigate how flammability-related traits vary in plant communities under different fire regimes to understand fire behavior and improve management decisions.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70110"},"PeriodicalIF":2.7,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145285393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fires in rainforests: Quantifying litter bed flammability of cool temperate rainforests in eastern Australia.","authors":"Jamie E Burton, Trent D Penman, Ross J Peacock","doi":"10.1002/ajb2.70111","DOIUrl":"https://doi.org/10.1002/ajb2.70111","url":null,"abstract":"<p><strong>Premise: </strong>Rainforests are usually too wet to burn, acting as natural barriers to fire spread and as refuges for biodiversity. However, climate change is increasing the risk of fire incursion into rainforests. Our capacity to manage these impacts is hindered by limited research on rainforest flammability.</p><p><strong>Methods: </strong>Fallen leaf and litter bed samples were collected from cool temperate rainforest and eucalypt forest in Willi Willi and Werrikimbe National Parks, New South Wales, Australia. Litter bed flammability of 13 common temperate rainforest species was measured in the laboratory. The flammability of rainforest litter beds and fire-prone eucalypt forest litter beds were compared for 0.07 m² and 7.2 m² beds. We also examined links between flammability and key structural and chemical leaf traits.</p><p><strong>Results: </strong>Rainforest species varied in their litter bed flammability; 64% of the species had lower flammability than litter comprising eucalypt leaves, which typically occur in more fire-prone environments. Species with smaller leaves and less leaf cellulose were associated with lower flammability. Rainforest litter beds had slower flame spread rates, smaller flames, and less material consumed compared to eucalypt litter beds.</p><p><strong>Conclusions: </strong>Fire characteristics in cool temperate rainforests will vary depending on the species composition of the litter bed, which depends on the litterfall composition of the rainforest stand. This study provides key insights into litter bed flammability in cool temperate rainforests in Australia, which will inform decisions on management of wildfires.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70111"},"PeriodicalIF":2.7,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145290565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modifications in fire frequency impact belowground plant components in old-growth grasslands, posing risks to their resilience.","authors":"Aline Bertolosi Bombo, Alessandra Fidelis, Soizig Le Stradic","doi":"10.1002/ajb2.70108","DOIUrl":"https://doi.org/10.1002/ajb2.70108","url":null,"abstract":"<p><strong>Premise: </strong>In edaphic old-growth grasslands, the low nutrient content of the soil restricts plant species establishment. Additionally, fire remains an important factor in shaping vegetation structure and belowground biomass investment in old-growth grasslands, such as the campos rupestres. However, how fire frequency affects the belowground components of these grasslands remain poorly understood. Addressing this gap is essential for understanding plant resilience and regeneration strategies in fire-prone ecosystems worldwide and advancing trait-based perspectives on plant persistence under recurrent disturbances.</p><p><strong>Methods: </strong>We compared plant belowground components across three campos rupestres sites differing in fire frequencies (1, 6, and 10 fires in 34 years). At each site, we quantified fine root biomass, specialized belowground organ biomass, bud bank size, bud-bearing organ density, and organ composition to evaluate how repeated fires shape belowground traits related to persistence and regeneration.</p><p><strong>Results: </strong>High fire frequencies reduced bud bank size and belowground organ density, but altered organ composition: Graminoid and forb rhizomes declined in number, whereas woody rhizomes became more common. Overall, belowground organ biomass increased with increasing fire frequency, but fine root biomass decreased.</p><p><strong>Conclusions: </strong>Our study indicates that changes in belowground components driven by fire frequency may lead to irreversible shifts in community structure, where very frequent fires can jeopardize the resilience of the campos rupestres. For such systems, novel fire regimes can have devastating effects, threatening biodiversity, compromising conservation status, and reducing ecosystem services.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70108"},"PeriodicalIF":2.7,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A functional trait perspective on restored temperate grassland responses to changing winter insulation and managed disturbance by fire.","authors":"Katherine T Charton, Jonathan J Henn, Michelle A Homann, Christopher R Warneke, Ellen I Damschen","doi":"10.1002/ajb2.70109","DOIUrl":"https://doi.org/10.1002/ajb2.70109","url":null,"abstract":"<p><strong>Premise: </strong>Understanding how disturbance regimes influence temperate grasslands is crucial for adapting management strategies to climate change, particularly in response to the loss of winters. The interaction between disturbance and climate can alter winter soil insulation and potentially the plant community. Examining the role of functional traits in determining community outcomes can help inform whether grasslands will remain resilient to climate change or whether management will need to be adapted proactively.</p><p><strong>Methods: </strong>We analyzed 7 years of data from a restored temperate grassland experiment to assess how the interaction between management type and timing (i.e., unmanaged control, spring burn, fall burn, and fall mow) and winter snow manipulations (i.e., snow reduction, snow control, and snow addition) affects plant community composition and whether functional traits are related to community turnover.</p><p><strong>Results: </strong>Changes in the plant community were driven mainly by management type and timing, with minimal influence from winter snow manipulations. While greater stress tolerance was associated with colonization when winter soil insulation was low, overall functional traits had a relatively minor relationship with community turnover.</p><p><strong>Conclusions: </strong>The minimal effects of winter snow manipulations, combined with the community's shift toward stress-tolerant strategies when winter soil insulation was low, suggest that grasslands may be resilient to winter snow loss in the short term. However, limited colonization by species that are not stress tolerant could drive local extinctions over time. Management strategies that support colonization and retain soil insulation, such as spring burns that maintain disturbance while preserving insulating litter, may help prevent longer-term impacts.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70109"},"PeriodicalIF":2.7,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145249345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature and the evolution of flower color: A review.","authors":"Elizabeth P Lacey","doi":"10.1002/ajb2.70106","DOIUrl":"https://doi.org/10.1002/ajb2.70106","url":null,"abstract":"<p><p>Flower colors brighten our natural world. How and why have they evolved? How might ongoing global warming alter their evolutionary trajectories? In this review, I examine the influence of ambient temperature on the evolution of flower color. Given the wide body of literature on pollinator-mediated selection, I restricted the review to temperature-mediated selection and interactions between temperature and two other abiotic factors, drought and light. I focus on flavonoid-based colors because they are widespread, and their biosynthetic pathway is well characterized. Accumulated data suggest that temperature has been a selective factor in determining large- and small-scale geographic patterns in species having genetically fixed flower color and in species with temperature-sensitive plasticity in color. However, it is also clear that we have much to learn about direct and indirect selection on flower color related to ambient temperature and temperature's contributions to phylogenetic color patterns. Therefore, I conclude with questions to help advance understanding about temperature's role in past evolution and present and future changes arising from global warming.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70106"},"PeriodicalIF":2.7,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145243636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Environmental versus phylogenetic control of leaf anatomical traits in Fabaceae, across a continental scale.","authors":"Kexiang Huang, Ying Li, Jianming Wang, Wanting Liang, Keyu Zhao, Changsheng Long, Nianting Yu, Guowei Yang, Yang Yang, Wenrui Yang, Congcong Liu","doi":"10.1002/ajb2.70105","DOIUrl":"https://doi.org/10.1002/ajb2.70105","url":null,"abstract":"<p><strong>Premise: </strong>Leaf anatomical traits influence light absorption and gas exchange, thereby impacting plant growth and ecosystem function. However, the relative importance of environmental variables versus phylogenetic history in explaining leaf anatomical trait variation remains unclear.</p><p><strong>Methods: </strong>We analyzed eight leaf anatomical traits and 14 environmental variables across 141 species of Fabaceae from 62 genera and 108 sites across China, using phylogenetic comparative analyses and variance partitioning.</p><p><strong>Results: </strong>Our results reveal that the phylogenetic signal in leaf anatomical traits is relatively constant after considering growth form, indicating that phylogenetic conservatism in these traits is not driven by differences among growth forms. The relationships between leaf anatomical traits and environmental variables are stronger, and the regression slopes between them steeper, when phylogenetic history is accounted for. Variance partitioning demonstrates that phylogeny accounts for less trait variation than environmental variables.</p><p><strong>Conclusions: </strong>The first comprehensive analysis of leaf anatomical trait variation across Fabaceae species at a large spatial scale provides valuable insights into trait-environment relationships and underlines the importance of considering phylogeny to fully understand plant adaptation.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70105"},"PeriodicalIF":2.7,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stacked scattering: The key to bright flowers lies in the mesophyll.","authors":"Larissa De Paola, Thomas A Veldhuis, Marjan Kraaij, Doekele G Stavenga, Kira J Tiedge, Casper J van der Kooi","doi":"10.1002/ajb2.70104","DOIUrl":"https://doi.org/10.1002/ajb2.70104","url":null,"abstract":"<p><strong>Premise: </strong>The coloration of flowers is caused by wavelength-selective absorption by pigments and scattering of light by floral structures. Although the molecular, physiological, and chemical properties of floral pigments have been studied in considerable detail, how floral structures contribute to the visual signal remains largely unknown. A flower can be considered as a stack of layers, where each layer is characterized by specific pigmentation and scattering properties. Quantifying the contribution of different floral layers to visual signalling aids our understanding of the origin and maintenance of Earth's resplendent flora.</p><p><strong>Methods: </strong>We quantified the contribution of the cuticle, epidermal cell layer, and the mesophyll to the reflection of light by flowers for nasturtium (Tropaeolum majus), a St. John's wort hybrid (Hypericum 'Hidcote'), and the large-flowered evening primrose (Oenothera glazioviana). The obtained experimental and modelling data allowed the quantification of the absorption and scattering of light by different floral layers.</p><p><strong>Results: </strong>The mesophyll was by far the strongest reflecting layer. The reflectance from the epidermal layer was minor, and the cuticle reflected a very small percentage of the total. The strong scattering by the mesophyll is caused by its inhomogeneity and thickness.</p><p><strong>Conclusions: </strong>The strong light-scattering by the mesophyll crucially determines a flower's visual signal, whereas the cuticle and epidermal cells contribute less than generally assumed. Mesophyll thickness, cell properties and inhomogeneity, including porosity, are essential components of the flower's optical toolkit.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70104"},"PeriodicalIF":2.7,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145136058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sequoia and Sequoiadendron: Two paleoendemic megatrees with markedly different adaptive responses to recent high-severity fires.","authors":"Jon E Keeley, Juli G Pausas","doi":"10.1002/ajb2.70089","DOIUrl":"https://doi.org/10.1002/ajb2.70089","url":null,"abstract":"<p><strong>Premise: </strong>Coast redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum) are two iconic paleoendemic species with limited distributions, well known for their spectacular size. Recently, they have been exposed to high-severity crown fires, with starkly contrasting responses.</p><p><strong>Methods: </strong>We used all available published literature and field observations to understand the responses to fire in an evolutionary context.</p><p><strong>Results: </strong>Coast redwoods, found in California's coastal rainforests, were highly resilient to high-severity fires, with most trees surviving due to their ability to resprout from the base and trunk, though seedling regeneration was largely lacking. In contrast, giant sequoias, native to the Sierra Nevada, do not resprout, leading to significant tree mortality after very high-severity fires; they released seeds only in patches where some trees survived moderately high-severity fires.</p><p><strong>Conclusions: </strong>These high-severity fires were novel events for giant sequoias, but not for coast redwoods. Fire suppression has disrupted the natural fire regime in the giant sequoia ecosystem by preventing frequent lightning-caused surface fires, resulting in high-severity fires that killed a substantial number of these giants. In coast redwood forests, infrequent but high-severity crown fires were the norm before burning by Native Americans. Frequent, low-severity burning by Native Americans over the past few hundred years was localized and 20^th-century fire suppression has returned the natural fire regime to these forests. The recent crown fires do not represent a threat to redwood conservation; however, other management goals may require emulating Native American burning practices and in some cases may be best termed cultural restoration.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70089"},"PeriodicalIF":2.7,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insect visitation patterns in diploid Centaurea aspera and its related allotetraploid and triploid hybrids: Similar rates but distinct assemblages","authors":"Alfonso Garmendia,&nbsp;Hugo Merle,&nbsp;Pau Lucio-Puig,&nbsp;María Ferriol","doi":"10.1002/ajb2.70103","DOIUrl":"10.1002/ajb2.70103","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Polyploidy is key to plant evolution by contributing to speciation, diversification, and adaptability. However, the minority cytotype exclusion effect can limit the persistence of polyploids, which can be mitigated by reproductive barriers such as distinct insect visitation between cytotypes. In eastern Spain, the diploid <i>C. aspera</i>, its related allotetraploid <i>C. seridis</i>, and their sterile triploid hybrid <i>C</i>. ×<i>subdecurrens</i> coexist in contact zones. Here we assessed the diversity and behavior of insects visiting these <i>Centaurea</i> taxa, identified factors influencing insect visitation, and explored potential changes in visitor composition and frequency across taxa in the contact zone of El Saler (Valencia, Spain).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Five natural blocks (25–50 m²) on sand dunes, each with all three plant taxa in proximity, were monitored weekly when their flowering periods overlapped. Insect visitors were identified, and number of visits and of capitula were recorded. Linear modelling was used to identify factors predicting visit frequency and differences in insect composition among plant taxa.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Seventeen flying insect species visited <i>Centaurea</i> plants. The number of florets and the number of capitula were the strongest predictors of visit frequency, showing similar outcomes, rather than plant taxon or date. Although overall visitation rates did not significantly differ among plant taxa, insect assemblages varied. <i>Centaurea seridis</i> attracted a distinct set of insects compared to <i>C. aspera</i> and <i>C</i>. ×<i>subdecurrens</i>, with some insects displaying visitation biases at particular times.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Differences in insect assemblages suggest potential prezygotic barriers that could help <i>C. seridis</i> overcome minority exclusion, supporting its long-term establishment.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"112 9","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://bsapubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70103","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145124029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}