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  1. Ball, Marilyn (Ed.)
    Abstract We investigated how mangrove-island micro-elevation (i.e., habitat: center vs edge) affects tree physiology in a scrub mangrove forest of the southeastern Everglades. We measured leaf gas exchange rates of scrub Rhizophora mangle L. trees monthly during 2019, hypothesizing that CO2 assimilation (Anet) and stomatal conductance (gsw) would decline with increasing water levels and salinity, expecting more considerable differences at mangrove-island edges than centers, where physiological stress is greatest. Water levels varied between 0 and 60 cm from the soil surface, rising during the wet season (May–October) relative to the dry season (November–April). Porewater salinity ranged from 15 to 30 p.p.t., being higher at mangrove-island edges than centers. Anet maximized at 15.1 μmol m−2 s−1, and gsw was typically <0.2 mol m−2 s−1, both of which were greater in the dry than the wet season and greater at island centers than edges, with seasonal variability being roughly equal to variation between habitats. After accounting for season and habitat, water level positively affected Anet in both seasons but did not affect gsw. Our findings suggest that inundation stress (i.e., water level) is the primary driver of variation in leaf gas exchange rates of scrub mangroves in the Florida Everglades, while also constraining Anet more than gsw. The interaction between inundation stress due to permanent flooding and habitat varies with season as physiological stress is alleviated at higher-elevation mangrove-island center habitats during the dry season. Freshwater inflows during the wet season increase water levels and inundation stress at higher-elevation mangrove-island centers, but also potentially alleviate salt and sulfide stress in soils. Thus, habitat heterogeneity leads to differences in nutrient and water acquisition and use between trees growing in island centers versus edges, creating distinct physiological controls on photosynthesis, which likely affect carbon flux dynamics of scrub mangroves in the Everglades. 
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  2. Societal Impact Statement

    Botanical careers are more important than ever, given that environmental challenges such as climate change and deforestation threaten plants daily and because plants contribute to solutions to these problems. Plants act as our sources of food, medicine, textiles, and oxygen, which means finding ways to mitigate these environmental challenges is crucial. Despite this, little is known about what career opportunities exist for botanists outside of academia and how well academia is training graduate students for these careers. This study centers on the current state of academic botanical careers and how well students completing post‐baccalaureate degrees (herein referred to as graduate students) are being prepared to fill careers within the botanical workforce.


    Plant science plays a crucial role in our society and in ongoing efforts to address many global challenges, including food insecurity and climate change. Despite a predicted increase in botanical career opportunities, little is known about how well academia is training graduate students for careers outside of academia.

    To further our understanding of the current state of academic training for botanical careers, we surveyed 85 faculty and 40 graduate students working in academia in the plant sciences in the United States.

    We found that the top challenges to university professors in academia are lack of support staff and funding, whereas students completing their post‐baccalaureate degrees cited finances and lack of supportive mentoring as their top challenges. Despite the fact that most graduate students surveyed wanted a career at a research‐intensive university, many botanists in academia are retiring without being replaced by more botanists. Faculty expertise is also misaligned with needs from industry and government employers, causing challenges to training graduate students for these careers outside of academia. Although our data point to a lack of career opportunities within academia, we also note that current graduate student education still emphasizes such careers and is not properly preparing graduate students for the careers they are more likely to obtain within the private and government sectors.

    We discuss the implications of these findings and present several recommendations for preparing future generations of plant scientists for more realistic career trajectories.

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  3. Societal Impact Statement

    Humans are dependent upon plants for oxygen, food, textiles, and medicines. Climate change and deforestation represent serious threats to our planet, causing significant disruptions to our ability to access and utilize these plant resources; this makes a botanically literate workforce and plant science careers more important than ever. Unfortunately, the current state of botanical career opportunities and training programs in the United States remains unclear. This study focuses on the current employment trends of government and private sector botanists and what skills future plant scientists will need to be successful in these careers.


    Plant science plays a crucial role in our society and in ongoing efforts to address many global challenges, including food insecurity and climate change. Yet, despite a predicted increase in plant science career opportunities in the United States, the botanical career landscape outside of academia is not well understood.

    To further our understanding of the training required for non‐academic botanical careers, the botanical sub‐disciplines used on the job, and career challenges faced by plant scientists, we surveyed 61 scientists working in government and 59 scientists working in the private sector in the United States.

    In both career sectors, > 80% of survey participants reported recent hires at the bachelor's degree level. New personnel with master's degrees were more commonly reported in the government sector (95%) than in the private sector (69%). Most plant scientists working in government reported a focus on plant ecology and resource management. By contrast, most industry/non‐profit work involved horticulture and biotechnology, with some specific skills spanning both sectors. Notably, one prediction made nearly a decade ago appears to be manifesting: plant scientists seem to be retiring more quickly than they are being replaced. Survey respondents reported that attempts to hire full‐time staff are met with obstacles, including insufficient funding. Plant science professionals in both career sectors emphasized their routine use of botanical skills developed as students, highlighting the need for effective training at the undergraduate level.

    We discuss the implications of these findings and present several recommendations for preparing future generations of plant scientists and increasing the scientific community's botanical capacity.

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  4. Abstract

    Road construction and paving bring socio-economic benefits to receiving regions but can also be drivers of deforestation and land cover change. Road infrastructure often increases migration and illegal economic activities, which in turn affect local hydrology, wildlife, vegetation structure and dynamics, and biodiversity. To evaluate the full breadth of impacts from a coupled natural-human systems perspective, information is needed over a sufficient timespan to include pre- and post-road paving conditions. In addition, the spatial scale should be appropriate to link local human activities and biophysical system components, while also allowing for upscaling to the regional scale. A database was developed for the tri-national frontier in the Southwestern Amazon, where the Inter-Oceanic Highway was constructed through an area of high biological value and cultural diversity. Extensive socio-economic surveys and botanical field work are combined with remote sensing and reanalysis data to provide a rich and unique database, suitable for coupled natural-human systems research.

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  5. Summary

    Changes in fine‐root morphology are typically associated with transitions from the ancestral arbuscular mycorrhizal (AM) to the alternative ectomycorrhizal (ECM) or nonmycorrhizal (NM) associations. However, the modifications in root morphology may also coincide with new modifications in leaf hydraulics and growth habit during angiosperm diversification. These hypotheses have not been evaluated concurrently, and this limits our understanding of the causes of fine‐root evolution.

    To explore the evolution of fine‐root systems, we assembled a 600+ species database to reconstruct historical changes in seed plants over time. We utilise ancestral reconstruction approaches together with phylogenetically informed comparative analyses to test whether changes in fine‐root traits were most strongly associated with mycorrhizal affiliation, leaf hydraulics or growth form.

    Our findings showed significant shifts in root diameter, specific root length and root tissue density as angiosperms diversified, largely independent from leaf changes or mycorrhizal affiliation. Growth form was the only factor associated with fine‐root traits in statistical models including mycorrhizal association and leaf venation, suggesting substantial modifications in fine‐root morphology during transitions from woody to nonwoody habits.

    Divergences in fine‐root systems were crucial in the evolution of seed plant lineages, with important implications for ecological processes in terrestrial ecosystems.

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  6. Abstract Here we provide the ‘Global Spectrum of Plant Form and Function Dataset’, containing species mean values for six vascular plant traits. Together, these traits –plant height, stem specific density, leaf area, leaf mass per area, leaf nitrogen content per dry mass, and diaspore (seed or spore) mass – define the primary axes of variation in plant form and function. The dataset is based on ca. 1 million trait records received via the TRY database (representing ca. 2,500 original publications) and additional unpublished data. It provides 92,159 species mean values for the six traits, covering 46,047 species. The data are complemented by higher-level taxonomic classification and six categorical traits (woodiness, growth form, succulence, adaptation to terrestrial or aquatic habitats, nutrition type and leaf type). Data quality management is based on a probabilistic approach combined with comprehensive validation against expert knowledge and external information. Intense data acquisition and thorough quality control produced the largest and, to our knowledge, most accurate compilation of empirically observed vascular plant species mean traits to date. 
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  7. null (Ed.)
  8. Abstract

    A major challenge remains to understand the relative contributions of history, dispersal, and environmental filtering to the assembly of hyperdiverse communities across spatial scales. Here, we examine the extent to which biogeographical history and habitat specialization have generated turnover among and within lineages of Amazonian trees across broad geographic and environmental gradients. We replicated standardized tree inventories in 102 0.1‐ha plots located in two distant regions—the western Amazon and the eastern Guiana shield. Within each region, we used a nested design to replicate plots on contrasted habitats: white‐sand, terra firme, and seasonally flooded forests. Our plot network encompassed 26,386 trees that together represented 2,745 distinct taxa, which we standardized across all plots and regions. We combined taxonomic and phylogenetic data with detailed soil measurements and climatic data to: (1) test whether patterns of taxonomic and phylogenetic composition are consistent with recent or historical processes, (2) disentangle the relative effects of habitat, environment, and geographic distance on taxonomic and phylogenetic turnover among plots, and (3) contrast the proportion of habitat specialists among species from each region. We found substantial species turnover between Peru and French Guiana, with only 8.8% of species shared across regions; genus composition remained differentiated across habitats and regions, whereas turnover at higher taxonomic levels (family, order) was much lower. Species turnover across plots was explained primarily by regions, but also substantially by habitat differences and to a lesser extent by spatial distance within regions. Conversely, the composition of higher taxonomic levels was better explained by habitats (especially comparing white‐sand forests to other habitats) than spatial distance. White‐sand forests harbored most of the habitat specialists in both regions, with stronger habitat specialization in Peru than in French Guiana. Our results suggest that recent diversification events have resulted in extremely high turnover in species and genus composition with relatively little change in the composition of higher lineages. Our results also emphasize the contributions of rare habitats, such as white‐sand forests, to the extraordinary diversity of the Amazon and underline their importance as conservation priorities.

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