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Summary: Leaf phenology variations within plant communities shape community assemblages and influence ecosystem properties and services. However, questions remain regarding quantification, drivers, and productivity impacts of intra‐site leaf phenological diversity.With a 50‐ha subtropical forest plot in China's Heishiding Provincial Nature Reserve (part of the global ForestGEO network) as a testbed, we gathered a unique dataset combining ground‐derived abiotic (topography, soil) and biotic (taxonomic diversity, functional diversity, functional traits) factors. We investigated drivers underlying leaf phenological diversity extracted from high‐resolution PlanetScope data, and its influence on aboveground biomass (AGB) using structural equation modeling (SEM).Our results reveal considerable fine‐scale leaf phenological diversity across the subtropical forest landscape. This diversity is directly and indirectly influenced by abiotic and biotic factors (e.g. slope, soil, traits, taxonomic diversity; r2 = 0.43). While a notable bivariate relationship between AGB and leaf phenological diversity was identified (r = −0.24, P < 0.05), this relationship did not hold in SEM analysis after considering interactions with other biotic and abiotic factors (P > 0.05).These findings unveil the underlying mechanism regulating intra‐site leaf phenological diversity. While leaf phenology is known to be associated with ecosystem properties, our findings confirm that AGB is primarily influenced by functional trait composition and taxonomic diversity rather than leaf phenological diversity. [ABSTRACT FROM AUTHOR]

Summary: Plant pollen is rich in protein, sterols and lipids, providing crucial nutrition for many pollinators. However, we know very little about the quantity, quality and timing of pollen availability in real landscapes, limiting our ability to improve food supply for pollinators.We quantify the floral longevity and pollen production of a whole plant community for the first time, enabling us to calculate daily pollen availability. We combine these data with floral abundance and nectar measures from UK farmland to quantify pollen and nectar production at the landscape scale throughout the year.Pollen and nectar production were significantly correlated at the floral unit, and landscape level. The species providing the highest quantity of pollen on farmland were Salix spp. (38%), Filipendula ulmaria (14%), Rubus fruticosus (10%) and Taraxacum officinale (9%). Hedgerows were the most pollen‐rich habitats, but permanent pasture provided the majority of pollen at the landscape scale, because of its large area. Pollen and nectar were closely associated in their phenology, with both peaking in late April, before declining steeply in June and remaining low throughout the year.Our data provide a starting point for including pollen in floral resource assessments and ensuring the nutritional requirements of pollinators are met in farmland landscapes. [ABSTRACT FROM AUTHOR]

Summary: Phosphorus (P) for carbon (C) exchange is the pivotal function of arbuscular mycorrhiza (AM), but how this exchange varies with soil P availability and among co‐occurring plants in complex communities is still largely unknown.We collected intact plant communities in two regions differing c. 10‐fold in labile inorganic P. After a 2‐month glasshouse incubation, we measured 32P transfer from AM fungi (AMF) to shoots and 13C transfer from shoots to AMF using an AMF‐specific fatty acid. AMF communities were assessed using molecular methods.AMF delivered a larger proportion of total shoot P in communities from high‐P soils despite similar 13C allocation to AMF in roots and soil. Within communities, 13C concentration in AMF was consistently higher in grass than in blanketflower (Gaillardia aristata Pursh) roots, that is P appeared more costly for grasses. This coincided with differences in AMF taxa composition and a trend of more vesicles (storage structures) but fewer arbuscules (exchange structures) in grass roots. Additionally, 32P‐for‐13C exchange ratios increased with soil P for blanketflower but not grasses.Contrary to predictions, AMF transferred proportionally more P to plants in communities from high‐P soils. However, the 32P‐for‐13C exchange differed among co‐occurring plants, suggesting differential regulation of the AM symbiosis. [ABSTRACT FROM AUTHOR]

Summary: Quantifying the abundances of fungi is key to understanding natural variation in mycorrhizal communities in relation to plant ecophysiology and environmental heterogeneity. High‐throughput metabarcoding approaches have transformed our ability to characterize and compare complex mycorrhizal communities. However, it remains unclear how well metabarcoding read counts correlate with actual read abundances in the sample, potentially limiting their use as a proxy for species abundances.Here, we use droplet digital PCR (ddPCR) to evaluate the reliability of ITS2 metabarcoding data for quantitative assessments of mycorrhizal communities in the orchid species Neottia ovata sampled at multiple sites. We performed specific ddPCR assays for eight families of orchid mycorrhizal fungi and compared the results with read counts obtained from metabarcoding.Our results demonstrate a significant correlation between DNA copy numbers measured by ddPCR assays and metabarcoding read counts of major mycorrhizal partners of N. ovata, highlighting the usefulness of metabarcoding for quantifying the abundance of orchid mycorrhizal fungi. Yet, the levels of correlation between the two methods and the numbers of false zero values varied across fungal families, which warrants cautious evaluation of the reliability of low‐abundance families.This study underscores the potential of metabarcoding data for more quantitative analyses of mycorrhizal communities and presents practical workflows for metabarcoding and ddPCR to achieve a more comprehensive understanding of orchid mycorrhizal communities. [ABSTRACT FROM AUTHOR]

Summary: Tropical forest root characteristics and resource acquisition strategies are underrepresented in vegetation and global models, hampering the prediction of forest–climate feedbacks for these carbon‐rich ecosystems. Lowland tropical forests often have globally unique combinations of high taxonomic and functional biodiversity, rainfall seasonality, and strongly weathered infertile soils, giving rise to distinct patterns in root traits and functions compared with higher latitude ecosystems. We provide a roadmap for integrating recent advances in our understanding of tropical forest belowground function into vegetation models, focusing on water and nutrient acquisition. We offer comparisons of recent advances in empirical and model understanding of root characteristics that represent important functional processes in tropical forests. We focus on: (1) fine‐root strategies for soil resource exploration, (2) coupling and trade‐offs in fine‐root water vs nutrient acquisition, and (3) aboveground–belowground linkages in plant resource acquisition and use. We suggest avenues for representing these extremely diverse plant communities in computationally manageable and ecologically meaningful groups in models for linked aboveground–belowground hydro‐nutrient functions. Tropical forests are undergoing warming, shifting rainfall regimes, and exacerbation of soil nutrient scarcity caused by elevated atmospheric CO2. The accurate model representation of tropical forest functions is crucial for understanding the interactions of this biome with the climate. [ABSTRACT FROM AUTHOR]

Summary: Plants possess a large variety of nonacquisitive belowground organs, such as rhizomes, tubers, bulbs, and coarse roots. These organs determine a whole set of functions that are decisive in coping with climate, productivity, disturbance, and biotic interactions, and have been hypothesized to affect plant distribution along environmental gradients.We assembled data on belowground organ morphology for 1712 species from Central Europe and tested these hypotheses by quantifying relationships between belowground morphologies and species optima along ecological gradients related to productivity and disturbance. Furthermore, we linked these data with species co‐occurrence in 30 115 vegetation plots from the Czech Republic to determine relationships between belowground organ diversity and these gradients.The strongest gradients determining belowground organ distribution were disturbance severity and frequency, light, and moisture. Nonclonal perennials and annuals occupy much smaller parts of the total environmental space than major types of clonal plants. Forest habitats had the highest diversity of co‐occurring belowground morphologies; in other habitats, the diversity of belowground morphologies was generally lower than the random expectation.Our work shows that nonacquisitive belowground organs may be partly responsible for plant environmental niches. This adds a new dimension to the plant trait spectrum, currently based on acquisitive traits (leaves and fine roots) only. [ABSTRACT FROM AUTHOR]

Summary: Understanding and predicting recruitment in species‐rich plant communities requires identifying functional determinants of both density‐independent performance and interactions.In a common‐garden field experiment with 25 species of the woody plant genus Protea, we varied the initial spatial and taxonomic arrangement of seedlings and followed their survival and growth during recruitment. Neighbourhood models quantified how six key functional traits affect density‐independent performance, interaction effects and responses.Trait‐based neighbourhood models accurately predicted individual survival and growth from the initial spatial and functional composition of species‐rich experimental communities. Functional variation among species caused substantial variation in density‐independent survival and growth that was not correlated with interaction effects and responses. Interactions were spatially restricted but had important, predominantly competitive, effects on recruitment. Traits increasing the acquisition of limiting resources (water for survival and soil P for growth) mediated trade‐offs between interaction effects and responses. Moreover, resprouting species had higher survival but reduced growth, likely reinforcing the survival–growth trade‐off in adult plants.Resource acquisition of juvenile plants shapes Protea community dynamics with acquisitive species with strong competitive effects suffering more from competition. Together with functional determinants of density‐independent performance, this makes recruitment remarkably predictable, which is critical for efficient restoration and near‐term ecological forecasts of species‐rich communities. [ABSTRACT FROM AUTHOR]

Summary: Woody biomass is a large carbon store in terrestrial ecosystems. In calculating biomass, tree stems are assumed to be solid structures. However, decomposer agents such as microbes and insects target stem heartwood, causing internal wood decay which is poorly quantified.We investigated internal stem damage across five sites in tropical Australia along a precipitation gradient. We estimated the amount of internal aboveground biomass damaged in living trees and measured four potential stem damage predictors: wood density, stem diameter, annual precipitation, and termite pressure (measured as termite damage in downed deadwood).Stem damage increased with increasing diameter, wood density, and termite pressure and decreased with increasing precipitation. High wood density stems sustained less damage in wet sites and more damage in dry sites, likely a result of shifting decomposer communities and their differing responses to changes in tree species and wood traits across sites.Incorporating stem damage reduced aboveground biomass estimates by > 30% in Australian savannas, compared to only 3% in rainforests. Accurate estimates of carbon storage across woody plant communities are critical for understanding the global carbon budget. Future biomass estimates should consider stem damage in concert with the effects of changes in decomposer communities and abiotic conditions. [ABSTRACT FROM AUTHOR]

Summary: Controlled experiments at the level of individual plants show that legume species use different strategies for the regulation of symbiotic dinitrogen fixation in response to nitrogen availability. These strategies were suggested to improve legume fitness in the context of the plant community, although rarely studied at this level. We evaluated how nitrogen availability and conspecific vs heterospecific interactions influenced the strategy of regulation of nitrogen fixation.We grew two species of herbaceous legumes representing two different strategies of regulation without interaction, under treatments of deficient and sufficient nitrogen availability, with conspecific or heterospecific interaction.We found that Hymenocarpus circinnatus maintained a facultative strategy of downregulating nitrogen fixation when nitrogen was available under both con‐ and heterospecific interactions, as was also found for this species when grown alone. Vicia palaestina also downregulated nitrogen fixation under both con‐ and heterospecific interactions but did not regulate fixation when grown alone. Our results showed that under nitrogen limitation, interaction with a neighboring plant reduced fitness, reflecting a competitive effect.Our findings suggest that when interacting with other plants, downregulation of nitrogen fixation is more likely, therefore reducing the energetic cost of fixation, and improving plant performance in competitive ecological communities, especially when nitrogen is available. [ABSTRACT FROM AUTHOR]

Summary: Allelopathy is a common and important stressor that shapes plant communities and can alter soil microbiomes, yet little is known about the direct effects of allelochemical addition on bacterial and fungal communities or the potential for allelochemical‐selected microbiomes to mediate plant performance responses, especially in habitats naturally structured by allelopathy.Here, we present the first community‐wide investigation of microbial mediation of allelochemical effects on plant performance by testing how allelopathy affects soil microbiome structure and how these microbial changes impact germination and productivity across 13 plant species.The soil microbiome exhibited significant changes to 'core' bacterial and fungal taxa, bacterial composition, abundance of functionally important bacterial and fungal taxa, and predicted bacterial functional genes after the addition of the dominant allelochemical native to this habitat. Furthermore, plant performance was mediated by the allelochemical‐selected microbiome, with allelopathic inhibition of plant productivity moderately mitigated by the microbiome.Through our findings, we present a potential framework to understand the strength of plant–microbial interactions in the presence of environmental stressors, in which frequency of the ecological stress may be a key predictor of microbiome‐mediation strength. [ABSTRACT FROM AUTHOR]

Summary: Epiphytes and their associated biota are increasingly recognized as contributing to biodiversity and to filling critical ecosystem functions in world forests. However, the attributes that have made them successful in canopy environments also make them vulnerable to natural and human‐induced disturbances. Drawing upon ecological frameworks to understand disturbance, I categorized and synthesized the drivers and the consequences of disturbances on epiphytic materials. Across all impacts, disturbance agents were significantly more likely to lead to negative, rather than positive, effects in both tropical and temperate locales. Significantly more studies reported negative effects on abundance, diversity, community composition and connectivity, but some studies showed that disturbances enhanced these attributes. Although particular disturbance agents did not differently influence individual consequences, they explained a significant portion of variation in aggregated totals. Surprisingly, relative to human disturbances, natural disturbances were more likely to lead to negative effects. Many studies provided recommendations for effective societal responses to mitigate negative impacts, such as retaining large, old trees in forestry operations, patch‐clearing for epiphyte harvest, maximizing forest fragment size, using epiphytes as bioindicators of disturbance, and applying principles of community forestry to land management. Future actions should also include communication of these results to policymakers and land managers. [ABSTRACT FROM AUTHOR]

Summary: Age‐related resistance to microbe invasion is a commonly accepted concept in plant pathology. However, the impact of such age‐dependent interactive phenomena is perhaps not yet sufficiently recognized by the broader plant science community. Toward cataloging an understanding of underlying mechanisms, this review explores recent molecular studies and their relevance to the concept. Examples describe differences in genetic background, transcriptomics, hormonal balances, protein‐mediated events, and the contribution by short RNA‐controlled gene silencing events. Throughout, recent findings with viral systems are highlighted as an illustration of the complexity of the interactions. It will become apparent that instead of uncovering a unifying explanation, we unveiled only trends. Nevertheless, with a degree of confidence, we propose that the process of plant age‐related defenses is actively regulated at multiple levels. The overarching goal of this control for plants is to avoid a constitutive waste of resources, especially at crucial metabolically draining early developmental stages. [ABSTRACT FROM AUTHOR]

Summary: Nutrient allocation is central to understanding plant ecological strategies and forest roles in biogeochemical cycles. Thought to be mainly driven by environmental conditions, nutrient allocation to woody organs, especially to living tissues, is poorly understood.To examine the role of differences in living tissues (sapwood, SW, vs inner bark, IB), organs, ecological strategies, and environmental conditions in driving nutrient allocation and scaling in woody plants, we quantified nitrogen and phosphorus in main stems and coarse roots of 45 species from three tropical ecosystems with contrasting precipitation, fire regime, and soil nutrients.Nutrient concentration variation was mostly explained by differences between IB and SW, followed by differences between species and, in the case of phosphorus, soil nutrient availability. IB nutrient concentrations were four times those of SW, with root tissues having slightly higher concentrations than stem tissues. Scaling between IB and SW, and between stems and roots, was generally isometric. In cross‐sections, IB contributed half of total nutrients in roots and a third in stems.Our results highlight the important role of IB and SW for nutrient storage, the coordination in nutrient allocation across tissues and organs, and the need to differentiate between IB and SW to understand plant nutrient allocation. [ABSTRACT FROM AUTHOR]

Summary: Resource complementarity can contribute to enhanced ecosystem functioning in diverse plant communities, but the role of facilitation in the enhanced complementarity is poorly understood.Here, we use leaf manganese concentration ([Mn]) as a proxy for rhizosheath carboxylate concentration to explore novel mechanisms of complementarity mediated by phosphorus (P) facilitation.In pot experiments, we showed that mixtures involving Carex korshinskyi, an efficient P‐mobilizing species, exhibited greater biomass and relative complementarity effect than combinations without C. korshinskyi on P‐deficient soils. Compared with monocultures, leaf [Mn] and [P] of species that are inefficient at P mobilization increased by 27% and 21% when grown with C. korshinskyi (i.e. interspecific P facilitation via carboxylates) rather than next to another inefficient P‐mobilizing species. This experimental result was supported by a meta‐analysis including a range of efficient P‐mobilizing species. Phosphorus facilitation enhanced the relative complementarity effect in low‐P environments, related to a greater change in several facilitated species of their root morphological traits relative to those in monoculture.Using leaf [Mn] as a proxy, we highlight a vital mechanism of interspecific P facilitation via belowground processes and provide evidence for the pivotal role of P facilitation mediated by the plasticity of root traits in biodiversity research. [ABSTRACT FROM AUTHOR]

Summary: Shade tolerance is an ecological concept used in a wide range of disciplines, from plant physiology to landscaping or gardening. It refers to the strategy of some plants to persist and even thrive in environments with low light levels because of the shade produced by the vegetation proximity (e.g. in the understory). Shade tolerance influences the organization, structure, functioning, and dynamics of plant communities. However, little is known about its molecular and genetic basis. By contrast, there is a good understanding on how plants deal with the proximity of other plants, a divergent strategy used by most crops to respond to vegetation proximity. While generally shade‐avoiding species strongly elongate in response to the proximity of other plants, shade‐tolerant species do not. Here we review the molecular mechanisms that control the regulation of hypocotyl elongation in shade‐avoiding species as a reference framework to understand shade tolerance. Comparative studies indicate that shade tolerance is implemented by components also known to regulate hypocotyl elongation in shade‐avoiding species. These components, however, show differential molecular properties that explain how, in response to the same stimulus, shade‐avoiding species elongate while shade‐tolerant ones do not. [ABSTRACT FROM AUTHOR]

Summary: Climate change is driving changes in disturbance regimes world‐wide. In forests adapted to infrequent, high‐severity fires, recent anomalously short fire‐return intervals (FRIs) have resulted in greatly reduced postfire tree regeneration. However, effects on understory plant communities remain unexplored.Understory plant communities were sampled in 31 plot pairs across Greater Yellowstone (Wyoming, USA). Each pair included one plot burned at high severity twice in < 30 yr and one plot burned in the same most recent fire but not burned previously for > 125 yr. Understory communities following short‐interval fires were also compared with those following the previous long‐interval fire.Species capable of growing in drier conditions and in lower vegetation zones became more abundant and regional differences in plant communities declined following short‐interval fire. Dissimilarity between plot pairs increased in mesic settings and decreased with time since fire and postfire winter snowfall. Reduced postfire tree density following short‐interval fire rather than FRI per se affected the occurrence of most plant species.Anomalously short FRIs altered understory plant communities in space and time, with some indications of community thermophilization and regional homogenization. These and other shifts in understory plant communities may continue with ongoing changes in climate and fire across temperate forests. [ABSTRACT FROM AUTHOR]

Summary: The 'One Hundred Important Questions Facing Plant Science Research' project aimed to capture a global snapshot of the current issues and future questions facing plant science. This revisiting builds on the original 2011 paper. Over 600 questions were collected from anyone interested in plants, which were reduced to a final list of 100 by four teams of global panellists. There was remarkable consensus on the most important topics between the global subpanels. We present the top 100 most important questions facing plant science in 2022, ranging from how plants can contribute to tackling climate change, to plant‐defence priming and epigenome plasticity. We also provide explanations of why each question is important. We demonstrate how focussing on climate change, community and protecting plant life has become increasingly important for plant science over the past 11 years. This revisiting illustrates the collaborative and international need for long‐term funding of plant science research, alongside the broad community‐driven efforts to actively ameliorate and halt climate change, while adapting to its consequences. [ABSTRACT FROM AUTHOR]

Summary: Invasive plants can change soil properties resulting in improved growth. Although invaders are known to alter soil chemistry, it remains unclear if chemicals secreted by roots facilitate invasive plant–soil mutualisms.With up to 19 confamilial pairs of invasive and native plants, and most of which were congeners, we explored the root exudate‐induced changes in plant–arbuscular mycorrhizal (AM) fungal mutualisms.We found that, relative to natives, invaders had greater AM colonization, greater biomass and their root exudates contained higher concentrations of two common chemical signals – quercetin and strigolactones – which are known to stimulate AM fungal growth and root colonization. An exudate exchange experiment showed that root exudates from invaders increased AM colonization more than exudates from natives. However, application of activated carbon led to greater reduction in AM colonization and plant biomass for invaders than natives, suggesting stronger effects of chemical signals in root exudates from invaders.We show that nonnative plants promote interactions with soil mutualists via enhancing root exudate chemicals, which could have important implications for invasion success. See also the Commentary on this article by Lekberg & Callaway, 236: 797–799. [ABSTRACT FROM AUTHOR]

Summary: How mycoheterotrophic plants that obtain carbon and soil nutrients from fungi are integrated in the usually mutualistic arbuscular mycorrhizal networks is unknown. Here, we compare autotrophic and mycoheterotrophic plant associations with arbuscular mycorrhizal fungi and use network analysis to investigate interaction preferences in the tripartite network.We sequenced root tips from autotrophic and mycoheterotrophic plants to assemble the combined tripartite network between autotrophic plants, mycorrhizal fungi and mycoheterotrophic plants. We compared plant–fungi interactions between mutualistic and antagonist networks, and searched for a diamond‐like module defined by a mycoheterotrophic and an autotrophic plant interacting with the same pair of fungi to investigate whether pairs of fungi simultaneously linked to plant species from each interaction type were overrepresented throughout the network.Mycoheterotrophic plants as a group interacted with a subset of the fungi detected in autotrophs but are indirectly linked to all autotrophic plants, and fungi with a high overlap in autotrophic partners tended to interact with a similar set of mycoheterotrophs. Moreover, pairs of fungi sharing the same mycoheterotrophic and autotrophic plant species are overrepresented in the network.We hypothesise that the maintenance of antagonistic interactions is maximised by targeting well linked mutualistic fungi, thereby minimising the risk of carbon supply shortages. [ABSTRACT FROM AUTHOR]

Summary: Climate extremes pose enormous threats to natural ecosystems. Arbuscular mycorrhizal (AM) fungi are key plant symbionts that can affect plant community dynamics and ecosystem stability. However, knowledge about how AM fungal communities respond to climate extremes in natural ecosystems remains elusive.Based on a grassland extreme drought experiment in Inner Mongolia, we investigated the response of AM fungal communities to extreme drought in association with plant communities. The experiment simulated two types of extreme drought (chronic/intense) of once‐in‐20‐year occurrence.AM fungal richness and community composition exhibited high sensitivity to extreme drought and were more sensitive to intense drought than chronic drought. This community sensitivity (i.e. decline in richness and shifts in community composition) of AM fungi can be jointly explained by soil moisture, plant richness, and aboveground productivity. Notably, the robustness of the plant–AM fungal community co‐response increased with drought intensity.Our results indicate that AM fungal communities are sensitive to climate extremes, and we propose that the plant community mediates AM fungal community responses. Given the ubiquitous nature of AM associations, their climate sensitivity may have profound consequences on plant communities and ecosystem stability under climate change. [ABSTRACT FROM AUTHOR]

Summary: Plants and microbes coinhabit the earth and have coevolved during environmental changes over time. Root metabolites are the key to mediating the dynamic association between plants and microbes, yet the underlying functions and mechanisms behind this remain largely illusive. Knowledge of metabolite‐mediated alteration of the root microbiota in response to environmental stress will open avenues for engineering root microbiotas for improved plant stress resistance and health. Here, we synthesize recent advances connecting environmental stresses, the root metabolome and microbiota, and propose integrated synthetic biology‐based strategies for tuning the plant root metabolome in situ for microbe‐assisted stress resistance, offering potential solutions to combat climate change. The current limitations, challenges and perspectives for engineering the plant root metabolome for modulating microbiota are collectively discussed. [ABSTRACT FROM AUTHOR]

Summary: Plants evolved in association with a diverse community of microorganisms. The effect of plant phylogeny and domestication on host–microbiome co‐evolutionary dynamics are poorly understood.Here we examined the effect of domestication and plant lineage on the composition of the endophytic microbiome of 11 Malus species, representing three major groups: domesticated apple (M. domestica), wild apple progenitors, and wild Malus species.The endophytic community of M. domestica and its wild progenitors showed higher microbial diversity and abundance than wild Malus species. Heirloom and modern cultivars harbored a distinct community composition, though the difference was not significant. A community‐wide Bayesian model revealed that the endophytic microbiome of domesticated apple is an admixture of its wild progenitors, with clear evidence for microbiome introgression, especially for the bacterial community. We observed a significant correlation between the evolutionary distance of Malus species and their microbiome.This study supports co‐evolution between Malus species and their microbiome during domestication. This finding has major implications for future breeding programs and our understanding of the evolution of plants and their microbiomes. [ABSTRACT FROM AUTHOR]

Summary: The post‐Miocene climatic histories of arid environments have been identified as key drivers of dispersal and diversification. Here, we investigate how climatic history correlates with the historical biogeography of the Atacama Desert genus Cristaria (Malvaceae).We analyze phylogenetic relationships and historical biogeography by using next‐generation sequencing (NGS), molecular clock dating, Dispersal Extinction Cladogenesis and Bayesian sampling approaches. We employ a novel way to identify biogeographically meaningful regions as well as a rarely utilized program permitting the use of dozens of ancestral areas.Partial incongruence between the established taxonomy and our phylogenetic data argue for a complex historical biogeography with repeated introgression and incomplete lineage sorting. Cristaria originated in the central southern part of the Atacama Desert, from there the genus colonized other areas from the late Miocene onwards. The more recently diverged lineages appear to have colonized different habitats in the Atacama Desert during pluvial phases of the Pliocene and early Pleistocene.We show that NGS combined with near‐comprehensive sampling can provide an unprecedented degree of phylogenetic resolution and help to correlate the historical biogeography of plant communities with cycles of arid and pluvial phases. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Wei et al. (2023), 240: 1802–1816. [ABSTRACT FROM AUTHOR]

Summary: Herbivore population dynamics are strongly influenced by the interactions established through their shared host. Such plant‐mediated interactions can occur between different herbivore species and different life developmental stages of the same herbivore. However, whether these interactions occur between leaf‐feeding herbivores and their soil‐dwelling pupae is unknown.We studied whether tomato (Solanum lycopersicum) leaf herbivory by the American serpentine leafminer Liriomyza trifolii affects the performance of conspecific pupae exposed to the soil headspace of the plant. To gain mechanistic insights, we performed insect bioassays with the jasmonate‐deficient tomato mutant def‐1 and its wild‐type, along with phytohormones, gene expression and root volatiles analyses.Belowground volatiles accelerated leafminer metamorphosis when wild‐type plants were attacked aboveground by conspecifics. The opposite pattern was observed for def‐1 plants, in which aboveground herbivory slowed metamorphosis. Leafminer attack induced jasmonate and abscisic acid accumulation and modulated volatile production in tomato roots in a def‐1‐dependent manner.Our results demonstrate that aboveground herbivory triggers changes in root defence signalling and expression, which can directly or indirectly via changes in soil or microbial volatiles, alter pupal development time. This finding expands the repertoire of plant–herbivore interactions to herbivory‐induced modulation of metamorphosis, with potential consequences for plant and herbivore community dynamics. [ABSTRACT FROM AUTHOR]

Summary: Plants simultaneously interact with a range of biotrophic symbionts, ranging from mutualists such as arbuscular mycorrhizal fungi (AMF), to parasites such as the potato cyst nematode (PCN). The exchange of mycorrhizal‐acquired nutrients for plant‐fixed carbon (C) is well studied; however, the impact of competing symbionts remains underexplored.In this study, we examined mycorrhizal nutrient and host resource allocation in potato with and without AMF and PCN using radioisotope tracing, whilst determining the consequences of such allocation.The presence of PCN disrupted C for nutrient exchange between plants and AMF, with plant C overwhelmingly obtained by the nematodes. Despite this, AMF maintained transfer of nutrients on PCN‐infected potato, ultimately losing out in their C for nutrient exchange with the host. Whilst PCN exploited the greater nutrient reserves to drive population growth on AMF–potato, the fungus imparted tolerance to allow the host to bear the parasitic burden.Our findings provide important insights into the belowground dynamics of plant–AMF symbioses, where simultaneous nutritional and nonnutritional benefits conferred by AMF to hosts and their parasites are seldom considered in plant community dynamics. Our findings suggest this may be a critical oversight, particularly in the consideration of C and nutrient flows in plant and soil communities. [ABSTRACT FROM AUTHOR]

Summary: Tropical forests are important to the regulation of climate and the maintenance of biodiversity on Earth. However, these ecosystems are threatened by climate change, as temperatures rise and droughts' frequency and duration increase. Xylem anatomical traits are an essential component in understanding and predicting forest responses to changes in water availability.We calculated the community‐weighted means and variances of xylem anatomical traits of hydraulic and structural importance (plot‐level trait values weighted by species abundance) to assess their linkages to local adaptation and community assembly in response to varying soil water conditions in an environmentally diverse Brazilian Atlantic Forest habitat.Scaling approaches revealed community‐level tradeoffs in xylem traits not observed at the species level. Towards drier sites, xylem structural reinforcement and integration balanced against hydraulic efficiency and capacitance xylem traits, leading to changes in plant community diversity.We show how general community assembly rules are reflected in persistent fiber–parenchyma and xylem hydraulic tradeoffs. Trait variation across a moisture gradient is larger between species than within species and is realized mainly through changes in species composition and abundance, suggesting habitat specialization. Modeling efforts to predict tropical forest diversity and drought sensitivity may benefit from adding hydraulic architecture traits into the analysis. [ABSTRACT FROM AUTHOR]

Summary: Forests are a critical carbon sink and widespread tree mortality resulting from climate‐induced drought stress has the potential to alter forests from a carbon sink to a source, causing a positive feedback on climate change. Process‐based vegetation models aim to represent the current understanding of the underlying mechanisms governing plant physiological and ecological responses to climate. Yet model accuracy varies across scales, and regional‐scale model predictive skill is frequently poor when compared with observations of drought‐driven mortality. I propose a framework that leverages differences in model predictive skill across spatial scales, mismatches between model predictions and observations, and differences in the mechanisms included and absent across models to advance the understanding of the physiological and ecological processes driving observed patterns drought‐driven mortality. [ABSTRACT FROM AUTHOR]

Summary: Biodiversity can reduce or increase disease transmission. These divergent effects suggest that community composition rather than diversity per se determines disease transmission. In natural plant communities, little is known about the functional roles of neighbouring plant species in belowground disease transmission.Here, we experimentally investigated disease transmission of a fungal root pathogen (Rhizoctonia solani) in two focal plant species in combinations with four neighbour species of two ages. We developed stochastic models to test the relative importance of two transmission‐modifying mechanisms: (1) infected hosts serve as nutrient supply to increase hyphal growth, so that successful disease transmission is self‐reinforcing; and (2) plant resistance increases during plant development.Neighbouring plants either reduced or increased disease transmission in the focal plants. These effects depended on neighbour age, but could not be explained by a simple dichotomy between hosts and nonhost neighbours. Model selection revealed that both transmission‐modifying mechanisms are relevant and that focal host–neighbour interactions changed which mechanisms steered disease transmission rate.Our work shows that neighbour‐induced shifts in the importance of these mechanisms across root networks either make or break disease transmission chains. Understanding how diversity affects disease transmission thus requires integrating interactions between focal and neighbour species and their pathogens. [ABSTRACT FROM AUTHOR]

Summary: Plants allocate resources to processes related to growth and enemy defence. Simultaneously, they interact with complex soil microbiomes that also affect plant performance. While the influence of individual microbial groups on single plants is increasingly studied, effects of microbial interactions on growth, defence and growth–defence relationships remain unknown, especially at the plant community level.We investigated how three microbial groups (bacteria, fungi, protists), alone and in full‐factorial combinations, affect plant performance and potential growth–defence relationships by measuring phenolics composition in early‐ and mid‐successional grass and forb communities in a glasshouse experiment.Microbial groups did not affect plant growth and only fungi increased defence compounds in early‐ and mid‐successional forbs, while grasses were not affected. Shoot biomass–defence relationships were negatively correlated in most microbial treatments in early‐successional forbs, but positively in several microbial treatments in mid‐successional forbs. The growth–defence relationship was generally negative in early‐successional but not in mid‐successional grasses. The presence of different microbiomes commonly removed the observed growth–defence relationships.We conclude that soil microorganisms and their interactions can shift growth–defence relationships differentially for plant functional groups and the relationships vary between successional stages. Microbial interaction‐induced growth–defence shifts might therefore underlie distinct plant strategies and fitness. See also the Commentary on this article by Bender, 233: 1015–1017. [ABSTRACT FROM AUTHOR]

Summary: Forests harbour large spatiotemporal heterogeneity in canopy structure. This variation drives the microclimate and light availability at the forest floor. So far, we do not know how light availability and sub‐canopy temperature interactively mediate the impact of macroclimate warming on understorey communities.We therefore assessed the functional response of understorey plant communities to warming and light addition in a full factorial experiment installed in temperate deciduous forests across Europe along natural microclimate, light and macroclimate gradients. Furthermore, we related these functional responses to the species' life‐history syndromes and thermal niches.We found no significant community responses to the warming treatment. The light treatment, however, had a stronger impact on communities, mainly due to responses by fast‐colonizing generalists and not by slow‐colonizing forest specialists. The forest structure strongly mediated the response to light addition and also had a clear impact on functional traits and total plant cover.The effects of short‐term experimental warming were small and suggest a time‐lag in the response of understorey species to climate change. Canopy disturbance, for instance due to drought, pests or logging, has a strong and immediate impact and particularly favours generalists in the understorey in structurally complex forests. [ABSTRACT FROM AUTHOR]

Summary: Interactions between individual plant pathogens and their environment have been described many times. However, the relative contribution of different environmental parameters as controls of pathogen communities remains largely unknown.Here we investigate the importance of environmental factors, including geomorphology, climate, land use, soil and plant community composition, for a broad range of aboveground and belowground fungal, oomycete and bacterial plant pathogens.We found that plant community composition is the main driver of the composition and richness of plant pathogens after taking into account all other tested parameters, especially those related to climate and soil.In the face of future changes in climate and land use, our results suggest that changes in plant pathogen community composition and richness will primarily be mediated through changes in plant communities, rather than the direct effects of climate or soils. [ABSTRACT FROM AUTHOR]

Summary: The functioning of present ecosystems reflects deep evolutionary history of locally cooccurring species if their functional traits show high phylogenetic signal (PS). However, we do not understand what drives local PS. We hypothesize that local PS is high in undisturbed and stressful habitats, either due to ongoing local assembly of species that maintained ancestral traits, or to past evolutionary maintenance of ancestral traits within habitat species‐pools, or to both.We quantified PS and diversity of 10 traits within 6704 local plant communities across 38 Dutch habitat types differing in disturbance or stress.Mean local PS varied 50‐fold among habitat types, often independently of phylogenetic or trait diversity. Mean local PS decreased with disturbance but showed no consistent relationship to stress. Mean local PS exceeded species‐pool PS, reflecting nonrandom subsampling from the pool. Disturbance or stress related more strongly to mean local than to species‐pool PS.Disturbed habitats harbour species with evolutionary divergent trait values, probably driven by ongoing, local assembly of species: environmental fluctuations might maintain different trait values within lineages through an evolutionary storage effect. If functional traits do not reflect phylogeny, ecosystem functioning might not be contingent on the presence of particular lineages, and lineages might establish evolutionarily novel interactions. [ABSTRACT FROM AUTHOR]

Summary: Endoparasitic plants are the most reduced flowering plants, spending most of their lives as a network of filaments within the tissues of their hosts. Despite their extraordinary life form, we know little about their biology. Research into a few species has revealed unexpected insights, such as the total loss of plastome, the reduction of the vegetative phase to a proembryonic stage, and elevated information exchange between host and parasite. To consolidate our understanding, we review life history, anatomy, and molecular genetics across the four independent lineages of endoparasitic plants. We highlight convergence across these clades and a striking trans‐kingdom convergence in life history among endoparasitic plants and disparate lineages of fungi at the molecular and physiological levels. We hypothesize that parasitism of woody plants preselected for the endoparasitic life history, providing parasites a stable host environment and the necessary hydraulics to enable floral gigantism and/or high reproductive output. Finally, we propose a broader view of endoparasitic plants that connects research across disciplines, for example, pollen–pistil and graft incompatibility interactions and plant associations with various fungi. We shine a light on endoparasitic plants and their hosts as under‐explored ecological microcosms ripe for identifying unexpected biological processes, interactions and evolutionary convergence. [ABSTRACT FROM AUTHOR]

Although we promote combined structural, functional and taxonomic definitions of mycorrhiza types in I new i diagnostic studies of mycorrhiza (Brundrett & Tedersoo, 2018; Soudzilovskaia I et al i ., 2020), it is often impossible to apply these criteria to pre-existing data. Keywords: arbuscular mycorrhiza; database; ecological terminology; ectomycorrhiza; mycorrhizal fungi EN arbuscular mycorrhiza database ecological terminology ectomycorrhiza mycorrhizal fungi 1689 1691 3 08/04/22 20220901 NES 220901 Acknowledgements NAS acknowledges the Netherlands Organization for Scientific research, which supported this work through a VIDI (grant no. 016.161.318). FungalRoot v.2.0 - an empirical database of plant mycorrhizal traits: A response to Bueno et al. (2021) 'Towards a consistent benchmark for plant mycorrhizal association databases' Conclusions Taken together, FungalRoot is the largest empirical database of plant mycorrhizal traits, including mycorrhiza type and level of colonization. [Extracted from the article]

Summary: Community trait assembly in highly diverse tropical rainforests is still poorly understood. Based on more than a decade of field measurements in a biodiversity hotspot of southern Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in a widely used dynamic vegetation model (the Lund‐Potsdam‐Jena General Ecosystem Simulator, LPJ‐GUESS) to explore the main drivers of community assembly along an elevational gradient.In the model used here (LPJ‐GUESS‐NTD, where NTD stands for nutrient‐trait dynamics), each plant individual can possess different trait combinations, and the community trait composition emerges via ecological sorting. Further model developments include plant growth limitation by phosphorous (P) and mycorrhizal nutrient uptake.The new model version reproduced the main observed community trait shift and related vegetation processes along the elevational gradient, but only if nutrient limitations to plant growth were activated. In turn, when traits were fixed, low productivity communities emerged due to reduced nutrient‐use efficiency. Mycorrhizal nutrient uptake, when deactivated, reduced net primary production (NPP) by 61–72% along the gradient.Our results strongly suggest that the elevational temperature gradient drives community assembly and ecosystem functioning indirectly through its effect on soil nutrient dynamics and vegetation traits. This illustrates the importance of considering these processes to yield realistic model predictions. [ABSTRACT FROM AUTHOR]

Summary: Global vegetation and land‐surface models embody interdisciplinary scientific understanding of the behaviour of plants and ecosystems, and are indispensable to project the impacts of environmental change on vegetation and the interactions between vegetation and climate. However, systematic errors and persistently large differences among carbon and water cycle projections by different models highlight the limitations of current process formulations. In this review, focusing on core plant functions in the terrestrial carbon and water cycles, we show how unifying hypotheses derived from eco‐evolutionary optimality (EEO) principles can provide novel, parameter‐sparse representations of plant and vegetation processes. We present case studies that demonstrate how EEO generates parsimonious representations of core, leaf‐level processes that are individually testable and supported by evidence. EEO approaches to photosynthesis and primary production, dark respiration and stomatal behaviour are ripe for implementation in global models. EEO approaches to other important traits, including the leaf economics spectrum and applications of EEO at the community level are active research areas. Independently tested modules emerging from EEO studies could profitably be integrated into modelling frameworks that account for the multiple time scales on which plants and plant communities adjust to environmental change. [ABSTRACT FROM AUTHOR]

Summary: Soil invertebrates make significant contributions to the recycling of dead plant material across the globe. However, studies focussed on the consequences of decomposition for plant communities largely ignore soil fauna across all ecosystems, because microbes are often considered the primary agents of decay. Here, we explore the role of invertebrates as not simply facilitators of microbial decomposition, but as true decomposers, able to break down dead organic matter with their own endogenic enzymes, with direct and indirect impacts on the soil environment and plants. We recommend a holistic view of decomposition, highlighting how invertebrates and microbes act in synergy to degrade organic matter, providing ecological services that underpin plant growth and survival. [ABSTRACT FROM AUTHOR]

Summary: Plant–soil feedback (PSF) may change in strength over the life of plant individuals as plants continue to modify the soil microbial community. However, the temporal variation in PSF is rarely quantified and its impacts on plant communities remain unknown.Using a chronosequence reconstructed from annual aerial photographs of a coastal dune ecosystem, we characterized > 20‐yr changes in soil microbial communities associated with individuals of the four dominant perennial species, one legume and three nonlegume. We also quantified the effects of soil biota on conspecific and heterospecific seedling performance in a glasshouse experiment that preserved soil properties of these individual plants. Additionally, we used a general individual‐based model to explore the potential consequences of temporally varying PSF on plant community assembly.In all plant species, microbial communities changed with plant age. However, responses of plants to the turnover in microbial composition depended on the identity of the seedling species: only the soil biota effect experienced by the nonlegume species became increasingly negative with longer soil conditioning. Model simulation suggested that temporal changes in PSF could affect the transient dynamics of plant community assembly.These results suggest that temporal variation in PSF over the life of individual plants should be considered to understand how PSF structures plant communities. [ABSTRACT FROM AUTHOR]

Summary: Latitudinal gradients provide opportunities to better understand soil fungal community assembly and its relationship with vegetation, climate, soil and ecosystem function. Understanding the mechanisms underlying community assembly is essential for predicting compositional responses to changing environments.We quantified the relative importance of stochastic and deterministic processes in structuring soil fungal communities using patterns of community dissimilarity observed within and between 12 natural forests and related these to environmental variation within and among sites.The results revealed that whole fungal communities and communities of arbuscular and ectomycorrhizal fungi consistently exhibited divergent patterns but with less divergence for ectomycorrhizal fungi at most sites. Within those forests, no clear relationships were observed between the degree of divergence within fungal and plant communities. When comparing communities at larger spatial scales, among the 12 forests, we observed distinct separation in all three fungal groups among tropical, subtropical and temperate climatic zones. Soil fungal β‐diversity patterns between forests were also greater when comparing forests exhibiting high environmental heterogeneity.Taken together, although large‐scale community turnover could be attributed to specific environmental drivers, the differences among fungal communities in soils within forests was high even at local scales. [ABSTRACT FROM AUTHOR]

1a,b) consider the mere presence or absence of AM fungi, irrespective of whether other mycorrhizal structures are apparent in plant roots, to define AM and NM plant species (hereafter the I colonization i criterion; Table 1). However, given the high share of AM and NM plant species in the previous largest mycorrhizal database (73.1% and 18.0%, respectively, in WQ) and in the FungalRoot database (76.6% for AM, 15.5% for NM), these are critical issues to be resolved. FungalRoot defines AM and NM plant species based on the presence or absence of arbuscules (hereafter the I arbuscule i criterion; Table 1). In fact, many empirical observations of AM plant species indicate that plant individuals present at a particular location or time do not associate with mycorrhizal fungi, while other individuals do. [Extracted from the article]