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Abstract Plant ecological strategies are shaped by numerous functional traits and their trade‐offs. Trait network analysis enables testing hypotheses for the shifting of trait correlation architecture across communities differing in climate and productivity.We built plant trait networks (PTNs) for 118 species within six communities across an aridity gradient, from forest to semi‐desert across the California Floristic Province, based on 34 leaf and wood functional traits, representing hydraulic and photosynthetic function, structure, economics and size. We developed hypotheses for the association of PTN parameters with climate and ecosystem properties, based on theory for the adaptation of species to low resource/stressful environments versus higher resource availability environments with greater potential niche differentiation. Thus, we hypothesized that across community PTNs, trait network connectivity (i.e., the degree that traits are intercorrelated) and network complexity (i.e., the number of trait modules, and the degree of trait integration among modules) would be lower for communities adapted to arid climates and higher for communities adapted to greater water availability, similarly to trends expected for phylogenetic diversity, functional richness and productivity. Further, within given PTNs, we hypothesized that traits would vary strongly in their network connectivity and that the traits most centrally connected within PTNs would be those with the least across‐species variation.Across communities from more arid to wetter climates, PTN architecture varied from less to more interconnected and complex, in association with functional richness, but PTN architecture was independent of phylogenetic diversity and ecosystem productivity. Within the community PTNs, traits with lower species variation were more interconnected.Synthesis. The responsiveness of PTN architecture to climate highlights how a wide range of traits contributes to physiological and ecological strategies with an architecture that varies among plant communities. Communities in more arid environments show a lower degree of phenotypic integration, consistent with lesser niche differentiation. Our study extends the usefulness of PTNs as an approach to quantify tradeoffs among multiple traits, providing connectivity and complexity parameters as tools that clarify plant environmental adaptation and patterns of trait associations that would influence species distributions, community assembly, and ecosystem resilience in response to climate change. 

Forest diversity is the outcome of multiple species-specific processes and tolerances, from regeneration, growth, competition and mortality of trees. Predicting diversity thus requires a comprehensive understanding of those processes. Regeneration processes have traditionally been overlooked, due to high stochasticity and assumptions that recruitment is not limiting for forests. Thus, we investigated the importance of seed production and seedling survival on forest diversity in the Pacific Northwest (PNW) using a forest gap model (ForClim). Equations for regeneration processes were fit to empirical data and added into the model, followed by simulations where regeneration processes and parameter values varied. Adding regeneration processes into ForClim improved the simulation of species composition, compared to Forest Inventory Analysis data. We also found that seed production was not as important as seedling survival, and the time it took for seedlings to grow into saplings was a critical recruitment parameter for accurately capturing tree species diversity in PNW forest stands. However, our simulations considered historical climate only. Due to the sensitivity of seed production and seedling survival to weather, future climate change may alter seed production or seedling survival and future climate change simulations should include these regeneration processes to predict future forest dynamics in the PNW. This article is part of the theme issue ‘Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere’. 

Abstract Studies of community assembly often explore the role of niche selection in limiting the diversity of functional traits (underdispersion) or increasing the diversity of functional traits (overdispersion) within local communities. While these patterns have primarily been explored with morphological functional traits related to environmental tolerances and resource acquisition, plant metabolomics may provide an additional functional dimension of community assembly to expand our understanding of how niche selection changes along environmental gradients. Here, we examine how the functional diversity of leaf secondary metabolites and traditional morphological plant traits changes along local environmental gradients in three temperate forest ecosystems across North America. Specifically, we asked whether co‐occurring tree species exhibit local‐scale over‐ or underdispersion of metabolomic and morphological traits, and whether differences in trait dispersion among local communities are associated with environmental gradients of soil resources and topography. Across tree species, we find that most metabolomic traits are not correlated with morphological traits, adding a unique dimension to functional trait space. Within forest plots, metabolomic traits tended to be overdispersed while morphological traits tended to be underdispersed. Additionally, local environmental gradients had site‐specific effects on metabolomic and morphological trait dispersion patterns. Taken together, these results show that different suites of traits can result in contrasting patterns of functional diversity along environmental gradients and suggest that multiple community assembly mechanisms operate simultaneously to structure functional diversity in temperate forest ecosystems. 

Tectonically driven physiographic evolution in early Miocene of eastern Africa significantly shaped landscapes, climates, and vegetation, resulting in habitat heterogeneity. Early hominoids inhabited these landscapes, and their evolutionary history was likely influenced by these heterogenous environments. In western Kenya, around the extinct Tinderet Volcano (ca. 19-21Ma), fossil-rich exposures offer crucial insights into this history with evidence of early hominoids. Here we use analyses of sedimentology, paleosol paleoclimate proxies, fossil leaves, and forestry metrics, to reconstruct the paleoclimate and paleoecological reconstruction of the Koru-16 fossil site. Sedimentological and stratigraphic analyses at Koru-16 reveal a landscape marked disturbance created by periodic volcanic eruptions and stable intervals marked by moderately to poorly developed paleosols. Paleoclimate reconstructions based on paleosol geochemistry indicates warm and wet conditions. Over 1000 fossil leaves were collected from the Koru-16 site, representing 17 morphotypes across two stratigraphic intervals. Mean annual precipitation estimates based on leaf size of shape indicate >2000mm/yr. Leaf lifespan reconstructions reveal predominantly evergreen taxa with a distribution leaf lifespan, similar to modern equatorial African rainforests. Fossil tree stump casts suggest an open forest, similar to contemporary tropical forests supporting large-bodied primates. Importantly, fossil leaves, the tree stump casts, a medium-sized pythonid, and multiple specimens of large-bodied primates occur in the same stratigraphic layer demonstrating their cooccurrence in the Koru-16 ecosystem. The multi-proxy paleoclimate and paleoecological reconstructions for Koru-16 converge on a very wet and warm climate supporting a closed, tropical seasonal forest to rainforest biome. This environment likely provided an ideal habitat for early hominoids, emphasizing the role of forested habitats in their early Miocene evolution. Additional work is ongoing on refining the paleosol paleoclimate estimates with a more recent model and δ13C analysis of soil organic matter will help to further refine these reconstructions. 

Background The increased interest in why and how trees die from fire has led to several syntheses of the potential mechanisms of fire-induced tree mortality. However, these generally neglect to consider experimental methods used to simulate fire behaviour conditions. Aims To describe, evaluate the appropriateness of and provide a historical timeline of the different approaches that have been used to simulate fire behaviour in fire-induced tree mortality studies. Methods We conducted a historical review of the different actual and fire proxy methods that have been used to further our understanding of fire-induced tree mortality. Key results Most studies that assess the mechanisms of fire-induced tree mortality in laboratory settings make use of fire proxies instead of real fires and use cut branches instead of live plants. Implications Further research should assess mechanisms of fire-induced tree mortality using live plants in paired combustion laboratory and landscape fire experiments. 

Hominoids exhibited high diversity in the early Neogene. The Early Miocene, in particular, is the inferred timing of the origin of the crown Hominoidea. Thus, understanding the paleoecology and paleoenvironments of the Early Miocene is critical for understanding the selective pressures that led to the evolution and diversification of hominoids. The Early Miocene fossil sites of Koru, Legetet, and Chamtwara occur on the southwestern flank of the now-extinct Tinderet volcano in western Kenya. While not as well- known as the Songhor site on the northwestern flank of the same volcano, the Chamtwara, Legetet, and Koru sites surrounding the village of Koru document surprising taxonomic diversity of Early Miocene hominoids; yet relatively little paleoenvironmental work has been conducted to contextualize this taxonomic diversity. Our recent geological, paleontological, and paleoenvironmental work has focused on reconstructing the paleoclimate and paleoecology of these fossil sites using a variety of proxies. Sedimentological analyses of the fossil sites indicate periodic disturbance of the landscape due to volcanic activity and that most of the fossiliferous strata are moderately to poorly developed paleosols and fluvial channels. Paleosol features are nearly identical across sites and demonstrate relatively wet and well-drained conditions with some evidence of seasonality and/or periodic water deficit. Paleosol based proxies for paleoclimate indicate wet conditions with mean annual precipitation greater than 175 cm/year. Paleobotanical proxies from fossil leaves and fossil tree stump casts indicate a warm and very wet climate indicating a tropical seasonal forest to tropical rainforest biome. Paleoclimate estimates based on habitats of extant relatives and vertebral ecomorphology of fossil snakes similarly indicate very warm and wet conditions consistent with tropical rainforests. Faunal analyses of the mammal community composition and dietary ecology also indicate forested environments. Taken together, our multi-proxy reconstructions of paleoclimate and paleoenvironment indicate that the Chamtwara, Legetet, and Koru sites were warm and very wet forested habitats connecting early hominoids to closed habitats. 

Abstract Improved estimation of climate niches is critical, given climate change. Plant adaptation to climate depends on their physiological traits and their distributions, yet traits are rarely used to inform the estimation of species climate niches, and the power of a trait‐based approach has been controversial, given the many ecological factors and methodological issues that may result in decoupling of species' traits from their native climate.For 107 species across six ecosystems of California, we tested the hypothesis that mechanistic leaf and wood traits can robustly predict the mean of diverse species' climate distributions, when combining methodological improvements from previous studies, including standard trait measurements and sampling plants growing together at few sites. Further, we introduce an approach to quantify species' trait‐climate mismatch.We demonstrate a strong power to predict species mean climate from traits. As hypothesized, the prediction of species mean climate is stronger (and mismatch lower) when traits are sampled for individuals closer to species' mean climates.Improved resolution of species' climate niches based on mechanistic traits can importantly inform conservation of vulnerable species under the threat of climatic shifts in upcoming decades. Read the freePlain Language Summaryfor this article on the Journal blog. 

Tectonically driven physiographic evolution has profound effects on the climate and vegetation of Early Miocene terrestrial ecosystems across eastern Africa, creating habitat heterogeneity. Early hominoids were present on these dynamic landscapes, which likely influenced their evolutionary history. In western Kenya, a series of Early Miocene (ca.19-21Ma) fossiliferous exposures around the now-extinct Tinderet volcano document this history through preservation of hominoid fossils, fossil leaves, tree stump casts, and paleosols. Here, we use multiple proxies to reconstruct the paleoclimate and paleoecology of the fossil site Koru-16. Sedimentological and stratigraphic analysis indicate the landscape was disturbed by periodic eruptions of the volcano followed by intervals of stability, as shown by features of moderate to poorly developed paleosols. Paleoclimate estimates using the paleosol-paleoclimate model (PPM) indicate warm and wet climate conditions. Over 1000 fossil leaves were collected from two stratigraphic intervals. Seventeen morphotypes were identified across both sites, with an unequal distribution of morphotypes. Average leaf size estimate is mesophyll to megaphyll, with mean annual precipitation estimates using leaf physiognomic methods indicate >2000mm/yr. Leaf lifespan reconstructions based on leaf mass per area (MA) proxy indicate the site was predominately evergreen, with few deciduous taxa, with a MA distribution like modern tropical rainforests and tropical seasonal forests in equatorial Africa. Forest density estimates based on fossil tree stump casts indicate an open forest, with density similar to modern tropical forests that support large-bodied primates. Importantly, fossil leaves, tree stump casts, a medium-sized pythonid, a large-bodied hominoid and Proconsul africanus are all found within the same strata, indicating that these early apes lived within the reconstructed Koru-16 ecosystem. Our multi-proxy paleoclimate and paleoecological reconstructions indicate Koru-16 site sampled a very wet and warm climate that supported a tropical seasonal forest to rainforest biome. This likely provided an ideal habitat for hominoids and suggests that forested habitats played a role in the evolution of Early Miocene hominoids.