The functional diversity-productivity relationship of woody plants is climatically sensitive.

Plot-scale experiments indicate that functional diversity (FD) plays a pivotal role in sustaining ecosystem functions such as net primary productivity (NPP). However, the relationships between functional diversity and NPP across larger scale under varying climatic conditions are sparsely studied, despite its significance for understanding forest-atmosphere interactions and informing policy development. Hence, we examine the relationships of community-weighted mean (CWM) and functional dispersion (FDis) of woody plant traits on NPP across China and if such relationships are modulated by climatic conditions at the national scale. Using comprehensive datasets of distribution, functional traits, and productivity for 9120 Chinese woody plant species, we evaluated the distribution pattern of community-weighted mean and functional dispersion (including three orthogonal trait indicators: plant size, leaf morphology, and flower duration) and its relationships with NPP. Finally, we tested the effects of climatic conditions on community-weighted mean/functional dispersion-NPP relationships. We first found overall functional diversity-NPP relationships, but also that the magnitude of these relationships was sensitive to climate, with plant size community-weighted mean promoting NPP in warm regions and plant size functional dispersion promoting NPP in wet regions. Second, warm and wet conditions indirectly increased NPP by its positive effects on community-weighted mean or functional dispersion, particularly through mean plant size and leaf morphology. Our study provides comprehensive evidence for the relationships between functional diversity and NPP under varying climates at a large scale. Importantly, our results indicate a broadening significance of multidimensional plant functional traits for woody vegetation NPP in response to rising temperatures and wetter climates. Restoration, reforestation actions and natural capital accounting need to carefully consider not only community-weighted mean and functional dispersion but also their interactions with climate, to predict how functional diversity may promote ecosystem functioning under future climatic conditions.

Biodiversity responses to agricultural practices in cropland and natural habitats.

Largely driven by agricultural pressures, biodiversity has experienced great changes globally. Exploring biodiversity responses to agricultural practices associated with agricultural intensification can benefit biodiversity conservation in agricultural landscapes. However, the effects of agricultural practices may also extend to natural habitats. Moreover, agricultural impacts may also vary with geographical region. We analyze biodiversity responses to landscape cropland coverage, cropping frequency, fertiliser and yield, among different land-use types and across geographical regions. We find that species richness and total abundance generally respond negatively to increased landscape cropland coverage. Biodiversity reductions in human land-use types (pasture, plantation forest and cropland) were stronger in tropical than non-tropical regions, which was also true for biodiversity reductions with increasing yield in both human and natural land-use types. Our results underline substantial biodiversity responses to agricultural practices not only in cropland but also in natural habitats, highlighting the fact that biodiversity conservation demands a greater focus on optimizing agricultural management at the landscape scale.

Tree communities and functional traits determine herbivore compositional turnover.

There are many factors known to drive species turnover, although the mechanisms by which these operate are less clear. Based on comprehensive datasets from the largest tree diversity experiment worldwide (BEF-China), we used shared herbivore species (zeta diversity) and multi-site generalized dissimilarity modelling to investigate the patterns and determinants of species turnover of Lepidoptera herbivores among study plots across a gradient in tree species richness. We found that zeta diversity declined sharply with an increasing number of study plots, with complete changes in caterpillar species composition observed even at the fine spatial scale of our study. Plant community characteristics rather than abiotic factors were found to play key roles in driving caterpillar compositional turnover, although these effects varied with an increasing number of study plots considered, due to the varying contributions of rare and common species to compositional turnover. Our study reveals details of the impact of phylogeny- and trait-mediated processes of trees on herbivore compositional turnover, which has implications for forest management and conservation and shows potential avenues for maintenance of heterogeneity in herbivore communities.

Incorporating global change reveals extinction risk beyond the current Red List.

Global changes over the past few decades have caused species distribution shifts and triggered population declines and local extinctions of many species. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Red List) is regarded as the most comprehensive tool for assessing species extinction risk and has been used at regional, national, and global scales. However, most Red Lists rely on the past and current status of species populations and distributions but do not adequately reflect the risks induced by future global changes. Using distribution maps of >4,000 endemic woody species in China, combined with ensembled species distribution models, we assessed the species threat levels under future climate and land-cover changes using the projected changes in species' suitable habitats and compared our updated Red List with China's existing Red List. We discover an increased number of threatened species in the updated Red List and increased threat levels of >50% of the existing threatened species compared with the existing one. Over 50% of the newly identified threatened species are not adequately covered by protected areas. The Yunnan-Guizhou Plateau, rather than the Hengduan Mountains, is the distribution center of threatened species on the updated Red Lists, as opposed to the threatened species on the existing Red List. Our findings suggest that using Red Lists without considering the impacts of future global changes will underestimate the extinction risks and lead to a biased estimate of conservation priorities, potentially limiting the ability to meet the Kunming-Montreal global conservation targets.

Mapping Asia Plants: The Threat Status and Influencing Factors of Rare and Endangered Vascular Plant Species in North Asia (Asian Russia).

In order to effectively protect rare and endangered plants, 27 provincial-level administrative regions in North Asia (the Asian part of Russia) have compiled and published local Red Data Books. In this study, the names (with synonyms) of vascular plants in the 27 provincial Red Books were digitalized and merged into a database of rare and endangered vascular plants in North Asia. The purpose is to reflect the species composition, geographic distribution pattern, and protection level of these plants and their inclusion in the national Russian Red Data Book and the IUCN Red List, and provide a reference for formulating conservation strategies. The dataset has a total of 2079 species, 160 subspecies, and 53 varieties belonging to 667 genera and 143 families. It contains data on 2292 taxa, including family name, genus name, species name and synonyms, protection level, and other information. We also analyzed the main influencing factors, existing problems of rare and endangered vascular plant species, and suggestions for addressing them. We conclude that, to date, the IUCN criteria have not been applied consistently in all regions, leading to an excessive number of species being recorded in the Red Data Books of Asian Russia; specifically, one-third of all floral species are in the regional Red Data Books.

Diversity and biogeography of plant phyllosphere bacteria are governed by latitude-dependent mechanisms.

Predicting and managing the structure and function of plant microbiomes requires quantitative understanding of community assembly and predictive models of spatial distributions at broad geographic scales. Here, we quantified the relative contribution of abiotic and biotic factors to the assembly of phyllosphere bacterial communities, and developed spatial distribution models for keystone bacterial taxa along a latitudinal gradient, by analyzing 16S rRNA gene sequences from 1453 leaf samples taken from 329 plant species in China. We demonstrated a latitudinal gradient in phyllosphere bacterial diversity and community composition, which was mostly explained by climate and host plant factors. We found that host-related factors were increasingly important in explaining bacterial assembly at higher latitudes while nonhost factors including abiotic environments, spatial proximity and plant neighbors were more important at lower latitudes. We further showed that local plant-bacteria associations were interconnected by hub bacteria taxa to form metacommunity-level networks, and the spatial distribution of these hub taxa was controlled by hosts and spatial factors with varying importance across latitudes. For the first time, we documented a latitude-dependent importance in the driving factors of phyllosphere bacteria assembly and distribution, serving as a baseline for predicting future changes in plant phyllosphere microbiomes under global change and human activities.

Geographical patterns and determinants in plant reproductive phenology duration.

Biodiversity is and always has been an important issue in ecological research. Biodiversity can reflect niche partitioning among species at several spatial and temporal scales and is generally highest in the tropics. One theory to explain it is that low-latitude tropical ecosystems are dominated by species that are generally only distributed over a narrow area. This principle is known as Rapoport's rule. One previously unconsidered extension of Rapoport's rule may be reproductive phenology, where variation in flowering and fruiting length may reflect a temporal range. Herein, we collected reproductive phenology data for more than 20,000 species covering almost all angiosperm species in China. We used a random forest model to quantify the relative role of seven environmental factors on the duration of reproductive phenology. Our results showed that the duration of reproductive phenology decreased with latitude, although there was no obvious change across longitudes. Latitude explained more of the variation in the duration of flowering and fruiting phases in woody plants than in herbaceous plants. Mean annual temperature and the length of the growing season strongly influenced the phenology of herbaceous plants, and average winter temperature and temperature seasonality were important drivers of woody plant phenology. Our result suggests the flowering period of woody plants is sensitive to temperature seasonality, while it does not influence herbaceous plants. By extending Rapoport's rule to consider the distribution of species in time as well as space, we have provided a novel insight into the mechanisms of maintaining high levels of diversity in low-latitude forests.

Patterns of floristic inventory and plant collections in Myanmar.

Myanmar is one of the most biodiverse countries in the Asia-Pacific region due to a wide range of climatic and environmental heterogeneity. Floristic diversity in Myanmar is largely unknown, resulting in a lack of comprehensive conservation plans. We developed a database of higher plants in Myanmar derived from herbarium specimens and literature sources, and analyzed patterns of diversity inventories and collection inconsistencies, aiming to provide a baseline floristic data of Myanmar and act as a guide for future research efforts. We collected 1,329,354 records of 16,218 taxa. Results show that the collection densities at the township level was variable, with 5% of townships having no floristic collections. No ecoregion had an average collection density of greater than 1 specimen/km2 and the lowest collection density was found in the Kayah-Karen Montane Rainforests, which covered 8% of Myanmar's total area. The highest sampling densities were found in Mandalay Region, Chin State, and Yangon Region. Despite floristic collections over the past three centuries, knowledge of the distribution of the vast majority of plant taxa remained limited, particularly for gymnosperms, pteridophytes, and bryophytes. More botanical surveys and further analyses are needed to better describe Myanmar's floristic diversity. An important strategy to promote knowledge of the biodiversity patterns in Myanmar is to improve the collection and digitalization of specimens and to strengthen cooperation among countries.

Flora of Northeast Asia.

As a component of the MAP project, the study of the flora in Northeast Asia (comprising Japan, South Korea, North Korea, Northeast China, and Mongolia) convincingly underscores the indispensability of precise and comprehensive diversity data for flora research. Due to variations in the description of flora across different countries in Northeast Asia, it is essential to update our understanding of the region's overall flora using the latest high-quality diversity data. This study employed the most recently published authoritative data from various countries to conduct a statistical analysis of 225 families, 1782 genera, and 10,514 native vascular species and infraspecific taxa in Northeast Asia. Furthermore, species distribution data were incorporated to delineate three gradients in the overall distribution pattern of plant diversity in Northeast Asia. Specifically, Japan (excluding Hokkaido) emerged as the most prolific hotspot for species, followed by the Korean Peninsula and the coastal areas of Northeast China as the second richest hotspots. Conversely, Hokkaido, inland Northeast China, and Mongolia constituted species barren spots. The formation of the diversity gradients is primarily attributed to the effects of latitude and continental gradients, with altitude and topographic factors within the gradients modulating the distribution of species.

Dear neighbor: Trees with extrafloral nectaries facilitate defense and growth of adjacent undefended trees.

Plant diversity can increase productivity. One mechanism behind this biodiversity effect is facilitation, which is when one species increases the performance of another species. Plants with extrafloral nectaries (EFNs) establish defense mutualisms with ants. However, whether EFN plants facilitate defense of neighboring non-EFN plants is unknown. Synthesizing data on ants, herbivores, leaf damage, and defense traits from a forest biodiversity experiment, we show that trees growing adjacent to EFN trees had higher ant biomass and species richness and lower caterpillar biomass than conspecific controls without EFN-bearing neighbors. Concurrently, the composition of defense traits in non-EFN trees changed. Thus, when non-EFN trees benefit from lower herbivore loads as a result of ants spilling over from EFN tree neighbors, this may allow relatively reduced resource allocation to defense in the former, potentially explaining the higher growth of those trees. Via this mutualist-mediated facilitation, promoting EFN trees in tropical reforestation could foster carbon capture and multiple other ecosystem functions.

Mapping Asia Plants: Historical Outline and Review of Sources on Floristic Diversity in South Asia.

South Asia, which is composed of eight countries, including Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka, is an important global biodiversity hotspot. As a part of the Mapping Asia Plants (MAP) project, we reviewed the history of botanical investigations, floristic works, and publications in this region, as well as the key floras, checklists, and online databases in South Asia. The botanical survey of this region, which began during the 17th century, has two distinct phases: surveys conducted during the British India period and those conducted in the post-British period. The seven volumes of The Flora of British India are the most important contributions to flora research in South Asia because of their wider geographical coverage, which was performed by British botanists. Following on from this, different countries have launched independent floristic surveys. At the country level, Afghanistan, Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka have completed, or partially completed, their flora surveys at the country level, while Maldives has not yet published its national flora survey. According to currently available information, the approximated numbers of plant taxa for each country in South Asia are as follows: Afghanistan, 5261 (vascular plants); Bangladesh, 3470 (vascular plants); Bhutan, 5985 (flowering plants); India, 21,558 (flowering plants); Maldives, 270 (common plants); Nepal, 6500 (flowering plants); Pakistan, 6000+ (vascular plants); and Sri Lanka, 4143 (flowering plants). Additionally, there are 151 books devoted to the key floras and checklists in South Asia. A total of 1.1 million digital records of specimens from this region can be found on the website of the Global Biodiversity Information Facility (GBIF). However, there are still major gaps and limitations-such as out-of-date publications, national floras that are mainly detailed only in local languages, massive non-digitized specimens, and the lack of a comprehensive online database or platform-which should be addressed in terms of their global applications.

Multitrophic arthropod diversity mediates tree diversity effects on primary productivity.

Forests sustain 80% of terrestrial biodiversity and provide essential ecosystem services. Biodiversity experiments have demonstrated that plant diversity correlates with both primary productivity and higher trophic diversity. However, whether higher trophic diversity can mediate the effects of plant diversity on productivity remains unclear. Here, using 5 years of data on aboveground herbivorous, predatory and parasitoid arthropods along with tree growth data within a large-scale forest biodiversity experiment in southeast China, we provide evidence of multidirectional enhancement among the diversity of trees and higher trophic groups and tree productivity. We show that the effects of experimentally increased tree species richness were consistently positive for species richness and abundance of herbivores, predators and parasitoids. Richness effects decreased as trophic levels increased for species richness and abundance of all trophic groups. Multitrophic species richness and abundance of arthropods were important mediators of plant diversity effects on tree productivity, suggesting that optimizing forest management for increased carbon capture can be more effective when the diversity of higher trophic groups is promoted in concert with that of trees.

Global beta-diversity of angiosperm trees is shaped by Quaternary climate change.

As Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleoclimate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (richness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta-diversity in regions that experienced large temperature change, reflecting phylogenetically and functionally selective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide.

Carbon-biodiversity relationships in a highly diverse subtropical forest.

Carbon-focused climate mitigation strategies are becoming increasingly important in forests. However, with ongoing biodiversity declines we require better knowledge of how much such strategies account for biodiversity. We particularly lack information across multiple trophic levels and on established forests, where the interplay between carbon stocks, stand age, and tree diversity might influence carbon-biodiversity relationships. Using a large dataset (>4600 heterotrophic species of 23 taxonomic groups) from secondary, subtropical forests, we tested how multitrophic diversity and diversity within trophic groups relate to aboveground, belowground, and total carbon stocks at different levels of tree species richness and stand age. Our study revealed that aboveground carbon, the key component of climate-based management, was largely unrelated to multitrophic diversity. By contrast, total carbon stocks-that is, including belowground carbon-emerged as a significant predictor of multitrophic diversity. Relationships were nonlinear and strongest for lower trophic levels, but nonsignificant for higher trophic level diversity. Tree species richness and stand age moderated these relationships, suggesting long-term regeneration of forests may be particularly effective in reconciling carbon and biodiversity targets. Our findings highlight that biodiversity benefits of climate-oriented management need to be evaluated carefully, and only maximizing aboveground carbon may fail to account for biodiversity conservation requirements.

Tree mycorrhizal association types control biodiversity-productivity relationship in a subtropical forest.

Mycorrhizae are symbiotic associations between terrestrial plants and fungi in which fungi obtain nutrients in exchange for plant photosynthates. However, it remains unclear how different types of mycorrhizae affect their host interactions and productivity. Using a long-term experiment with a diversity gradient of arbuscular (AM) and ectomycorrhizal (EcM) tree species, we show that the type of mycorrhizae critically controls the effect of diversity on productivity. With increasing diversity, the net primary production of AM trees increased, but EcM trees decreased, largely because AM trees are more effective in acquiring nitrogen and phosphorus. Specifically, with diversity increase, AM trees enhance both nutrient resorption and litter decomposition, while there was a trade-off between litter decomposability and nutrient resorption in EcM trees. These results provide a mechanistic understanding of why AM trees using a different nutrient acquisition strategy from EcM trees can dominate in subtropical forests and at the same time their diversity enhances productivity.