Abstract. Plant carbon (C) content is one of the most important plant traits and is critical to the assessment of global C cycle and ecological stoichiometry; however, the global variations in plant C content remain poorly understood. In this study, we conducted a global analysis of the plant C content by synthesizing data from 4318 species to document specific values and their variation of the C content across plant organs and life forms. Plant organ C contents ranged from 45.0 % in reproductive organs to 47.9 % in stems at global scales, which were significantly lower than the widely employed canonical value of 50 %. Plant C content in leaves (global mean of 46.9 %) was higher than that in roots (45.6 %). Across life forms, woody plants exhibited higher C content than herbaceous plants. Conifers, relative to broad-leaved woody species, had higher C content in roots, leaves, and stems. Plant C content tended to show a decrease with increasing latitude. The life form explained more variation of the C content than climate. Our findings suggest that specific C content values of different organs and life forms developed in our study should be incorporated into the estimations of regional and global vegetation biomass C stocks.

<p><strong>Abstract.</strong> Abstract. Plant carbon (C) content is one of the most important plant traits and is critical in the assessment of global C cycle and ecological stoichiometry. However, the global variation in plant C content remains poorly understood. We conducted a global analysis of the plant C content by synthesizing data from 4318 species to provide specific values of C content and to assess their variation across plant organs and life forms. Our results showed that C content varied markedly across plant organs. Plant organ C content ranged from 45.01 % in reproductive organs to 47.88 % in stems at global scales, which were significantly lower than a canonical value of 50 % that has been widely employed in previous studies. Plant C content in leaves was higher than that in roots. Across life forms, woody plants exhibited higher C content than herbaceous plants. Conifers, relative to broad-leaved woody species, had higher C content in roots, leaves and stems. Plant C content tended to decrease with the increasing latitude. The life form explained more variation of the C content than climate due to plant structural requirements. Our findings suggest that specific C content values from different organs and life forms may be more suitable to evaluate global vegetation C stock and plant ecological stoichiometry.</p>

A key challenge in ecology is to understand the relationships between organismal traits and ecosystem processes. Here, with a novel dataset of leaf length and width for 10 480 woody dicots in China and 2374 in North America, we show that the variation in community mean leaf size is highly correlated with the variation in climate and ecosystem primary productivity, independent of plant life form. These relationships likely reflect how natural selection modifies leaf size across varying climates in conjunction with how climate influences canopy total leaf area. We find that the leaf size-primary productivity functions based on the Chinese dataset can predict productivity in North America and vice-versa. In addition to advancing understanding of the relationship between a climate-driven trait and ecosystem functioning, our findings suggest that leaf size can also be a promising tool in palaeoecology for scaling from fossil leaves to palaeo-primary productivity of woody ecosystems.

Aim Leaf margin states have been found to be strongly related to temperature, and hence have been used to reconstruct palaeotemperatures. Here, we aimed to explore the uncertainties and conditions of use of this technique in China by testing the influences of plant life‐form, precipitation and evolutionary history on the relationship between percentage of untoothed species and temperature. Location China. Methods Using distribution maps and leaf margin states (untoothed versus toothed) of 10,480 Chinese woody dicots and dated family‐level phylogenies, we evaluated the phylogenetic signal of leaf margin state, and demonstrated the variation in the patterns of leaf margin percentage and the relationship with temperature across different life‐forms (evergreen and deciduous; trees, shrubs and lianas), regions with different precipitation and species quartiles with different family ages. Results Significant phylogenetic signals were found for the percentage of untoothed species within families. Relationships between leaf margin percentage and temperature were: (1) weak or insignificant for all woody dicots, shrubs, evergreen and deciduous dicots, but strong for trees and lianas; (2) significantly enhanced with increasing precipitation, and (3) significantly weakened for trees belonging to old families. Main conclusions Our results showed the complete leaf margin spectrum found in China and revealed great uncertainties in its relationship with temperature induced by life‐form, precipitation and evolutionary history. These findings suggest that analysis of leaf margins for palaeotemperature reconstruction should be done cautiously: (1) only dicot trees with a relatively young family age can be used and their leaf margin states are more strongly affected by winter cold than by mean annual temperature; (2) the transfer function between leaf margin percentage and temperature is only reliable in humid and semi‐humid regions of China.

Aims Morphological variation of leaves is a key indicator of plant response to climatic change. Leaf size and shape are associated with carbon, water and energy exchange of plants with their environment. However, whether and how leaf size and shape responded to climate change over the past decades remains poorly studied. Moreover, many studies have only explored inter- but not intraspecific variation in leaf size and shape across space and time. Methods We collected >6000 herbarium specimens spanning 98 years (1910–2008) in China for seven representative dicot species and measured their leaf length and width. We explored geographical patterns and temporal trends in leaf size (i.e. leaf length, leaf width and length × width product) and shape (i.e. length/width ratio), and investigated the effects of changes in precipitation and temperature over time and space on the variation in leaf size and shape. Important Findings After accounting for the effects of sampling time, leaf size decreased with latitude for all species combined, but the relationship varied among species. Leaf size and shape were positively correlated with temperature and precipitation across space. After accounting for the effects of sampling locations, leaf size of all species combined increased with time. Leaf size changes over time were mostly positively correlated with precipitation, whereas leaf shape changes were mostly correlated with temperature. Overall, our results indicate significant spatial and temporal intraspecific variation in leaf size and shape in response to climate. Our study also demonstrates that herbarium specimens collected over a considerable period of time provide a good resource to study the impacts of climate change on plant morphological traits.