Chlorophyll (Chl) is an important photosynthetic pigment to the plant, largely determining photosynthetic capacity and hence plant growth. However, this concept has not been verified in natural forests, especially at a large scale. Furthermore, how Chl varies in natural forests remains unclear. In this study, the leaves of 823 plant species were collected from nine typical forest communities, extending from cold-temperate to tropical zones in China, to determine the main factors influencing leaf chlorophyll content in different regions and at different scales. We measured chlorophyll a (Chl a), chlorophyll b (Chl b), Chl (Chl a+Chl b), and the ratio of Chl a and Chl b (Chl a/b). The results showed that Chl a, Chl b, and Chl a/b values were in the range of 0.87–15.92 mg g⁻¹ (mean: 4.18 mg g⁻¹), 0.32–6.42 mg g⁻¹ (mean 1.72 mg g⁻¹), and 1.43–7.07 (mean: 2.47). The values of these three Chl parameters significantly differed among plant functional groups (trees < shrubs < herbs, coniferous trees < broadleaved trees, and evergreens < deciduous trees). Unexpectedly, Chl a, Chl b, and Chl a+b increased slightly with increasing latitude. Climate, soil, and phylogeny exert only a small effect on the spatial variation of Chl in natural forests, with large variation in the Chl of coexisting species masking the spatial patterns. This study is the first to report variations in Chl among different types of natural forests at a large scale, demonstrating that the fuzzy regulation of Chl makes it very difficult to take Chl as the main input parameter to the models of natural forests.

Leaf traits may reflect the adaptation mechanisms of plants to the environment. In this study, we investigated leaf morphological and anatomical traits in nine cold-temperate to tropical forests along a 4,200-km transect to test how they vary across latitudinal gradients. The results showed that leaf dry weight decreased (P < 0.05), while specific leaf area (SLA) increased (P < 0.05) with increasing latitude. Stomatal length and stomatal density did not change significantly, while stomatal pore area index increased (P < 0.05) with increasing latitude. The palisade-leaf mesophyll thickness ratio increased (P < 0.01), while the spongy-leaf mesophyll thickness ratio decreased, with increasing latitude (P < 0.01). Climate and leaf nutrients were the main factors that regulated leaf morphological and anatomical traits. Furthermore, we identified positive correlations between leaf area and leaf dry weight, leaf thickness and palisade mesophyll thickness, but negative correlations between stomatal length and stomatal density (all P < 0.01). The observed negative correlations represented the adaptive mechanisms of leaves through their morphological and anatomical traits. These findings provided new insights into the responses of leaf morphological and anatomical traits to climate changes and important parameters for future model optimization.

Leaf anatomical traits may reflect plants adaption to environmental changes and influence ecosystem functions, as they regulate light absorption and gas exchange to some extent. Here, we hypothesized that leaf anatomical traits were closely related to gross primary productivity (GPP) because photosynthesis commonly occurs in the chloroplasts of palisade and spongy tissues in leaf. Eight leaf anatomical traits were measured in 916 plant species inhabiting from tropical to cold‐temperate forests in eastern China: adaxial epidermis thickness (AD), abaxial epidermis thickness (AB), leaf thickness (LT), palisade tissue thickness (PT), and spongy tissue thickness (ST), palisade–spongy tissue ratio (PT/ST), palisade tissue–leaf thickness ratio (PT/LT), and spongy tissue–leaf thickness ratio (ST/LT). Leaf anatomical traits showed significant latitudinal patterns at species, plant functional group (PFG), and community levels (p < .05), and they differed between PFG and community. Temperature and precipitation were the main factors influencing AD, AB, PT/ST, and PT/LT, explaining 33–72% of the total variation at large scale. Furthermore, AB, LT, PT/ST, and PT/LT were significantly correlated with the aridity index. Our findings filled the data gap of plant anatomical traits at regional scales, and broadened current knowledge on the adaptation strategies of plant anatomical traits, which also provided new evidence for linkages of plant traits and functioning across natural communities. A plain language summary is available for this article.

Nitrogen deposition has increased rapidly in eastern China, which can affect the stoichiometric characteristics of plants. However, the effects of N addition on the nitrogen (N) and phosphorous (P) allocation strategies for various plant life forms (e.g. trees, shrubs, and herbs) have rarely been studied. This study evaluated the effects of N addition on N and P stoichiometry and their scaling exponents in the leaves and fine roots of the different life form groups. N and P concentrations in the leaves of shrubs and herbs increased under N addition treatments, whereas tree leaves exhibited a more stable response. In contrast, N addition has no significant effect on N and P concentrations in the fine roots of the three plant life forms. N addition accelerated the allocation of more N and P to the leaves than to the fine roots in all three life forms. Furthermore, the N-P allocation scaling exponents of the leaves and fine roots of the trees were equal to 1.0, indicating an isometric pattern. In contrast, the N-P allocation scaling exponents of shrubs and herbs were less than 1.0, indicating an allometric pattern. Although high N availability promoted shrubs and herbs to distribute P to leaves at a higher proportion than N, only slight effects were detected in tree leaves. These changes in N-P allocation patterns indicate that life forms and N addition levels work together to modulate plants allocation strategies. This suggests the importance of life form categories when evaluating N-P allocation strategies in forest plants.

Stomata control carbon and water vapor exchange between the leaves and the atmosphere, thus influencing photosynthesis and transpiration. Combinations of forest patches with different stand ages are common in nature, however, information of which stomatal traits vary among these stands and how, remains limited. Here, seven different aged forest stands (6, 14, 25, 36, 45, 55, and 100 years) were selected in typical temperate, mixed broadleaf-conifer forests of northeast China. Stomatal density, size and relative area of 624 species, including the same species in stands of different ages were selected. Stomatal density, size and relative area were distributed log-normally, differing across all species and plant functional groups. Stomatal density ranged from 4.2 to 1276.7 stomata mm^–2, stomatal size ranged from 66.6 to 8315.7 μm², and stomatal relative area 0.1–93.3%. There was a significant negative relationship between density and size at the species and functional group levels, while the relative stomatal area was positively correlated with density and size. Stomatal traits of dominant species were relatively stable across different stand ages but were significantly different for herbs. The results suggest that stomatal traits remain relatively stable for dominant species in natural forests and therefore, spatial variation in stomatal traits across forest patches does not need to be incorporated in future ecological models.