Variation of stomatal traits from cold temperate to tropical forests and association with water use efficiency

Abstract

Abstract1. Stomata control carbon and water vapour exchange between leaves and the atmosphere, thus it can influence water use efficiency (WUE) and reflect plant adaptation to climate. However, the spatial patterns of leaf stomatal traits and relationships between stomatal trait and WUE across natural communities remain unclear.2. We measured stomatal density, stomatal size and stomatal area fraction for 737 plant species from nine forests ranging from tropical to cold temperate forests.3. Stomatal density, stomatal size and stomatal area fraction were all log-normally distributed, and different across species, plant functional groups (trees, shrubs, and herbs), and communities. At the regional scale, variation in stomatal traits was primarily related to species, followed by climate and soil types.4. The community-weighted mean of stomatal size increased linearly with latitude, whereas those of stomatal density and stomatal area fraction showed humpbacked relationship. The community-weighted mean of stomatal area fraction was correlated with climatic aridity, consistent with the adaptation strategies of plant species to achieve high maximum rates of gas exchange in arid regions when water is available. Further, community-weighted mean of stomatal area fraction was positively correlated with WUE in natural forest communities, indicating that plants have lower stomatal conductance in order to adapt greater aridity conditions. 5. These findings highlight the strong associations of stomatal traits with plant functional group and climate at a regional scale, representing the adaptation strategies of stomatal traits across natural forest communities to climate. K E Y W O R D Scommunity, phylogeny, plant functional group, stomata, water use efficiency

Variation in leaf anatomical traits from tropical to cold‐temperate forests and linkage to ecosystem functions

“…Through an investigation of stomatal density and stomatal size across 737 common species, Liu et al. () found that stomatal area fraction (the product of stomatal density and size) correlated positively with forest WUE, providing a new ecological parameter in modelling CO 2 and H 2 O exchange at the community scale. In this study, we found that leaf anatomical traits were closely related to GPP and WUE, providing new parameters for modelling optimization.…”

Trait selection and community weighting are key to understanding ecosystem responses to changing precipitation regimes

“…Anatomical traits related to hydraulic transport and water‐use efficiency, such as stomatal pore index (SPI; % of leaf area composed of stomata; Sack, Cowan, Jaikumar, & Holbrook, ), can be easily measured at the community level as samples can be collected and preserved for later trait determination. Indeed, recent work suggests that community‐weighted SPI is well correlated with MAP across both herbaceous and woody‐dominated ecosystems and is linked to spatial variation in NPP (Forrestel et al., ; Liu et al., ; Figure ). These findings suggest that SPI, and other anatomical traits linked to hydraulic function, are promising trait candidates for predicting NPP responses to chronic alterations in water availability (Suding et al., ; Smith et al., ; Figure ).…”

Functional traits along a transect

“…Similarly Liu et al. () demonstrated that ecosystem WUE correlated well with stomata traits only at the community level. Those studies provided new insights to better understand the relationship between plant traits and ecosystem functioning.…”

“…To answer the above questions, the papers in this issue explored the spatial patterns and controlling factors of leaf stomatal and anatomical traits, root traits from species to community level (He et al., ; Liu et al., ; Wang, Wang, Zhao, et al, ; Zhao et al., ). Across the papers, the spatial patterns of plant functional traits were distinctly different at various levels.…”

“…Moreover, the variations of six first‐order root traits (root diameter, specific root length, root tissue density, root carbon concentration, root nitrogen concentration and root C:N ratio) measured along the transect were mainly determined by species phylogenetic history, while community‐level traits were mainly driven by temperature through shifts in species composition (Wang, Wang, Zhao, et al, ). Furthermore, two papers in this special issue comprehensively illustrated the spatial patterns and their underlying mechanisms of leaf stomatal traits (density, size and relative area) (Liu et al., ) and leaf anatomical traits (adaxial epidermis thickness, abaxial epidermis thickness, leaf thickness, palisade‐spongy tissue ratio, palisade tissue‐leaf thickness ratio and spongy tissue‐leaf thickness ratio) (He et al., ) at the species, plant functional group and community level from tropical to cold‐temperate forests. Those findings filled the gaps about large‐scale patterns of plant traits and their controlling environmental factors, which is fundamentally important for benchmarking trait‐based models.…”