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

1.Stomata control carbon and water vapor exchange between leaves and the atmosphere, thus it can influence water use efficiency and reflect plant adaptation to climate. However, the spatial patterns of leaf stomatal traits and relationships between stomatal trait and water use efficiency 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 water use efficiency 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.

1. 气孔（stomata）调控叶片与大气间的碳与水汽交换，因此可影响植物水分利用效率（water use efficiency），并反映植物对气候的适应能力。然而，自然群落中叶片气孔性状（stomatal traits）的空间分布格局，以及气孔性状与水分利用效率之间的关联仍尚不明确。
2. 我们对涵盖热带至寒温带的9类森林中的737种植物，测定了其气孔密度（stomatal density）、气孔大小（stomatal size）及气孔面积占比（stomatal area fraction）。
3. 气孔密度、气孔大小及气孔面积占比均呈对数正态分布，且在物种、植物功能群（plant functional groups，乔木、灌木与草本）以及群落间存在显著差异。在区域尺度上，气孔性状的变异主要与物种相关，其次为气候与土壤类型。
4. 气孔大小的群落加权平均值（community-weighted mean）随纬度呈线性增加趋势，而气孔密度与气孔面积占比的群落加权平均值则呈现驼峰型关联。气孔面积占比的群落加权平均值与气候干旱度（climatic aridity）呈相关关系，这与植物物种在水分可获得的干旱区域实现高最大气体交换速率的适应策略相一致。进一步研究发现，在自然森林群落中，气孔面积占比的群落加权平均值与水分利用效率呈正相关，表明植物会通过降低气孔导度（stomatal conductance）以适应更强的干旱环境。
5. 本研究结果揭示了区域尺度下气孔性状与植物功能群及气候间的紧密关联，体现了自然森林群落中气孔性状对气候的适应策略。