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Abstract Background Plant traits and plant adaptive strategies have been affected by the increasing intensity and severity of environmental changes. Given the uncertainty surrounding future environmental conditions, investigating plant trait variations under various stresses is crucial for unraveling plant survival strategies. Leaf anatomical traits are closely responsible for plants’ photosynthesis, respiration and transpiration. However, knowledge of how the multi-species leaf anatomical traits varied in extremely and moderately stressful environments is limited. Our objective was to compare the variation of leaf anatomic traits and adaptation strategies in two different stressful regions of the Qinghai-Tibet Plateau (TP) and Mongolian Plateau (MP) of China. Methods We sampled ten sites in each of the two regions (MP and TP) along an environmental gradient. Seven leaf anatomical traits and two leaf economic traits were measured for all leaf samples. Leaf anatomical traits include the traits related to leaf physiological processes (mesophyll thickness (MT), palisade tissue thickness (PT), spongy tissue thickness (ST), palisade-spongy tissue thickness ratio (PST) and epidermal thickness (ET)) and the traits related to trait construction investment (epiderm-leaf thickness ratio (ET/LT) and mesophyll-leaf thickness ratio (MT/LT)). Leaf economic traits include specific leaf area (SLA) and leaf nitrogen content (LN). Results The results revealed that leaf anatomical traits in the TP exhibited greater phylogenetic conservation with thicker structures, being less susceptible to environmental impacts than those in the MP. Additionally, the leaf anatomical and economic traits decoupled both in the MP and TP. Conclusion These findings highlight that plants adopt diverse strategies to cope with extremely and moderately environmental stresses, but multidimensional trait patterns are generally favored in stressful environments.

Grasses are widely distributed in various habitats with significantly different characteristics than non-grass species. However, an understanding of the multi-species differences in leaf anatomical traits variation and adaptive strategies between grass and non-grass species is limited. We measured leaf anatomical traits of 242 species from 10 sampling sites along an environmental gradient on the Loess Plateau (from east to west, environmental temperature, precipitation, and soil nutrients decreased, but radiation increased). Nine leaf anatomical traits were measured, and these traits related to the leaf physiological functions of photosynthesis (mesophyll thickness (MT), palisade tissue thickness (PT), spongy tissue thickness (ST)), defense (epidermal thickness (ET) and leaf thickness (LT)), and transport (xylem conduit diameter (CD) and major vein diameter (MVD)). Subsequently, we calculated the trait ratios, which reflect the proportion of investment in trait construction (epiderm-leaf thickness ratio (ET/LT) and mesophyll-leaf thickness ratio (MT/LT)). The results of linear regression analysis showed that non-grasses living under harsh environmental conditions have thicker leaf tissues responsible for photosynthesis and defense compared to grasses from the same environment. However, grasses and non-grasses living under stressful environmental conditions have higher MT/LT and lower ET/LT compared to species living in environments with a more proper resource supply, which indicated that both preferred to invest less in defense-related traits (e.g., epidermal thickness) while cost more in photosynthesis-related traits (e.g., mesophyll thickness) under the limited resource conditions. These findings highlight that grass and non-grass species have different trait characteristics and adaptive strategies in response to environmental changes. More importantly, a new inspiration is provided for exploring the plants’ general investment rule from the perspective of leaf anatomical trait-ratio values.