The responses of angiosperms and gymnosperms to environmental variables (e.g., rainfall [MAP], temperature [MAT] and pCO₂) remain ambiguous and require systematic investigation. This study monitored the plants' responses to changing environments and measured variations in molecular n-alkane indices, δ¹³C_bulk, δ¹³C_n-alkanes, and δ²H_n-alkanes values in woody gymnosperms (n = 36) and angiosperms (n = 17) from an altitudinal gradient (0.9 to 3.8 km) in the Himalayas The results indicate that δ¹³C_bulk values in angiosperms show a moderate correlation with altitude, MAP, and pCO₂, while gymnosperms show no response in their δ¹³C_bulk. The δ¹³C_n-alkanes values in angiosperms remain unaffected by MAP, MAT, and pCO₂, whereas gymnosperms exhibit a moderate negative correlation. The fractionations between δ¹³C_n-alkanes and δ¹³C_bulk values (ɛ_alk/leaf) are approximately –4.0 ± 1.6 ‰ and –5.6 ± 1.5 ‰ for gymnosperms and angiosperms, respectively. In gymnosperms, the fractionation between δ²H_n-alkane and δ²H_rain (ɛ_alk/rain) is –133.2 ± 39.8 ‰ and –122.8 ± 38.0 ‰ (C₃₁), while in angiosperms, it is –88.5 ± 44.6 ‰ (C₂₉) and –62.4 ± 22.9 ‰ (C₃₁). The δ²H_n-alkane values in gymnosperms and angiosperms are weakly and positively influenced by MAT and MAP, respectively. We found that gymnosperms are enriched in ¹³C (∼1.5–3.0 ‰) and depleted in ²H (∼56–60 ‰) compared to angiosperms; this pattern is consistent throughout the latitudes sampled in this study. The species-specific isotopic response to environmental factors is primarily driven by lower stomatal conductance, smaller leaf-size, and presence of complex tracheids in gymnosperms compared to angiosperms. The statistical K-means algorithm of dual isotope analysis (δ¹³C_n-alkanes and δ²H_n-alkane) provided two distinct clusters with an accuracy of 70 % for angiosperms and gymnosperms, which has implications for studying past vegetation transitions.

被子植物和裸子植物对环境变量（例如降雨量 [MAP]、温度 [MAT] 和 pCO ₂ ）的响应仍然不明确，需要系统研究。这项研究监测了植物对环境变化的反应，并测量了分子正烷烃指数的变化，δ ¹³ C _bulk 、 δ ¹³ C _n 和 δ ² H _{n -alkanes} 值）来自喜马拉雅山的海拔梯度（0.9 至 3.8 km） 结果表明，被子植物中的 δ ¹³ C _bulk 值与海拔、MAP 和 pCO ₂ ，而裸子植物的 δ ¹³ C _bulk 没有表现出任何反应。被子植物中的 δ ¹³ C _{n -alkanes} 值不受 MAP、MAT 和 pCO ₂ 的影响，而裸子植物表现出中度负值相关性。 δ ¹³ C _{n -alkanes} 和 δ ¹³ C _bulk 值之间的分数 (ɛ _alk/leaf H _{n -alkane} 和 δ ² H _rain (ɛ _alk/rain ）为 –133.2 ± 39.8 ‰ 和 –122.8 ± 38.0 ‰ (C ₃₁ )，而在被子植物中，为 –88.5 ± 44.6 ‰ (C ₂₉ )和 –62.4 ± 22.9 ‰ (C ₃₁ )。裸子植物和被子植物的 δ ² H _{n -alkane} 值分别受 MAT 和 MAP 的弱影响和正影响。我们发现，与被子植物相比，裸子植物富含 ¹³ C（∼1.5–3.0 ‰），缺乏 ² H（∼56–60 ‰）；这种模式在本研究采样的整个纬度地区都是一致的。 与被子植物相比，裸子植物对环境因素的物种特异性同位素反应主要是由较低的气孔导度、较小的叶片尺寸和复杂管胞的存在驱动的。双同位素分析的统计K-means算法（δ ¹³ C _{n -alkanes} 和δ ² H _{n -alkane} ）为被子植物和裸子植物提供了两个不同的簇，准确度为 70%，这对于研究过去的植被转变具有重要意义。