To understand the cause of known isotopic differences between grasses and trees, their seasonal variability and environmental drivers, we present a parallel study of a perennial grass, Stipa bungeana, and an evergreen tree, Quercus aquifolioides, in the monsoon-dominated southeastern Tibetan Plateau (TP), by conducting fortnightly paired δ²H analyses of precipitation (δ²H_p), leaf water, and n-alkanes (δ²H_wax) over a period of 2 y. Similar to previous investigations, we show that δ²H_wax in both species are correlated to δ²H_p throughout two growing seasons. However, for the first time, we identified a time lag of 2 months in variation of δ²H_wax relative to δ²H_p in new Q. aquifolioides leaves, whereas nearly no lagged phenomena were observed in S. bungeana and old mature Q. aquifolioides leaves. The δ²H_wax in new Q. aquifolioides leaves correlated significantly with the total amount of n-alkanes. These findings suggest that the turnover rate of n-alkanes in new Q. aquifolioides leaves is possibly changing with their synthesis, and that is a possible mechanism of the observed delayed phenomenon. A paired t-test showed that the difference of δ²H_wax between trees and grasses becomes insignificant after time-lag correction. Moreover, the apparent fractionation in Q. aquifolioides was significantly correlated with weekly or fortnightly precipitation amount, temperature, relative humidity, and wind velocity, while in S. bungeana only weekly or fortnightly precipitation amount. Our high temporal resolution observations hence confirm that climate variables are important drivers of plant δ²H_wax and, give significant implications for δ²H_wax-base paleoclimate reconstructions in global monsoonal regions.

为了了解草和树木之间已知同位素差异的原因、它们的季节性变化和环境驱动因素，我们对青藏高原东南部季风主导的多年生草、白针茅和常绿乔木Quercus aquifolioides 进行了平行研究（ TP)，通过在^{2 年的时间内}对沉淀 ( δ ² H _p )、叶水和正烷烃 ( δ ² H_蜡)每两周进行一次配对δ ² H 分析。与之前的研究类似，我们表明两个物种中的δ ² H_蜡与δ ² H _p贯穿两个生长季节。然而，我们第一次发现新Q. aquifolioides叶子中δ ² H_蜡相对于δ ² H _{p 的}变化存在 2 个月的时间滞后，而在S. bungeana和老成熟Q 中几乎没有观察到滞后现象. aquifolioides叶子。新Q. aquifolioides叶子中的δ ² H_蜡与正构烷烃的总量显着相关。这些发现表明n的周转率新Q. aquifolioides叶子中的烷烃可能随着它们的合成而改变，这可能是观察到的延迟现象的机制。配对t检验表明，经过时滞校正后，树木和草之间δ ² H_蜡的差异变得不显着。此外，Q. aquifolioides的表观分馏与每周或每两周的降水量、温度、相对湿度和风速显着相关，而在S. bungeana 中仅与每周或每两周的降水量相关。因此，我们的高时间分辨率观测证实气候变量是植物δ ^{2 的}重要驱动因素H_蜡，对全球季风区δ ² H_蜡基古气候重建具有重要意义。