Climate change may alter microscale-effective ecosystem properties such as atmospheric water vapour pressure, but consequences for plant growth are insufficiently understood. Within a northwest German heathland an open-top chamber experiment was established to analyse the effects of elevated vapour pressure deficit (eVPD) on growth responses of Calluna vulgaris considering both plant origin (Atlantic (AP), sub-Atlantic (SAP), sub-Continental (SCP)) and life-history stage (1-year vs. 10-year old plants). We hypothesised that the plants’ sensitivity to eVPD decreases (i) from AP to SCP and (ii) with progressing life-history stage. Elevated VPD caused a provenance-specific decrease of shoot increment whilst aboveground biomass productivity remained unaffected. AP and SAP responded with increasing belowground biomass δ¹³C signatures to eVPD, whereas δ¹³C values decreased for SCP. Moreover, eVPD increased and decreased belowground biomass δ¹³C signatures of 1- and 10-year old plants, respectively. These responses to eVPD were related to differences in morphological-chemical traits and the plants’ trait plasticity in response to eVPD. SCP showed the highest aboveground tissue mass density and significantly increased tissue C:N ratios under eVPD. One-year old plants had a tenfold higher shoot:root ratio than 10-year old plants, making young plants more sensitive to eVPD. Our findings demonstrate that the atmospheric water status affects the morphology and physiology of Calluna independent of the soil water status. The results have implications for the conservation of heathlands under climate change: (i) SCP may constitute an appropriate ecotype for assisted migration-approaches, and (ii) management needs to weigh different options for heathland rejuvenation.

气候变化可能会改变微尺度有效的生态系统特性，例如大气中的水蒸气压，但对植物生长的后果知之甚少。在德国西北的欧石南丛生的荒地上，建立了一个开放式室内实验，以分析蒸气压不足（eVPD）对寻常红菜的生长反应的影响。同时考虑植物起源（大西洋（AP），亚大西洋（SAP），亚大陆（SCP））和生活史阶段（1年对10年龄植物）。我们假设植物对eVPD的敏感性随着（i）从AP到SCP的降低以及（ii）随着生命历史阶段的发展而降低。VPD升高导致出苗率增加，但地上生物量生产力未受影响。AP和SAP响应随地下生物量δ ^13个Ç签名EVPD，而δ ¹³ C值降低为SCP。此外，EVPD增大和减小地下生物量δ ¹³1年和10年龄植物的C签名。这些对eVPD的响应与eVPD响应的形态化学性状和植物性状可塑性的差异有关。在eVPD下，SCP表现出最高的地上组织密度，并且组织C：N比显着增加。一岁的植物的苗：根比比十岁的植物高十倍，这使年轻植物对eVPD更加敏感。我们的发现表明，大气中的水分状况会影响卡卢纳草的形态和生理与土壤水分状况无关。结果对气候变化下的荒地保护具有重要意义：（i）SCP可能构成适合于辅助迁徙方法的生态类型，并且（ii）管理层需要权衡荒地复兴的不同选择。