Under global warming, both air temperature and vapor pressure deficit (VPD) have been consistently increasing. These two factors influence vegetation productivity via different physiological and ecological pathways. However, their individual effects have remained unclear at larger spatial scales.
In a study published in Journal of Hydrology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators assessed the individual impacts of temperature or VPD on vegetation productivity across China. Their work represented a first attempt to distinguish the relative contributions of temperature and VPD to vegetation productivity at a regional scale.
Using solar-induced chlorophyll fluorescence and gross primary productivity as proxies for vegetation health, the research team employed advanced statistical methods, including convergent cross mapping and partial least squares structural equation modeling (PLS-SEM), to disentangle the effects of temperature and VPD on gross primary productivity.
They found that VPD consistently exhibited a significant negative effect on vegetation productivity,with this influence being especially strong in arid and semi-arid regions. In contrast, air temperature generally showed a positive effect on productivity when its interactions with other factors were statistically isolated. However, this positive temperature effect was significantly weakened when high temperatures co-occurred with high VPD, highlighting a critical synergistic effect.
Furthermore, their results indicated that the negative effect of VPD is expected to intensify in the future, while the positive effect of temperature is projected to diminish. These shifts are forecasted to be most significant in mid-latitude regions.
“Our work shows that the vapor pressure deficit is not only a side effect but a critical regulator of ecosystem function. Its growing negative impact could severely undermine the ability of vegetation to act as a carbon sink in the future, particularly in mid-latitude regions,” said YANG Jie of XTBG.
In order to enhance ecosystem and agricultural drought resilience, the researchers recommended planting drought-tolerant species in humid regions, establish integrated early warning systems for agricultural drought, modernizing irrigation infrastructure, and optimizing water resource allocation.
Available online: 18 October 2025
