Elevated CO 2 concentration alleviates the negative effect of vapour pressure deficit and soil drought on juvenile poplar growth

Abstract

The growth performance of short-rotation woody coppice (SRWC) is strongly influenced by successful establishment in the initial months after planting. Future climates, expected to be warmer due to elevated atmospheric CO 2(eCO2), may bring about more frequent soil droughts alongside increased vapour pressure deficit (eVPD). Hence,this growth chamber experiment aimed to explore the interactive effects of eVPD, eCO2, and soil drought on growth and physiology traits of juvenile hybrid poplars under warmer climates. Our findings with juvenile hybrid poplarJ-105 revealed that eVPD resulted in reductions in leaf area (–21%), root (–20%) and stem biomass (–9%), as well as in net assimilation (–15%), stomatal conductance (–26%), and transpiration (–13%). However, these decreases were relatively minor compared to the compensating effect of eCO2, which generally exerted a stronger influence than eVPD. While soil drought emerged as the primary growth-limiting factor in our study, elevated VPD is not expected to pose a significant additional threat to central European SRWC plantations of juvenile hybrid poplars under future conditions of ongoing climate change. Elevated CO 2 concentration alleviates the negative effect of vapour pressure deficit and soil drought on juvenile poplar growth.