Coppicing Modulates Physiological Responses of Sessile Oak (Quercus Petraea Matt. Lieb.) to Drought

Droughts negatively affect tree vitality, growth and mortality in temperate forests. Appropriate forest management may help mitigate these adverse effects. One such technique is coppicing, which increases a stand’s drought resistance compared to high forests, but the underlying mechanisms are not well explored. Here, we aimed to deepen our mechanistic understanding of the performance of sessile oak ( Quercus petraea ) in response to drought stress in two silvicultural systems (high forest and coppice) and two stages of ontogeny (mature trees, seedlings and young coppice). We measured tree water status, seasonal variation and biochemistry of photosynthesis, and biometric traits of sessile oak over three growing seasons. Coppicing improved water use and photosynthesis both under drought stress conditions and favorable conditions. During mild to severe drought, coppiced trees had better access to water and assimilated more carbon per unit of leaf area than seedlings and mature trees. The lowest predawn water potential of -4.21 MPa was recorded in seedlings, which was by 0.8 MPa less than in the coppice. Water use efficiency of the coppice appeared to vary between mature trees (best WUE i ) and seedlings (worst WUE i ), but photosynthesis rates were highest in the coppice. Combined measurements of chlorophyll fluorescence and gas exchange suggested that coppice, seedlings and mature trees responded differently to drought. Coppice was the most effective in both light-dependent and carbon reactions of photosynthesis. In contrast, photosynthesis in mature trees was mostly limited by CO 2 fixation, and seedlings downregulated the effectivity of the photosynthetic light-harvesting system. All combined, coppice was most effective at avoiding two main drivers of drought-induced dieback: hydraulic failure by maintaining the highest water potential and carbon starvation by promoting the highest rates of photosynthesis. Coppicing improves tree physiological vitality which makes it a suitable silvicultural system for dry sites.