Climate-sensitive modelling of poplar short-rotation plantations: 3-PG growth predictions considering water limited-conditions

The production of woody biomass for bioenergy and bioproducts is crucial in the transition towards sustainable energy systems in the context of bioeconomy development. Poplar short-rotation coppice (SRC) plantations represent a promising lignocellulosic resource. Climate-sensitive, process-based models are therefore essential for projecting biomass yields under global change. Their relevance becomes even more evident for SRC plantations under Mediterranean conditions, where irrigation is often required, given the upcoming scenarios of increasing water limitation. This study adapt and validate the 3-PG (Physiological Principles in Predicting Growth) model for poplar SRC systems, focusing on the biomass-oriented hybrid Populus ‘AF2’ to improve yield predictions across successive rotations. We evaluated biomass production under contrasting irrigation scenarios: optimal (T1) and restricted water availability (T2), with a detailed analysis of net primary production allocation to foliage, stems, and roots. High precision was achieved for leaf area index, leaf and stem biomass, especially in rotation 1, while root estimates showed greater variability and remained the most challenging component to simulate. Water limitation markedly reduced growth, decreasing stem, leaf, and root biomass by 39.25 %, 47.85 %, and 45.13 %, respectively. Future climate simulations (SSP3-7.0, 2040–2070) revealed site-specific responses: productivity declined slightly at the driest site, whereas northern locations experienced moderate gains where warming coincided with stable or increased precipitation. These results indicate that water availability will remain the dominant constraint on SRC productivity under future Mediterranean climates. Overall, the adapted 3-PG model provides a valuable tool for assessing productivity, carbon allocation, biomass partitioning, and climate–water interactions in poplar SRC systems. • The presented 3-PG model adaptation improves biomass estimates for poplar SRC. • Model adaptation for successive rotations shows good performance in validation. • Monthly NPP rates are key for improving estimates of tree growth patterns. • Root biomass presents the greatest modelling challenges. • Simulations show a 39.25 % average reduction in stem biomass under 50 % irrigation.