Does optimality partitioning theory fail for belowground traits? Insights from geophysical imaging of a drought-release experiment in a Scots Pine forest.

We investigate the impact of a 20-yr irrigation on root water uptake (RWU) and drought stress release in a naturally dry Scots pine forest. We use a combination of electrical resistivity tomography to image RWU, drone flights to image the crown stress and sensors to monitor soil water content. Our findings suggest that increased water availability enhances root growth and resource use efficiency, potentially increasing trees' resistance to future drought conditions by enabling water uptake from deeper soil layers. This research highlights the significant role of ecological memory and legacy effects in determining tree responses to environmental changes.