Abstract
Large and old trees dominate pollarded oak woodlands such as the Spanish dehesas, which preserve exceptional ecological values but are still understudied. We characterized the diameter, age and radial growth of a pollarded mixed oak (Quercus petraea and Q. pyrenaica) - European holly (Ilex aquifolium) dehesa in northern Spain. Tree-ring data were used to reconstruct pollarding events associated with severe growth suppressions. In addition, wood δ13C, a proxy of intrinsic water-use efficiency (iWUE), and chemical element concentrations were quantified in 5-year intervals over the period 1776–2025. The maximum diameters and ages of pollarded oak and holly trees were 239.0 and 60.0 cm and 720 and 301 years, respectively. The oak population was exceptionally old as compared to other similar dehesas. Oaks showed a positive growth trend, but holly trees showed recent growth decline due to the negative impact of warmer growing seasons, albeit management abandonment (pollarding cessation) could have also contributed. In contrast, oak growth was enhanced by warmer April and wetter June conditions. Growth suppressions peaked in the mid-1810s and early 1890s in oak and holly trees, respectively. Two hypotheses supported by indirect evidence rather than definitive conclusions are presented: (i) iWUE increased and wood K and Ca concentrations decreased linked to pollarding events, and (ii) the age structure of old pollarded oaks suggests recruitment pulses after the demographic crisis and reforestation linked to the 14th-century Black Death pandemic. The preliminary associations found between pollarding events and dendrochemical signatures should be tested with more samples to enable more robust reconstructions of historical forest use. Our results highlight the ecological value of pollarded oak woodlands dominated by ancient trees and the need for their conservation.