Unlocking the potential of pollarded oaks: a 375-year hydroclimate reconstruction from northcentral Spain

Abstract

Abstract. Pollarded trees – traditionally pruned and maintained for centuries near rural settlements – represent an untapped resource for climate reconstruction in Mediterranean lowlands. In this study, we evaluate the potential of 102 pollarded deciduous oaks from two communal woodlands (dehesas) in northcentral Spain as proxies for past hydroclimatic variability. Using the correlation between latewood and November–June precipitation, we reconstruct regional precipitation variability from 1649 to 2023, achieving calibration/validation correlations of 0.84–0.71 against regional and large-scale instrumental datasets. The reconstruction reveals pronounced interannual to multidecadal variability, with precipitation ranging from 257 to 838 mm. The longest dry spell lasted 25 years (1818–1842), while the wettest sustained period extended over 21 years (1719–1739). We identify 8 extremely dry years and 19 extremely wet years consistently detected across the three threshold criteria considered. Pre-instrumental drought extremes are further supported by historical evidence, including Catholic pro pluvia rogations – ceremonies traditionally held in response to agricultural drought. Our findings demonstrate that pollarded trees, when sampled from sites with asynchronous management, preserve robust climate signals and provide reliable high-resolution information on precipitation variability across Mediterranean dehesas.