Species-specific growth dynamics and vulnerability to drought at the single tree level in a Mediterranean reforestation

• DOI: 10.1007/s00468-021-02151-6
• Publication Date: 2021-05-31T13:03:07Z
• Authors: Gianluigi Mazza; Loukia Markou; Dimitrios Sarris
• Keywords: Pinus brutia; Reforestation; Thinning

Understanding the potential of using tree-rings to identify the most vulnerable species and trees to future drought intensification may support the conversion of pure pine plantations to more resilient mixed oak-pine stands. We carried out the first dendroecological analysis at the single tree level for a coniferous plantation with Pinus nigra, Pinus brutia, and Quercus cerris in the Mediterranean. We focused on a forest from Central Italy densely overgrown, characterized by poor stand stability and a large amount of deadwood accumulation (75.1 m3ha−1, with 18% of standing dead trees) because of non-thinning at the dry-end (lower) elevation limits of P. nigra. Drought-related indices based on tree-rings were tested for 80 trees to identify growth changes under drought and recovery together with climate–growth relationships for precipitation, SPEI, and temperature (monthly, seasonal, and annual). P. nigra trees appeared as the most drought affected, with very low growth rates during the current year of drought up to three years after (for 67% to 31% of trees), followed by P. brutia and Q. cerris trees. Oaks displayed a higher post-drought recovery rate compared to pines (76% vs. 56% of trees), up to 2 years after drought. Oak growth was driven by monthly seasonal climatic variables, while pine by multiple-year precipitation/SPEI, most likely related to the use of deeper water reserves to avoid interspecific competition with oaks at the upper soil layers. The single-tree dendroecological analysis appeared very useful in supporting the conversion towards a more drought-resilient mixed pine-oak stand, suggesting that ca. 1/3 of P. nigra trees at a site close to the pines’ dry-end distribution could be thinned or/and substituted by the less drought-sensitive Q. cerris.