Monthly foliar-nutrient pattern in a semiarid Aleppo pine plantation five years after thinning

• Leaf Ca concentrations were higher and K and Zn lower than those shown in literature.
• Differences between thinned and control stands were time dependent.
• Monthly patterns of all nutrients decreased over the study period except for Ca.
• Partial correlations among nutrient concentrations differed from the general patterns.
• Foliar-nutrients and paired relationships were influenced by the sampling period.

Foliar-nutrient concentrations in tree species have traditionally been used to assess the nutrient status of forests. Monitoring these parameters in artificial forest plantations could be crucial to planning the best silvicultural practices as a basic strategy for improving stand resilience. This work examines the monthly patterns of foliar-nutrient concentrations over a 13-month period in a Pinus halepensis plantation five years after four different thinning regimes were applied (T0 treatment: control plots; T75, T60, and T48 treatments: 75%, 60%, and 48% of mean basal area was removed, respectively). Mean leaf-nutrient concentrations reported were among the normal and adequate ranges shown in the literature for P. halepensis, with the exception of Ca (higher), as well as K and Zn (lower). Thinning did not affect the leaf P or K concentrations in any case or sampling period. Moreover, we found no clear differences between thinned and control stands for other nutrients. Only B was higher in control stands and Zn in thinned stands. Exceptionally, N, Mg, Fe, Zn, and Ca concentrations proved higher in the most intense thinning (T75), for specific sampling periods. Patterns of foliar-nutrient concentrations were similar among thinned treatments and control. All nutrient concentrations decreased over the study period except the Ca concentration (and Mg in T75), which increased. Foliar-nutrient concentrations showed a positive linear correlation between nutrients (especially N–P, P–B and N–B), except K–Ca, K–Mg, and Fe–Ca, which proved negative. Partial correlations (month by month) among nutrient concentrations differed from the general patterns. Foliar-nutrient concentrations and paired relationships were influenced mainly by the sampling period, suggesting the importance of standardized leaf-sampling designs in studies analyzing and comparing foliar-nutrient concentrations.