Goran Jelić

This study investigated the hydrochemical linkage between rainwater and stream water in an Aleppo pine-dominated Mediterranean karst catchment in Croatia during 2020–2022, focusing on ion sources, seasonal patterns, and processes governing the transformation of atmospheric inputs into stream-water chemistry. Rainwater reflected mixed atmospheric inputs, with sea-salt fractions accounting for 94.8% of Cl⁻ and 97.9% of Mg²⁺, whereas 97.5% of Ca²⁺ and 79.2% of K⁺ originated from non-sea-salt sources. Stream water was substantially more alkaline and mineralised, with a higher pH (8.23 vs. 6.53), electrical conductivity (327 vs. 19.63 µS cm⁻¹) and Ca²⁺ concentrations (65.08 vs. 6.22 mg L⁻¹). These differences reflect carbonate weathering during subsurface flow, whereby the dissolution of calcite and dolomite releases Ca²⁺ and Mg²⁺, increases alkalinity and buffering capacity, and results in approximately tenfold-higher stream-water Ca²⁺ and Mg²⁺ concentrations. Seasonal variability was evident, with ion enrichment during low-flow conditions and dilution during wetter periods. Limited synchronous hydrochemical correspondence between rainwater and stream water indicates that atmospheric inputs are modified during catchment transport. Overall, atmospheric deposition provides the initial hydrochemical signal, whereas carbonate weathering, hydrological flow paths, and seasonal biogeochemical processes are the predominant controls on stream-water chemistry.

Considering the fragility of the Mediterranean environment, there is an increasing need to improve the knowledge of this forest environment. The aim of this study was to examine the effects of air pollution on the forest ecosystem’s condition by analyzing tree vitality. The study area was chosen to represent the most important and the most common species in Mediterranean forest ecosystems of the Eastern Adriatic coast. Quercus pubescens, Quercus ilex, Pinus halepensis, and Pinus nigra plots were equipped with rain collectors and dendrometer bands. Sampling, measurements, and analyses of atmospheric deposition, foliar nutrient, defoliation, and growth were all carried out. Results showed that actual N deposition loads were the lowest in Aleppo pine forest and the highest in holm oak forests. This, however, did not have an effect on the concentrations of N in foliage. Most elements’ concentrations were in the plausible range. No relevant differences in mean defoliation between the plots were observed. The plots with a lower percentage of basal area increment (BAI%) were found to have lower defoliation. The research was conducted to bridge the gap in the knowledge of air pollutants and vitality indicators in different forest types. These findings are a valuable contribution to the sustainable forest management of Mediterranean forest.