Mediterranean forest ecosystems in Croatia are of very high significance because of the ecological functions they provide. This region is highly sensitive to abiotic stresses such as air pollution, high sunlight, and high temperatures alongside dry periods; therefore, it is important to monitor the state of these forest ecosystems and how they respond to these stresses. This study was conducted on trees in situ and focused on the four most important forest species in the Mediterranean region in Croatia: pubescent oak (Quercus pubescens Willd.), holm oak (Quercus ilex L.), Aleppo pine (Pinus halepensis Mill.) and black pine (Pinus nigra J. F. Arnold.). Trees were selected and divided into two groups: trees with defoliation of >25% (defoliated) and trees with defoliation of ≤25% (undefoliated). Leaves and needles were collected from selected trees. Differences in chlorophyll content, hydrogen peroxide content, lipid peroxidation and enzyme activity (superoxide dismutase, catalase, ascorbate peroxidase, non-specific peroxidase), and nutrient content between the defoliated and undefoliated trees of the examined species were determined. The results showed that there were significant differences for all species between the defoliated and undefoliated trees for at least one of the examined parameters. A principal component analysis showed that the enzyme ascorbate peroxidase can be an indicator of oxidative stress caused by ozone. By using oxidative stress indicators, it is possible to determine whether the trees are under stress even before visual damage occurs.
Mediterranean forests along the eastern Adriatic coast have an important ecological role. However, few studies have been conducted on nitrogen deposition so far. To improve this knowledge, the main aims of our study were: (i) to estimate nitrogen inputs and determine differences among the four Mediterranean forests, (ii) to determine the seasonal behaviour of N deposition compounds, and (iii) to discuss the results in relation to forest type and precipitation. Measurements were carried out over a two-year period on four plots in two regions: holm oak and pubescent oak in Istria, Aleppo pine and black pine in Dalmatia. Bulk open field and throughfall deposition were sampled with continuously exposed collectors. Measurements, analyses and data validation of precipitation and N compounds were carried out. The results showed that the highest average monthly precipitation was recorded in the black pine plot and the lowest in the Aleppo pine plot. Nitrate and ammonia in conifer plots in throughfall samples were lower than in bulk open field samples, indicating possible retention by the tree canopy. The results revealed a higher amount of N deposition collected in broadleaved forests than in conifer forests indicating the washing out of N compounds previously deposited and accumulated in forest canopy. The chemistry of N deposition was strongly influenced by local and anthropogenic sources as well as neighbouring countries. Our results may fill the knowledge gap in understanding the influence of precipitation and seasonality of N compounds in different Mediterranean forest types along the eastern Adriatic coast.
The flora of the minute islet of Mrduja (1.3 ha), located between the Middle Adriatic islands of Brač and Šolta, was studied in 2017, resulting in the recording of 63 taxa of vascular plants and six bryophytes. The predominance of the Poaceae (13%) and Fabaceae (8%), terophytes (30%) and Mediterranean floral elements (73%) clearly demonstrates the Mediterranean phyto-geographical position of the islet. Nearly one third of taxa were found on anthropogenic habitats, even though they are exceptionally rare on the islet, proving that even a slight human presence can have a profound influence on the flora of an island. Tijekom 2017. provedena su istraživanja vaskularne flore i flore mahovina otočića Mrduje (1.3 ha), smještenog između srednjodalmatinskih otoka Brača i Šolte. Utvrđene su 63 svojte vaskularne flore, te šest svojti mahovina. Dominacija porodica Poaceae (13%) i Fabaceae (8%), terofitskog životnog oblika (30%) i mediteranskih flornih elemenata (73%) jasno ukazuje na mediteranski fitogoegrafski položaj otočića. Gotovo trećina svojti zabilježena je na antropogenim staništima koja su vrlo rijetka na otočiću, što dokazuje da čak i slaba prisutnost ljudi može značajno utjecati na floru otoka.
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