Investigation of the effects of salty water on growth and leaf chemical compounds of alder and ash trees in Karacabey floodplain forests

The climate change that the Earth is witnessing due to human activities is causing an increase in temperatures, a rise in sea levels, and the crossing of its waters to neighboring areas. The aim of this study is to investigate the effect of saline seawater on the growth and leaf chemical compounds of ash and alder trees, which are the dominat tree species in Karacabey floodplain forest trees in Bursa, Türkiye. For that, fresh leaf samples of alder and ash trees were collected from three zones (Z1: 0-1 km, Z2: 1 to 2 km and Z3: 2 to 3 km) according to the inner border of the floodplain forest and the Sea of Marmara. Soil samples were also taken under the trees, where the fresh leaf samples were collected. The fresh leaf samples were analyzed for photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), anthocyanine, total phenolic compound, soluble tannis, total nitrate, total soluble amino acid, proline, total soluble protein, glucose, sucrose, total soluble sugar. The soil samples were analysed for soil pH, electrical conductivity and soil texture. For both tree species, soil pH, EC and sand content showed a decrease with the distance away from the sea site, whereas soil clay and silt contents increased.In general, mean chlorophyll-a, chlorophyll-b, total chlorophyll, total carotenoids, anthocyanin, xanthophyll, free amino acids, total nitrate and proline decreased with increasing the distance from the sea, whereas mean total polyphenols, total soluble tannin and total phenolic compounds increased. Because these species often have a high tolerance threshold for environmental changes, the shift of pigments in leaf tissue may not exhibit a significant decline or rise in woody forms. Additionally, more chlorophyll pigments are present in resistant species than in susceptible species. These results indicate that the increase in seawater inside the forest leads to an increase in salinity in it, increased salinity affects physiological functions and chemical components, and changes soil texture, chemistry and biology, and affects the growth and lifespan of ash and alder trees. The percentage of salts was varied with the different distances from the sea, as it increased with the decrease in the distance from the sea and decreased with the increase in the distance from the sea. In addition, it was discovered that these two species, especially ash trees, are salt-resistant plants that try to adapt to the saline environment by changing the physiological mechanisms that provide the plant with some resistance to salt stress to a certain extent. The continued intrusion of sea water and the continued increase in salinity may lead to an increase in the weak growth and death of trees.