Effect of deposition substances on the quality of throughfall and soil solution of pedunculate oak and common hornbeam forest

Sa？etak Abstract Background and Purpose: Soil pollution is one of the important stress factors which lead to vitality decrease and forest dieback. For this reason, monitoring of the flux of pollutants into the soil is important activity in forestmanagement and protection. This type of monitoring, comprising quantity and quality of throughfall and soil solution in Croatian lowland forests, was started in 1991 in the Forest Research Institute Jastrebarsko, following the ICP Forest method (International Cooperative Programme on Assessment and Monitoring of Air Pollution on Forests). Materials and Methods: This paper relates to monitoring whichwas established on 3 sample plots in pedunculate oak and common hornbeam forests (Carpino betuli-Quercetum roboris, Ani？ 56/emed. Rau？ 1969), in the regions of Bjelovarska ？esma, Pokupski Basin and Repa？ (all in NW Croatia). Rain-gauges and bulks were set up on the plots under tree crowns, as well as in open space without vegetation (for the purpose of control). Modified Ebermayer lysimeters were installed in the soil profile under the humus horizon at 10–20 cm, and in the mineral part of soil at a depth of 100 cm. The field sampling was carried out once a month, and selected ions were analyzed in the water (K+,Na+, Ca2+,Mg2+,NH4+–N, Cl–,NO3––N,SO4 2––S). Results: The results indicate an increase in the amount of deposited substances in forest ecosystems. According to analyses most chloride was found in lysimeters at a depth of 10 and 100 cm in the region of the Pokupski Basin; followed by ？esma and then Repa？. Most SO4 2––S reached lysimeters at a depth of 10 cm in all regions i.e., in Repa？, followed by ？esma and Pokupski. An increase in sulfur also occurred in lysimeters at a depth of 100 cm in the region of Pokupski and ？esma, with smaller increase recorded at Repa？. Increase of NO3 ––N was highest at a depth of 10 cm in the regions of ？esma and Pokupski. Contents of sodium and chlorine increased most in the region of the Pokupski Basin, in a lysimeter at a depth of 100 cm. Potassium on average was most abundant at ？esma in lysimeters at a depth of 10 cm, and somewhat less in the region of Pokupski and Repa？. Calcium on average wasmost found in the region of ？esma, in lysimeters at a depth of 100 cm, which can be explained by the increased amount of CaCO3 in deep layers of soil profile. Magnesium was most registered in ？esma at a depth of 100 cm, and then at a depth of 10 cm. A somewhat smaller increase occurred in the Pokupski Basin. Conclusions: All three regions are characterized by significant acidification of