Effects of litter layer on some exchangeable cations in Belgrad Forest, Turkey

Abstract

The paper presents a synthesis of a set of experiments, implemented to investigate the acid buffering mechanism of Belgrad Forest soils. Previous studies carried out in the region, pointed out the exposure of Belgrad Forest ecosystems to acid deposition. Between 1999 and 2001, we performed a set of supplementary studies, focusing on the hydrogen buffering, part of the issue. Ceramic cup lysimeters were installed to various soil depths, and the soil water ionic composition was monitored to determine the main buffering, zones among the horizons. The upper 20 cm, litter layer and Ah horizon, were identified to have the main exchange mechanisms, decreasing the hydrogen ion activity from 22.82 mu eq L-1 to 0.56 mu eq L-1. To identify the role of litter layer, a litter removal parcel study was employed. After the litter removal, soil samples were taken bimonthly from two depths (0-12 and 12-20 cm) for a 1-year period of time, to determine changes in soil properties. Organic matter content and pH were slightly higher in the upper 12 cm. Finally, the exchange capacities of single-valenced base cations, Na+ and K+ were compared with a retention curve experiment in laboratory. The cation retention capacities of the soil samples rich in organic matter were lower than the ones with less organic matter. The results of the three experiments revealed that, even though the upper soil horizons were responsible of hydrogen buffering in the region, the litter layer or humus layer did not have a particular role.