Application of ITGL in the assessment of post-agricultural soils with natural regeneration of silver birch

The aim of the study was to apply the forest soil trophic index (ITGL) in the assessment of post−agricultural soil under naturally regenerated silver birch (Betula pendula Roth.) stands. The study was conducted in Mazowieckie region (central Poland) in 10 locations (tab. 1). In each location we established 4 study plots with naturally regenerated silver birch of different age. The age of the investigated stands ranged from 2 to 17 years. On each study plot samples from three upper soil horizons (0−5 cm, 5−15 cm and 15−50 cm) were collected for laboratory analysis. The following characteristics were determined in the soil samples: pH, organic carbon (C) and total nitrogen (N) content, particle size and the content of exchangeable base cations (Ca, Mg, Na and K). These soil characteristics were on used for ITGL calculation. Chemical properties of soils under silver birch regeneration varied with regard to trees age, whereas physical attributes turned to be rather stabile over the time (tab. 2). According to ITGL value investigated soils were classified as eutrophic. It is probably the effect of high base cations content, which is a result of systematic fertilization during the long term agricultural use. The insignificantly different ITGL values for the studied soils (tab. 3) indicated their similarity in terms of site productivity potential and soil−geological characteristics. The soil properties, especially the quality of soil organic matter described with C/N ratio, improved several years after the cessation of agricultural activity and spontaneous afforestation. The obtained results indicate that silver birch can be used in the stand composition on post−agricultural areas