Assessment of soil quality index changes in scots pine (Pinus sylvestris L.) plantation areas with different ages in erzurum Palandoken Mountain

The aim of this study was to determine soil quality index (SQI) in the afforestation areas established in different times for erosion control in Erzurum Palandöken Mountain, Turkey. For this purpose, three afforestation areas were selected considering their establishment times (>40 years old, 10-40 years old, and <10 years old) and 30 soil samples were taken from each field of study. A total of 90 soil samples were taken and analysed for clay content (CC), silt content (SC), sand content (SaC), mean weight diameter (MWD), aggregate stability (AS), pH, electrical conductivity (EC), total nitrogen (TN), total carbon (TC), and total sulphur (TS). These properties were used as indicators, and the expert opinion and principle component analysis were used for weighting the indicators. Indicators were scored using the linear score functions and expert opinion. For determining SQI, the additive method (SQIA), the weighted method with AHP (SQIAHP), and the weighted method with principle component (SQIFA) were used. In order to determine the difference between sampling layers and afforestation areas, variance analysis was used in terms of soil properties and soil quality index values. As a result of the evaluations, it was found that the properties examined did not show a significant difference between the sample layers, but the characteristics other than pH and TS showed a significant difference in afforestation areas. It was found that the SQI values indicated by all three methods did not change in the sampling layers, but they tended to decrease in the afforestation areas from the first to the end and this difference between the afforestation areas was statistically significant. The results show that afforestation studies have a significant positive effect on soil properties and quality index values, but biological properties of soils should be included in the evaluation for more consistent results.