Productivity differences between southern and northern slopes of Southern Carpathians (Romania) for Norway spruce, silver fir, birch and black alder

Forest vegetation across Southern Carpathians is distributed in altitudinal layers. The aim of this study was to highlight the productivity differences between the Southern and Northern slopes of the Southern Carpathians for Norway spruce, silver fir, birch and black alder. Data from 45 forest management plans (46.329 stands from the Southern slopes and 32.787 stands from the Northern slopes) were used. For each stand, the mean diameter, mean height, age, standing volume, current volume increment and production class were assessed. Elementary statistical methods were used to identify the factors influencing productivity. Significant differences between the Southern and Northern slopes were recorded for silver fir. The volume and the current volume increment were higher on the Northern slopes. In the case of birch and black alder, the same two parameters recorded higher values on the Southern slopes. As regards Norway spruce, insignificant differences were recorded between the two slopes. The correlation between structure type and stand volume was positive and statistically significant in the case of Norway spruce, silver fir and birch, but it was negative in the case of alder. Analysing the correlation between stand volume and the main stand characteristics also revealed a statistically significant positive correlation between age and stand volume for all analysed species. The results of this study are especially interested for the forest managers and forest owners whose aim is to obtain a higher productivity for the studied species.