Needle traces as indicators of growing conditions in Scots pine (Pinus sylvestris L.)

Abstract

Needle retention (number of needle sets) and needle density (number of needle pairs per centimeter of shoot) were surveyed on Scots pines in five forest regions of Slovakia. The Needle Trace Method (NTM) was used to determine needle retention and needle density along the main stem retrospectively for the last four decades. In all forest regions, the values of these indicators varied from year to year. However, in Záhorská lowland, Vtáčnik, Krupinská plain, and High Tatras, the trends of both observed indicators were constant over the time series. The situation was different in the Levočské hills, where the needle retention displayed a decreasing trend and needle density an increasing trend. These trends probably reflected a long-term stress of air pollution on pines in this forest stand.