Methodological approach for long-term ecological research in forest sites

The dynamic of the processes in an ecosystem requires long-term observations. This paper presents a specific methodology for estimating forest ecosystem characteristics as a part of the Long-Term Ecological Research (LTER) network. Permanent sample plots in Western Stara Planina in Bulgaria are determined to monitor the processes in forest ecosystems. Methods based on remotely sensed vegetation index are commented on. The main phenology's life cycle events, such as the start, peak, end, and length of the growing season, are described. Methods for phytocoenotic structure are presented: complete floristic composition, total projective coverage of horizons, and species abundance. Methods for stand growth and yield estimation, diameter calculation, basal area, volume increment, and description of tree diameter distribution are summarized. Chemical methods for deposition determination are commented on.