New insights on the dynamic of the forest vegetation from the Romanian Carpathian Mountains | Nový pohľad na dynamiku lesnej vegetácie v rumunských Karpatoch

In the framework of the established long-term monitoring of the Carpathian forest ecosystems, the assessment of changes in the plant species richness, type of plant communities and biometric characteristics and health status of forest trees, for getting relevant insights regarding the effects of the type of management, pollution and climate changes upon forest biodiversity and health, is one of the major objectives. The joint monitoring activities in the Carpathians from the Romanian territory were launched in 1998 by including six study sites in the network of twenty- six sites established for monitoring and assessment changes in the Carpathian forests at the scale of the entire Carpathian Mountain range. The paper addresses the results gained by repeating field studies protocols in 2005, in the same study sites from the Romanian stretch of Carpathian Mts, and shows first findings of the attempt of comparative analysis of two sets of empirical results collected in 1998 and 2005. The biometric characteristics of the investigated forest stands have changed between the years 1998–2005, due to moderate (Retezat) or intensive (Fundata) silvicultural interventions, progressive improvement of the amount of precipitations and significant decrease of pressure exerted by air pollution (Badea et al, 2006). Except a relatively low volume increment (4.8 cubic mper yr per ha) estimated for Fundata forest stands, which is located at the upper altitudinal limit (1360 m asl), good (6.7–7.1 cubic m per yr per ha) and high (10–11 cubic m per yr per ha) volume increment were estimated for Magura Odobesti and Stana de Vale, respectively Obcina Mare and Retezat sites, according with the tree species composition and yield class. The data related to the share of damaged trees (defoliation classes 2–4) indicate that between 1998 and 2005 the health status of forests from the Romanian Carpathians has been slightly improved, as well as for all Romanian forests (Badea et al, 2006). The recorded data indicate also that the dominant plant species have not been changed, and thus, the type of plants associations. However, they indicate an increase with 5 species (SdV), 8 species (F; MO; R), 16 species (RA) and 19 species (OM) in the plant species richness between 1998 and 2005. In addition, the results of the comparative analysis based on Jaccard coefficient of similarity, show profound changes (78 percent) in species composition, in particular subordinate and transient species.