Spruce Trees Growth and Forest Landscape Depending on Microstational Factors and Ecological Conditions

Abstract

Spruce (Picea abies (L.) Karst) is an important forest tree species in Romania, occupying approximately 24% of the total forest area. Due to its variable temperament, the spruce is generally considered a semi-shadow species. Through the research carried out in Valea Ierii (N-W of Romania), the response of spruce was evaluated according to different microstational conditions (e.g. exposure, altitude, density etc.), in nine sample plots, each of them with a surface of 500 m², on a total area of 10 hectares. There were noted interaction responses to several ecological factors. Results showed that the trees with South-West exposure and at an altitude of 1,200-1,370 m have accumulated the largest amount of biomass, showing significant differences from the trees exposed on North-East plots and at altitudes comprised between 1,170-1,380 m. Behavioural differences regarding growth and biomass accumulation capacity was statistically ascribed to slope exposition, which was therefore considered as principal factor regulating landscape function of the forest, with a strong ecological impact. In the whole set of populations, the response function varied considerably within the S-W expositional plots compared to the N-E  plots exposition, but without significant differences related to trees density and altitudinal level. Because all stands under study were pure, composed of even-aged spruce trees, differences may be related to a range of habitats as geosystem and/or geofacies levels, respectively altitudinal forest, exposition, density and other local conditions. The superior growth of the trees on the S-W exposition slope was explained due to the young stage of the spruce, and the trees preference until this age for sunny and more dried conditions. Probably, in the next years, the trees' evolution will confirm that the spruce prefer low temperatures, low insolation inside the forest, high and permanent humidity. Further spatio-temporal analysis will be useful for reliable hypothesis to be inferred as functions of the forest, but also landscaping, depending of the trees' age and ecological conditions.