Research Highlights: Management of the risks forests are exposed to is based on the dynamics of the composition and structure of the stands and the forest. Background and Objectives: This study aimed to document the dynamics of the composition and structure of stands and forest in the Romanian Carpathians over the last five decades, as well as estimate the forecast composition of the forest in the near future (i.e., 2070). Materials and Methods: The obtained results were based on long-term monitoring and analysis of the species and structures in the stands in long-term research areas (over five decades). We performed an inventory of all the trees (on 7.5 ha) in order to characterize the stand structure in sampling plots of 0.25–1.0 ha, located in representative stands of five forest formations. Bitterlich sampling was performed in order to determine the composition of each stand (on 2930.4 ha). The future composition was established in accordance with the characteristics of the natural forest types and was based on seedling dynamics and forest management plans. Results: In mixed beech–coniferous stands, over the last five decades, the area of beech has increased by 38%, while conifers have decreased proportionally—fir by 31% and spruce by 5%. The seedling area increased from 23% to 65%, with fir contributing 22% to the composition and beech 42%. Stand density decreased by an average of 14%, with the current increment decreasing by 3.8%. The slenderness index for fir decreased from 73 to 61. In the near future, there will be an increase in the proportion of fir, from 15 to 33%, and a reduction in beech, from 49 to 45%. The proportion of spruce will be reduced from 17 to 12%. Conclusions: Based on the forest dynamics, management adaptation strategies need to be developed to improve the stability of the forest ecosystems.

Research Highlights: This study highlighted the possibility of estimating the productivity of mountain sites (mixed beech-coniferous stands) based on tree and stand dendrometric characteristics. Background and Objectives: The mountainous region of Romania offers suitable conditions for the formation and development of mixed beech-coniferous stands with complex, multi-aged structures. Based on the dendrometric characteristics of the trees, established indicators were used to estimate the productivity of the sites, with other quantitative indicators being proposed to better capture the particularities of mixed multi-aged stands. Materials and Methods: To evaluate the productive potential of the sites, a combined in situ mapping method was applied. Laboratory analyses of soils, and information provided indirectly by indicator plant and tree overstories, led to the characterization of soil types and the identification of forest sites for study. The productivity of the sites was estimated using quantitative indicators established based on the dendrometric characteristics of the trees and stands. Results: Indicators based on stand production and growth are relevant for multi-aged stands of mixed beech-coniferous formation. The ratio between tree volume and the basal area is the result of basal area and height increments, both of which are variable and depend on the quality of the site. Thus, a form height stand can be used as an indicator to characterize the productivity of the site in mixed multi-aged stands. Conclusions: Knowing the ecological specificity of sites in the formation of mixed beech-coniferous forests is a first condition necessary to achieving stable stands that are able to continuously fulfill multiple functions. The favorability of forest sites for a certain assortment of species is a fundamental character of the sites, which is essential for the management of these forest formations.

This research aimed to determine the values of chemical properties and the relationships between the main pedoecological factors that characterize the soils in the Gurghiu Mountains. The mapping surveys were carried out on an area of 4,647.36 ha located in the mixed mountain forest sites (FM2) (1,000–1,400 m altitude). The area was stratified into homogeneous site units in terms of climate, hydricity, and trophicity. At the level of the elementary site units, 35 main soil profiles and 46 control profiles were placed. The number of profiles was determined statistically to ensure an error of no more than 10%. Soil samples collected from the main profiles were analyzed in the laboratory. Soil’s properties values decreased on the soil’s profile (humus content from 15 to 2%, nitrogen from 1.1 to 0.5%, sum of exchangeable hydrogen from 20 to 9 me/100 g soil, and total cationic exchange capacity from 38 to 20 me/100 g soil), except the pH and the base saturation degree (the pH increased on profile from 4.5 to 6, and the base saturation degree from 40 to 70%). The soil properties, except for moisture, were significantly affected by altitude, and decreased when the altitude increased. Soil trophicity can be characterized by a soil index, the values of which were between 17 and 42 for the analyzed soils. These values indicated soil-specific trophicity levels from oligotrophic to eutrophic.