## Abstract  
The present research was carried out in stands of Scots pine and black pine, pure or mixed with deciduous trees, installed on degraded lands from the Curvature Subcarbpathian area, Romania, in a representative network of permanent research plots and followed the analysis of the structural diversity and stability indicators of these stands at different ages and in different conditions of degraded lands. The relationships between the quantitative variables with reference to the structure were established by analyzing the significance of the Pearson correlation coefficient (\(r\)) and also including datasets of slenderness indexes, which were classed into three domains of vulnerability to abiotic factors (like wind and snow). The compositional diversity of pine stands (pure or mixed with deciduous ones) is different in relation to age and is correlated with the structural diversity. The obtained correlation coefficients (\(r\) Pearson) express very strong and significant relationships between biometric parameters (h x Dbh, h x Le%, Dc x Dbh, and Lc% x Dbh) of the structural diversity (\(r\) = 0.800-0.930), which is important for the analysis of the stability and vulnerability of pine forests. The strong correlation between the analyzed variables expresses a weak vulnerability to the action of harmful abiotic factors and the increase in the stability and resilience of the studied stands, especially of over 50 years old. In the old pine stands, the low-vulnerability domain (I \(<\) 0.80) is the best represented one, with an average of 64.01% from the total number of trees. At this age, trees with DBH? 22 cm fall into the low-vulnerability category. The explanation is that the stands were affected in their youth by the action of snow and wind, which, combined with the silvotechnical works performed, led to their compositional and structural diversification and increased stability. The young (\(<\)45 years) and pure-pine stands with higher consistency (\(>\)0.8) and even-aged structure are the most vulnerable to abiotic factors due to the fact that a large number of trees are passing gradually into the higher conotic classes. p p  
biometric, structural, and qualitative parameters in stands from degraded lands (that reflect their health and diversity) is realized under the influence of environmental conditions, silvotechnical works, and a complex of harmful biotic (insects, mushrooms, and game) and abiotic factors (wind, snow, and drought). Their action can cause strong imbalances in the development of ecosystems, while their condition, behavior, and evolution are unpredictable [7]. In line with this, recent research has more often taken into consideration stability issues and the structure, regeneration, and dynamics of stands development in general but also, as in this paper, stands from degraded lands [8; 9]. Pine stands located outside their habitat, composed by a single type of species, have a high vulnerability towards abiotic factors [10]. In some experiments carried out for establishing diversity in the disturbed stands, Scots pine is the species used to created homogenous clusters for hardwood species such as oak, beech, and even spruce for the richness of biodiversity and favoring the mixture of broadleaved species [11]. Structure derangement and degradation are the consequences of exogenous factors such as wind and snow. Health alterations have been found to be caused by drought, leading to a decrease of ecosystem stability [12; 13; 14], leading to significant negative ecological consequences [15]. Furthermore, the influence of harmful factors leads to downgrading the remaining trees and, as the stand's crown thins out, decreasing the stand's stability, health state, biological diversity, and regeneration capacity. Many stands are affected by dryness and breaks, among other things, after climate changes [16]. The causes of injuries produced in pine stands on degraded lands are multiple, one of them being the big density (big number of trees) due to unapplicable stand-tending operations [17].