## 2 Materials and Methods
### Data Analysis  
The characteristics of pine stands located on degraded lands have been permanently monitored through periodic works (at 5 to 10 years) regarding the main biometric and structural parameters (diameter, height, etc.). The research plots (EP) from each experimental perimeter (EP) were inventoried in the period 2019 to 2020, with the next inventory being at the end of vegetation season from the current year (2024) and in the beginning of the previous one (2025). The works consisted of quantitatively evaluating the trees by determining the following dendrometric parameters: basal diameter (DBH); total height (h); pruned height (hc); diameter of the crown (Dc); the crown's relative length (L%); and the slenderness index (I) as well as stand structural evaluation (participation of the species in composition (%), number of trees per hectare (N\({}^{-1}\)), and density index by the number of trees (I\({}_{N}\)) and by the basal area (I\({}_{G}\))). The data's statistical process emphasizes the structural diversity and the qualitative and stability characteristics of pine stands from degraded lands by using general statistical parameters (mean, median, standard deviation (s), minimum and maximum, and variation coefficient (cv%) for the basal diameter (DBH) and total height (h). The basal diameter (DBH) was measured for all trees at breast height (DBH at 1.30 m height) on two perpendicular directions. The Mantax Blue forest caliper was used to measure the basal diameter. The reading of the basal diameter values was realized at a millimeter scale. The total height (h) and the pruned height (hc) was measured for all the trees from the stand by using the Vertex IV precision device. The diameter of the crown (Dc) in meters was measured on two axes (one axis in the north direction and one axis in the south direction). The measurements were carried out using the model of Spencer forest roultete with 20 m length. Usually, the slenderness index (I) is situated in the interval [0, 1], but in some cases, this index can take values over the maximum limit [31]. The relationships between the quantitative variables referring to the structure were established by analyzing the Pearson correlation coefficient (\(r\)). Significant tests were applied for the vulnerability classes established by the slenderness index's values (I) by analyzing the means and variations between the groups (the pairwise \(t\)-test and F test). We tested the null hypothesis by using the one-way ANOVA single factors (H0: All the slenderness index means obtained in different site areas for the crown section are equally distributed). When the ANOVA results had a \(p\)-value < 0.05, the null hypothesis was rejected, and we could conclude that significant differences were considered between the groups. Furthermore, the pairwise \(t\)-test method was applied to find all the significant differences between the means divided on groups, including the datasets of crown biometry and slenderness indexes (I). For comparing the means of slenderness indexes obtained in certain conditions, we used a scale of vulnerability divided in three domains: (a) domain 1--low vulnerability: I less than 0.8; (b) domain 2--moderate vulnerability: I between 0.8