## 3 Results
### The Effect of Damaging Factors on the Composition and Structure of Pine Stands on Degraded Lands
#### 3.2.2 Analyzing the Stability of Scots Pine and Black Pine Stands  
The effect of wind and snow on pine stands is different based on the stand age and composition as well as density (the number of trees per hectare). As a consequence of damage, the number of trees was reduced, including the consistency, leading to an increase in vital growing space. The effect of naturally reducing the number of trees causes increasing stability and is reflected in a reduced average slenderness index. Analyzing the relationship between diameter (DBH) and the slenderness index (I) in relation to the vulnerability domains for the main base species, i.e., pine, shows that as the diameter increases, the slenderness index decreases according to the power regression equation (Figure 18a-f). The relationships between the two analyzed parameters are negative and significant and are expressed for all vulnerability domains (Figures 18a-d, 19a,b and 20a,b). Figure 19: The distribution of the slenderness index in regard to the basal diameter and the distribution of vulnerability domains: (**a**) RP6, Pi, and EP4; (**b**) RP9, Pi.n, and EP4. Figure 20: The distribution of the slenderness index in regard to the base diameter and the distribution of vulnerability domains: (**a**) RP9, Pi.n, and EP1; (**b**) RP5, Pi.n, and EP1. Figure 18: The distribution of the slenderness index in regard to the basal diameter and the distribution of vulnerability domains: (**a**) RP10, Pi, and EP3; (**b**) RP9, Pi.n, and EP3; (**c**) RP1, Pi.n, and EP2; (**d**) RP9, Pi.n, and EP2. Pine Stands with Age between 55 and 65 Years (RP1 and RP9-EP2; RP4, RP9 and RP10-EP3) and over 70 Years (RP6 and RP9-EP4)  
_In the pine stands aged between 55 and 65 years_, the value of the average slenderness index per stand for the pine species indicates a low vulnerability of pine species towards wind and snow (Figure 18a-d). The main species from the stand's composition are situated in the low-vulnerability domain (Scots pine) and in the moderate-vulnerability domain (black pine). The explanation resides in the stand's age (55 years) as well as in the strong damages suffered previously, in which trees with small diameters and high slenderness index were affected (I! 1.00). This is typical for the even-aged pine stands and expresses the presence of a large number of trees that, in the presence of light and with high thickness, migrate from an inferior conotic class towards the middle or even superior ones. The growth in height becomes superior to that in basal diameter, generating slenderness indexes that exceed the value of 1.00. In regard to the distribution of the number of remaining trees (\(\%\)) on vulnerability domains, we concluded that the low-vulnerability domain (I! 0.80) is the best represented one, with an average of 64.01% of the total number of pine trees (N) (Figure 18a,d), and it is characterized by values between 50.45% (RP9 and EP2) and 81.82% (RP10 and EP3). The moderate-vulnerability domain (I between 0.80 and 1.00), with an average of 30.11% from N, has a percentage of trees remaining in N being situated between 18.18% (RP10 and EP3) and 39.64% (RP9 and EP2). The high-vulnerability domain (I! 1.00) has an average of 5.88% from N, with values between 3.77% (RP1 and EP2) and 9.91% (RP9 and EP2), which were significant only in the black pine stands mixed with Scots pine or in pure pine stands (RP9--Pi.n; RP10--Pi) (Figure 18b,c). _In the pine stands aged over 70 years, from the internal forest-step site (Ssd)_, the moderate vulnerability domain is the most representative one, with a proportion of 52.63% from the total number of Scots pine trees, with a mean basal diameter (\(\overline{d}\)) of 24.97 \(\pm\) 3.23 cm and with corresponding a mean height (\(\overline{h}\)) of 22.11 \(\pm\) 3.28 m (EP4 and RP6).