# Assessment of the Mass and Surface Area of the Scots Pine (_Pinus sylvestris_ L.) Needles
## 4 Discussion  
The importance of the assimilation surface results from the fact that the amount of generated biomass depends on the surface area of the needles (an allometric relationship). The usefulness of the biometric features of trees, for instance, DBH, tree height, or length of the crown, for the estimation of the surface area of leaves at the tree level was demonstrated in several studies [26, 27, 60, 61, 62]. In comparison with other features of a single tree, the DBH was a better predictor of the surface area of needles than the tree height or length of the crown. For the quantification of total needle area in the field, DBH is a reliable and easy-to-measure scalar, and the relationships of the needle area with DBH are highly significant, confirming similar findings for the needle biomass [9]. In addition, in our studies, DBH proved to be the best parameter for the calculation of the mass of the needles and their surface area. Generally, a growing crown seeks to develop as high an assimilation surface as possible in given habitat conditions and stock density. The stock density combined with other abiotic and biotic factors results in pronounced differences in the surface area of needles for the respective individuals, regardless of their age. Incomparable habitat conditions prevailing in a fresh mixed coniferous forest, the surface area of needles in Scots pine trees varied from 0.49 to 73.16 m\({}^{2}\) for 9-year-old trees and from 10.9 to 94.3 m\({}^{2}\) for 70-year-old ones [3]. Significant differences can be seen in the surface area of needles, depending on the biosocial position of a given tree. This is probably connected with stock density in a community and the resulting varied access to sunlight--one of the key factors preventing needle drop. Scots pine is a heliophytic species that does not tolerate shade. Its needle longevity reaches 2 to 6 years, so the trees do not develop such large canopies as spruces, in which the needle longevity is 7 to 15 years [63]. Thus, the leaf longevity and canopy structure influence the potential maximum LAI [64]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Number of** & **LAI** & **SN** & **FMN** & **Stand Density** \\
**Plots** & **(m\({}^{2}\).m\({}^{-2}\))** & **(m\({}^{2}\). ha\({}^{-1}\))** & **(kg\(\cdot\)ha\({}^{-1}\))** & **(pcs\(\cdot\)ha\({}^{-1}\))** \\ \hline  
\hline \hline \end{tabular}
\end{table} 
Table 3: Differences in needle surface area in 33 years old Scots pine stand (data sorted in ascending order by LAI). [PERSON] and [PERSON] [65] analyzed the impact of stock density on the LAI in _Pinus contorta_ var. _latifolia_. The mean surface area of needles per tree varied from 7 to 190 m\({}^{2}\) at a stock density from 6300 to 208 trees\(\cdot\)ha\({}^{-1}\), and the LAI was increasing with the stock density. The same relationship was observed for the stand described in this paper. On the other hand, we also demonstrated that the same or similar values of the LAI can be obtained for different stock densities. In a study performed on a 50-year-old tree stand in Sweden [66], the fresh mass of needles and the corresponding surface area of the needles for five Scots pine trees were: 8.81 kg-62.7 m\({}^{2}\); 6.35 kg-47.4 m\({}^{2}\); 6.60 kg-48.9 m\({}^{2}\); 5.86 kg-44.3 m\({}^{2}\); and 2.48 kg-23.5 m\({}^{2}\). The coefficient of correlation between the mass and the surface area of the needles in that study was very high (r = 0.99), similar to our study (r = 0.94; \(p\) < 0.0001). Nonetheless, it should be observed that, for similar masses of needles, we obtained assimilation surfaces nearly 50% lower (8.38 kg-38.4 m\({}^{2}\), 6.69 kg-22.0 m\({}^{2}\), 5.43 kg-31.7 m\({}^{2}\), 2.14 kg-9.36 m\({}^{2}\); Figure 1) than those obtained in the Swedish study. This may have resulted from the structure of needles, i.e., their length and width. The surface area of 1 g of shorter needles is larger than that of longer needles [3].