The aim of current study was to investigate the spectral separability trends of different tree species due to varying foliage spectral reflectance properties during the growing season. Five tree species prevailing in Lithuania were chosen for the study: aspen (Populus Tremula L.), black alder (Alnus Glutinosa (L.) Gaertn.), Norway spruce (Picea Abies L.), Scots pine (Pinus Sylvestris L.) and silver birch (Betula Pendula Roth). The hyperspectral reflectance data was collected under laboratory conditions scanning the foliage samples from two healthy middle aged stands. Hyperspectral scanning was implemented using Themis Vision Systems LLC VNIR 400H hyperspectral imaging camera in 400-1000 nm range. Principal component analysis and the Jeffries-Matusita distance measure were applied for the analysis of hyperspectral data. The wavelengths providing the best separability between tree species were determined. They were discovered to vary during the growing season: in late spring – early summer the most informative wavelengths were concentrated in blue and near infrared spectral zones, in summer they shifted towards green and red zones, and in autumn they moved further to longer waves - the red and near infrared - spectral zones. The investigated tree species were determined to be spectrally separable during the whole growing season, but the particular periods were revealed to contribute for improved spectral separability between certain tree species. The separability between coniferous species was best in September, while deciduous species were best separable when the samples were collected in August.

The article presents an analysis of the existing situation of forests of the Republic of Lithuania. The situation is analysed in ten counties of the country. In the Republic of Lithuania, forests occupied 2,178,958.04 ha, country’s forest coverage – 33.38% in 2017. The highest forest coverage was established in Alytus (48.80%) and Vilnius (43.47%) counties. Only in three counties of Lithuania (Panevėžys, Telšiai and Utena) the prevailing type of ownership is private forests. In all counties of Lithuania mostly there are Group IV commercial forests, which make up 71.4% of the total forest area. The least are Group I reserved forests. Coniferous species (56.2%) prevail in the country’s forests, of which pine forests are dominant. It is crucial today to analyse the current state of forests and anticipate changes in trends, preventing potential threats. Following the analysis of Lithuanian forest change, it was determined that during the period between the years 2006 and 2017, the forest area increased by 78,616.40 ha or 3.74%. The largest forest development took place in Utena (17,324.13 ha or 7.32%) and Šiauliai (14,798.15 ha or 6.87%) counties. In order to implement the forestry development prospects, from 2018 to 2030, 106,068.87 ha of forests should be planted. In 2030, 2,285,026.91 hectares of forest would occupy Lithuania and would make up to 35% of the country’s area.