The changes of areas of eight tree species in Lithuania during the past century were analysed. Aiming to apply the different approaches in forest studies, the Exponential smoothing method for forecasting the changes of the tree areas for the 25 years was used. The data dating from 1922 was analyzed as a time series. The descending trend was identified for Scots pine (Pinus sylvestris L.) and European ash (Fraxinus excelsior L.) and increasing trend – for Norway spruce (Picea abies (L.) H. Karst.), common oak (Quercus robur L.), birch species (Betula pubescens Ehrh. and Betula pendula Roth), black alder (Alnus glutinosa (L.) Gaertn.), European aspen (Populus tremula L.) and grey alder (Alnus incana (L.) Moench). The Exponential Trend with Multiplicative Seasonality (ET-MS) model was fitted for almost all investigated tree species with exception of European ash. For the latter species, the Damped Trend with Multiplicative Seasonality (DT-MS) model was chosen. Mean absolute percentage error of the model in all cases did not exceed 2%.

This paper discusses some aspects of introducing a new agricultural crop in Latvia – truffles Tuber spp. Truffles are mycorrhiza–forming mushrooms with edible fruit bodies developing in the upper layer of soil. In Latvia, there is a growing interest among farmers to start cultivate truffles. From several cultivated truffle species, the Burgundy truffle Tuber aestivum syn. T. uncinatum is the most suitable to cultivate in Latvia. There are both autochthonous and introduced tree species in Latvia, which are suitable for the Burgundy truffle cultivation and it is suggested to use Quercus robur, Corylus avellana, Tilia cordata and Fagus sylvatica. In order to find the regions in Latvia with the highest potential for successful Burgundy truffle cultivation, climate and soil characteristics had been co-analysed. By superimposing soil and climate maps of Latvia, the most suitable regions for truffle cultivation are situated in the central and southern part of the country. Considering the variability in soil composition even within regions in Latvia, it is thereafter also of great importance to investigate site-specific soil characteristics in order to find the most favourable grounds for truffle cultivation. Other truffle species which might be suitable for cultivation in the future are also discussed, as well as some general recommendations in establishing truffle orchards.

Leaf morphology was assessed in Pajiesys and Seirijai field trials of oaks. Oaks in these trials are the progenies of oak trees (Quercus genus) that grow in the Trakas forest of Seirijai district of Alytus forest enterprise of Lithuania. The aim of the study was to determine the number of hybrid trees between the progenies of the Trakas forest in Pajiesys and Seirijai field trials. 251 oaks belonging to 40 half-sib families were sampled. Twenty three leaf morphological variables were measured on each of 5 leaves collected from each tree and analysed by principal component analysis (PCA) and discriminant analysis (DA). The study concluded that Q. robur and Q. petraea leaves are most clearly identified by six morphological traits. Discriminant function of two traits for oak species separation was proposed. The study has also revealed a high degree of interspecific hybridization in field trials. Study results were compared with earlier reports about hybridization occurring in mixed oak stands in other parts of Europe.