W pracy zaprezentowano analizę struktury gatunkowej drzew i krzewów z terenu Elektrowni „Dolna Odra” w Nowym Czarnowie. Prace inwentaryzacyjne przeprowadzono w roku 2001 a uzyskane wyniki skonfrontowano z wynikami takich prac uzyskanymi 10 lat wcześniej. W roku 1991 stwierdzono na obszarze elektrowni obejmującym powierzchnię 250 ha 2110 drzew, a 10 lat później ich liczba wzrosła do 2916. W strukturze gatunkowej drzew z tego terenu 30% stanowią obecnie drzewa owocowe głównie z gatunku Prunus sp. a kolejne 30% to różne odmiany i mieszańce topoli (Populus). Trzeci, co do wielkości udział w strukturze gatunkowej drzew stanowią wierzby (Salix) z dominacją dynamicznie rozwijającego się samosiewu wierzby Iwy (Salix caprea). W stosunku do roku 1991 zaobserwowano znaczne zmniejszenie liczby krzewów: z 10530 egzemplarzy pozostało obecnie 6629 szt. Znacznie obniżyła się przede wszystkim reprezentacja półkrzewu Artemisia abrotanum, który jest sukcesywnie wykaszany z powierzchni pielęgnowanych trawników. Obecnie w strukturze krzewów dominują: forsycja pośrednia (Forsythia intermedia), tawuła van Houtte'a (Spiraea x vanhouttei), i śnieguliczka biała (Symphoricarpos albus).
In Polish forest management planning, the species composition of stands in a forest district is established by adding up the volumes of tree species from individual forest stands. These volumes are calculated according to the estimated share of species cover and the estimated volume of the entire forest stand. The species structure of stands in a forest district, established on the basis of such a method, may be different than that obtained from sample plots. The aim of the study was to compare three ways of determining the tree species structure of stands in a forest district. In Method 1, the species composition was estimated on the basis of the volume of trees measured on sample plots as part of a periodic forest inventory based on stratified sampling. The same data were used in Method 2, but the share of species was calculated on the basis of the basal area. In Method 3, the species structure was estimated according to the volume of trees estimated in each forest stand based on the cover of a given species. The empirical material was collected in 53 forest districts. In method 1 and 2, data from an average of 740 sample plots within the forest district were used. In Method 3, data from the forest stand descriptions contained in the database of the State Forests Information System were used. For each forest district, species composition was calculated, including 6 tree species and 8 groups of tree species. For all forest districts, the average shares of individual species and groups of species differed, depending on the applied method (tab. 1). In case of methods 1 and 2, the biggest difference was found for pine – the most numerous species – but it was also big for less numerous ones: birch and oak (tab. 2). In case of methods 1 and 3, the biggest difference in share was also found for pine (tab. 3). The greater the species diversity of a forest district (determined according to Simpson’s index of diversity), the greater was the average difference in the estimated share of an individual species (figs. 1 and 2). The method of determining the species structure in a forest district used in forest management practice nowadays was considered insufficient. It was proposed to establish it in larger units (subclass, age class, forest district) only according to the volume of trees measured on the sample plots (without rounding and ‘switching’ of species), using the stratified sampling method.