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The work presents the results of a study on the biodiversity of agrocenoses using ecological indices. In order to calculate the measures, phytosociological relevés were made and exact methods were applied in winter cereals, spring cereals, tuber crops and stubble fields. The objective of the work was to compare ecological indices (Simpson’s index of dominance C, Simpson’s index of species richness D, and Shannon-Wiener index of biodiversity H’) calculated using the number of plants and their cover determined based on the degree of presence. Moreover, correlation analysis was conducted between the indices computed using the two approaches applied.The results of the study revealed significant differences between all the indices calculated using the exact and approximate methods. In turn, comparisons of the measures computed for individual crops showed significant differences only for potato crops and winter cereals. No significant differences were found between the indicators calculated for spring cereals and stubble fields.

Expansive character of Anthoxanthum aristatum Boiss. in agricultural crops and stubble fields of the Kałuszyńska Upland is presented in the paper. Analysis of occurrence of the species was made according to floristic lists and 802 phytosociological records made between the 1980 and 2002 in rye and poor cereal-fodder soil complexes. In the first period of studies ( 1980-1985) Anthoxanthum aristatum was hardly known from 6 localities and was included in the group of rare species. Between 1994 and 2002 occurrence of the species in the whole studied area (61 localities) was recorded. The weed infested rye canopy in great quantities and overgrown stubble fields on the poorest sandy soils. It was also noted on the most fertile habitats in spring cereals and potato canopy.

There has been a vast and numerous literature concerning seed longevity. Most of these works however has focused solely on theoretical and biological aspects of this problem. Some works although deal with practical problems of seed storage. vigour or deterioration. have had relatively little connection with agricultural crops. practical farming or gardening. Therefore, there has been a need to look at this problem from the seednian's and farmer's point of view. The paper comments on how long seeds of agricultural crops species can keep their longevity, how long it is economically reasonable to store them. the effect of the seeds chemical composition on their longevity, how seeds storage conditions can be modified in order to eventually improve their longevity and environment circumstances influence on the final seed longevity. The paper contains a synthetic summary of expected seed longevity of the most important agricultural species and many examples of long longevity of agricultural species.

The research on the localities of Avena strigosa and on its increased occurrence in agricultural crops of the Podlaski Przełom Bugu was carried out in 1994-1998. The documentation of this research consists of 600 phytosociological relevés and the floristic records. The paper presents the composition and structure of the field plant communities where Avena strigosa was found. It occurs frequently on various soil types of the Podlaski Przełom Bugu. However, on the area examined it was found just in small numbers, covering up to 5% of the area, while in the eastern part of the area an increase in its occurrence was observed. In the area of the Podlaski Przełom Bugu Avena strigosa occurred in spring cereals in the communities of Arnoserido-Scleranthetum and Vicietum tetraspermae as well as in the poor field communities, with the character species of Aperion spicae-venti and Panico-Setarion. Additionally, Avena strigosa was also found in the field communities of root crops belonging to Panico-Setarion alliance; however, it was present there just in small numbers.