Zmienność pokrycia traw w runie wybranych typów lasów w sezonie wegetacyjnym

The paper shows the results of the occurrence of grass species and the determination of the reasons of changing their participation in the undergrowth during the growing season. The obtained results showed that the stand structure constituting ecological factors, especially the amount of light reaching to the bottom of the forest determines the changing participation of grass species. These relations were particularly confirmed for Deschampsia flexuosa, Arrhenatherum elatius and Poa nemoralis.