Occurrence of brambles (Rubus L.) in young forest plantations on the Kolbuszowa Plateau

In forests of the Kolbuszowa Plateau, bramble thickets are common mainly in young forest plantations and clear-cut areas. 11 bramble species were found in 20 plantations visited during the field study. The most frequent bramble species in young forest plantations include: Rubus plicatus, R. nessensis, R. hirtus, R. idaeus, while less frequent are: R. gracilis, R. ambrosius and R. apricus. The largest patches of brambles were found in plantations established on sites of mixed pine-oak forest, subcontinental lime-oak-hornbeam forest and dried alder carrs. Rubus thickets in young forest plantations occur together with numerous species characteristic of communities classified into the following classes: Vaccinio-Piceetea, Querco-Fagetea, Epilobietea angustifolii, Molinio-Arrhenatheretea and Nardo-Callunetea. Brambles growing in young forest plantations can be roughly divided into three groups: I - species with thin, prostrate and rooting stems (R. hirtus, R. apricus, R. pedemontanus), which may significantly affect the growth of tree seedlings if bramble specimens or diaspores are present at the time of tree planting; II - species with strong, poorly branched and arcuate stems (R. plicatus, R. gracilis, R. ambrosius, R. glivicensis), whose negative effect on tree seedlings depends on the potential of a tree species to produce quickly a high and dense thicket thereby overshadowing the lower vegetation; III - species with erect and relatively sparsely growing stems (R. idaeus), which do not pose any threat to young forest plantations. Species with intermediate biological traits (e.g. R. nessensis) may have a negative impact on young plantations, as they generate large and dense bush, however, in most cases, their populations grow rather sparsely and do not hinder the development of tree seedlings.