Az oldal 2020-tól nem frissül. Friss információkért látogasson el az alábbi oldalra: https://ojs.lib.unideb.hu/kitaibelia

Kivonat:

One of the most invasive plants on basic sand soils in Hungary is Cenchrus incertus a grass native to America. Nowadays this species is wide-spread in different weed-communities and in open annual (Brometum tectorum) and perennial (Festucetum vaginatae) grasslands on sand. The recent study tries to examine to what extent the sandbur has spread and in what kind of phytosociological environment it persists in undisturbed semi-natural sand grasslands. The study area is a 0.7×1.1 km size that have been strictly protected and left undisturbed for about three decades. Detailed mapping of the area showed that Cenchrus has only a few very restricted populations inside the area despite the fact that it is abundant in the roads around, in fact no considerable colonization was observed from the roads. Steep south-facing slopes of sand dunes seem to be preferred habitats for the sandbur. Evaluation of 45 representative 2×2 m relevés and a transect consisting of 0.5×0.5 m quadrates showed that the vegetation where Cenchrus is found has the same species-pool that Festucetum vaginatae and Brometum tectorum. Pioneer and disturbance tolerant species are always present in the relevés, the coverage of cryptogams is usually very low. Greater dominance is reached in quadrates the vegetation of which is closer to the perennial grassland. Successive changes towards a more closed Festucetum vaginatae or degradative changes towards a nutrient-rich Brometum tectorum are probably not favorable to the sandbur. This explains why Cenchrus persists on steep slopes on moving sand where succession is very slow and nutrient cannot accumulate. The recent populations are probably remnants of past disturbance events, when larger areas became bare and thus prone to colonization of the sandbur. Further invasion to undisturbed vegetation is therefore unlikely.