The effects of successional stage and size of gaps on recruitment of clonal plants in overgrowing Molinietum caeruleae meadows

In majority of plant communities with a closed canopy, the disturbances created by abiotic factors and biotic agents contribute to origin of an area free of existing vegetation and considered as safe sites for seedling recruitment. Although the gaps are characterized by several features, the size is proposed to be the most important characteristic. The investigations of recruitment of clonal taxa in different–sized gaps were conducted in the years 2011–2012 in Molinietum caeruleae meadows representing various successional stages and dominated by different species. Patch ES, representing early-successional stage, was dominated by small meadow species, Patch MS, representing mid-successional stage, was prevailed by tall-growing macroforbs, while Patch LS representing late-successional stage was overgrown by macroforbs and willows. In the successive sites the mean height of plant canopy, as well as the period of spring inundation increased gradually. The total number of species and seedlings decreased from the Patch ES, through the Patch MS, to the Patch LS. Almost all plants presenting positive correlation between seedling number and gap area created hypogeogenous stems with substantial lateral growth and considerable number of short-lived daughter ramets allowing the fast colonization of neighbourhood. The majority of species showing negative relationship formed epigeogenous stems with slight lateral growth, as well as low number of long-lived ramets contributing to slow colonization of area. In light of performed studies, it might be concluded, that making disturbance in continuous plant canopy and litter might be very effective way of conservation of Molinietum caeruleae meadows. The creation of different-sized gaps seems to be especially valuable due to the maintenance of heterogeneity of clonal species, which is particularly important in advanced successional stages.