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2 Polish Journal of Ecology

2 2014

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The influence of standing vegetation height on the reproductive allocation In populations of Serratula tinctoria L. (Asteraceae)

Kostrakiewicz-Gierałt K., Bąba W.

Polish Journal of Ecology

2014

Vol. 62, nr 1

89--99

The advantage of the clonal plants over the nonclonal species in colonization of all biomes and biogeographical regions primarily is due to occurrence of two modes of reproduction. The creating of vegetative propagules with high vitality and survivability, enables the spread in the newly colonized site, while seed production increases the chances for successful recruitment of seedlings, ensuring the genetic diversity of the population. The differences in allocation into vegetative reproduction and generative propagation in relation to rising height of adjacent plants was investigated in populations of Serratula tinctoria L., occurring in Molinietum caeruleae meadows localized in Southern Poland. Each locality was represented by randomly established three permanent study plots: dominated by small meadow species (LOW), prevailed by large-tussock grasses (INTER) and overgrown by shrubs and trees (HIGH). In the years 2009–2011 the number of leaf rosettes and length of the longest leaf in rosette (as a measure of allocation in vegetative propagation), as well as height of generative stems, number of capitula per stem and number of seeds per capitulum (as indicators of investment in generative reproduction) were observed. The allocation in vegetative reproduction decreased along the gradient of vegetation height. The gradually decline of number of rosettes might be caused by lack of free space suitable for establishment of new ramets, whereas the small leaf size could be due to drastically augmentation of shading. The allocation in generative reproduction increased along the gradient of vegetation height. The placement of structures necessary for generative propagation in higher layers of herbaceous canopy, as well as considerable number of capitula and seed production might increase the chances for successful recruitment of seedlings. On the basis of obtained results combining with published data it should be assumed, that the substantial allocation in vegetative reproduction and the slight investment in generative propagation seems to be sufficient for persistence of Serratula tinctoria populations in patches dominated by small meadow species, while the considerable allocation in generative reproduction could be crucial for maintenance of population viability under competitive conditions.

The effect of neighboring plant height, disturbance level and gap size on spontaneous recruitment of large-seeded and small-seeded species in Molinietum caeruleae meadows

Kostrakiewicz-Gierałt K.

Polish Journal of Ecology

2014

Vol. 62, nr 2

289--306

The seed size is considered as a key feature, which effects both: colonizing and competitive abilities of species. The disturbance dependent small-seeded taxa are regarded as superior colonists, whereas the large-seeded taxa are considered as best competitors able to survive the competition from adjacent plants and negative effect of litter. The impact of character of standing vegetation, disturbance level and size of gaps on spontaneous recruitment of seedlings of selected light-seeded species (Gentiana pneumonanthe L., Dianthus superbus L.) and heavy-seeded taxa (Serratula tinctoria L., Gladiolus imbricatus L.) were conducted. The investigations were carried out in two areas (A and B). Both of them were consisted of three adjacent patches of Molinietum caeruleae: dominated by small meadow species (labeled MC), prevailed by large-tussocks grasses (labeled GR), and overgrown by willows (labeled SA). In the year 2007, in all patches, ten permanent experimental plots were randomly arranged. In Area A, plots were divided in four square-shaped, neighboring subplots subjected to: no treatment; the removal of litter and moss layers; the removal of litter, bryophytes, and above-ground parts of plants; the removal of litter, moss and the plants, as well as top soil stripping. In the Area B, plots were divided into four subplots measuring from 0.16 m2 to 0.01 m2. In each of them the litter and above-ground part of plant biomass were clipped and removed. The recruitment of seedlings was monitored from 2007 through 2010. In both studied areas, regardless of seed mass, the greatest abundance of seedlings were found in patches MC, and decreased gradually in sites GR and SA. Irrespective of seed size, in subplots where plant cover and litter stayed intact no new genets was noted, moderate appearance of seedlings was observed in subplots without plant necromass, whereas the greatest number of generative progeny was found in subplots without necromass and aboveground parts of plants. The lower abundance of seedlings in subplots without litter, plants and topsoil might have been caused by depletion of seed bank reserves. Moreover, in all patches the number of seedlings of small- and large-seeded taxa increased significantly with augmentation of gap size. In light of performed studies it might be concluded, that the disturbances might play very important role in active protection of studied taxa. The positive impact of disruption diminishes with increasing of plant canopy height. The removal of plant cover and litter contributes to the greatest seedling recruitment but its beneficial effect diminishes with decreasing of opening size.