Sylvie Pecháčková

Within population genetic differentiation in traits affecting clonal growth: Festuca rubra in a mountain grassland

Festuca rubra , a clonal grass of mountain grasslands, possesses a considerable variability in traits related to spatial spreading (rhizome production, length and branching; tussock architecture). Since these traits highly influence the success of the species in a spatially heterogeneous system of grasslands, a combined field and growth chamber approach was adopted to determine the within‐population variation in these parameters. Clones were sampled in a mountain grassland (The Krkonoše Mts., Czech Republic); the environment (mean neighbour density) of individual clones varied highly. Before the clones were collected, shoot demography and tussock architecture within these clones were recorded in the field for four seasons. Their clone identity was determined using DNA RAPD. Vegetatively propagated plants from these clones were cultivated in a common garden experiment to demonstrate variation in tussock growth and architecture. Their response to change in red/far red light ratio was determined in the growth chamber.

Is a grassland community composed of coexisting species with low and high spatial mobility

Patterns of grasslands species mobility were compared between communities and within plant species. Data from high spatial resolution permanent plots with fine scale recording system, experiment with removal of the dominant recorded also at a fine scale were used. The permanent plots showed large variation within a community in the patterns of species mobility. The species mobility was partly dependent on the site and was higher in a more nutrient rich and climatically more favourable community. Mobility also varied within species. In some species (Nardus stricta, Anthoxanthum spp.) it differed between communities (it was higher in more nutrient rich and climatically more favourable community) and did not respond to removal of the dominant species. In another species,Festuca rubra, mobility also differed between plots; in contrast, it did not show consistent variation attributable to community type and showed strongly increased spatial persistence in plots with the dominant species removed. In this species the mobility seems to be dependent on the competitive pressure of the coexisting species.

Climatic variability and grassland community composition over 10 years : separating effects on module biomass and number of modules

1. Data from permanent grassland plots, collected yearly over a 10 year period were analysed for correlation between weather variables and plant performance. Number of modules and mean biomass of the module were recorded separately. Because the two variables are inter-related, both with each other and with the values in preceding years, regression residuals were used to quantify the response in the particular year. The performance variables were correlated with the monthly averages of temperature and bimonthly averages of precipitation. 2. There was a large year-to-year component of variation in species performance. For biomass, the year-to-year variation is largely explained by correlations with weather ; in number of modules, some species show variation which is not explained by the weather variables studied. Weather variables of both current and preceding years showed significant correlations with species performance. 3. Species responded characteristically to weather variables and in any one species, the number of modules and the biomass do not necessarily respond in the same way. This may be an important mechanism creating time lags in the community response to weather variables and, more generally, may be responsible for non-linearity of the community response to the weather.

Fine-scale species interactions of clonal plants in a mountain grassland : a removal experiment

A removal experiment (one species removed per treatment) in a species poor mountain grassland community was established to (1) determine the horizontal competitive effect at the fine scale, and distinguish them from the effects at the plot level, (2) identify species specific competition effects and (3) determine the overall structure of competitive network within a community. Observation of the species response at the fine spatial scale was done using the grid of 3.3 x 3.3 cm cells. The competitive effects at the level of cells were measured by the correlation between the presence of the removed species in the cell before the removal and the density change of the target species in the cell. Significance of the correlation was estimated by a permutation procedure. At the level of the whole 25 x 25 cm plot, there was no clear tendency in the response to removal of any species except for Nardus stricta, which increased significantly in treatments with Deschampsia flexuosa and Anthoxanthum alpinum removed. Anthoxanthum alpinum increased its biomass per shoot in the treatments with other species removed. At the fine scale level of 3.3 x 3.3 cm cells, some species began to occupy the empty space made by the removal of their neighbours, indicating release from competition following removal. The most pronounced change was the increase of Deschampsia flexuosa following removal of Nardus stricta. Some responses were species-pair specific. Two species pairs (Deschampsia-Anthoxanthum, Deschampsia-Fesiuca) showed reciprocal response at the fine scale; each species increased if the other one was removed. In two species (Nardus stricta, Deschampsia flexuosa) the effects observed at the level of the whole plot and at the level of the individual cells differed. This is attributed to (1) different role of belowground competition (which has wider horizontal range and appears at the scale of the plot) and aboveground competition (which is rather short range and appears already at the scale of the cell) and (2) different plasticity in their clonal growth architecture.

Efficient nitrogen economy: Key to the success ofPolygonum bistorta in an abandoned mountain meadow

The dominance ofPolygonum bistorta in abandoned mountain meadows was studied. Successional and seasonal changes in biomass, nitrogen concentration and content were studied at the community level. During the successionP. bistorta increases its biomass both in absolute and mainly in relative values compared to the surrounding species. Nitrogen stored in its rhizomes seems to be quickly translocated into above-ground parts at the beginning of the growing season. High amounts of nitrogen allow rapid growth of both vegetative and generative plant parts. The success ofP. bistorta is probably the result of efficient use of stored nitrogen, suppression of surrounding vegetation by above-ground cover of leaves and by decrease in the level of soil nitrogen, and the effect of a large amount of litter. Management consisting in the combination of mowing and fertilization is proposed.

Root response to above-ground light quality – Differences between rhizomatous and non-rhizomatous clones of Festuca rubra

Root response to reduced red/far red ratio above ground was studied in an experiment with 12 vegetatively propagated clones of Festuca rubra, a rhizomatous grass species. A new method suitable for describing the node position within rhizome systems was developed. It uses a combination of developmental and functional directions of ordering, adopting methods of topology. At each node the root structure was defined as consisting of three root types: unbranched, long branched and fine branched. Root system size was expressed as the number and length of roots of these individual types. Rhizomatous and non-rhizomatous clones of Festuca rubra differed in the size and structure of their root systems and in the response to lowered red/far red light ratio. This response was caused more by the behaviour of the rhizomes than of the roots alone. In rhizomatous clones, the largest differences in root system structure were between the mother-nodes and the nodes on the rhizomes. The size of the root system also depended on the node position. Response to the red/far red ratio was clone specific only in some of the root parameters, especially in traits of unbranched roots at young nodes. The role of the three root morphotypes in the plants ontogeny, nutrient uptake and ability to cope with environmental heterogeneity both above- and below ground, is discussed.