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Measuring allocation pattern

Fragmentation in many European landscapes is accompanied by a slow deterioration of many of the remaining habitats. This deterioration is largely due to change in the landscape management, such as cessation of grazing or mowing, increased load of nutrients etc. which typically lead to increased intensity of competition from grasses and/or all tall forbs. While the rare plants are often able to survive in these deteriorated habitats for some time, their response to the changed habitat conditions affects their ability to produce seeds that otherwise might serve as means for colonization of other habitats. The major part of the research in the WP4 concentrated on quantification of this response by manipulating the competitive stress (as a proxy for habitat deterioration) and observing changes in plant demography and allocation patterns. These experiments were conducted both in the experimental garden (using seeds collected in the sampling phase) and in field habitats.

The experiments showed that increased competition of neighbours leads to a change in allocation pattern of experimental plants. In both common garden experiments and in the field sites, increased competition negatively influenced fecundity; survival was not affected. Decrease in investment to sexual reproduction was a function of smaller plant size of individuals growing with competitor (Hypochoeris radicata, Succisa pratensis); there was little evidence of shift to reproductive functions in worse conditions. In Hypochoeris radicata, size-independent effects of competition on allocation pattern were detected. Namely, plants grown without competitor produced more seeds than plants of the same size cultivated with competitor. However, increased allocation to generative reproduction did not result in lower investment to survival (to root biomass). This should be interpreted as the absence of resource-based trade-off between these two essential life functions.

In one target plant (Succisa pratensis), the allocation shifts were compared over the European scale (the Czech Republic, the Netherlands and Sweden) to identify site-independence of the effects and the possibility to generalize the results. This comparison of the species response over the European scale showed strong site-dependent effects in the allocation pattern and its response to competition. While the Succisa populations from the Netherlands showed increased flowering at the expense of further survival at deteriorating habitats, no similar response was found for populations coming from other sites. This means that there is no general patterns of the species response to the habitat deterioration; always site or country specific information has to be sought to assess the species response to deterioration and assessing its change in dispersal capacities in response to that.

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