A population census of endangered plant, the cross gentian, is taking place in a nature reserve maintained by large ungulates. The first days show that the large ungulates have helped the plants significantly

2021 - 10 - 12

A population census of endangered plant, the cross gentian (Gentiana cruciata), is taking place in a nature reserve maintained by wild horses, European bison and back-bred aurochs located in the former military area Milovice, near Prague. The data that scientists have collected so far show that the arrival of large ungulates has significantly helped the endangered flora.

“The cross gentian is a perennial that takes many years to respond to changes in the environment. After germination, the seedlings undergo three to seven years of maturation. Then they are very vulnerable, and can be killed by drought or as a result of shading by the surrounding vegetation. If the seedlings survive this critical period, they will bloom for the first time at the age of about five. Only then can it be said whether the young plants survived and the population has increased, decreased, or stagnated,“ explained Miloslav Jirku from the Biological Centre of the Czech Academy of Sciences.

According to him, it makes no sense to map gentians every year, but rather at longer intervals. Therefore, the census is being conducted by scientists now, five years after the first mapping in 2016. This is the interval after which measurable population changes can be expected.

Interim results from the first few days have yielded notably positive results. “On the pastures near Milovice, maintained by the grazing of wild horses and aurochs, we have so far processed half of the area mapped in 2016. And now we can already talk about a several-fold increase in the population of gentians. In the area mapped so far, back in 2016 the cross gentian was found in 22 places. At each site one or more gentians were found. This year, in the same area the occurrence of gentians was recorded in 69 places, of which only 18 were already inhabited by gentians in 2016. This is almost fourfold increase in the number of places where gentians grow,“ emphasised Miloslav Jirku.

Thus far, the scientists have mapped areas where there were significantly fewer gentians in 2016. “On the remaining eight hectares, which we will finish mapping by the end of this week, we can expect an even higher increase in occurrence, as there were more mature gentians in this area, which have been a source of seeds for the past five years,” added Miloslav Jirku.

According to him, the new places were probably inhabited by gentians due to the spread of gentian seeds by large ungulates. “The gentian has tiny seeds that are released in the autumn when passing animals hit the plants with their legs. Mixed with the autumn mud, the seeds can then easily be spread across the pastures on their hooves. This explains the frequent occurrence of new gentians along trails trodden by large ungulates,“ added Miloslav Jirku.

The significant increase in the number of gentians is good news not only for the rare plant. The life of the cross gentian is inextricably bound to that of the critically endangered Alcon blue, a butterfly species which went extinct in much of its European range including the Czech Republic. A major positive shift can be seen in the Alcon blue population compared to 2016. “Back then, eggs were recorded on between half to two thirds of gentians, whereas today eggs are present on vast majority of gentians. The increase in the population of the Alcon blue is also indicated by the annual census of butterflies, which this year showed its widespread occurrence in pastures, including places where the Alcon blue was not previously observed,“ added Miloslav Jirku.

In contrast to the situation five years ago, this year scientists have utilised modern mapping technology. “We now use geographic information systems tools to map gentians. These GIS applications are gradually becoming indispensable in field biology. In 2016, individual points with the presence of gentians were recorded using a GPS device, the number of plants and other data were recorded in a paper notebook and then laboriously transcribed into a computer. Now everything is different, the development and availability of GIS applications has greatly improved the field mapping process. Now we can see in a tablet an aerial map of the pastures divided into six-metre-wide strips, so-called transects, we can also see both new occurrence points and the points where gentians were found in 2016, as well as our actual location,” explained Daria Jirku from the Faculty of Science at the University of South Bohemia, who is technical supervisor of the mapping of gentians.

Scientists systematically walk the mapped areas along the six-metre strips and record all field data, including photo documentation, directly in the field into the application. “Thanks to the fact that we can also see the points of occurrence in 2016, we are now able to verify, after five years, all the places where gentians have or have not survived from the past and how their abundance has changed, as well as new findings. In addition, there is no lengthy transcribing of data to a computer, so the resulting dataset can be analysed straight away, as it is immediately ready for statistical evaluation,“ added Daria Jirku.

The results of the gentian census will provide an important evidence for assessing the impact of wild horses and other large ungulates grazing in the former military area. “The initial data look very optimistic and we are looking forward the final results,” said Dalibor Dostal, director of the European Wildlife conservation organisation. “The scientists are doing a great job because despite the use of modern technology, gentian mapping is still associated with demanding fieldwork activities. All the more so with this chilly autumn weather we are having,“ added Dalibor Dostal, praising the work of the scientists.

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