Free-ranging Konik horses grazing in old forest stands in northeast Poland increased biodiversity in both the ground layer and shrub layer, according to researchers.
A team of researchers examined both deciduous and coniferous forest stands for their study, reported in the journal Forests.
The work by Sergii Boiko and his colleagues centered on two forest complexes, the first in the fenced area of the Popielno Research Station of the Polish Academy of Sciences where free-living Polish primitive horses grazed among the 130-year-old stands. The other was an open 116-year-old managed (harvested) forest area in Maskulińskie which did not have horses.
In both areas, the stands are inhabited by free-living red and roe deer.
The impact of forest animals on ground-cover layers as well as on the understory shrub layer and undergrowth was compared.
“Very significant differences in the structure of the understory and undergrowth (above 0.5 meters) layer vegetation communities between both areas and type of stands were found,” the researchers reported.
“The results suggest that the presence of the Polish horse substantially changed the species composition and increased the species diversity of the ground layer and shrub layer, both in the coniferous forest and deciduous forest habitats.”
The height of the shrub-layer trees was lower by 30% in the area with the horses.
The level of biodiversity of forest plants was dependent on the presence of the Polish horse, which in the past was one of the natural inhabitants of forests in the area of research, they said.
In general, equids live most of their lives in the open, on pastures and meadows, but may also use available tree stands. In the case of the Polish primitive horse, they may use forest not only as a feeding place, but also as protection against vexing insects or heat.
“The grazing of the Polish primitive horse, like the Exmoor pony, is increasingly … used as a natural means to maintain the non-forested status of areas that are not agriculturally used.
“Free-living horses help to preserve vast meadow and pasture or dune areas, contributing to the preservation of semi-natural open communities, just like large herbivorous mammals in the past.
“Polish primitive horses were used, for instance, not only to restrain the succession of forest species in grass areas and moors, but also to contribute to maintaining their biodiversity.
“Grazing on mid-forest meadows in extensive conditions favors the diversity of the undergrowth structure, and the dispersed dung left by horses contributes to the herb layer diversification.” This results in increasing the number of plant species, previous studies have shown.
In conclusion, they said: “The impact of the Polish primitive horses on the studied forest environment was generally positive.
“In similar habitats, it did not affect the biodiversity of the herbs and undergrowth below 0.5 meters when compared with the managed forests.
“However, in the undergrowth higher than 0.5m and the understory layer a significant effect of the habitat quality on species diversity was found.
“The presence of the Polish primitive horse significantly increased the species diversity index for the undergrowth higher than 0.5m, and the understory layer, but the average height of these layers was 30% shorter in the forest stands with the presence of the horse.”
The full study team comprised Boiko, with the Forest Culture Center in Gołuchów; and Ernest Bielinis, Zbigniew Sierota, Anna Zawadzka, Alicja Słupska, Maciej Nasiadko and Jakub Borkowski, all with the Department of Forestry and Forest Ecology at the University of Warmia and Mazury in Olsztyn.
Polish Pony Changes Lower Layer Biodiversity in Old Growth Scots Pine Stands
Sergii Boiko, Ernest Bielinis, Zbigniew Sierota, Anna Zawadzka, Alicja Słupska, Maciej Nasiadko and Jakub Borkowski.
Forests 2019, 10(5), 417; https://doi.org/10.3390/f10050417