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Hedgerows: The Older, the More Species-Rich

A research team from the Institute of Ecology at the University of Bremen has compared the plant community of old and young hedgerows in Schleswig-Holstein. This showed that there were significantly more forest plant species in the old shrubs.

Large or small hedgerows at the edges of fields and meadows adorn the typical countryside picture of Schleswig-Holstein. They are the legacy of the “living fences”, which were planted in the 18th century during the coupling in order to provide borders for the newly redistributed agricultural areas. The “knicks”, as they are called in North Germany, run through the sparsely wooded agricultural land like a dense network and thus increase the connection of otherwise isolated habitats. Due to their forest-like conditions, hedgerows can offer forest plant species, such as anemones, greater stitchwort or arum maculatum, an important habitat. However, many wild plants only spread very slowly and they are not equipped with an efficient diffusion mechanism. “This can become a challenge for nature conservation as the newly created habitats are populated in a delayed manner”, said ecologist Kathrin Litza from the University of Bremen. She is researching hedgerows for her PhD dissertation.

Age Is a Deciding Factor

Many hedgerows come from the time of the redistribution of agricultural land in the 18th and 19th centuries and have had time to develop since them. This makes it possible for many living organisms to live there. A research team from the University of Bremen has now investigated whether old hedgerows are more species-rich than younger ones based on their longer life. In order to do this they compared pairs of old hedgerows (at least 140 years old) and young hedgerows (between 14 and 80 years old) with regard to the number of herbaceous forest plant species. The hedges in a pair were located near to each other and exhibited similar structures and levels of care. Thus, all differences found could be traced back to the age of the hedgerows.

Significant for Ecological Balance

The researchers were able to prove that a great deal more forest plant species live in older hedgerows. The young hedgerows were, however, species-richer than expected. Especially the closeness to species-rich, old hedgerows or also to forests was helpful for a quick colonization. “This shows how important the preservation and care for the old, “colorful” hedgerows is. If their species diversity is missing in the countryside, it is not possible for the new habitats to be colonized”, explained Litza. The young hedgerows should not be underestimated either as they can develop into typical and valuable habitats within several decades. It is important that the shrub hedges are planted and cared for in the traditional manner.

Dense Structure is Optimal

Moreover, a wide layer of shrubs has been shown to be advantageous for forest plants. “One can imagine hedgerows as being two forest borders, which have moved closely together. The wider the hedgerow, the more forest-like the internal conditions become”, stated Litza. It is above all a matter of the higher moisture level and more stable temperatures on the inside, whereas it can become very hot on the outside in the summer depending on the position of the sun. The forest plants can therefore often be found in the middle of the row or on the north side. Widely overhanging shrubs also form a suitable habitat for many forest plants but are rarely to be located on intensively used agricultural land.

You can read the article “Hedgerow age affects the species richness of herbaceous forest plants. Journal of vegetation Science” here: https://doi.org/10.1111/jvs.12744

Further information:

A summary in simple English:
https://jvsavsblog.org/2019/05/22/hedgerow-age-affects-the-species-richness-of-herbaceous-forest-plants/

A German summary:
https://kathrin.litza.de/forschungsprojekte/forschungsprojekt-vergleich-von-historisch-alten-und-jungen-knicks

www.uni-bremen.de/en/

Contact:

Kathrin Litza
Institute of Ecology
Faculty of Biology/Chemistry
University of Bremen
Phone: +49 421 218-62915
Email: kathrin.litzaprotect me ?!uni-bremenprotect me ?!.de

Landschaft mit Felden und Bäumen und Hecken dazwischen
Important for a high diversity of plants: hedgerows between fields and meadows.