Laurophyllization

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Laurophyllisierung (also Laurophyllisation) is the process of spreading evergreen deciduous shrubs (ger .: evergreen broad-leaved vegetation) in deciduous forests.

The name Laurophyllisierung derives from the vegetation type of the laurel forest , more precisely from the eponymous family of the same, the laurel family (Lauraceae) . In a narrower sense, therefore, laurophylls are also in focus as characteristic species.

The laurophyllization represents a biome change, as the species spectrum and thus the vegetation structure shifts from a deciduous deciduous forest to an evergreen laurel forest . The process is interpreted as the so-called "fingerprint" of global warming , i.e. as the ecological impact of global warming.

background

The phenomenon of laurophyllization was first described in the late 1980s for the region of Insubria ( Ticino ). The change in vegetation described above was shown by the addition of evergreen deciduous trees. Research continues to focus on this region (see for example). Few other studies deal with the laurophyllization outside of insubria, which is probably due to the narrowly defined site or climatic conditions on which laurophylls depend and which are limited to relatively small areas worldwide. An example of a German study can be found in Dierschke (2005). Furthermore, the University of Cologne (for the Rhineland region ) and the University of Bochum (for the Ruhr area ) are dealing with this topic in a broader sense. It should be added that on the French side of the Upper Rhine Graben in Munchhausen, the first signs of a laurophyllous change in vegetation were described.

Development (in insubria)

In the following, the sequence of the laurophyllization process will be briefly presented using the example of Insubria:

  1. Such species were introduced into the region and cultivated in gardens as early as 1900. However, there was initially no natural rejuvenation .
  2. In the first half of the last century there were few isolated free-growing individuals. These occurrences were limited to azonal (protected) locations in southern Switzerland .
  3. The first natural regeneration in gardens was observed in the middle of the last century.
  4. In the second half of the 20th century, more and more freely growing individuals could be detected. Regeneration now also took place in the wild and the occurrences were no longer isolated. Initially only represented in the shrub layer , in the last decade laurophylls grew increasingly into the tree layer .
  5. Today there is a sustained expansion and the formation of laurophyll- dominated stands (at least in the shrub layer). In the meantime, laurophyllisation has also found its way into northern Switzerland, albeit with (still) few individuals and species.
  6. For the future, stagnation or even a decline is not expected, but rather the formation of more dominated stocks. In addition, a spatial expansion of the laurophyllization process is expected. Forecasts name parts of Istria , some slopes of the Apennines , the strip along the coast of the Bay of Biscay and the southwest slope of the Caucasus .

Species involved

Indigenous laurophyll species include: common privet ( Ligustrum vulgare L.), rust-leaved alpine rose ( Rhododendron ferrugineum L.), common box ( Buxus sempervirens L.) and European holly ( Ilex aquifolium L.). Sometimes conifers such as juniper ( Juniperus ) or yew ( Taxus ) are also included (evergreen). Important alien species include a. Camphor tree ( Cinnamomum camphora L.), gloss privet ( Ligustrum lucidum ), laurel ( Laurus nobilis L.), laurel cherry ( Prunus laurocerasus L.) and the Chinese hemp palm ( Trachycarpus fortunei (Hook.) H. Wendl.).

causes

Two possibilities are named as the cause of the increasing occurrence of evergreen deciduous trees (in Insubria):

  1. Existence of an unoccupied niche: The Insubrian area is the traditional distribution area of the laurel forest, which, however, was not reoccupied after the end of the Pleistocene - until today.
  2. Climate change: Biological change is promoted by climatic changes in insubria (increased mean and extreme temperatures).

In general, the two causes mentioned are to be regarded as complementary to one another.

consequences

The following are mentioned as possible consequences:

  1. Species enrichment: It is mainly alien species that settle there , as only a few native species are available to occupy this niche .
  2. Displacement of native species: In some cases, native deciduous species are under pressure, as evergreen species have the advantage of a longer assimilation phase (they can also photosynthesize on mild winter days, for example ).
  3. Influence on soil chemistry : The material composition of laurophyllous species is different from that of deciduous species, which is why the litter and thus the soil / humus are also subject to material changes. Changes in C / N ratios , lower proportions of fulvic and humic acids , and an influence on the iron balance have already been determined .
  4. Change in the water balance : Since evergreen species also transpire in winter , the water balance can change.
  5. Change in material flows : As in the case of the water balance, substances are also converted by evergreen species in winter.
  6. Influencing fauna and microorganisms : The question arises, for example, whether new species are accepted as food or whether appropriately adapted destructors are available. In addition, it was found that the spread of the species occurs primarily through birds, which therefore obviously adopt the fruits of the new species.

literature

  1. ↑ a b Gianoni, Carraro, Klötzli (1988): Thermophilic, rich in plant species laurophyllous Waldgesellschaften Ticino in hyperinsubrischen lakes area. Reports from the Geobotanical Institute of the ETH, Rübel Foundation, Zurich 54, pp. 164–180.
  2. ↑ Klötzli, Walther, Carraro, Grundmann (1996): Beginning Biomwandel in Insubrien. Negotiations of the Society for Ecology, Vol. 26, pp. 537-550.
  3. ↑ Carraro, Gianoni, Mossi, Klötzli, Walther (2001): Observed changes in vegetation in relation to climate warming. In: Burga, Kratochwil (Ed.): Biomonitoring, pp. 195–205.
  4. ^ Walther (2002): Weakening of climatic constraints with global warming and its consequences for evergreen broad-leaved species. Folia Geobotanica 37, pp. 129-139.
  5. ↑ Berger, Walther (2006): Distribution of evergreen broad-leaved woody species in Insubria in relation to bedrock and precipitation. Botanica Helvetica 116, pp. 65-77.
  6. ↑ Dierschke (2005): Laurophyllization - also a phenomenon in northern Central Europe? On the current distribution of Hedera helix in deciduous deciduous forests. Reports of the Reinhold-Tüxen-Gesellschaft 17, pp. 151–168.
  7. ^ Christophe Neff: Natural history observations in Munchhausen (France) Sauer delta and laurophyllization in Munchhausen. In: Joachim Vogt et al. (Ed.): Karlsruhe, city and region. A regional guide to well-known and unknown excursion destinations . Karlsruhe, Regional Scientific Publishing House, 2007, pages, 201 - 215, ISBN 978-3-9811189-2-6
  8. ^ Walther (2001): Laurophyllisation - a sign of a changing climate ?. In: Burga, Kratochwil (Ed.): Biomonitoring, pp. 207–223.
  9. ↑ Carraro, Gianoni, Mossi (1999): Climatic influence on vegetation changes: a verification on regional scale of the laurophyllisation. In: Klötzli, Walther (Hrsg.): Recent shifts in vegetation boundaries of deciduous forests, especially due to general global warming, pp. 31–51.
  10. ↑ Walther (2001): Climatic forcing on the dispersal of exotic species. Phytocoenologia 30, pp. 409-430.
  11. ↑ Zanelli, Egli, Giaccai, Mirabella (2005): The influence of laurophyllous species on organic matter and geochemistry in soils of Southern Switzerland and Northern Italy as a response to climate change. Geophysical Research Abstracts 7, 00451
  12. ↑ Walther (1999): Distribution and limits of evergreen broad-leaved (laurophyllous) species in Switzerland. Botanica Helvetica 109, pp. 153-167.