Geranium _ sanguineum
point towards fluctuations and their significance in dryland agriculture. In mountains of moderate latitude, simple or complex snow patch communities are formed depending on the time scale and thus document fluctuations. Figure 4.1.36 shows the phenological spectrum of species of woodland edges for two different annual sequences, documenting the extent of such fluctuations.
Fluctuations may also occur because of a massive attack by herbivores. Genetically determined fluctuations are, for example, the so-called mast years with production of many fruits. Ultimately, fluctuations are often the result of human intervention, e.g. changing the rotation in grazing management or changing crops in agriculture. Rabotnov (1974) gives a classification of fluctuations according to their cause and progression.
Evaluations of synecological and biocenologi-cal links are only emerging, e.g. of the temporal niches of flowering species in plant communities, of the synchronisation of insects and animals which eat and distribute pollen, fruits and seeds. This would not only make pollen calendars available for those with allergies, but also help those protecting nature, i.e. by providing dates for mowing, for extensive maintenance, or as a control for the success of different types of land use.
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