University of Tübingen: The type of forest use influences the life rhythm of the wild plants

Due to global warming, the seasonal rhythms of many plants, for example the flowering period, are shifting. A study by the University of Tübingen has now found that the way in which the land is used at the location of the plants can also significantly influence the rhythm of their life cycles. A research team from the Evolutionary Ecology of Plants working group examined a hundred forest areas with different uses in a comparative study. It found that in forests that are used intensively for forestry, the spring bloomers in the undergrowth, such as wood anemones, wild garlic or wood violets, bloom an average of two weeks later than in near-natural forest areas. The study was published in the journal Ecological Applications .

In order to thrive and survive, important events in the life of plants must be coordinated with favorable environmental conditions. Above all, this includes reproduction. “For flowering plants, there is no more important event than flowering. Timing is crucial, ”explains Franziska Willems, lead author of the study. Only when the flowers are pollinated at the right time will fruits grow with seeds that can produce new plants.

Spruce forest on the Swabian Alb
Study areas in April 2017: Spruce forest on the Swabian Alb.
The spring flowers in the undergrowth of our local forests, which also include spring pea, celandine and woodruff, must not develop their flowers too early in the year. “You run the risk of being damaged in frost and snow. Or their pollinators, often insects, are not yet on their way, ”says Willems. “But if they are too late, the leaves of the trees take away the light.” The researchers have now investigated how, in addition to global warming, another driver of global change, intensive land use, influences the rhythm of life of these flowering plants.

Weekly examination of the state of development
“We followed the development status of the wildflowers on a hundred forest areas weekly for one spring,” explains working group leader Professor Oliver Bossdorf. The forest areas are part of the so-called biodiversity exploratories, an interdisciplinary project of the German Research Foundation to study biodiversity in Germany. The spectrum ranges from unused nature reserves to forests that are used intensively for forestry purposes. “The fact that plants in heavily used forests bloomed an average of two weeks later than in near-natural areas can largely be explained by the different structures of the forests,” says Bossdorf. For wood production, tree species are often planted in commercial forests that do not naturally occur there, mainly conifers.

16 types of early flowering wild plants
16 species of early flowering wild plants in the undergrowth of the forest were included in the study. At the bottom of each picture it is noted on how many of the 100 examined areas the species occurred.
“Such changes affect the microclimate on the forest floor,” adds Willems. “The proportion of conifers has the greatest influence. But the age of the trees, the size of their crowns and the structural complexity of the forests also play an important role. ”For example, conifers created a cooler forest climate than deciduous trees, which meant that the plants would later flower.

“What is particularly exciting, however, is that the differences in flowering times in our study cannot be explained by temperature alone,” says Willems. The planting of new tree species such as spruce and the changed structure in managed forests presumably lead to new environmental conditions. The availability of light or the properties of the soil could change, and these factors could also influence the timing of the plants’ flowering.

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