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| Photo Credit: Imat Bagja Gumilar |
The more tree-rich forests are, the faster the trees grow and the more CO2 they can bind. A joint study by the TU Dresden, Leuphana University of Lüneburg, Martin Luther University Halle-Wittenberg (MLU), University of Leipzig, University of Montpellier and the German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig shows which mechanisms lie behind it. The results have now been published in the journal Science Advances.
If many different tree species live together in mixed stands, this has a positive effect on their growth and thus wood production - many studies have already confirmed this. The greater the variety of tree species in a forest, the more complex the structures are. The species not only grow to different extents in a certain period of time and have very different tree tops, they also have individual demands on light, water and nutrients. It was previously unclear how the structural complexity in mixed stocks is related to productivity and which mechanisms work here.
The tree diversity experiment "MyDiv" was created at Bad Lauchstädt in southern Saxony-Anhalt in spring 2015: 140 young trees were planted in 80 plots of 121 square meters each - a total of ten native deciduous tree species in different combinations: as monocultures, with two and with four different tree species. In the past two years, the researchers have examined the importance of the structural complexity of the plots for productivity. In addition to the direct measurement of the tree height and the trunk diameter to calculate the wood volume of the trees, terrestrial laser scanning was used to calculate an index of three-dimensional structural complexity for each plot.
The results show that it is not the biodiversity per se, but the structural complexity that goes with it that ensures better tree growth. Structurally complex communities were almost twice as productive as structurally simple stocks. The mixture of shading-tolerant tree species and those who need a lot of light proved to be particularly effective.
A special feature of the "MyDiv" experiment is that five tree species each represent the two most important types of mycorrhiza, the arbuscular mycorrhiza and ektomycorrhiza. Mycorrhiza is the symbiotic community between fungi and plants, in which the thread mesh (mycelium) of the fungus is connected, for example, to a tree root and a nutrient exchange takes place in favor of both partners. In addition to the influence of the above-ground structures, the researchers were also able to investigate what is happening underground. It was found that a mixture of trees with different types of mycorrhiza had no influence on the tree growth.
The study provides valuable information for reforestation projects and shows that the correct composition of the tree species can ensure that the trees grow significantly faster. This is all the more important because trees are effective carbon stores and afforestation is an important tool in the fight against climate change.
Funding: The study was funded by the German Research Foundation as part of the international Research Training Group TreeDi, the University of the Chinese Academy of Sciences (UCAS) and the Saxon Ministry of Science, Culture and Tourism.
Published in journal: Science Advances
Source/Credit: Martin Luther University Halle-Wittenberg
Reference Number: es100923_01
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