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"Species range shifts, aboveground-belowground community reassembly and consequences for ecosystem functioning"

Final Report Summary - SPECIALS (Species range shifts, aboveground-belowground community reassembly and consequences for ecosystem functioning)

Climate warming promotes intra-continental range shifts of plants, animals and microbes from lower to higher latitudes and altitudes. Plants may shift their ranges independent of their co-evolved aboveground and belowground biota, however little is known about how these communities re-assemble in the new range and how that process influences community dynamics and ecosystem functioning. In the ERC-ADV SPECIALS project, we have made a next step towards predicting how terrestrial systems respond to climate warming by evaluating interactions between plants, aboveground and belowground multi-trophic communities in the original and new ranges.
The overall aim was to determine how aboveground and belowground multi-trophic level communities become disjointed and concomitantly re-assembled during plant range shifts. Consequences have been determined for community dynamics and ecosystem functioning in the new range. The overall hypothesis was that due to time-lags in range shifts between plants, and their aboveground and belowground biota, novel communities may develop in the new range that will alter functioning of ecosystems, their stability and resilience.
The project started with a survey along a latitudinal gradient from Greece to the Netherlands. In collaboration with local experts in Greece, Montenegro, Kroatia, Slovenia, Austria, Germany and the Netherlands, Over 600 individual plant samples were collected and from each plant the aboveground insect community was collected, as well as bacteria, fungi, protists, and nematodes from soil and roots. Several novel techniques had to be developed in order to handle and analyze all these data. The key results of this survey work was that range shifts lead to strongest changes in aboveground and belowground communities when the novel plants do not encounter closely related natives in their new range.
Then, we analyzed belowground community interactions in the new range while examining how belowground interactions between plants and soil biota differed between range-expanding and related native plant species. Interestingly, we found a variety of possible outcomes, ranging from range expanders being more toxic to root-feeding nematodes than closely related natives, until that natives were more toxic to range expanders. Moreover, in general, natural biological control of root-feeding nematodes was operating well in soil from the novel range, but there were again strong differences among range-expanding pant species. These differences could be related to the novelty of the chemistry of the range expanders compared to the related natives.
Plant effects on organic matter decomposition, which is one of the key ecosystem processes that drives carbon and nitrogen cycling on Earth, have been examined in order to study to what extent rage expanders were giving different responses than related natives. Interestingly, when keeping all other factors the same, there was no difference between a range expander and a congeneric related native plant species. Therefore, we concluded that climate warming has a higher chance to affect ecosystem functioning when the range-expanding plant species introduce novel traits in the invaded plant communities.
Testing effects of range expansions on the resilience of the invaded ecosystems showed that southern plant-soil communities respond less immediate to the end of extreme drought. We assumed that they may be more adapted to those conditions and that the apparent resilience of northern plant-soil communities after extreme drought might make them more vulnerable to recurrent extreme droughts throughout the growing season.
In conclusion, under climate warming, range-expanding plant species with novel traits will have strongest impact in the novel range. Range shifting is essential in order to have ecosystems adapting to the novel climate condition, however, the novel ecosystems will show lower resilience after extreme events have passed, but that might be an effective strategy, especially when extreme events will repeat themselves within the same growing season.