SLU news
Subarctic species richness and distribution influenced by climate
Published: 12 June 2024
Even remote, sparsely populated areas are affected by human-induced climate change. In his doctoral thesis, Pablo de la Peña Aguilera investigated what controls the distribution and species composition of insects, vascular plants and soil fungi across subarctic landscapes. He has found that species richness decreases with altitude and increases with soil temperature and moisture.
Pablo de La Peña Aguilera spent two field seasons in Varanger in northern Norway and Kilpisjärvi in northern Finland. High latitude areas are experiencing a more rapid rise in temperature than other parts of the world, so it is interesting to study what is happening to species there.
One of the most visible signs of climate change is migration of species into regions where they previously did not exist. Cold-adapted plants shifts toward higher altitudes in search of suitable habitats. Species that can now survive the earlier, harsher conditions are spreading into the area. A well-known example is the northward expansion of the red fox, which in some regions is displacing and competing with the arctic fox. A parallel process is the phenomenon known as “the greening of the Arctic”, which exemplifies the lengthening of the growing season and the expansion of woody plants across the tundra as the consequence of the warmer temperatures.
But how the distribution and composition of species will change is complex. And it is these patterns that Pablo de La Peña Aguilera has been studying.
"I found that the species richness of subarctic plant and arthropod communities is strongly influenced by local elevation, soil temperature and soil moisture. In short, the higher, colder and drier the landscape, the fewer species you will find," says Pablo de La Peña Aguilera.
Species richness was highest in the mountain birch forest, where soils are warmer and productivity is higher (there are more plants, they provide food for herbivores, etc.), and fewer species in the tundra, which is characterized by low productivity. The species were largely the same in both environments, with some specialists found only in the mountain birch forest or on the tundra.
The different groups of organisms showed different patterns, which may be related to their ability to disperse. Fungal spores and seeds can disperse widely and are more selective about their habitat. They were found where conditions were optimal. Flying insects and ground-dwelling arthropods cannot disperse as far and were more evenly distributed across the landscape.
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The conditions in the subarctic can be extreme, and the growing season lasts only 2-3 months of the year.
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This is one pitfall sample, where you can see spiders, ground beetles, and some flies.
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The subarctic region is characterized by high variability in conditions due to landscape heterogeneity and the effect of snow cover. This is probably the best example of it. While the growing season has not yet started on the left side, the right side is already very green.
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Pablo is emptying the insects in the Malaise trap. You also see the temperature and moisture sensors . Photo: Pablo de La Peña Aguilera
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Pablo de La Peña Aguilera is pleased to have contributed to the understanding of what shapes species composition and distribution, even though nature is complex.
"Climate change will change biodiversity, but it is difficult to predict exactly how. Productivity will increase, so species richness is likely to increase. However, different groups of organisms will be affected differently; even if insect species richness increases, plant diversity may not follow the same path. There is a clear risk that species that are dependent on each other will be mismatched in time and space," says Pablo de La Peña Aguilera.
The paper includes data from 75 sample sites, where Pablo de La Peña Aguilera inventoried plants, took soil samples to examine fungi, and collected arthropods (flying and ground-dwelling arhthropods) using Malaise traps and pitfall traps. He used DNA techniques to identify the arthropods and fungi. He also set up humidity and temperature loggers to measure microclimatic conditions that these organisms are more likely to experience.
"One of the biggest challenges we faced was reindeer raiding our sampling sites and drinking the contents of our traps," says Pablo de la Peña Aguilera.
Contact
Pablo de la Peña Aguilera, pablo.de.la.pena.aguilera@slu.se
Thesis
Community assembly across Subarctic landscapes : exploring patterns of diversity