In the Arctic, soil fungal communities may be intrinsically shaped by heavy grazing, which may locally induce an ecosystem change that couples with increased soil temperature and nutrients, and where climate change induced shrub encroachment is less likely to occur than in lightly grazed conditions. Due to these reasons, differences in grazing intensity may control the effects of climate change on fungal communities and thereby carbon and nutrient cycling.
We tested how contrasting long-term grazing intensities affect the responses of soil fungal communities to short-term warming and increased nutrient availability. We used a study design along a reindeer migration route, where 50-years history of an annually occurring pulse of heavy grazing during reindeer migration has shifted the subarctic tundra ecosystem towards increased graminoid dominance, higher soil temperature and nutrient availability. We found that heavy grazing had led to distinct shifts in soil fungal communities when compared to light grazing. Furthermore, the long-term grazing difference largely overrode the effects of short-term warming and fertilization, and the changes in the soil fungal communities caused by our experimental treatments were not unidirectional under different grazing intensities.
Our results demonstrate the determinant role of long-term difference in grazing intensity in shaping fungal communities and their responses to abiotic changes. Further, it reveals that if grazing shifts the fungal communities in Arctic ecosystems to a different state, this may dictate ecosystem responses to further abiotic changes. These results incline that the intensity of grazing cannot be left out when predicting future changes in fungi-driven processes in the tundra.
You can read the full article here: https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.17623
Reference: Ahonen, S.H., Ylänne, H., Väisänen, M., Ruotsalainen, A.L., Männistö, M.K., Markkola, A. and Stark, S. (2021) Reindeer grazing history determines the responses of subarctic soil fungal communities to warming and fertilization. New Phytologist.
Text by Saija Ahonen, PhD student University of Oulu
Picture: Reindeer in Ráisduoddar (photo credit Sari Stark)