In a recent paper published in Ecosystems, Henni Ylänne and Sari Stark compare how key processes behind ecosystem carbon cycling depend on the time passed since reindeer have induced a vegetation shift. The study makes use of an area that had become dominated by graminoids due to a high reindeer grazing intensity within the past 14 years, and compares the processes on this to the processes in an area of decades old grazing-induced graminoid dominance and in an area of shrub dominance with little grazer influence.
The paper shows that ecosystem carbon sink was similar under both old and recent grassification. Yet the individual carbon fluxes varied depending on the time passed since the vegetation shift: ecosystem respiration and mid-season photosynthesis were higher under old than recent grassification. In contrast, the extracellular enzyme activities for carbon and phosphorus acquisition were similar regardless of the time elapsed since grazer-induced vegetation change. These results show that both autotrophic and heterotrophic ecosystem processes develop over time in response to changes in the intensity of herbivory with varying time-lags.
Reference: Ylänne, H., Stark, S. (2019) Distinguishing rapid and slow C cycling feedbacks to grazing in subarctic tundra. Ecosystems 22: 1145– 1159.
https://doi.org/10.1007/s10021-018-0329-y
Picture: Reindeer grazing in Reisa (photo: Henni Ylänne, Lund University, 2013)