Figure - available from: Arctic Science
This content is subject to copyright. Terms and conditions apply.
Mean (±1 SE) relative cover for (a) Hierochloe alpina and (b) Betula nana in dry heath (DH) and (c) Eriophorum vaginatum and (d) B. nana in moist acidic tundra (MAT). Treatments began in 1996. For treatment abbreviations, see Fig. 1
Source publication
The interaction between bottom-up and top-down forces in regulating plant communities is a long-standing topic of interest in ecology. Factorial field experiments examining these factors have been relatively few, but recent meta-analyses provide predictions that can be tested in a range of ecosystems. We tested the prediction that added nutrients w...
Similar publications
Herbivorous mammals are important for natural ecosystems even today, but how much stronger would there effects be without human-linked extinctions and extirpations? The ranges of many mammal species have contracted and numerous species have gone extinct due to human pressures, so herbivore impacts in even seemingly natural ecosystems likely deviate...
Citations
... Elevated nutrient conditions can also impact plant community composition. Under fertilization experiments, dwarf birch (Betula nana) becomes more dominant in MAT tundra (Gough et al., 2012;Gough & Johnson, 2018;Klupar et al., 2021). Our study suggests that selective foraging by tundra voles may play a secondary role to post-fire nutrient release, further decreasing graminoid abundance. ...
Fire is an important ecological disturbance that can reset ecosystems and initiate changes in plant community composition, ecosystem biogeochemistry, and primary productivity. As herbivores rely on primary producers for food, changes in vegetation may alter plant–herbivore interactions with important—but often unexplored—feedbacks to ecosystems. Here we examined the impact of post‐fire changes in plant community composition and structure on habitat suitability and rodent herbivore activity in response to a large, severe, and unprecedented fire in northern Alaskan tundra. In moist acidic tundra where the fire occurred, tundra voles (Microtus oeconomus) are the dominant herbivore and rely on the tussock forming sedge Eriophorum vaginatum for both food and nesting material. Tundra voles were 10 times more abundant at the burned site compared with nearby unburned tundra 7‐12 years after the fire. Fire increased the habitat suitability for voles by increasing plant productivity and biomass, food quality, and cover through both taller vegetation and increased microtopography. As a result of elevated vole abundance, Eriophorum mortality caused by vole herbivory was two orders of magnitude higher than natural mortality and approached the magnitude of the mortality rate resulting directly from the fire. These findings suggest that post‐fire increases in herbivore pressure on Eriophorum could, in turn, disrupt graminoid recovery and enhance shrub encroachment. Tundra state transitions from graminoid to shrub dominated are also evident following other disturbances and fertilization experiments, suggesting that as Arctic temperatures rise, greater available nutrients and increased frequencies of large‐scale disturbances may also alter plant–animal interactions with cascading impacts on plant communities and ecosystem function.
... Our sampling is part of an ongoing effort examining how herbivores influence ecosystem dynamics in these long-term exclosures (Gough, Ramsey, and Johnson 2007;Gough et al. 2008Gough et al. , 2012. Our data show little change from previous samplings, which also show relatively few changes over time (Gough and Johnson 2018), and provide valuable additional time points for this experiment and the examination of ecosystem functions in a changing arctic environment. Interestingly, in a study design similar to ours in another heath community but also including fertilization (Stark and Grellmann 2002), slower nutrient cycling under grazing after seven years of exclusion was reported. ...
Herbivores can play an important role in determining arctic ecosystem function with effects determined in part by herbivore identity. We examined the impact of long-term (twenty-two years) small and large mammal herbivore exclusion in two arctic plant communities in northern Alaska: dry heath (DH) and moist acidic tundra (MAT). Our aims were to examine how herbivore exclusion influences (1) plant communities and (2) soil nutrient pools and microbial processes. Though herbivore absence increased moss and decreased evergreen shrub cover in MAT, there were few other significant effects on vegetation in either community. We also observed no influence of exclusion on most soil properties. However, in DH, phosphatase activity was greater in areas where small mammals alone were present, suggesting that they are altering phosphorus (P) availability, perhaps through herbivores' influence on the plant community and subsequently on competition for P with the microbial community. We conclude that herbivore impacts in the Arctic are dependent on both the plant community and herbivore identity (size). We show the importance of understanding the roles of herbivores in the Arctic and contribute to a growing number of herbivore studies in a biome likely to experience future changes in herbivore communities and ecosystem function.
