| Studies of arctic terrestrial ecosystem responses to change have generally focused on abiotic drivers, such as temperature and precipitation. However, recent work has shown that herbivory may be of overwhelming importance to the structure and function of arctic ecosystems. We quantified the singular and interactive effects of herbivore exclusion and simulated warming on ecosystem CO2 exchange over two growing seasons in western Greenland. Removal of caribou and muskoxen led to dramatic increases in deciduous shrub abundance, leaf area and net ecosystem CO2 uptake. When plots were warmed in the presence of herbivores, limited changes in plant community composition, leaf area and ecosystem CO2 exchange occurred. In contrast, warming in the absence of herbivores resulted in further increases in deciduous shrub cover, leaf area and net CO2 uptake. Our results indicate that large herbivores can be of critical importance to arctic ecosystems and will mediate C cycle responses to climate change. |
