Plant green-up and herbivory in Greenland

A study links herbivory to phenology in the Arctic. Phenology is the study of the timing of events in the natural world. In recent decades, researchers have investigated how climate change is shifting many natural events. Eric Post and colleagues wanted to understand how a different variable—the presence or absence of herbivores—affects the timing of spring plant growth, or green-up, in Greenland. In an experiment lasting nine years, the authors excluded musk oxen and caribou from some areas, then compared the timing of the spring green-up of 9 tundra plant species in the areas with and without herbivores. Of the plants that showed altered green-up between the conditions, about two-thirds showed earlier green-up in plots with grazing than in plots without, including Draba nivalis, yellow arctic draba, and Salix glauca, gray willow. A few plants, including Betula nana, the dwarf birch, and Campanula Gieseckiana, harebell, showed later green-up under herbivory than under herbivore exclusion.  The team also measured plant abundance. Of the plants that showed a response to grazing, 75% were more abundant in the plots with herbivores. In general, early green-up under herbivory led to high abundance later in the growing season. The only plant that did not see increased abundance in plots with herbivores as compared to plots without herbivores was dwarf birch, which was also the most common species on the study plots. According to the authors, herbivory that reduced birch cover likely also reduced shade on other species, hastening and boosting their growth.

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