Shrub Influence on Tundra Herbaceous Communities at Niwot Ridge LTER

Climate change is helping shrubs and other woody plants to rapidly encroach on herbaceous plant communities in tundra all over the world. Shrubs are known to trap snow, potentially increasing winter soil temperatures and decomposition rates, and affecting soil nutrient content. Little research exists yet on how these new shrubs are affecting the herbaceous plants around them.

Collecting trait data (such as plant height and specific leaf area) across all species in a community allows us to quantify and track vegetation change. On Niwot Ridge, Salix glauca and Salix planifolia shrubs are abundant in three terrain types: Dry Meadow, Moist Meadow, and Wet Meadow. Ten shrubs were randomly selected from each terrain type and plots were created of plant communities bordering these shrubs as well as a shrub-free plot nearby. Representative leaf samples were collected and trait data from them was compared between shrub and non-shrub plots.

Our results indicated that shrubs had an influence on community-wide plant traits. Plants behind shrubs had a higher mean height and higher specific leaf area, meaning that their leaves tended to be larger and thinner, indicating less conservative growth strategies. Separating these results by species and terrain type revealed that this influence varied greatly depending on these factors.

By measuring trait differences in herbaceous plants on Niwot ridge, we can better understand how ongoing shrub encroachment is changing the tundra. Data from this research will help us to build more detailed models of tundra ecosystems, and better predict the future of these areas.