Inferring community assembly mechanisms

Marko Spasojevic and Katharine Suding have a paper in Early View in the Journal titled “Inferring community assembly mechanisms from functional diversity patterns: the importance of multiple assembly processes“.  Read it here.  We posted an interview with Marko here.

Marko has provided a short synopsis of the paper and a photo of the study site. Enjoy.

Photo Credit: Marko J. Spasojevic

Alpine tundra is known for stunning views and beautiful displays of wildflowers. Even though it is a harsh environment, alpine tundra is a very diverse habitat. Much of the diversity we see in alpine tundra is a result of how snow gets blown across the landscape by wind. However, at smaller scales there is not a good understanding of how different factors may lead to the patterns of diversity we see. The importance of factors such as competition, facilitation, and tolerance to harsh environments likely change as we move from the wind-scoured summits to the warmer more protected subalpine. In lieu of experiments to test these mechanisms, patterns of functional diversity can indicate which mechanisms are operating. Functional diversity describes the diversity of traits among species; how similar or different species are to each other in traits.

To understand how different factors influence plant communities, we analyzed the functional diversity of 5 traits: specific leaf area (SLA), leaf area, stomatal conductance, plant height and chlorophyll content. We found that functional diversity was high in both the high alpine and near the subalpine, but for different traits. In the more benign subalpine high resource availability was associated with greater functional diversity in height and leaf area. In the more stressful high alpine lower resource availability was associated with greater functional diversity in SLA, stomatal conductance, and chlorophyll content. Additionally, environmental stress from wind and cold likely reduced functional diversity for height and leaf area in the high alpine. These patterns suggest that at least three different factors play an important role in structuring alpine plant communities. Tolerance wind and cold exposure may reduce functional diversity in height and leaf area in the high alpine. Additionally, increasing functional diversity in the other three traits suggests competition for nitrogen and water, two essential plant nutrients that are in limited supply in this habitat. At the resource rich end of the gradient, increased functional diversity in height and leaf area suggests increased competition for light. Our results suggest that multiple factors operate simultaneously to create the diversity of plants along a gradient from the harsh alpine to the more benign subalpine.

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