This graph is from Tilman and Downing (1994) from the journal Nature. In this experiment, the researchers were looking at the relationship between species diversity and ecosystem stability (i.e. does diversity beget stability?). Specifically, they asked the question how does species richness (the number of species in a given area) affect an ecosystem’s response after a major disturbance. For this study, there was a large scale drought during the years of 1987-1988. Experimentally, they created plots with different numbers of grass species to test their hypotheses.
The x-axis on this graphs is species richness before drought. The y-axis on the left is their metric of drought resistance, the rate of plant community biomass change from 1986 (pre-drought) to 1988 (peak of drought). Values closer to zero imply greater drought resistance as the rate of biomass lose was smaller. The right side y-axis shows the proportionate decrease in biomass due to the disturbance. Notice that it is in a log scale — don’t worry too much about the detail here — the patterns is more important. Plots with less species richness lost not only more biomass (right side) but also lost it at a faster rate (left side).
1. How does this study relate to climate change?
2. What is the difference between resistance (this study) and the idea of resilience?
3. How could you design an experiment that tested the idea of resilience?
4. What are other types of diversity?
5. What are other types of disturbance?
6. This experiment occurred at Cedar Creek one of the many Long Term Ecological Research (LTER) sites around the United States. To learn more about Cedar Creek and the diversity plots please visit: http://www.esa.org/tiee/vol/v2/issues/data_sets/cedar_creek/overview.html.