Diverse plant species in prairie grasslands support a long-term, stable ecosystem because they exhibit complementary functionality.

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An ecosystem is a biological community of interacting organisms and their physical environment. A healthy ecosystem includes multiple species that serve similar functions or roles – for example, more than one species that fertilizes the soil and more than one that controls the population of a certain predator. This redundancy is crucial to supporting the long-term stability of the ecosystem because natural disturbances – such as fires, disease, or changing climate – can sometimes eliminate entire species unable to survive the change. With redundancy in environmental function, if one species dies off, another species that serves a similar role is more likely able to react and thrive after the disturbance. It can then take the place of the previously dominant species, thereby keeping the ecosystem resilient.

For example, consider a situation in which a prairie grassland ecosystem’s main food-producing plant is completely destroyed by a fire. A plant species that was previously less abundant may now be better suited to live in the new soil conditions, and therefore become the new dominant food-producing plant species serving the grassland. As long as the post-fire composition of plant species fills the same functional role as the pre-fire plant community, then the prairie will be able to survive the fire intact.

This summary was contributed by Ashley Meyers.

The diagram below provides additional detail:

1a. A low diversity system has high productivity in the short term, but is severely affected by a fluctuation in conditions (represented by the red shape in 1b). This is because those changes could cause the entire system to lose all functions (1c), leading to low or no productivity (1d and 1e). 

2a. A high diversity system containing members that serve multiple, overlapping functional roles (shown along the bottom) may not be as productive in the short term, but show long-term stability and productivity. If there is any fluctuation in conditions (represented by the red shape in 2b), the conditions only impact a small portion of the system (2c). As a result, those changes only briefly affect productivity (2d) as the remaining members and replacement members continue to provide all ecosystem functions (2e). 

Artist: Emily Harrington. Copyright: All rights reserved. See image in gallery for details.

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Journal article
Biodiversity: Population Versus Ecosystem StabilityEcologyMay 9, 2006
David Tilman

Journal article
Compensation and the Stability of Restored Grassland CommunitiesEcological ApplicationsOctober 2, 2007
Eric W. Seabloom

“More diverse communities have been shown to have higher and more temporally stable ecosystem functioning than less diverse ones, suggesting they should also have a consistently higher level of functioning over time. Diverse communities could maintain consistently high function because the species driving function change over time (functional turnover) or because they are more likely to contain key species with temporally stable functioning. Across 7 y in a large biodiversity experiment, we show that more diverse plant communities had consistently higher productivity, that is, a higher level of functioning over time. We identify the mechanism for this as turnover in the species driving biomass production; this was substantial, and species that were rare in some years became dominant and drove function in other years. Such high turnover allowed functionally more diverse communities to maintain high biomass over time and was associated with higher levels of complementarity effects in these communities. In contrast, turnover in communities composed of functionally similar species did not promote high biomass production over time. Thus, turnover in species promotes consistently high ecosystem function when it sustains functionally complementary interactions between species. Our results strongly reinforce the argument for conservation of high biodiversity.” (Allan et al. 2011:17034)

Journal article
More diverse plant communities have higher functioning over time due to turnover in complementary dominant speciesProceedings of the National Academy of SciencesSeptember 27, 2011
E. Allan, W. Weisser, A. Weigelt, C. Roscher, M. Fischer, H. Hillebrand

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