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Constraints in the compensatory response of a tallgrass prairie plant community to the loss of a dominant species

Date

2020

Authors

Chaves Rodríguez, Francis Andrea, author
Smith, Melinda, advisor
Knapp, Alan, committee member
Ocheltree, Troy, committee member
Sala, Osvaldo, committee member
Webb, Colleen, committee member

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Abstract

Biodiversity loss is one of the major consequences of global change driven by human activities. The loss of a dominant species is expected to have profound consequences on ecosystem processes (e.g. aboveground productivity) given their highest relative abundance and proportionally large contribution to community biomass production. However, through competitive release, the newly available resources following its lost, are expected to be utilized by the remaining species in the community to increase in abundance and compensate for the function lost. Complete functional compensation does not occur in every ecological community following the loss of dominant species or entire functional groups, and 1) limited resource availability, 2) absence of functionally redundant species, and 3) lack of functional traits that promote compensation have been proposed as possible constraints on compensation. In this dissertation, I evaluate the effect of removing these constraints on the biomass compensation response of a tallgrass prairie plant community following the loss of the dominant species, the C4 tallgrass, Andropogon gerardii Vitman. I experimentally removed the dominant species from a native intact tallgrass prairie plant community at Konza Prairie Biological Station, Kansas, where I selected two contrasting sites, one with functionally redundant species Panicum virgatum L. and Sorghastrum nutans (L.) Nash in low abundances, and a second site where those functionally redundant were codominants with A. gerardii. The first site was irrigated to alleviate water limitation during four growing seasons and fertilized with nitrogen during the final season of the experiment. The second site did not exhibit water limitation and was fertilized during the second growing season of the two-year experiment. My results show that in the short-term removing resource limitation promoted aboveground primary productivity but not enough to produce full biomass compensation. The presence of functionally redundant species, also C4 tall grasses with similar functional effect traits as A. gerardii, did increase aboveground biomass production, but did not promote full biomass compensation, not even when they were present in high abundance. I hypothesize that additional to the constraints proposed, compensation is limited by response traits in the remaining species that limit their demographic response to the increased available space, light, water and soil resources following the loss of the dominant species. Overall, my results show the compensation approach is important to evaluate not only the effect of species loss on ecosystem processes, but also the response of the remaining species and their ability to compensate for the function lost. They also suggest the existence of additional mechanisms in play that need to be identified and tested in order to improve the understanding of how communities recover in the face of biodiversity loss.

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Subject

compensation
Andropogon gerardii
redundancy
tallgrass prairie
dominant removal
resources

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