Plant-soil feedbacks in a grassland ecosystem: Effects of plant functional groups and soil fertility
Luu, Kobe N.
AdvisorHouseman, Gregory R.
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Plant-soil feedbacks (PSFs) occur when plants alter soil conditions, subsequently affecting plant success. This process may play a key role in maintaining biodiversity and ecosystem functioning. Many PSF experiments have reported species-specific responses and there is growing interest in determining whether the response of plant functional groups (PFGs), in which species are grouped by similar plant functional traits, can be used to predict the likelihood of PSFs. One reason for the variable responses reported is that PSFs can be dependent on soil fertility, which can serve as a general indicator of succession and ecosystem development. To test how plant functional groups and soil fertility relate to PSF, we grew 19 grassland species from 3 functional groups (graminoids, forbs, legumes) in 3 levels of soil fertility for 4 years. We used this field conditioned soil to conduct greenhouse assays of plant growth rates for species representing each PFG. We found that on average, forbs exhibited positive PSF in the most-developed soil, while the graminoids and legumes exhibited negative PSFs regardless of soil fertility. Despite these trends, we found strong species-specific and soil fertility effects on PSF. These results most likely emerged due to the species-specific soil biota that accumulates over time during the conditioning phase, which includes both harmful and beneficial biota, with the net PSF effect determined by the dominant influence. Generally, we found that PSFs became more positive/less negative as soil fertility increased, most likely due to the increased nutrient concentrations and beneficial soil biota outweighing the effects of the harmful soil biota and lack of soil nutrients. These findings help to understand that different species have unique roles in plant community dynamics, and that their roles within the community are going to change over time, as is total ecosystem productivity.
Thesis (M.S.)-- Wichita State University, College of Liberal Arts and Sciences, Dept. of Biological Sciences