Biology ETDs

Publication Date

Summer 7-29-2017

Abstract

Grassland communities change in response to disturbance and chronic resource alterations. Temporal community dynamics were examined within mesic tallgrass prairie at Konza Prairie in northeastern Kansas, and semiarid desert grassland and shrubland in central New Mexico. In both grasslands, producer and consumer communities changed over time in response to fire frequency and shrub encroachment. Directional change was driven by changes in abundances of species already in the community, rather than turnover in species composition. Despite directional change, species richness was highly stable, making species abundance rather than richness a better indicator of future community change. Species reordering also occurred during a long-term precipitation manipulation experiment at Konza Prairie. Fewer larger rain events resulted in limited changes in plant community composition and structure, but instead caused reordering among forb species. Thus, mesic tallgrass prairie was resistant to long-term changes in precipitation variability and resilient to short-term extremes through species reordering. Further, community dynamics can influence ecological processes. In a shrub encroachment experiment in semiarid grassland, soil respiration was altered in plant-soil monoliths moved between creosotebush shrubland and desert grassland. Grassland respiration was less responsive than shrubland, and microbial activity in both grassland and shrubland soils responded like soils from which they originated. Thus, soil processes lag behind changes in vegetation composition under shrub encroachment. Alterations of species abundances and community composition are likely to continue under global environmental change. Understanding how grasslands respond to long-term changes in resource variability is important because changes in species composition can alter ecological processes.

Language

English

Keywords

community composition, temporal community dynamics, semiarid grasslands, tallgrass prairie, long-term research

Document Type

Dissertation

Degree Name

Biology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

Dr. Scott Collins

Second Committee Member

Dr. Marcy Litvak

Third Committee Member

Dr. William Pockman

Fourth Committee Member

Dr. Bruce Hungate

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