Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2004
Publication Date: August 1, 2004
Citation: Hickman, K.R., Derner, J.D., Polley, H.W. 2004. Response of species diversity within plant functional groups to altered precipitation regimes in tallgrass prairie. Ecological Society of America Abstracts. V. 89. p. 219. Technical Abstract: Results from Global Circulation Models (GCMs) differ, but models generally predict that precipitation regimes will be altered and that variability in precipitation will increase. Precipitation change in water-driven rangelands may impact species diversity within plant functional groups (i.e., response diversity). By experimentally removing variability in precipitation, we may gain insight into the sensitivity of grassland diversity to intra- and inter-annual variability in water availability. We used two, 9X10 m rainout shelters to remove inherent intra- and inter-annual variability of precipitation by manipulating precipitation amounts and distribution from 1999 to 2001 on a relict tallgrass prairie in central Texas. Within each shelter, three, 3X10 m areas, each with eight 1X1 m plots, were randomly assigned one of three precipitation regimes: 1) normal distribution (spring-dominated, April-May), 2) even distribution, or 3) ambient precipitation amounts and distribution. The 62-year mean annual precipitation of 87 cm was applied to the normal and even distribution areas in all years; 50, 106 and 114 cm were applied to the ambient areas in 1999, 2000 and 2001, respectively. Plant species cover was visually estimated using a modified Daubenmire technique in mid-May and mid-June each year. Precipitation regime significantly influenced Shannon species diversity within all functional groups (perennial, annual and total forbs and C3 perennial grass) except the C4 perennial grasses. Removal of intra-and inter-annual variability in precipitation through the even and normal precipitation distributions increased species diversity within the C3 perennial grass and annual forb groups, but not within the perennial forb group. How this reduction in species diversity within functional groups may affect resilience of this tallgrass prairie to disturbances remains unclear, however, as changes in the variability of precipitation did not elicit a directional shift in species composition nor alter species diversity within the dominant group of C4 perennial grasses.