Document: PHI-3-34-18

Initial plant productivity and species composition responses to lengthened inter-rainfall intervals in a grassland: Possible consequences of altered rainfall patterns.

FAY, P.A.*, J.M.BLAIR, J.D.CARLISLE, A.K.KNAPP and M.S.LETT

Kansas State University, Manhattan, KS, U.S.A. ¹

Abstract:
Climate models predict altered growing season rainfall patterns for the Central Plains grasslands. One scenario is reduced growing season rainfall quantity, repackaged into fewer, larger individual rainfall events. A ten-year rainfall manipulation experiment is being conducted at Konza Prairie in northeastern Kansas, to assess the implications of this scenario for tallgrass prairie productivity and species composition. Rainfall quantities of 100% or 70% of ambient are being applied either at natural inter-rainfall intervals or at intervals lengthened by 50% in a 2 x 2 factorial design. Rainfall manipulations are conducted using 9 x 14-m open-sided, fixed-location rainout shelters. During the first two growing seasons of experimental rainfall manipulations, lengthened inter-rainfall intervals caused reductions in aboveground net primary productivity, plant species richness, and cover of C₄ species (primarily dominant tall grasses) that were generally equal or greater than reductions caused by reduced rainfall quantity. Soil CO₂ fluxes also decreased in response to altered rainfall timing, which may have future implications for soil organic matter and plant-available nitrogen. These early results from a long-term experiment suggest that altered timing of rainfall events may be an under-appreciated facet of the predicted rainfall scenarios for Central Plains grassland ecosystems.

Keywords: climate change, rainfall, grassland, productivity, species composition

This abstract is being presented at: 8:45 AM in session:
Oral Session #43: Plant Community Responses to Climate Change.