Consequences of Altered Hydrologic Regimes on a California North Coast Meadow CommunityEPA Grant Number: U915787
Title: Consequences of Altered Hydrologic Regimes on a California North Coast Meadow Community
Investigators: Suttle, Kenwyn B.
Institution: University of California - Berkeley
EPA Project Officer: Carleton, James N
Project Period: August 1, 2000 through August 1, 2003
Project Amount: $87,269
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objective of this research project is to experimentally investigate the potential ecological effects of increased precipitation, which is predicted to accompany climate change, on the plants and herbivores of a California north coast grassland community, focusing on the importance of the timing/seasonality of the additional rainfall.
A direct manipulation of precipitation with sprinklers designed to mimic rainfall in their water distribution will be performed. Thirty-six circular plots measuring 75 m2 will receive one of three watering treatments (increased winter precipitation, increased spring precipitation, and watering control) for the next 3 years. Within each of these plots, 12 permanent 0.25 m2 subplots have been established to record changes in percent cover of four plant functional groups: perennial grass, annual grass, winter forb, and summer forb. Changes also are being tracked in plant biomass, nitrogen content, seed production, and seed germination under the three watering regimes. Grasshopper population responses to the different watering treatments are being studied, as these may affect the fate of the plant assemblage.
Competitive interactions within the plant assemblage may be modified by changes in precipitation patterns, and may further respond to precipitation-mediated changes in herbivore density and behavior. Increases in winter precipitation are expected to benefit primarily annual grasses and winter forbs, by alleviating periodic water limitation during the rainy season. An extension of the rainy season into the spring and summer, however, will likely produce dramatically different results. The Mediterranean annual grasses that have invaded California grasslands so extensively have been successful due in large part to their pre-adaptation to northern California?s climate of wet winters followed by long droughts. Because these annuals are hardwired in their reproductive phenology to complete their life cycle and set seed before the end of the rainy season, there is little potential for response to an extended rainy season. Native perennial plants, however, show increased productivity in response to late rains. This differential response by exotic annuals and native perennials should lead to changes in plant composition with late season rain, as native perennials increase vegetative growth and biomass accumulation and, together with summer forbs, produce larger numbers of seeds, which in turn should improve colonization success into disturbed areas.