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Non-native grass and forb control in a California grassland S.J.M. Dickens & E.B. Allen University of California-Riverside Outline • Overview: – non-natives in grasslands – prescribed burns • • • • • Santa Rosa Plateau Ecological Reserve Objectives and hypotheses Methods Results Conclusion, implications and future work Non-natives in California Grasslands • Non-native grasses arrived about 250 years ago • Pre-invasion plant community unknown • Non-native grasses compete with and displace native plant species. – Water, Nutrients, Space, Light • In the presence of non-native annual grasses, non-native forbs act as place holders for native forbs, without grasses they can become competitors (Gillespie & Allen 2004). Prescribed Fire • Can reduce seed input by 96% (Moyes et al 2005) • Prescribed fire may reduce non-native annual grass cover but may not increase native forb cover (Dickens & Allen 2009). 1cm • Non-native forbs, specifically Erodium spp., often replace non-native grass after fire (Dickens & Allen 2009). Santa Rosa Plateau Ecological Reserve • 8000 acres of land and 5 distinct habitats • 48cm precipitation annually, most of which falls from November to April • Historically grazed by cattle • Home to many rare and endangered plants and animals Major Non-native Grasses of Santa Rosa Plateau Amsinckia menziesii Calandrinia ciliata Viola pedunculata Nassella Avena fatua Bromus Hordeum Vulpia Bromus Bromus Eschscholzia californica Sidalcea malvaeflora pulchra & A. barbata rubens spp myuros hordeaceus diandrus Prescribed Fire History • 1988 Prescribed burning program began – Spring burns to capture seed on standing biomass – Burns reduce non-native grass seed input and thatch cover (Hervey 1949, Moyes et al 2005, White et al 2006) Objectives: Assess effectiveness of fire and weeding of non-natives in releasing native species from competition. Hypothesis: • fire will reduce exotic grass cover and increase native cover. • weeding of non-natives will further increase native cover and richness. Methods • Wildfire of 2006 Picture: Don Baccus • 27 1x1m plots were established in burned and unburned areas (unburned, burned, burn + weeded) • Plots were weeded up to 3 weeks before data collection. • Plant cover and richness recorded at peak of season Unburned Burned Burned + Weed Total Monthly Precipitation Total monthly precipitation (cm) 50 Annual Totals 2005 = 128 2006 = 41 2007 = 12 2008 = 50 2009 = 41 40 30 20 10 0 2005 2006 2007 2008 2009 Data supplied by Riverside County Flood Control and Water Conservation District Species Richness Non-native Native 10 10 8 Unburned Burned Burned + Weed A A 8 A B 6 B AA B 4 4 B A A 2 0 A A B 2006 2 AB B A B B 2007 2008 6 2009 2006 Total species richness per 0.5m2. ANOVA’s from individual years. 0 2007 2008 2009 Non-native Species Percent Cover Grass Forb 60 50 100 Unburned Burned Burned + Weed A A 80 A A 40 60 A B 30 40 20 A 10 2007 B C C B B 2006 20 A C 0 B A B B 2008 2009 0 2006 2007 Non-native species percent cover per 0.5m2. ANOVA’s from individual years. 2008 2009 Native Species Percent Cover Grass Forb 25 20 80 Unburned Burned Burned + Weed A A A 60 AB 15 40 B 10 B B B B 5 AB 0 2006 2007 2008 2009 2006 20 0 2007 Native species percent cover per 0.5m2. ANOVA’s from individual years. 2008 2009 Conclusions • Fire decreased non-native grass cover for the length of the study. • Native species richness was initially increased with both fire treatments. • The increase in native diversity is mainly in fire following species. • Non-native forb cover increased with burning • Native forb cover increased in burn + weeding treatments. • Erodium spp are competing with Nassella pulchra slowing recovery. Management Implications • Weeding is not logistically realistic for large areas. Further research using herbicide following fire is necessary. • Management practices may take multiple years of application. • Precipitation in the season of and following management will be important but unpredictable. Future work • Following the plant community recovery one more year. • Testing herbicide methods for non-native forb control after fire. – Roundup and Fusilade following Erodium spp germination. – seeding treatments to test seed-bank limitations. Acknowledgements • Dr. Edith Allen Funding Sources: • Carole Bell – Skinner-Shipley/Riverside • The Dr. E.B. Allen & Dr L. County Endowment Santiago Laboratories • Santa Rosa Plateau Ecological – University of California Riverside Department of Botany Reserve and Plant Sciences • California Department of Fish and Game • The Nature Conservancy