May 2005 CA Grassland Newsletter
1. CalIPC Symposium 2005
2. Job Opportunity – Bouverie Preserve
Symposium 2005 – Chico, CA October 6-8
CALL FOR PAPERS: Cal-IPC invites members of the wildland weed community to submit abstracts for contributed paper sessions or the poster session. We encourage talks and posters focusing on weed biology, treatment techniques, control and restoration projects, community-based efforts, and funding. Oral presentations are 12 minutes with 3 minutes for questions. Both oral and poster presenters receive a discount on registration. Space for presenters is limited. Submission guidelines at www.cal-ipc.org. Abstracts sent to contributed sessions organizer Dan Gluesenkamp at firstname.lastname@example.org. Deadline is Friday, June 17.
2. Please find attached the announcement for an Audubon Canyon Ranch position:
Bouverie Preserve Biologist. Deadline: May 16. We hope to have this person on staff by mid-July. It's a fantastic opportunity for someone special.
The person will work at ACR's Sonoma Valley preserve. There are nicer
places on the planet, but not many. The work includes a great diversity of
duties, including some involvement in research and restoration work.
Candidates should respond to www.egret.org <http://www.egret.org/> or
Haubensak, K., C.M. D’Antonio, and J.Alexander. Effects of nitrogen-fixing shrubs in Washington and coastal California. Weed Technology 18(Suppl. S):1475-1479.
ABSTRACT: Open grasslands in California and Washington are being invaded by two closely related European shrubs, French broom and Scotch broom, that are considered among the most invasive and damaging of wildland species in those habitats. In this study, we present evidence of their effects on soil nitrogen (N) and the implications for restoration. Using natural abundance 15N signatures of leaves, we show that N fixation by brooms varies across sites and may depend on a suite of site-specific factors. Nonetheless, in sites in both California and Washington, we observe up to a twofold increase in soil N availability, as assayed in the laboratory. Across a range of sites, we determined that burning decreases total soil N by nearly 40%. We found burning to have the simultaneous effect of decreasing the broom seedbank by 68% after one burn. In a separate experiment, we removed broom and added sawdust to the soil to test whether a N-immobilization effect would help slower growing native perennial grasses in competition with European annual grasses. We found that although sawdust effectively decreased N availability after a 2-yr application period, we could not effectively target which group of species would benefit most.
Henry, H. A. L., E.E. Cleland, C.B. Field, and P.M. Vitousek. 2005. Interactive effects of elevated CO2, N deposition and climate change on plant litter quality in a California annual grassland. Oecologia. 142: 465-473.
ABSTRACT: Although global changes can alter ecosystem nutrient dynamics indirectly as a result of their effects on plant litter quality, the interactive effects of global changes on plant litter remain largely unexplored in natural communities. We investigated the effects of elevated CO2, N deposition, warming and increased precipitation on the composition of organic compounds in plant litter in a fully-factorial experiment conducted in a California annual grassland. While lignin increased within functional groups under elevated CO2, this effect was attenuated by warming in grasses and by water additions in forbs. CO2-induced increases in lignin within functional groups also were counteracted by an increase in the relative biomass of forbs, which contained less lignin than grasses. Consequently, there was no net change in the overall lignin content of senesced tissue at the plot level under elevated CO2. Nitrate additions increased N in both grass and forb litter, although this effect was attenuated by water additions. Relative to changes in N within functional groups, changes in functional group dominance had a minor effect on overall litter N at the plot level. Nitrate additions had the strongest effect on decomposition, increasing lignin losses from Avena litter and interacting with water additions to increase decomposition of litter of other grasses. Increases in lignin that resulted from elevated CO2 had no effect on decomposition but elevated CO2 increased N losses from Avena litter. Overall, the interactions among elements of global change were as important as single-factor effects in influencing plant litter chemistry. However, with the exception of variation in N, litter quality had little influence on decomposition over the short term.
Eisen, R. J., L. Eisen, and R.S. Lane. 2005. Remote sensing (Normalized difference vegetation index) classification of risk versus minimal risk habitats for human exposure to Ixodes pacificus (Acari: Ixodidae) nymphs in Mendocino County, California. Journal of Medical Entomology 42: 75-81.
ABSTRACT: In California, Ixodes pacificus Cooley & Kohls nymphs have been implicated as the primary bridging vectors to humans of the spirochetal bacterium causing Lyme disease (Borrelia burgdorferi). Because the nymphs typically do not ascend emergent vegetation, risk of human exposure is minimal in grasslands, chaparral, and woodland-grass. Instead, woodlands with a ground cover dominated by leaf litter (hereinafter referred to as woodland-leaf) have emerged as a primary risk habitat for exposure to B. burgdorferi-infected nymphs. As a means of differentiating woodand-leaf habitats from others with minimal risk (e.g., chaparral, grassland, and woodland-grass), we constructed a maximum likelihood model of these habitat types within a 7,711-ha area in southeastern Mendocino County based on the normalized difference vegetation index derived from Landsat 5 Thematic A-rapper imagery (based on a 30 by 30-m pixel size) over four seasons. The overall accuracy of the model to discriminate woodland-leaf, woodland-grass, open grassland, and chaparral was 83.85%, (Kappa coefficient of 0.78). Validation of the accuracy of the model to classify woodland-leaf yielded high values both for producer accuracy (93.33% of validated woodland-leaf pixels correctly classified by the model) and user accuracy (96.55% of model-classified validation pixels correctly categorized as woodland-leaf). Woodland-leaf habitats were found to be highly aggregated within the examined area. In conclusion, our model successfully used remotely sensed data as a predictor of habitats where humans are at risk for Lyme disease in the far-western United States.