PARENT SESSION
Poster Session 30: Soil Ecology.

Wednesday, August 4 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

Heterotrophic activity in cryptobiotic soil crusts of varying successional stages.

Dane, Laura ^*,1, Lipson, David¹, ¹ San Diego State University, San Diego, CA, USA

ABSTRACT- Little is known about heterotrophic microbial activities associated with cryptobiotic soil crust communities. Characteristics of the dominant primary producers in soil crusts may directly affect the species and functional diversity of heterotrophic microbes. The purpose of this research was to characterize the heterotrophic activities of two successional stages of cryptobiotic soil crusts. Crust samples were collected from Santa Margarita Ecological Reserve in Riverside County, California. Soil crust samples were collected from early-successional (cyanobacteria dominated) and late-successional (lichen dominated) crust patches, as well as under Salvia mellifera (black sage) as a control to understand how microbial functioning differs from soil located under vascular plants. Microbiological biomass and activity was concentrated in the upper 1-2 cm of the profile. In crust samples, chlorophyll was a better predictor of microbial biomass and activity than were levels of organic matter. Rates of glucose substrate-induced respiration (SIR) were highest under Salvia, intermediate in lichen dominated samples and lowest in cyanobacteria dominated samples. The relative proportion of the microbial communities able to degrade salicylate was highest in the lichen dominated crusts, possibly indicating a difference in microbial community composition. Similarly, degradation of algal products such as alginic acid was more rapid in lichen and cyanobacteria dominated crusts. While respiration rates were significantly higher under plants, the relatively small differences in biomass among the sample types indicates that this is likely due to the presence of roots. This research demonstrates that the microbial activity of soil crust communities is comparable to that associated with vascular plants. However, the distinct functional aspects of soil crusts potentially indicates a novel microbial community.

Key words: cyanobacteria, coastal sage scrub, lichens, soil respiration