Over the past century, numerous disturbances (such as nitrogen deposition, elevated CO2, invasive species, and fire) affect global climate and environments. These global change phenomena can cause direct and indirect impacts on plant community and soil biota. Understanding the interactions between plants and soil organisms under changed climate is very important for us to understand how ecosystem responds to these changes. My research focus on studying ecosystem responses, especially soil microbial response, to environmental changes. Some specific research questions would be: 1. what are the effects of disturbance (e.g. exotic species, nitrogen deposition, global warming) on soil microbial community and nutrient cycling in California chaparral shrubland? 2. Will soil microbes be able to sequester more carbon under elevated CO2 environment? 3. Why does the change of mycorrhizal fungal community affect aboveground plant specie diversity and density? What are the underlying mechanisms?
Cheng, X., and Baumgartner, K. 2006. Mycorrhizal effects on 15N uptake from vineyard cover crop litter and the soil microbial community. Soil Biology and Biochemistry. 38, 2665-2675.
Cheng, X., and Baumgartner, K. 2005. Overlap of grapevine and cover-crop roots enhances the interaction among grapevines, cover crops and arbuscular mycorrhizal fungi. In Proceedings of the Soil Environment and Vine Mineral Nutrition Symposium. 29-30 June 2004, San Diego, CA. P. Christensen and D. R. Smart (Eds.). American Society of Enology and Viticulture, Davis, CA. pp 171-174.
Cheng, X., and Bledsoe, C. 2005. Effects of annual grass senescence on 15NH4+ and 15N-glycine uptake by blue oak seedlings and soil microorganisms in California oak woodland. Soil Biology and Biochemistry. 37, 551-559.
Cheng, X., and Baumgartner, K. 2004. Survey of arbuscular mycorrhizal fungal community in Northern California vineyard and mycorrhizal colonization of grapevine nursery stock. HortScience. 39, 1702-1706.
Cheng, X., and Baumgartner, K. 2004. Arbuscular mycorrhizal fungi mediated nitrogen transfer from vineyard cover crops to grapevines. Biology and Fertility of Soils. 40, 406-412.
Cheng, X., and Bledsoe, C. 2004. Competition for inorganic and organic N by blue oak (Quercus douglasii) seedlings, annual grasses and soil microorganisms in a pot study. Soil Biology and Biochemistry. 36, 135-144.
Cheng, X., and Bledsoe, C. 2002. Contrasting seasonal patterns of fine root production for blue oaks (Quercus douglasii) and annual grasses in California oak woodland. Plant and Soil. 240, 263-274.
Cheng, X., and Bledsoe, C. 2002. Seasonal and site effects on oak fine root production and mycorrhizal colonization in California oak woodland. In Proceedings of a Symposium on Oak Woodland: Oaks in California’s Changing Landscape. Gen. Tech. Rep. PSW-GTR-184, pp99-106.