Friday, August 6, 2010

PS 92-165: Change in carbon utilization patterns of soil microbes after the alien invasive Mikania micrantha was parasitized by the native Cuscuta campestris

Junmin Li, Institute of Ecology, Taizhou University

Background/Question/Methods Recent studies show that the native parasitic herb Cuscuta campestris could restrain the invasiveness of the alien Mikania micrantha and contributed to the native community recovery in South China. Here we test the hypothesis that Cuscuta’s parasitizing on Mikania affects carbon utilization patterns of soil microbial communities. Fresh soil samples were collected under (1) native plant communities not invaded by Mikania, (2) Mikania-invaded communities without Cuscuta, (3) Mikania-invaded communities with Cuscuta just parasitizing the invader, and (4) Mikania-invaded communities with Cuscuta parasitizing the invader for three years. Community-level physiological profiles of soil microbes were assessed using BIOLOG 96-well Eco-plates.

Results/Conclusions  Average well color development (AWCD) and the number of carbon substrates utilized were the highest in samples collected in the Mikania-invaded communities without Cuscuta, smallest in the native communities not invaded, and intermediate in the Mikania-invaded communities parasitized by Cuscuta. The carbon utilization patterns of soil microbial communities could be changed after the invasion of Mikania and the parasitism of Cuscuta. Principal components analysis could separate the samples into four groups consistent with the four communities. Total soil organic carbon, total soil nitrogen, soil pH and water content were highly correlated with carbon utilization patterns of soil microbes in the four different communities. Cuscuta’s parasitizing may have increased C and N sink, changed root exudates of Mikania and/or modified soil nutrient through reentering of the nutrient-rich litters into soil. Cuscuta’s just parasitizing on Mikania may help restore the soil microbial communities contributing to native community recovery. But the Cuscuta’s three years parasitism on Mikania may form another community different from native community instead of restoring the soil microbial communities. These findings should therefore be considered during the management of exotic species Mikinia.