N-202. Metagenomics-Enabled Understanding of the Effect of Climate Warming on Underground Microbial Communities and Its Interaction with Aboveground Plant Populations

L. Wu, J. Xie, Z. He, L. Kellogg, Y. Luo, R. Sherry, J. Zhou;
The Univ. of Oklahoma, Norman, OK.

The climate warming experiment has been conducted at the Kessler Farm Field Laboratory in McClain County, Oklahoma, which is a 137.6-ha farm located in the Central Redbed Plains of Oklahoma. The experiment uses a paired nested design with warming as the main factor and clipping as a secondary factor. Twelve 2m × 2m plots were divided into six pairs of control (i.e. unwarmed) and warmed plots. The warming treatment is implemented by installing a 165 cm by 15 cm infrared radiator over the middle of each plot at the height of 1.5 m. We set the heater at a constant output of ~100 Watts m-2 to generates an approximately 2 oC increase in soil temperature above the ambient plots, which is at the low range of the projected climate warming by IPCC. Each 2m × 2m plot is divided into four 1m × 1m subplots. Two diagonal subplots in each plot are clipped at 10cm above the ground yearly at peak biomass, usually in July. Clipping mimics hay harvesting and removes biomass from subplots. The other two subplots are the unclipped control. We have conducted an experiment with both warming and clipping treatments for eight years. The data collected so far indicates that warming extended growing season, enhanced C4 plant dominance, and increased plant biomass growth. The increased growth was associated with increased plant nitrogen uptake and use efficiency. Warming also increased soil respiration, which was roughly balanced by increased C uptake via plant growth. Due to increased dominance of C4 plants in the grassland, quality of bulk litter decreased under warming, which likely leads to decreased soil N availability over time although warming may initially increase N availability. The analysis of the effect of climate warming on underground microbial community is in process. 16S rDNAs were amplified by PCR with tags from DNAs extracted from the soil samples of 4 treatments replicated on 6 plots and were being sequenced using 454 sequencing method. Functional gene array (FGA) analysis of the microbial community is also on going using our GeoChip 3.0 which contains about 27,000 of functional gene probes representing about 80,000 genes.