Liming Alters Soil Microbial Community Structure and Function in Northern Mixed Hardwood Forests.

LIMING ALTERS SOIL MICROBIAL COMMUNITY STRUCTURE AND FUNCTION IN NORTHERN MIXED HARDWOOD FORESTS
Bhavya Sridhar1, Spencer J. Debenport2, Timothy J. Fahey3, Christine L. Goodale1 and Daniel H. Buckley2, (1)Ecology & Evolutionary Biology, Cornell University, Ithaca, NY, (2)School of Integrative Plant Science, Cornell University, Ithaca, NY, (3)Department of Natural Resources, Cornell University, Ithaca, NY Soil pH is known to structure microbial community composition from continental to field scales, yet few studies have directly manipulated soil pH to understand its impact on microbial community structure and function. Here, we examine how increasing soil pH through watershed liming has changed fungal and bacterial community structure and decomposition processes 25 years after lime application. Our study was conducted at Woods Lake, in the Adirondack region of New York, where a watershed scale liming experiment was conducted in 1989. In response to liming, we observed a doubling of organic matter stocks in the forest floor soil horizons. We hypothesize liming has caused organic matter accumulation through suppression of extracellular enzyme activity and that these changes in soil activity are associated with corresponding changes in microbial diversity. We measured microbial biomass, carbon mineralization, extracellular enzyme activities, and used the Illumina MiSeq platform to sequence soil bacterial and fungal DNA (16S rRNA genes and ITS regions respectively). Liming increased soil pH from 4.5 to 5.5 and significantly reduced the activities of seven decomposition enzymes in the Oa horizon, where the largest accumulation of organic matter was observed. Soil pH positively correlated with bacterial and fungal diversity, and liming significantly altered bacterial and fungal communities in the Oa horizon. Most bacterial taxa (75-80%) that had a significant response to liming increased in relative abundance, while most fungal taxa that were responsive to liming (~78%) decreased in relative abundance in the Oa. This study demonstrates that liming can have a long-term impact on soil pH. Furthermore, these long-term effects manifest in long-term shifts in bacterial and fungal community structure, lasting decreases in soil enzyme activities, and increased rates of carbon storage in soils at Woods Lake.