Responses of redwood soil microbial community structure and N transformations to climate change
This article is part of a larger document. View the larger document here.Abstract
Soil microorganisms perform critical ecosystem functions, including decomposition, nitrogen (N) mineralization and nitrification. Soil temperature and water availability can be critical determinants of the rates of these processes as well as microbial community composition and structure. This research examined how changes in climate affect bacterial and fungal community structures and rates of N mineralization and nitrification in coast redwood forest soils. Soils were reciprocally transplanted between three redwood sites located across a latitudinal climate gradient, from near the southern extent of redwoods to near their northern extent and collected one year later at the end of the summer. A molecular community fingerprinting technique was used to examine changes in fungal and bacterial community structures, and 15N-isotope pool dilution was used to measure gross rates of N mineralization and nitrification. After one year, soil fungal and bacterial community structures in transplanted soils had changed to become more similar, but not identical, to those native to their new destination sites. Both climatic and edaphic variables were correlated with the variability in microbial community structure. While there were few significant differences in gross N mineralization rates between soil-climate combinations, gross nitrification rates were influenced by a change in climate. Rates of gross nitrification were highest in soils when located in the wetter, most northern site. While rates of gross nitrification varied widely in soils with water potentials above -0.05 MPa, rates were low in soils below -0.05 MPa. Changes in redwood climate, fog frequency and summer water availability will likely alter soil microbial community structure and rates of gross nitrification. Greater magnitude changes in climate or more than one year of exposure may be necessary to cause alterations in rates of gross N mineralization.