Forest canopy structure controls the timing, amount, and chemical character of precipitation supply to soils through interception and drainage along crown surfaces (primarily as throughfall). Yet, few studies have examined forest canopy structural connections to soil microbial communities, and none have measured how throughfall affects microbial nitrogen (N) functions. Maritime Quercus virginiana Mill. (southern live oak) forests on St Catherine’s Island (GA, USA) provide an ideal venue to study this interaction as its throughfall patterns are spatially heterogeneous due to the arboreal epiphyte, Tillandsia usneoides L. (Spanish moss), and its edaphic conditions are relatively homogeneous. To test the hypothesis that throughfall patterns alter soil microbial community N-function, we examined soil microbial community N-functional (ammonia oxidizing and chitinolytic) genes, soil chemistry/texture, and throughfall amounts/chemistry for points along a canopy coverage continuum: large canopy gaps (0%), bare Q. virginiana canopy (50–60%), and Q. virginiana canopy hosting heavy T. usneoides (>=85%) over a typical growing season (Mar–Sep 2014). Denaturing Gradient Gel Electrophoresis (DGGE) and quantitative Polymerase Chain Reaction (qPCR) analyses were used to assess changes in the diversity and abundance, respectively, of soil chitinolytic bacterial and ammonia oxidizing archaeal genes. Significant differences in throughfall water and solute delivery (Na+, Cl−, PO43−, SO42−, K+, Ca2+, NO3−, NH4+) were found to alter soil sodicity and salinity. Diversity of chitinolytic bacterial and ammonia oxidizing archaeal communities significantly differed across cover classes and negatively correlated to soil salinity, soil Na+ concentration, and throughfall Cl−, SO42−, and PO43- concentrations. Results suggest throughfall can alter patterns in the soil microbial community’s N-functional gene diversity.
Available at: http://works.bepress.com/john_vanstan/58/