Microbes, which use plant primary p

Microbes, which use plant primary production from above- and
belowground litter and soil organic matter (SOM) as their sources
of C, play a critical role in mediating soil C and mobilizing nutrients
in forest soils. However, changes in N availability also affect, and are
affected by, the soil microbial community, as these organisms
regulate many fundamental processes that determine the
ecosystem N availability (Paul and Clark, 1997). Nitrogen availability
affects soil heterotrophic respiration, which comprises an
annual source of atmospheric CO2 nearly an order of magnitude
larger than fossil fuel emissions (Schimel et al., 2001). Moreover,
changes in soil N status have been shown to markedly alter the
community level physiological profile (CLPP) of soil microorganisms
in terms of utilization patterns of individual carbon (C) substrates
(Collins and Cavigelli, 2003).