Human activities such as fossil fuel and
fertilizer-use have doubled the amount of biologically active nitrogen entering
ecosystems each year [Vitousek et al.,
1997]. N is the limiting nutrient in many ecosystems
and N availability has been shown to affect plant, root, and soil
respiration. For several temperate
forests, experimental addition of N is associated with a decline in soil CO2
efflux [Bowden et al.,
2004; Burton et al., 2004; Nohrstedt et al., 1989; Swanston et al., 2004]. This decline
could be due to either (1) decreased allocation of C to root metabolism and
growth because N demand of plants can be met with less energy expended
belowground, or (2) decomposition rate due to changes in leaf or root tissue
chemistry, or to changes in the decomposer community. In contrast, the few studies of more water
limited systems do not show decreased soil respiration fluxes [Schaeffer et
al., 2003; Verburg et al., 2004], which could reflect hydrologic control of
belowground C allocation.
Author: N.S. Nowinski, S.E. Trumbore, E.B. Allen, et al (nnowinsk at uci dot edu)
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