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• • <br /> <br />2 <br />Plants are not the only organisms competing for soil N during <br />secondary succession. The decomposer subsystem can be a major <br />temporal N sink in terrestrial ecosystems. Any increase in <br />decomposer biomass will result in increased N use by the decomposer <br />subsystem as available soil N is incorporated into decomposer <br />biomass (i.e., N immobilization). This in turn reduces the amount <br />of N available to plants until incorporated N, within both plant <br />and decomposer detritus, can be released back into the available <br />soil N pool (i.e., N mineralization). <br />We used this concept of N immobilization by decomposers to <br />test the effect of an induced N availability gradient on secondary <br />succession. In our study, we used the addition of sucrose as a <br />rapidly utilizable energy source for the purpose of decreasing <br />available soil N by increasing decomposer biomass (Lamb 1980, Hunt <br />et al. 1988). We then compared successional dynamics for three <br />years following a disturbance on these plots receiving sucrose (low <br />available N) to those receiving supplemental N (high available N) <br />and to those receiving no amendments (control). <br />METHODS <br />The study area was located in the Piceance Basin of northwest <br />Colorado, approximately 70 km northwest of Rifle, Colorado, at an <br />elevation of 2020 m. The climate is semiarid with a mean annual <br />precipitation of approximately 28 cm, with half occurring as <br />snowfall. Annual precipitation (September-August basis) totals for <br />the three years of the study were below average (23.4, 27.5, and <br />