Laserfiche WebLink
<br />s <br /> <br />a pattern similar to that reported for early old-field succession <br />in Ohio (Carson and Barrett 1988). <br />The control plots in this study followed this pattern. Annual <br />forbs dominated these plots initially and annual grasses became <br />increasingly important by the third year (Table 1). Nitrogen <br />addition plots were still strongly dominated (90 ~) by annual forbs <br />the third year and, compared to control plots, had lower amounts of <br />annual grasses and perennials, although these differences were not <br />significant at the 95$ level. Annual forb dominance on the sucrose <br />plots was weak by the third year (58 ~) and perennials had <br />increased to 23 ~ relative canopy cover. Compared to N plots, <br />sucrose plots had significantly higher amounts of perennial forbs <br />and annual grasses and lower amounts of annual forbs. All three of <br />these significant differences are characteristic of more advanced <br />seral development on the site. <br />Secondary succession on these sites requires 3-4 years before <br />a significant divergence in species composition occurs between <br />control plots and those receiving nitrogen (McLendon and Redente <br />1991). It is not unreasonable therefore, to expect that in 1-2 <br />more years the sucrose plots will show significant differences in <br />shrub and perennial grass components compared to both control and <br />nitrogen addition plots. <br />The treatments succeeded in establishing the desired available <br />soil N gradient (Fig. 2). The addition of sucrose decreased soil <br />nitrate concentration to half the level of control plots and the <br />addition of N increased it by a factor of ten. If available soil <br />