The purpose of this study is to test the hypothesis that plant species diversity in young agricultural old-fields is maximal at moderately low levels of available soil nitrogen, a growth-limiting resource, under conditions of moderate and fine-grained disturbance to the plants in the field. This hypothesis will be tested by creating a nitrogen availability gradient in the old-field by enhancing availability with nitrogen fertilizer and by reducing availability by adding sugar to microbially immobilize nitrogen. This approach represents the first experimental reduction of nitrogen availability to look for a peak plant species diversity response. Many studies have shown that nitrogen fertilization of natural ecosystems leads to reductions in biological diversity. The research should be of interest because it tries to examine the lower levels of nitrogen availability which may allow for maximal biological diversity. These results should be of interest to land managers trying to conserve existing biological diversity and restorationists trying to create new species- diverse ecosystems.
