The relationships among root and leaf traits of 76 grassland species and relative abundance along fertility and disturbance gradients

For 76 annual, biennial, and perennial species common in the grasslands of central Minnesota, USA, we determined the patterns of correlations among se ven organ-level traits (specific leaf area, leaf thickness, leaf tissue den sity, leaf angle, specific root length, average fine root diameter, and fin e root tissue density) and their relationships with two traits relating to growth form (whether species existed for part of the growing season in basa l, non-caulescent form and whether species were rhizomatous or not). The fi rst correlation of traits showed that grasses had thin, dense leaves and th in roots while forbs had thick, low-density leaves and thick roots without any significant differences in growth form or life history. The second corr elation of traits showed a gradient of species from those with high-density roots and high-density erect leaves to species with low-density roots and low-density leaves that were held parallel to the ground. High tissue densi ty species were more likely to exist as a basal rosette for part of the sea son, were less likely to be rhizomatous, and less likely to be annuals. We examined the relationships between the two axes that represent the correlat ions of traits and previously collected data on the relative abundance of s pecies across gradients of nitrogen addition and disturbance. Grasses were generally more abundant than forbs and the relative abundance of grasses an d forbs did not change with increasing nitrogen addition or soil disturbanc e. High tissue density species became less common as fertility and disturba nce increased.