The effect of shoot damage on plant performance depends partly on a plant's ability to recover by growth compensation. Plant populations in tallgrass prairie likely experience, or historically experienced, high risks of damage and therefore might be expected to have evolved significant compensation ability. We investigated shoot damage and subsequent growth compensation in Iowa populations of the annuals Linum rigidum and L. sulcatum. To estimate damage rate and responses to damage under natural conditions, we collected two data sets. The first consisted of over 200 herbarium specimens collected over a 113-y period and the second consisted of field data for four populations in the same growing season. A companion experiment investigated damage responses under controlled greenhouse conditions and identified possible mechanisms of compensation. The study species frequently experience apical meristem removal in nature. Per-individual damage-rate estimates ranged from 33–54% in L. rigidum and from 12–24% in L. sulcatum. Both species compensate substantially in mature height, branch number and biomass under field conditions. Compensation in the greenhouse tended to be incomplete, perhaps because the greenhouse experiment may have failed to simulate natural conditions and ended before maximum sizes had been reached. The major mechanism of compensation appears to be rapid activation of axillary meristems, without contributions from altered root-shoot partitioning. Shoot damage and subsequent growth compensation appear to be significant features of individual and population biology in these annual forbs.
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The American Midland Naturalist
Vol. 159 • No. 1
January 2008
Vol. 159 • No. 1
January 2008