Allometric relationships of field populations of two clonal species with contrasting life histories, Cladium jamaicense and Typha domingensis

Allometric analysis was used to examine morphological relationships in field populations of two clonal plants, Cladium jamaicense and Typha domingensis, in a Florida Everglades wetland. We found that allometric relationships of individuals sampled from field populations could be adequately derived and applied to analyzing both leaf and ramet growth responses to site differences along a nutrient gradient. Overall, the allometric relationships showed a significant departure from isometry which indicates that the relationships were size-dependent. Leaf-level morphological relationships were significantly different between species and between sites along the nutrient gradient. These differences, however, were not expressed on the ramet-level. Neither species expressed a plastic allocation response to site differences along the nutrient gradient. Biomass allocation between above- and below-ground for both species indicated significant size-dependent relationships with decreasing relative allocation below-ground with increasing size. Models for predicting total plant biomass (above- and below-ground) for both C. jamaicense and T. domingensis were developed based on two non-destructive measurements that are easily obtainable in the field. The models followed the equation log (biomass) = α + β₁ × log (height) + β₂ × log (basal area), where α was species specific while β₁ and β₂ were similar for both species but significantly different according to site along the nutrient gradient. Analysis of this model showed that plant height had a relatively greater influence on biomass than basal area at all sites. This difference was greatest at the un-enriched area where plants tend to be short and thick and the least at the moderately enriched site where the relative influence of both parameters was similar.