Root Nodulation in the wetland tree Pterocarpus officinalis along coastal and montane systems of northeast of Puerto Rico

Background/Question/Methods: In Puerto Rico, brackish water wetlands were dominated by P. officinalis previous to extensive deforestation due to agriculture.  Today remnant wetlands are limited to small areas that are threatened by rise in sea level.  We examined the root nodules of P. officinalis in montane and coastal sites and at 0, 10, 20 cm from the surface to determine if the environmental conditions relate to the formation and characteristics of nitrogen fixing nodules.

Results/Conclusions: We found no significant difference in nodule quantity between montane and coastal ecosystems.  However, although all the montane sites experienced nodule growth, there were sites in the coast that did not.  The montane sites had 96.3 percent active, whereas the coastal had 82.2 percent.  Nodule mass and diameter were significantly larger near the surface of the soil and montane sites.  More research is needed to understand if nitrogen fixing and accumulation rates also differ between the coastal and montane sites where P. officinalis occurs.  Studying the presence, distribution, and potential environmental conditions that are related to nodule formation will be helpful in developing management strategies and conservation initiatives to maintain this species and the wetland forest in which it occurs.