Response of baldcypress (Taxodium distichum L. var.Distichum) to increases in flooding salinity in Louisiana’s Mississippi River deltaic plain

Abstract

Baldcypress (Taxodium distichum L. var.distichum) plants were subjected to flooding with tap water and salt water with salinity ranging from two to seven parts per thousand (ppt) under controlled environment conditions. Imposition of flooding and salinity stresses was designed to simulate the increase in submergence and salinity level which Louisiana’s extensive cypress swamps are currently experiencing due to rapid subsidence. The effect of flooding and salt water intrusion on stomatal behavior and net photosynthesis were measured. Stomatal conductance was reduced between 40% and 65% and net photosynthesis declined between 51% and 70% in response to flooding and increases in salinity within three days of flooding and salt application. Both responses were rapid, occurred shortly after treatment began, and Jasted throughout experiment. However, stomatal conductance recovered within three weeks after flooding was initiated. Net photosynthesis recovery was up to 75% of pre-flood levels within three weeks. Increase in salinity, however, caused more extensive impact and greater reductions of stomatal conductance, and net photosynthesis. Stomatal conductance and net photosynthesis did not recover when salinity exceeded three ppt. Results presented suggest that baldcypress swamps of the Gulf Coast area will be adversely affected if salt water intrusion is not contained or if the predicted global increase in sea level occurs.